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Renovation of wastewater by a short rotation intensive culture hybrid poplar plantation in Vernon, B.C. Nercessian, George 1994

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RENOVATION OF WASTEWATER BY A SHORT ROTATION INTENSIVE CULTUREHYBRID POPLAR PLANTATION IN VERNON, B.C.byGEORGE NERCESSIANB.Sc., The University of TehranM.SC., The University of TehranM.SC., MacDonald College of McGill UniversityA THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR DEGREE OPDOCTOR OF PHILOSOPHYinTHE FACULTY OF GRADUATE STUDIESDepartment of Forest ScienceWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAAPRIL 1994© George NercessianIn presenting this thesis in partia ment f e ents n de e of h I e shall e tef udy. agr t eyi f s s h y e t e head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.Department ofc-The University of British ColumbiaVancouver, CanadaDate q/DE.6 (2/88)iiAbstractA three—year study in Vernon B.C. considered the effects oftwo levels of wastewater irrigation on tree growth, nutrientuptake rates by the foliage and wood, nutrient leaching, andchemical properties of soils in a short rotation intensiveculture (SRIC) hybrid poplar plantation where fourteen differentclones were planted in separate subplots in a 5—ha area.Wastewater irrigation levels were determined on the basisof the calculated values of the local monthly potentialevapotranspiration (ETp). In the first year, all plots receivedalmost equal amounts of wastewater. In the second and thirdyears, treatment 1 and the freshwater (control) plots wereirrigated at the rate of ETp + 30%ETp. Treatment 2 receivedapproximately twice this amount.The effect of wastewater irrigation on increased height,basal diameter, total leaf area, leaf biomass and woody biomasswas measured as early as the end of the first growing season.During the third year, woody biomass production of theplantation was 11, 20, and 24 Mg/ha for control, treatment1and treatment 2, respectively.Concentration of N,P, and K in the foliage of wastewaterirrigated trees increased significantly in the third year.Nutrients in the soil solution were monitored in samplesfromsuction lysimeters. In the first growing season, concentrations111of N, P, K, in soil solution were significantly higher than inthe following two years. This was attributed to cultivation ofthe land at the time of establishment of the plantation. At theend of the third year, concentrations of N and P in thefoliage of wastewater-irrigated plots were higher than in thefreshwater plot. Other nutrients remained unchanged indifferent irrigation treatments. Soil N, P, Na and Mn decreasedwhile K, Ca, Mg, Zn, Cu and Fe remained unchanged from 1988through 1990. Efficiency of the soil—plant system in removingnutrients added through wastewater was: N, 97% and 95%; P, 97%and 94%; K, 40% and 0%; Na, 12% and 0%; Mn, 79% and 66%; Zn,93% and 80%; Cu, 100% and 100%; and Fe, 100% and 92%; fortreatments 1 and 2, respectively. Because of the highconcentrations of Ca and Mg in the soils, removal efficienciesof these elements were not measurable.Nutrient uptake rates by the woody biomass were N, 71%and 42%; P, 29% and 20%; K, 50% and 33%; Ca, 21% and 14%; Mg,8% and 5%; Na, 0.6% and 0.5%; Mn, 46% and 36%; Zn, 78% and70%; Cu, 18% and 4%; and Fe, 30% and 22% for treatments 1 and2, respectively. Based on these data, it was concluded that theoptimal wastewater irrigation level for the plantation in thefirst three years would be treatment 1 (1.3 x ETp), wherenutrient uptake levels by woody biomass and nutrient removalefficiencies were higher than for treatment 2 (2.6 x ETp),therefore the groundwater contamination level would be lower.ivTable of contents:PageAbstract...... . . . . . . . . . . . . . . . . . . . .. . . . . . . . •....... . . . • . • • . • • . . . . .iiList of tables...................................................xiList of figures.................................................xviList of photos..... .. . . . . . . . . . . . • .. . .. • . • • .. • . . . ... .. .... ..... .xixAcknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2 Literature review..... •........................2.1 Irrigation and forestry 62.1.1 Asia 82.1.2 Earope 92.1.3 Africa 102.1.4 Australia and New Zealand 102.1.5 South America 112.1.6 NorthAmnerica 112.2 Land treatment of wastewater 132.3 Wastewater and agriculture systems 152.4 Wastewater and forest systems 162.5 Wastewater land application systems 172.5.1 Rapid infiltration process172.5.2 Overland flow process 182.5.3 Slow—rate process182.6 Approaches towastewater land application21V2.7 Transport of chemicals and hazardousateria is in the soil . . . . 2 22.7 • 1 Nitrogen . Nitrogen transformation in soil ..242.7.2 322.7.2.1 Phosphorus concentrations andforiiis in soils 352.7.2.2 Phosphorus transformations in soils 362.7.2.3 Soil process affecting P movement 372.7.2.4 Effect of irrigation with sewage effluenton soil P and P movement in soil profiles 392.7.2.5 Phosphorus uptake by forest crops 412.7.3 Cat.ions 422.7.4 Trace elements 452.7.4.1 Traceelementsreactionsinsoil • 472.7.4.2 Beneficial and hazardous effects of traceelements on plants and animals 512.7.5 Suspended solids 522 . 7 . 6 Pat1lc,gens 522.7.7 Organics 532.8 Site selection • • 532.8.1 Topograph’ 542.8.2 Soil Properties 542.8.3 Geologic factors 572.8.4 Grourkdwater 572.8.5 Climatic factors 582.9 Ideal sites • 592 • 10 Irrigation scheduling • . . . .602. . 12. 13. 13 . 1.42.13. 1.52 . 13 . 22. 13. 2. 12 .13 .2 .22 . 13 . 2 . 32. 13 .2.42 . 13 . 2 . 52. 13 . 2. 62.13 • 2.72 . 142 . 14. 12.14.2viCrop water requirements .60Estimation based on direct measurements 61Estimation based on climatological factors..... 61Selected methods of estimating ofevapotranspiration 62Irrigation—fertilization interrelations 63Nitrogen management . 64Phosphorus, potassium, calcium, magnesium andsulphate management 65B iomass production 66Short rotation intensive culture forestry 68Stand management 69Pests and diseases 70Rotation age 70SRIC and agroforestry .71Wastewater irrigation and intensiveforest culture 73Poplar culture .75Hybridization ofpoplars 76Nutrition of poplars 79Fertilization 84Soil pH 89Iiming 89Soil texture 90SRIC poplar plantations and fertilizers 91Foliar analysis 93Expressionofnutrientcomposition 94Choiceofsampletissue 99vii3 Materials and methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1003 . 1 Site characteristics 1003 . 1. 1 Location and climate 1003.1.2 Geology and topography 1013 . 1 . 3 Soils. . . 1003.2 Sewage effluent and groundwater 1123.3 Selection of poplar clones 1123.4 Experimental design and field layout 1133.5 Calculation of the total number of trees 1143.6 Establishment of the plantation 1173.7 Itrigation 1173.8 Tending 1253.9 Samplingandfieldmeasurements 1253.9.1 Soils sampling 1253.9.1.1 Determination of infiltration rates 1263.9.2 Waterandwastewatersampling 1263.9.3 Plant sampling 1273.10 Laboratoryanalysesofsoils 1283.11 Laboratoryanalyses of water 1303.12 Laboratory analyses of plants andmeasurements . .1303.13 Statistical analyses and graphics 1313.14 Foliar diagnosis system 1323.15 Determination of leaf weight units infigures 3.6 and 3.7 . .... ... 13544. and Discussion....... . . ... ... . . . .. . .. . ..... .136Chemical quality and application rates ofwastewater, and nutrient input 137Nutrient losses to percolation. .141Volume of soil solution and percolate 141Effect of wastewater irrigation on soils 144Soil pH 148Soil organic matter 148Soil C/N ratio 148Effect of wastewater irrigationonpoplargrowth 148Woody biomass 153Leaf biomass 153Total leaf area (TLA) 157Tree height 161Basal diameter (bd) 161Estimation of leaf area index, woody and foliarbiomass per hectare and nutrient uptake ratesbywood,leavesandgrass 165Concentration of nutrients in thewoody biomass 168Nitrogen (N) 169Nitrogen in soil solution 169Nitrates (N03) 169A.itnnonium (NH4+) 170‘I’otal—N 170Soil total—N 176Foliar and wood N 176ix4.8.4 Nitrogen uptake and removal efficiency 1764.9 Phosphorus (P) 1824.9.1 SolublePinsoilsolution 1824.9.2 Soil P . .1854.9.3 Phosphorus sorption capacity of soils 1874 . 9 . 4 Fo1 jar and ‘wood P 1874.9.5 Phosphorus uptake and removal efficiency 1914 . 10 Potass ium (K) 19 14.10.1 SolubleKinsoilsolution 1914.10.2 Soil K 1944.10.3 Foliar K 1944.10.4 Potassiuiii uptake and removal efficiency 1994.11 Calcium (Ca) 2024.11.1 SolubleCainsoilsolution 2024 . 1 1 . 2 Soil Ca 2 024.11.3 Foliar Ca 2064.11.4 Calcium uptake and removal efficiency 2064.12 Magnesium(Mg) 2104.12.1 SolubleMginsoilsolution 2104.12.2 Soil Mg 2104.12.3 Foliar Mg 2144.12.4 Magnesium uptake and removal efficiency 2144.13 Sodium (Na) 2184.13.1 SolubleNainsoilsolution 2184.13.2 Soil Na 2184.13.3 Sodium uptake and removal efficiency. .218x4.14.2 Soil Mn .2274.14.3 Foliar !4ri 2274.14 • 4 Manganese uptake and removal efficiency 2274.15 Zinc (Zn) 2324.15.1 SolubleZninsoilsolution 2324.15.2 Soil Zn 2324.15.3 Foliar Zn 2364.15.4 Zincuptakeandremovalefficiency 2364.16 Copper (Cu) 2404.16.1 SolubleCuinsoilsolution 2404.16.2 Soil Cu 2404.16.3 Foliar Cu 2404.16.4 Copper uptake and removal efficiency 2404.17 Iron (Fe) 2464.17.1 SolubleFeinsoilsolution 2464.17.2 Soil Fe 2464.17.3 Foliar Fe 2514.17.4 Iron uptake and removal efficiency 2514.18 Graphical vector analysis 2555 Summary and Conclusions.............................2586 Bibiliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264Appendix A...... . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .310Appendix B...... . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .315xiList of Tables:Page2.1 Advantages and disadvantages ofsprinkler distribution 202.2 Concentrations of N in wastewater used inforest irrigation studies . . . 252.3 Foliar N levels in forests irrigated withwastewater 302.4 Nitrogen uptake by vegetation irrigated withwastewater 312.5 Nitrogen transformation and utilisation inwaste effluent—irrigated forests 332.6 Trace element behaviour during slow rateland treatment 5027 Typical steady infiltration rate of varioussoil trpes 562.8 Summary of climatic analyses 592.9 Comparison of mean annual dry weight productionbetween different clones 782.10 Nutrient content per tree in years 1 through4inacottonwoodplantation 802.11 Selected nutrient concentrations ofseven populus hybrids 832.12 Composition of deficiency levels of somenutrients in the foliage of poplars fromdifferent sources 852.13 Composition of the best and worst conditions of soilsfor poplars 923.1 Mean daily temperature (M.D.T.) and monthlyprecipitation (M.P.) for Vernon, B.C 1003.2 Constants used in the modified Penman method 1223.3 Calculation of ET in Vernon, B.C., usingmodified Penman method . . . . . . 123xii3.4 Calculation of mean monthly irrigation ratesfor treatment 1, control and treatment 2 ..1244.1 Some properties of the applied municipalwastewater and freshwater 1384.2 Annual (growing season) application of wastewaterand freshwater irrigation to irrigation plots 1394.3 Annual (growing season) input of somenutrients to wastewater irrigation 1404.4 Results of regression analysis betweennutrient inputs and outputs of nutrients .1424.5 Calculation of volume of soil solution passingthrough the depth of 75 cm. of soil fromMay 1 to Oct. 15 1434.6 Baseline data for nutrient concentrations in twodifferent layers of soil and added nutrientsthrough seven years of wastewater irrigation 1454.7 Some physical characteristics of theproject soils 1464.8 Changes in soil pH, organic matter (O.M.)and C/N ratio resulting from irrigationtreatments 1494.9 Regression equations for estimation of woodbiomass (Wb), leaf biomass (Lb) and totalleaf area (TI..A) 1524.10 woody biomass (Wb) response of a three-year-oldpoplar plantation to wastewater irrigation 1564.11 Leaf biomass (Lb) response of a three—year—oldpoplar plantation to wastewater irrigation 1584.12 Total leaf area (TLA) response of a three—year—oldpoplar plantation to wastewater irrigation 1604.13 Height growth response of a three-year-old poplarplantation to wastewater irrigation .1624.14 Basal diameter (bd) response of a three—year—oldpoplar plantation to wastewater irrigation 1644.15 Actual and potential woody, foliar and grassbiomass production and total leaf area (TLA)of the plantation . 166xiii4.16 Mean annual concentration of N in soil solutionat 75 cm depth under each irrigation treatmentwith percentage of establishment yearconcentration. . . . . . . . . . . . 1754.17 Mean concentration of N in foliage and woodof all clones under three irrigation treatments. 1784.18 Nitrogen uptake of wood and foliage comparedwith its inputs by wastewater irrigation 1794.19 Nitrogen removal efficiency by thesoil—plant system. . . . . . . . . . . . . . . . . . . . 1814.20 Mean annual concentration of P in soil solutionunder each irrigation treatment with percentage ofestablishment year concentration 1844.21 Phosphorus sorption capacity of theproject soils 1894.22 Mean concentration of P in foliage and woodof all clones under three irrigation treatments 1904.23 Phosphorus uptake of wood and foliage comparedwithitsinputsbywastewater 1924.24 Phosphorus removal efficiency by thesoil—plant system 1934.25 Mean annual concentration of K in soil solutionunder each irrigation treatment with percentageof establishment year concentration 1964.26 Mean concentration of K in foliage and woodof all clones under three irrigation treatments 1984.27 Potassium uptake of wood and foliage comparedwith its inputs by wastewater irrigation 2004.28 Potassium removal efficiency by the soil—plantsystem 2014.29 Mean annual concentration of Ca in soil solutionunder each irrigation treatment with percentageof establishment year concentration 2044.30 Mean concentration of Ca in foliage and woodof all clones under three irrigation treatments 2074.31 Calcium uptake of wood and foliage comparedwith its inputs by wastewater irrigation 208xiv4.32 Calcium removal efficiency by the soil—plants’stem. . . . . . . .2094.33 Mean annual concentration of Mg in soil solutionunder each irrigation treatment with percentageof establishment year concentration .2124.34 Mean concentration of Mg in foliage and woodof all clones under three irrigation treatments 2154.35 Magnesium uptake of wood and foliagecompared with its inputs by waste-water irrigation 2164.36 Magnesium removal efficiency by the soil—plant system 2174.37 Mean annual concentration of Na in soil solutionunder each irrigation treatment with percentage ofestablishment year concentration 2204.38 Sodium uptake of wood and foliagecompared with its inputs by wastewaterirrigation .2234.39 Sodium removal efficiency by the soil—plant system 2244.40 Mean annual concentration of Mn in soil solutionunder each irrigation treatment with percentage ofestablishment year concentration 2264.41 Mean concentration of Mn in foliage and woodof all clones under three irrigation treatments 2294.42 Manganese uptake of wood and foliagecompared with its inputs by wastewaterirrigation 2304.43 Manganese removal efficiency by the soil-plant system 2314.44 Mean annual concentration of Zn in soil solutionunder each irrigation treatment with percentage ofestablishment year concentration 2344.45 Mean concentration of Zn in foliage and woodof all clones under three irrigation teatments 2374.46 Zinc uptake of wood and foliage compared withits inputs by wastewater irrigation . 238xv4.47 Zinc removal efficiency by the soil—plantsystem 2394.48 Mean annual concentration of Cu in soil solutionunder each irrigation treatment with percentage ofestablishment year concentration 2424.49 Mean concentration of Cu in foliage and woodof all clones under three irrigation treatments 2444.50 Copper uptake rates of wood and foliage comparedwith its inputs by wastewater irrigation 2454.51 Copper removal efficiency by the soil-plantsystem 2474.52 Mean annual concentration of Fe in soil solutionunder each irrigation treatment 2484.53 Mean concentration of Fe in foliage and woodof all clones under three irrigation treatments 2524.54 Iron uptake of wood and foliage comparedwith its inputs by wastewater irrigation 2534.55 Iron removal efficiency by the soil-plantsystem 2545.1 Potential nutrient uptakes by woody biomass aspercentages of the input rates attreatments 1 and 2 260xviList of Fiqures:VPage2.1 General interactions and processesrelevant to the chemistry of P in the land treatmentof wastewater 342.2 Sorption of added inorganic phosphate byfive horizons of Miami silt Loam 382.3 Generalized representation of yield as afunction of nutrient concentration in tissueof plants 972.4 Schematic relationship between crop yield,nutrient concentration and available nutrientsupply’ 972.5 Relationship between N concentration, N content,and dry weight of current needles of blackspruce 3 years after fertilization 983.1 Pluviometric graph of Vernon B.C 1023.2 Location of the project site 1033.3 Topographic map of the project site 1043.4 Distribution of poplar clones in sub-plots 1153.5 Field Layout of the project site 1163.6 Schematic relationship between concentrationand absolute content of leaves 1333.7 Directional relationships between foliarconcentration and absolute content of anelement following treatment such asfertilization 1334.1 Infiltrationtestresults 1474.2 Effect of irrigation on total woodbiomass(alll2clones) 1554.3 Effect of irrigation on total leafbiomass (all 12 clones) 1554.4 Effect of irrigation on total leafarea (all 12 clones) 159xvii4.5 Effect of irrigation on tree heightgrowth (all 12 clones) . 1594.6 Effect of irrigation on basal diametergrowth (all 12 clones) . 1634.7 Comparison of the inputs (wastewater)and the outputs (soil solution) of NOjat different irrigation treatments 1714.8 Comparison of the inputs (wastewater)and the outputs (soil solution) of NH4at different irrigation treatments. ... . . .. .1724.9 Comparison of the inputs (wastewater) andthe outputs (soil solution) of N at differentirrigation treatments . . 1744.10 Effect of irrigation on concentration of total—NinsoilatO—3Oand3O—6Ocmdepths .1774.11 Comparison of the inputs (wastewater) andthe outputs (soil solution) of P at differentirrigation treatments 1834.12 Effect of irrigation on concentration of plant-availableP in soil at 0—30 and 30—60 cm depths. . 1864.13 Phosphorus sorption isotherms of two typicalsoil samples at the project site 1884.14 Comparison of the inputs (wastewater) and theoutputs (soil solution) of K at differentirrigation treatments . . 1954.15 Effect of irrigation on concentration of plant-availableK in soil at 0—30 and 30—60 cm depths . 1974.16 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Ca at differentirrigation treatments 2034.17 Effect of irrigation on concentration of plant-availableCa in soil at 0—30 and 30—60 cm depths . 2054.18 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Mg at differentirrigation treatments . . . . . . . 211xviii4.19 Effect of irrigation on concentration of plant—availableMg in soil at 0—30 and 30—60 cm depths.. ....2134.20 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Na at differentirrigation treatments . 2194.21 Effect of irrigation on concentration of plant-availableNa in soil at 0—30 and 30—60 cm depths...4.22 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Mn at differentirrigation treatments. . . . . . . 2254.23 Effect of irrigation on concentration of plant-availableMn in soil at 0—30 and 30—60 cm depths 2284.24 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Zn at differentirrigation treatments 2334.25 Effect of irrigation on concentration of plant—availableZn in soil at 0—30 and 30—60 cm depths 2354.26 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Cu at differentirrigation treatments 2414.27 Effect of irrigation on concentration of plant—availableCu in soil at 0—30 and 30—60 cm depths 2434.28 Comparison of the inputs (wastewater) and theoutputs (soil solution) of Fe at differentirrigation treatments . 2494.29 Effect of irrigation on concentration of plant-availableFe in soil at 0—30 and 30—60cm depths 2504.30 Relative response in nutrient concentration, nutrientcontent and dry weight of leaves in hybrid poplars(all 12 clones) irrigated with municipal wastewaterattwolevels(treatmentsland2) 257xixList of photosPage4.1.Damagecausedbyrodents...4.2 • A bird’s—eye—view of the project site 1514.3. Basal diameter of a typical tree (Oct. 1990) 1544.4. A typical poplar stand (Oct. 1990) 154xxkcknowledgementsI am appreciative of my supervisors Dr. J.V. Thirgood andDr. D.L. Golding for providing their support and effort inbringing this work to its fruition. I am also grateful to theother members of my supervisory Committee: Dr. A.A. Bomke, N.Carison and Dr. S. Chieng, for the time and effort they tookto review and provide constructive criticism of this thesis.In producing this thesis I wish to acknowledge thecontributions made by Mrs. Y. Kwan, Mr. D. Danallanko,Mr. E. A. Jackson, Mr. B. von Spindler and Mr. N. M. Nazhad.I would like to thank the various organizations whichprovided me with the financial and technical support whichallowed me to attend graduate school and conduct thisresearch. These are the The Corporation of the City of Vernon,Canadian Forestry Service, Ministry of Forests, Province ofBritish Columbia, The Natural Science and Engineering ResearchCouncil of Canada, and the Science Council of BritishColumbia.Finally, I am thankful to my family for their love,patience, support and encouragement. To the memory of myfather Mr. R. G. Nercessian I dedicate this thesis.TaM TOflOfl5 cocanH C T06013Cranxcb 3TH flPYTLR H poicaA Hh1H’e cepe6pwcTo}O JIHCTBOOCTyaT B OXHO BT0OFO BTa)fca.Terleph HX THb Hat ynxueci HBHCJIBTenepb .TIHCTBa HX rop,Do LijenecTHTHeycTo BIPHMb PCTYT OHH Tax JCTPOHim 3T0 IPOCTQ BPM5I Tax J1eTHT.MapK H. BepHecWe were planting poplar whips together.They were bending and shaking under the wind’s blow.Today their trembling, silvery leavesbrush the windows ofthe second floor.Today their shadow hangs over the alley.Today their leaves proudly rustle.Is it possible that they grow this fastor is it the time that flies this fast?A song by the Russiansinger Mark N. Berness (1911—1969)11. IntroductionIn every society, two general processes take place: 1)renewable and nonrenewable sources of energy and materials areexploited for production of goods and energy, and 2) wastes areproduced during the process of production and after the goods andenergy are used. As a result, in many cases, the sources of energyand raw materials have been depleted at an alarming speed, andaccumulation of wastes has caused serious hazards and economicallosses.A typical example of depleting sources of energy and rawmaterials is the forest. Demands for pulp, lumber, fuel and othermaterials derived from wood are increasing at an alarming rate,while wood’s renewal rate is decreasing due to several factors,such as neglect, mismanagement, over—exploitation and insufficientreforestation and protection. As a result, although the forest issupposed to be a “Renewable Resource” its depletion rate dominatesthe rate of renewal.For this reason there is an urgent need to grow trees asquickly as possible. Industrially—managed plantation systems arebeing studied in several countries, including Canada, in order tosatisfy these needs. Silvicultural biomass farms, energyplantations and agroforestry are some other terms covering theconcept of growing large quantities of tree biomass in the shortestpossible time. Poplar culture has many management and utilizationprerequisites for industrial biomass production (Zsuffa 1983), anddue to ease of genetic improvement, adaptability, and fast growth,its significance is increasing substantially.Municipal wastewater, on the other hand, is an example ofwaste production in urban communities. Many water pollution2problems have been created by disposal of treated municipalwastewaters into streams, lakes, and oceans. Treated wastewaters,although acceptable by public health requirements, are usuallyenriched with appreciable quantities of dissolved minerals andsynthetic detergent residues. As a result, the concentrateddischarge of large volumes of these effluents into a balancedaquatic environment, often causes ecological chaos and disrupts thenatural recycling process. The visible evidence is usuallyeutrophication which stimulates the growth of aquatic plants. Insome instances, fish kills may result from reduced dissolvedoxygen levels in the water resulting from respiration by theseplants and decomposition of organic matter.Increasing volumes of municipal wastewater are usuallycorrelated with increasing demands on the local water supply whichin times of drought can cause serious shortages. Hence, it issomewhat paradoxical that communities, while experiencing watershortages, will at the same time discharge millions of litres ofwastewater into local streams for rapid removal from the area.An obvious alternative method to disposal of wastewater insurface waters is to dispose of such wastewaters on the land so asto utilize the entire biosystem, soil and vegetation, as a “livingfilter” to renovate this wastewater prior to groundwater recharge.The hypothesis is that under controlled application rates so as tomaintain aerobic conditions within the soil, the mineral nutrientsand detergent residual might be removed and degraded by: 1)microorganisms in the surface soil horizons, 2) chemicalprecipitation, 3) ion exchange, and 4) biological transformationand biological absorption through the root systems of thevegetative cover. The utilization of higher plants as an integral3part of the system to complement the microbiological andphysiological systems in the soil, is an essentialcomponent.of theliving filter concept and provides maximum renovation capacity anddurability to the system (Sopper 1976).Wastewater disposal problems in Vernon B.C. are typical ofthose in many communities. In 1977 the City of Vernon beganirrigating treated wastewater to approximately 750 ha of nearbygrasslands with the principal goal to protect the water quality ofOkanagan Lake. Application of wastewater was regulated by theMinistry of Environment and was limited to the crop waterrequirement which means that after an allowance for a small amountof water to leach below the root zone the amount of wastewateradded must be evaporated and transpired by the crop. This approachwas in contrast to the living filter concept.As wastewater production increases with population growth,continuation of the current irrigation system based on waterrequirement of the crops would have required an expansion of theirrigation land base by approximately 2934 ha by the year 2000.The quantity of land suitable for hay crop production is notavailable, within an economically feasible distance from Vernon(Nutter 1988).One alternative to the existing system is a combination ofshort rotation intensive culture (SRIC) forest plantation concept,with the living filter concept. Under this system wastewaterdisposal rates would be increased to its highest level.The principle is that the SRIC plantations could benefit fromthe nutrients in the wastewater, which might increase biomassproductivity and shorten rotation periods, and at the same timeprovide a land treatment for renovation of wastewater. This system4removes nutrients from wastewater more effectively than wastewaterdisposal over grass and even natural forest stands.As a means of demonstrating this system a pilot project wasinitiated in 1988 with cooperation of the City of Vernon, Facultyof Forestry, U.B.C., and the B.C. Ministry of Forests, KalamalkaForestry Centre. An area of 5 ha was planted with different clonesof hybrid poplars. Since the knowledge about performance of thepoplar clones under the environmental conditions of Vernon waslimited, one of the goals was to determine biomass production ratesof poplars under wastewater irrigation. Based on this data futureimplementation of the living filter approach would be possible atlarger scales. For this reason, two wastewater irrigation levelswere selected at 1)the crop water requirement level +30% (treatment1) and 2) at approximately two times the treatment 1 level(treatment 2). To compare growth performance of the trees andnutrient loading rates in soils a freshwater treatment was alsoadded to the project.Specific objectives of the project were: (1) to determine howmuch woody and foliar biomass would be produced under eachirrigation treatment and whether wastewater irrigation wouldincrease biomass productivity, (2) to determine if SRIC poplarplantation can satisfactorily renovate the wastewater under thetreatment 2 irrigation rate, (3) to determine if the soil iscapable of immobilizing nutrients and cations added throughwastewater irrigation for direct groundwater recharge, and (4) todetermine whether the combination of soil and plant is capable ofacting as a living filter to renovate wastewater.The hypotheses of this research are: 1) woody biomass producedby the hybrid poplar plantation is capable of taking up and5removing macro— and micro—nutrients at quantities at least equal totheir inputs through wastewater irrigation rates in this research.2) If nutrient uptake of the woody biomass is less thanthe input,foliage and ground vegetation can take up and temporarilyimmobilize the added nutrients. 3) Soil at the rooting zone iscapable of sorbing that fraction of the added nutrients that werenot taken up by the trees and the ground vegetation. 4)The soilplant system can act as a living filter so thatmost of thenutrient will be retained in the upper 75 cm.of soil andconcentrations of nutrients in the soil solution at that depthwould not be different from those of the freshwater irrigatedplots.62. Literature review2.1. Irrigation and forestryThe history of irrigated tree plantations goes back to theearliest days of man’s history. The first well—recordedcivilizations of Mesopotamia which existed as early as 4000 B.C.,learned to produce crops from the desert by canal irrigation.Together with crops, trees were planted along canals for protectionof canals’ banks and also for production of fuel and constructionwood. Psalm 137 of the Old Testament, which was probably composedbetween 586 and 540 B.C., mentions willows growing “by the riversof Babylon”. The “rivers” were in fact irrigation canals whichconducted water from the Tigris to the arable lands and gardens ofBabylon. The Hanging Gardens of Babylon, which were considered oneof the seven wonders of the ancient world, were most likelyplantations irrigated by artificial means. There is strongevidence from the frescoes painted on the walls of Egyptian tombsand also from excavations at the temple and palace of PharaohAkhenaton (1277-1355 B.C.) that trees were planted and irrigatedalong with other crops in ancient Egypt. There is also evidencethat during the Ptolemaic period (3rd and 4th centuries B.C.) therewas a nation-wide tree planting project, which included plantingalong the banks of rivers and canals, to meet the acute needs forwood in Egypt (Thirgood 1981). Ancient Persians, who were themasters of digging underground aqueducts known as ‘qanats’,established gardens and groves which they called ‘pardiss’. Mostlikely the word paradise is a word borrowed from ancient Persian.Most of the Persians’ irrigation network fell into disrepair afterArab conquest of the country in the 7th century. Bas-reliefs inthe ruins of Persepolis in Iran, built between 559 and 333 B.C.7(Wilber 1976), represent trees with a strong resemblance to Quettapine (Pinus eldarica Medw.) or cypress (Cupressus sempervirens varfastigiata), which are still grown in that area. These conifers arenot indigenous to Persia (Mobayen and Tregubov 1970). It is likelythat these species were first introduced into the area and wereplanted around the palace for ornamental/recreational purposes.Since the climate of the area is too arid for these species tosurvive without man’s care,it is almost certain that these wereirrigated by artificial means.On the plains and high plateaus of Hither Asia, Iran andfurther afield in Central Asia the growing of poplars has a longhistory (FAQ 1979). In the Levant, introduction of irrigatedpoplar plantations goes back to the times of the conquest of Syriaand Palestine by the Romans, circa 60 B.C.,(Thirgood 1981).Irrigated poplar plantations are still the main sources of wood inthese regions and poplar groves are common scenes in the ruralareas along the mountain streams.Because irrigated tree plantation was seldom practised on itsown, separate from irrigated agriculture, the term ‘forestry’ asused today does not apply to it. The history of irrigated forestryis much more recent.In response to high demand and an inadequate supply, woodproduction systems have been intensified over several decades andare still being developed in this way. The first recordeddevelopment of an irrigated forest plantation began in the arid andthe semi arid Indus Basin, today’s Pakistan, in 1864, to meet thespecific need for fuel for operation of the railways and toproduce lumber. By 1926 the area planted reached 3550 ha; in 1967it had reached nearly 100,000 ha. The plantations were made up of8a large number of blocks of various sizes, from a few hundred toseveral thousand hectares, distributed through the extensiveirrigated agricultural area in the valleys of the Indus and itsmajor tributaries in the plains area (Armitage 1985). The principalspecies used were Dalbergia sisso, Acacia nhlotica, and Morus alba,with smaller amounts of Albizia lebbeck, Eucalyptus carnaldulensisand various clones of Populus euramericana (Lerche and Khan 1967).2.1.1 AsiaIrrigated forestry plantations subsequently became importantin other countries. From the early 1950’s, steps were taken todevelop irrigated plantations in Northern India: Gujarat, Hariana,Utarpradesh, West Bengal and in the southern states of the country(Singh 1963).In Iraq, trials of Eucalyptus camaldulensis produced as muchas 37 m3 of wood per ha per year at 5 years of age in the TigrisValley (Barbier 1978).In Kuwait, with harsh climatic conditions, high temperature,low precipitation and high soil salinity rates, some 3000 ha ofplantations were established by the government around Kuwait City,using treated sewage effluent for irrigation (Wood and Synott1978).In Iran, irrigated forestry exists in the form of poplarplantation along the mountain streams. Trees are generally denselyplanted and the wood output is almost entirely destined for localuse, therefore, no accurate data is available about the total areaunder plantation. The same methods of poplar plantation are alsopractised in Afghanistan, Syria, Lebanon, Iraq, Israel and Turkey.(FAO 1979).9In Israel, Rawitz and Karschon (1966) report the response ofPopulus deltoides and P. euramericana (1-214) plantations toirrigation.In the former Soviet Republics irrigated forestry is practisedin semi—arid regions of Central Asia and Caucasus. Numerous papersdiscuss irrigated forestry projects in those regions (Gruzdevl958;Alekberov and Mamedov 1958; Shirjaeva 1960; Voznesenskaja 1970;Bozhko 1974). Varfolomeeev (1988) conducted research in a hybridpoplar plantation irrigated with wastewater from a cardboard andcellulose mill in Kostroma, Russia. Lohinov and Stroina (1976),Siryk (1979), Lishenko and Siryk (1979) report on establishment offorest plantations on irrigated lands in Ukraine.2.1.2 EuropeIn Hungary, ni.rmerous studies have been conducted in the fieldof wastewater irrigation in forest plantations. A 130 ha areaofa six-year old poplar plantation was irrigated with municipalwastewater from Keczkeinet (Mikios 1971). A 53 ha hybrid poplarplantation was irrigated with wastewaters from the city of Gyula(Gal and Tihanyi 1975). Vermes (1985) also reports other successfulwastewater irrigated poplar plantations in Hungary.In Poland, forest and forest plantation irrigation has beenconcentrated mostly on wastewater disposal (Kermen and Pinkiewicz1976; Matusiewicz 1976; and Kurhanski 1978).In Italy, there are some irrigated plantations of poplars inP0 Valley (FAO 1979) and Pinus radiata near Rome (EccherandLubyano, 1969). Grossi (1976) reports enhanced survival and growthof Pinus maritima due to drip irrigation. A stand of Poplar ‘1-214’was planted and irrigated at Casale Monferrato to assessthe10effects of irrigation (Prevosto 1972).2.1.3 AfricaOver wide areas in the south of Tunisia and Algeria Eucalyptusoccidentalis and E. camaldulensis have been grown under irrigation(Armitage 1985).The oldest irrigated forest plantation scheme in Sudan had itsbeginnings with the initiation of species trial in 1932 intheGezira cotton and sorghum irrigation project. Thesecondsubstantial irrigated plantation to be undertaken in the countrywas the Khartum Greenbelt where Eucalyptus and Acacia inparticular grew successfully. This project was initiated tomakeuse of sewage effluent from the city of Khartoum (Wood 1977).In Nigeria and Niger, Eucalyptus plantations were establishedin 1960’s on lacustrine sands. Some provenances of E. camaldulensiswere 11 m tall and over 10 cm in dbh at 17 months (Arxnitage 1985).Irrigated plantation trials in Zimbabwe were developed from1959 onwards. Coniferous species such as Araucaria cunninghamia,Pinus taeda, P. eliottii, P. halepensis and Eucalyptus werealsotried with success (Barret and Woodvine 1971).2.1.4 Australia and New ZealandTrials of land disposal of pulpmill, winery and municipaleffluents compared with river irrigation were conducted infourlocations in Northern Victoria from 1972-1978. Thirteen Eucalyptusspecies, two poplars and one willow species were used inthesetrials (Stewart et al. 1990). An irrigation trial near Canberrawas established in a 15 year old radiata pine plantation.After 11years, the diameter and wood characteristics of the irrigatedtrees11were superior to those of non-irrigated (Nicholas and Waring 1977).In New Zealand, a radiata pine stand was irrigated with wastewater(Hames and Noonan 1988; Schipper et al. 1989).2.1.5 Bouth AmericaLittle published information is available on irrigated forestplantations in South and Central America. In Argentina, 300,000 haof tree plantations, mostly Populus deltoides and P. euramericanaclones are grown under irrigation in Rio de la Plata (Carretro1972). There are some 8000 ha of Eucalyptus globulus planted inthe valley of the river Mantaro in Peru. The U.S. Agency forInternational Development (USAID) established a Prosopis sp.plantation in a 100 ha tract of shifting sand dunes in the desertarea near Piura in north western Peru (USDAFS 1980).2.1.6 North AmericaUp to 1974, no irrigated forestry was practised in the U.S.A.In that year two irrigation studies were undertaken to determinewhether the growth of planted Populus deltoides could be increasedby irrigation in the North Central States (Belanger and Saucier1975). The effects of irrigation with and without the applicationof sewage sludge were tested on red alder and black cottonwood inthe Pacific Northwest (DeBell 1975). Later, in Wisconsin,irrigation of hybrid poplar plantations for five years increasedbiomass production and improved tree survival (Hansen 1988). TheUnited States has become a leader in the field of wastewaterirrigation in forestry. The longest continuous studies of forestirrigation with wastewater have been made at Pennsylvania StateUniversity using northern hardwoods, red pine, white spruce and oak12species. This project began in 1962 (Sopper and Kardos 1973;Richendorf et al. 1975; Sopper and Kerr 1979). The water used inthese experiments was secondary effluent from a municipalbiological treatment plant. In the Pacific Northwest, Alverson(1975) reviewed issues, choices, and actions regarding the use ofwastewater for irrigating Douglas fir and western hemlock forests.Scheiss and Cole (1981) conducted a forest wastewater irrigationstudy at the Charles Lathrop Park Experimental Forest ofUniversity of Washington. A five year wastewater irrigation studyin Washington provided data on Douglas fir seedlings and juvenileplantation of Lombardy poplar. A natural Douglas fir forest wasalso irrigated for four years (Scheiss and Cole 1984). However mostof these projects are in experimental or demonstration stages.The effects of irrigating a northern hardwood forest withwastewater at Sugarloaf Mountain, Maine, were studied by David andStruchtemeyer (1982). Demonstration of forest irrigation witheffluent from sewage ponds was made in Michigan in pole size andjuvenile red pine plantations, and with Christmas trees (Urie etal. 1984). The study at Unicoi State Park in Georgia has providedfield performance data over a 12 year period for a mixed pine andhardwood forest irrigated year—round with pond—treated , municipal-type wastewater (Nutter and Red 1985). Another study was conductedin a 98ha slash and loblolly pines plantation in Georgia wherewastewater produced by a navy base was used for irrigation purposes(Red and Nutter 1986).Although the scarcity of literature on irrigated forestrysuggests that tree plantation is of little interest in theextensive irrigated agricultural areas in California, Arizona, andColorado, it is pertinent to note that salinity problems are13widespread and are of great concern in the area. Controlling thiscondition requires the installation of drainage and leaching withfreshwater (Pillsbury 1981).In Canada, reported irrigated forestry activities are not manyand mostly are related to wastewater disposal. A wastewaterirrigation study was conducted over a five year period in aforested area located in the Kananaskis Valley west of Calgary,Alberta. The tree cover was predominantly lodgepole pine (Pinuscontorta) (Graveland 1980). Love (1985) irrigated a poplar andwillow plantation in Ontario with wastewater from a foodprocessing plant in Ontario for one growing season. A wastewaterirrigated poplar and willow plantation was established on the landsof Seneca College in Maple, Ontario, where local wastewater wasused for tree irrigation (Papadopol 1989; personal contacts). Asimilar plantation was established in London, Ontario, in 1983which was irrigated with wastewater from vegetable—processingindustries (Papadopol and Nolan 1987). Landfill leachate collectedfrom the Muskoka Lake sanitary landfill in Ontario was used toirrigate a northern hardwood stand of 4.3 ha (Gordon et al. 1989).2.2 Land treatment of wastewaterLand treatment is one of many popular alternatives to treatingmunicipal wastewater in a conventional—technology plant and thendischarging it to surface waters. Applying wastewater to the landis neither a new nor a novel approach to wastewater management. Ithas been practised throughout the world since ancient Greece andhas experienced several cycles of popularity. Utilization of thesoil system for disposal and treatment of waste has the potentialfor taking advantage of the soil’s unique physical, chemical, and14biological processes. The natural soil system offers a dynamicmedium for not only absorbing wastewater, but for treating andutilizing the constituents (Brockway et al. 1982). The pores ofsoil can provide an ideal medium for absorbing liquid effluent. Atortuous flow path through soil pores and voids that is neither toorapid nor too slow, allows for a variety of natural treatmentprocesses (Kleiss and Hoover 1988).Under application rates controlled to maintain aerobicconditions within the soil, the mineral nutrients and detergentresidual might be removed and degraded by 1) microorganisms in thesurface soil horizons, 2) chemical precipitation, 3) ion exchange,4) biological transformation, and 5) biological absorbtion throughthe root systems of the vegetative cover. The utilization of thehigher plants as an integral part of the system to complement themicrobiological and physicochemical systems in the soil is anessential component of the living filter concept and providesmaximum renovation capacity and durability to the system (Sopper1976).Treated municipal wastewater can be used to supplement thenatural water supply available for agricultural and silviculturalcrops. Application during periods of soil moisture deficit willincrease crop productivity. In addition, the nutrients inwastewater, particularly N and P, supplement soil nutrients and mayreduce the requirement for commercial fertilizer. The selection ofland treatment relative to other methods depends on size of thecommunity and the expertise of local system operators, as well asthe cost, quantity, and type of land available (Brockway et al.1982). Land treatment techniques may not be economically feasiblefor large communities with limited access to reasonably priced15rural lands and forests, however for small communities withpopulation of about 30,000, e.g., Vernon, B.C., land application ofwastewater is becoming a popular alternative to other techniques.2.3 Wastewater and agriculture systemsWastewater recycling by means of agricultural irrigationoffers a number of potential benefits. Wastewater irrigationreturns vital nutrients to the soil that would be expensive to addin other forms. Municipal wastewater normally contains most of therequired N for most agricultural crops and major portions of theessential P and K, as well as important micronutrients essentialfor plant growth and maintenance of soil fertility. Today,controlled wastewater irrigation is practised in many parts of theworld. Numerous projects for wastewater reuse in agriculture arealso under construction or are in the planning stages (Shuval etal. 1986).Row crops such as corn are attractive because of theirpotentially high rate of economic return as grain or silage. Non—row forage crops and old field vegetation (i.e., mixture ofperennial grasses and weeds) can provide high levels of renovationwith less operational and maintenance costs than row crops.Grasses, if planted in fine textured soils, are suitable foroverland flow as well as spray irrigation, and excessive leachingof nitrate-N is relatively easy to prevent (Papadopol 1984). Foragecrops other than grass can also be used for slow rate irrigationsystems (Brockway et al. 1986).Because of the nature of sewage effluent, fears have beenexpressed about the possible hazards associated with effluentreuse. Two aspects of wastewater reuse in agriculture have become16subjects of paramount importance: 1) the possible risks to health,and 2) the potential environmental damage. Health considerationsare centred around the pathogenic organisms that are, or could be,present in the effluent and the buildup of toxic materials withinthe soil, and subsequently within plant and animal tissues whichmight eventually reach the human food chain. The leaching ofmaterials such as nitrates and toxic soluble chemicals into thegroundwater is also a matter of concern. Environmental risksinvolve the effects of the use of wastewater containing dissolvedsubstances that have deleterious effects on soil as well asinhibitory effects on the development of plants (Pescod and Alka1988).2.4 Wastewater and forest systemsSince the pioneering research began at Pennsylvania StateUniversity in the early 1960’s (Evans and Sopper 1972), interesthas increased in utilizing forested sites for the renovation ofwastewater. The early work indicated that forest ecosystems couldeffectively improve the quality of wastewater by removing thenutrients. Subsequent research in Michigan, (Urie 1977) Georgia(Nutter et al. 1978), washington State (Cole et al. 1983), Ontario(Papadopol 1989), and other regions of North America examined awide variety of forest cover types and sites. Slow—rate irrigationis the only application technique that has been successfully usedin forest ecosystems (Nutter and Red 1985).wastewater irrigation rates and schedules should be managed soas to meet treatment criteria, with fertilization of vegetation toincrease yields as a secondary objective. In forest ecosystems, thecontrol of nitrate—N discharges in groundwater is usually the17foremost design constraint.Uptake in very young forest plantations of any species is lowbecause they do not fully occupy the site. During this stage ofdevelopment, vegetation other than trees serves as an importantnutrient sink. Until the stand closes, a high levelof management,approaching that for agronomic crops, is required to maintain theherbaceous ground cover without reducing tree survival or growth(Brockway et al. 1982).2.5 Wastewater land application systemsThere are three basic types of land applicationsystems thatare commonly used. There are many variations in some of thecomponents of each type of system, but the principles of operationof each system are the same. The principalsystems are rapid—infiltration (RI) overland-flow (OF) and slow—rate (SR).2.5.1 Rapid infiltration processRapid-infiltration land treatment is thecontrolledapplication of wastewater to earthen basinsin permeable soils ata rate typically measured in terms of metres of liquid per week.Any surface vegetation that is present hasa marginal role fortreatment performance due to the high wastewater disposal rates.At least 3.0 m. of soil is required between the bottom of therecharge pit and the top of the groundwater in a rapidinfiltration system. Renovated water is recovered from thesesystems using subsurface drains or wells (Athanas et al. 1981).182.5.2 Overland flow processOverland flow systems are used to provide secondary treatmentto wastewater which has received screening and primary treatmentprior to application. Overland flow systems apply water at theupper end of a sloped vegetated terrace and allow it to run overthe surface to a collection ditch at the toe of the slope wherethe water can be reused or sent to another type of landapplication system for final disposal. Soils used in constructingoverland flow systems generally have very low infiltration rates,since the objective is to keep the effluent on the soil surface tobe treated. Food processors have used these systemsextensively inthe United States to process their wastewater (Athanas et al.1981).2.5.3 Slow—rate processSlow—rate land treatment is the controlled application ofwastewater to a vegetated land surface. Low loadingrates of 0.5—2.5 rn/yr allow much of the applied wastewater to belost throughevapotranspiration (ET). The contribution to groundwater is largelydependent on these ET losses (Thomas and Law 1977). The surfacevegetation is an essential component in the treatment process.Recommended design criteria stipulate that at least 12 0cm ofunsaturated soil should exist between the soil surface and the topof the water table (Athanas 1981). Slow-rate landtreatment can beoperated to achieve a number of objectives including:191) Treatment of applied wastewater, 2) economic returnfrom use ofwater and nutrients to produce marketable agriculturaland forestrycrops, 3) exchange of wastewater for potable water for irrigationpurposes in arid climates to achieve overall waterconservation, 4) development and preservation of open space andgreenbelts.These goals are not mutually exclusive, but it is unlikelythat all can be brought to an optimum level within the same time(Reed and Crites 1984). In the case of Vernon, wastewater treatmentand economic return are the main objectives (Critesand Cole 1984).To date, sprinkle irrigation has been the most common slow-rate land treatment method adopted in North America. This systemcan be used on flat, extensively undulating, and very steep land ifthe soil is moderately to highly permeable and the location hasappropriate borders to protect the public from wind drift and fromspray aerosol (Brockway et al. 1982).Sprinkler distribution systems simulate rainfall bycreatinga rotating jet of water that breaks up into small droplets thatfall to the field surface. The advantages anddisadvantages ofsprinkler distribution systems relative to surface distributionsystems are summarized as follows (Table 2.1 ).20Table 2.1 Advantages and disadvantages of sprinklerdistributionAdvantages DisadvantagesFeasible for porous soils, High capital and energyshallow profiles, rolling costs.terrains, easily eroded High levels of maintenance.soils, small flows,frequent applications.Minimal interference with Traffic problems in claycultivation, soilsHigh system efficiency Wind influenceNo tailwater Nozzle cloggingFor all slow-rate sprinkler systems the design applicationrate should be less than the infiltration rate of thesurface soilto avoid surface runoff.Many forest and agricultural slow rate systems use solid setsprinkler distribution. A solid set sprinkler distribution systemremains in one position during the application season. This systemis favoured for odd—shaped areas, for fields with much soilvariation and wooded areas, and for sites with geologic constraintssuch as sink holes or steep slopes. The primary advantage of solidset systems are low labour requirements and maintenance costs andadaptability to all types of terrain, field shapes and crops. Themajor disadvantages are high installation costs. Permanent solid—state systems usually are used for forested areas (Crites and Reed1986, Nutter 1988).212.6 Approaches to wastewater land applicationThere are two principal approaches to application ofwastewater to the land to achieve further treatment. They are: 1)crop water requirement, and 2) renovation/recycling. Bothapproaches can achieve a high degree of wastewater treatment, theprimary difference being that in the crop water requirementapproach, almost all of the irrigated water is lost to theatmosphere by evapotranspiration (ET), whereas in therenovation/recycling approach a large portion of the renovatedwater is returned to the groundwater and ultimately to streamand/or lake waters. A short review of each approach is presented inthe following sections.Irrigation by amount of wastewater equivalent to the cropwater requirement is the method currently advocated by the BritishColumbia’s Ministry of Environment, BC. (Nutter 1988). Irrigationmay begin in the spring when soil moisture levels have dropped tothe point that added irrigation water will be evaporated from thesoil and transpired by the crop. Irrigation must cease in theautumn when the crop becomes dormant and no longer utilizestheadded water. To avoid the buildup of salts in the soil a leachingrequirement (LR) of 10% to 20% of the applied water and rainfallisspecified. This amount of water will leach salts from the surfaceto lower horizons. Thus the amount of water added to the crop(rainfall plus irrigated wastewater) is equal totheevapotranspiration plus the leaching requirement. Renovation ofwastewater by this method is usually high because nutrientsandother wastewater constituents are applied at well below thesoiland crop assimilative capacities. In fact, to achieve optimumcropproduction in most cases fertilizer must be added to supplementthe22wastewater nutrients (Nutter 1986). Crop requirement wastewaterirrigation return flows are also usually of high quality and in lowrainfall areas such as Vernon recharge to groundwater directly.When the renovation/recycling method is utilized, water andnutrients are applied at the amounts and rates dictated by the soilassimilative capacities for each wastewater constituent. Nutrientsare applied at the crop requirement level plus other losses thatmay occur (e.g., volatilization of ammonia N, sorption of P andmicronutrients). Water is applied in excess of the cropevapotranspiration rate and, as is common with many systems, for aperiod of time longer than the growing season, often year—roundeven in below freezing temperatures. Winter irrigation is feasiblefor most wastewaters because the applied crop nutrients are storedin the soil until the next growing season when biological activityincreases. Applied wastewater not utilized by evapotranspirationrecharges groundwater and emerges in intermittent stream channelsor larger streams and lakes down-gradient from the irrigated site.Quality of the recharge water can meet drinking water standardsandother specified environmental goals and is thus suitable forreuse/recycling. Examples of wastewater land application systemsthat recharge groundwater for reuse exist in both humid and semiarid regions (Nutter 1988).2.7 Transport of chemicals and hazardous materials in the soilGroundwater pollution is of major concern under wastewaterirrigation conditions. Water flowing below the root zone of plantscarries various contaminants to the vadose zone and eventuallyfurther to aquifers. An understanding of the transport of nutrientsin soil is important for good fertilization-irrigation using sewage23effluents.Extensive investigations during recent years have greatlyincreased our conceptual understanding of the major mechanismsaffecting flow and transport processes. Migration of chemicalsthrough the soil depends not only on conventional subsurface fluidflow but also upon a number of interactive processes by whichtheir concentrations may be attenuated (e.g., adsorption, exchange,precipitation, complexation and chelation, microbial activity andplant uptake). Considered as a whole, the soil is a complexphysical-chemical--biological system. Thus any transport model,however complex in its mathematics, is a mere simplificationofactual processes.As example, sulphate in irrigation-applied wastewater isweakly adsorbed by hydrous iron oxides present in forest soils, sothe amount of sulphate thus retained in relation to that appliedis generally negligible. Chloride and nitrate are not adsorbed inmineral soils, generally passing rapidly through the profile duringperiods of recharge to groundwater. Levels of chloride, nitrate andsulphate found in soil leachate may be expected to approximatethose in applied effluent minus adjustments for plant uptake anddenitrification of nitrate.2.7.1 NitrogenNitrogen is an essential nutrient element for livingorganisms. Irrigation with secondary sewage effluentaddsconsiderable amounts of N to the soil, depending on the content ofN in the effluent and the volume of water applied. Consequently,the actual quantity added to crops varies widely and isgreatlyaffected by climatic conditions, soil and effluent properties,24cropping and irrigation management.Since effluent N eventually enters the N cycle in soils,irrigation with sewage effluent affects N uptake by the crop, thelevel of available N in the soil, gaseous N losses and N leachingbelow the rooting depth (Feigin et al. 1991). Nitrogen Transformation in soilConcentration of total N, its distribution in the soil profileand its chemical form varies among soils. In the top layerofmineral soils, N ranges from 0.2—4 g/kg (Black 1968). Nitrogen,may be present as organically bound or in one or more ofitsmineralised forms, ammonia or nitrate. Ninety percent of this N isin organic form, while most of the remainder is clay—boundnonexchangeable NH4.Biological wastewater treatment plants often dischargeeffluent that is higher in the mineralized forms of N, while sewagelagoon systems may be managed to convert most effluent Ntoorganic forms. If sewage is stored in lagoons prior tolandapplication, nitrate may become an important effluent constituentbecause ammonia—N is typically lost as volatilised gas.Thisprocess of “ammonia stripping” may be useful in lowering effluentN content so as to enable use of higher hydraulic applicationrates. The average concentrations for the various formsof Nreported in effluents used in several forest applicationstudiesare shown in Table 2.2. The high degree of variation directlyinfluences nutrient loading rates and highlights the need toevaluate study results in terms of the nutrient dynamics unique toeach locale (Brockway et al. 1985).25Table 2.2 Concentrations of N in wastewater used inforest irrigation studies (mg/L).Source Total Mineral OrganicN N NNutter and Red 1984 18.0 7.610.4Hook and Kardos 1978 27.0 21.06.0Schiess and Cole 1981 18.6 17.11.5Brockway et al. 1985 5.4 2.13.3Harris and Urie 1983 12.6 7.65.0Urie et al. 1984 13.8 10.63.2The quantities of N added to soil through effluent-irrigationcan be similar or even exceed those applied by standardfertilization during similar periods of time (Feigin et al., 1978,1979). As soon as the effluent N reaches the soil,it becomes partof the soil N—cycle. The ammonium contained in the effluent, aswell as that derived from organic N, is usually oxidized to NO;by nitrification. Ammonia, derived from NH4 under alkalineconditions is susceptible to volatilization.Both NH4 and NO; are taken up by plants, and eventually becomeimmobilized as soil organic matter when plant residues arereturned to the soil. The same process occurs inthe tissue ofsoil microorganisms or their byproducts. Certain clays, such asillites can fix some of NH4 (Nommic and Vahtras 1982), however thesignificance of this process on recovery of N added by sewageeffluent is negligible. Losses of NO; by leaching below therooting depth and as gas (N20 or NO2) by denitrification are often26large (Feigin et al. 1991).The level of ammonia in effluent depends on the initialNH4content and the pH. When effluent containing NHj isused forirrigation volatilization may take place. In addition, NHj may beformed when effluent NH4 reacts with alkaline soils. Therelativeconcentrations of NH3 and NH4 in the solution dependson its pH (Feigin et al. 1991)..JIr3(ac-) + 11+ . . . . . . . . . (1)logtl1 ac)=p.Ff—9 .5 . (2)where NH3(aq) is NH3 in solution and brackets denote concentration.According to these equations, the concentrations of NH3(aq) at pH5, 7 and 9 are 0.0036%, 0.36% and 36% of the totalquantity ofammoniacal N in the soil solution, respectively.Loss of NH3 from calcareous soils is considerably greater thanfrom non—calcareous ones and involves formation of(NH4)2C03 orNH4CO3 (Fleisher et al. 1987). Ammonia losses duringwastewatertreatment do not represent such a long—term N loss from the soil—plant system as that resulting from denitrification(Ryden 1981).Secondary effluent contains organic N, sometimes athighlevels. Organic molecules are susceptible tomicrobialdecomposition into simple inorganic compounds such asNH4 and N03which are available to plants.Inorganic compounds (NO;, N02, NH4) of effluents might betransformed to organic N compounds, and therefore beimmobilized,27as a result of assimilation by plants and soil microorganisms.The net amount of N mineralized or immobilized within a giventime is a function of many factors including type of the organicsubstance, temperature, water, aeration, and pH (Keeney 1981). Theconcentration of organic C and total N in the soil or plantresidues, as well as C/N ratio, are widely used to characterjzethese organic materials. The average C/N ratio in mineral soils is10 (Stevenson 1985). Incorporation into the soil of organicmaterials having C/N ratios greater than 25 results in N immobilization while at lower C/N ratios a release of available N takesplace (Jansson and Perrson 1982). Typical “organic C/organic N”ratios of sewage effluent are around 5 or lower, thus irrigationwith sewage effluent will result in addition of available N tothe soil.Wastewaters from municipal sources commonly are dominated bythe NH form of N which is a product of mineralization of organicN, however NH4 is susceptible to oxidation, thereforeunderfavourable conditions, NO; is eventually formed and is themainavailable N form found in most soils after effluent irrigation(Nutter and Red 1984). Irrigation with sewage effluent affectsthelevels of NO; in the soil, subsoil and groundwater (Iskander 1978,Keeney 1981).Denitrification can represent a major sink in many wastewaterapplication systems (Keeney 1981). Addition of organic materialssupplying available C to soil microorganisms often results inenhanced denitrification. Sewage effluent, particularly when onlypartially treated, contains considerable quantities of organic C(Feigin et al. 1981). Consequently enhanced denitrificationratesmay occur in effluent—irrigated soils.28Soil accumulation of N has been measured in a few irrigatedforests. After 5 years of irrigation with facultative pondwastewater, Boyer loamy sand at Middleville, Michigan, accumulatedabout 600 kg/ha of N in the 0-10 cm of mineral soil. This increasewas related to an increase of 50% to 100% in organic matter,presumably including decomposed forest floor materials, since theincrease in N was independent of irrigation rates from 25 to 88mm/week (180 - 412 kg/ha of total N over 5 years). Thus, in thesetests, the added N could be more than accounted for in added soilN (Harris 1979).Schiess and Cole (1981) studied results of wastewaterapplication to a forest ecosystem for five years. They concludedthat below ground accumulation of N played an important role ineffluent renovation and reached up to 200 kg/ha/yr.Schipper et al. (1989) irrigated a radiata pine stand in NewZealand. They found that the main mechanisms for N removal fromleaching waters include denitrification and plant uptake.High NOj levels in drinking water are hazardous , causing“methaemoglobinaemia” in infants. The permissible N03-N level inNorth America is 10 mg/L. An undesirable effect of NOj in surfacewater is enhanced proliferation of algae, which occurs in thepresence of P and results in deterioration of potable waterquality. Numerous articles have been published in this field. Manyof these papers deal with pollution of groundwater with nutrientsderived from sewage effluent.Nitrates are a major concern in forests receiving sewageeffluent because they are not adsorbed by the soil in significantquantities. Wastewater applications import large quantities of N toa site. Over time some of the organic N and auuuonium is converted29to nitrate, which is either taken up by the vegetation and microbesor leached. There is ample research evidence that nitrate can beleached and the leachate concentration can exceed drinking waterstandards (Brockway and Urie 1983). The question of whatapplication rate is appropriate for a given forest type iscritical to maintenance of water quality.High-rate effluent application (infiltration-percolation)involves the addition of large quantities of water, and unlessthe N level in the effluent used is negligible, large amounts ofavailable N are also applied. Hence, the allowable annual quantityof effluent conforming with the permissible NO;-N level inleachate to groundwater must be considered. Bouer and Chaney(1974) reviewed methods using the addition of carbonaceousmaterials under anoxic conditions to enhance denitrificationand thus prevent NO; leaching from top soil layers to groundwater.Other methods, aimed at increasing N uptake efficiently by plantsand reducing NO; in the soil, are successful under slowinfiltration methods (Keeney 1982).Wastewater irrigation of forests has universally stimulatedincreased production of vegetation and concomitant increase in Nuptake. Increases in foliar N concentrations for numerous effluentirrigated forests are shown in Table 2.3.30Table 2.3 Foliar N levels in forests irrigated withwastewater (g N/kg)Vegetation LocationControl IrrigationConifer seedlings MI24 29Hardwwod seedlings MI21 22Hybrid poplar cuttings MI19 23Northern hardwoods MI20 26Mixed hardwoods PA22 30Red pine PA13 22Mixed hardwoods GA16 20Mixed pine GA11 16(After Brockway et al. 1985)Nitrogen uptake by wastewater irrigated forests may reachsubstantial proportions (Table 2.4.).Although the highest N uptake efficiencies appear in systemsdominated by herbaceous cover (Brockway et al., 1985), trees arethe most effective long-term competitors for soil N (Johnson 1992).The greatest total uptake is observed on sites with young, rapidlygrowing stands.Harvesting trees is a useful meansof removing accumulated Nfrom effluent—irrigated forest sites. The storage of N in aboveground vegetation can be substantial, ranging from 112 to 224kg/ha/year in established eastern forests to rates approaching 300kg/ha per year in rapidly growingjuvenile stands (McKiimn et al.,1982)31Table 2.4 Nitrogen uptake by vegetation irrigated withwastewatervegetation Location Irrigation Applied Assinii- Effiperiod lated ciency(years) (kg N/ha) (kg N/ha) (%)Grass WA 5 2215 627 28Douglas fir WA 5 1811 893 49seed1 ingsPoplar WA 5 2171 1247 57Hybrid poplar MI 4 500 400 80Old field MI 1 150 128 85Old field PA 9 208 195 94Pine andhardwoods GA 6 703 470 67(After Brockway et al. 1985)Nitrogen accumulates differently within tree tissues,concentrating most in foliage and least in xylem and phloem ofbranches and stems (Ralston and Prince 1963). Therefore, the typeas well as the timing of harvest may be a major management concern.If only stemwood is harvested in a young hybrid poplar stand, one-third as much N would be removed from the site as when whole treescontaining foliage are taken. As the proportion of stemwoodincreases with age, the importance of short—rotations to maximiseN removal becomes evident. Whole tree harvest at five to eight yearintervals could remove over 80% of the N stored in above—groundbiomass of an irrigated poplar planatation (Cooley 1978). Injuvenile stands, understorey vegetation constitutes an important32sink for N. With crown closure the importance of understoreyvegetation declines. Ground cover has also been established as acomponent instrumental in abating nitrate leaching in youngplantations (Brockway et al. 1986).Study results from the major forest regions have been compiledto assess ecosystem N utilisation trends (Table 2.5.). Nitrogenapplication rates have typically been moderate, ranging from 40to 500 kg/ha annually, and produced nitrate discharges togroundwater generally less than 10 mg/L. With minor exception, thisstandard was not exceeded until applied inorganic N approached200 kg/ha/year. High rates of effluent irrigation and N applicationresulted in higher concentrations of nitrate in leachate andincreased rates of overall loss of nitrate—N from the site.Generally, younger forests capable of substantial rates of N uptakehave shown the best on—site retention of this nutrient (Brockway etal. 1986).2.7.2 PhosphorusPhosphorus has been regarded as a major factor contributing toeutrophication in many lakes, reservoirs and rivers (Lee 1970). Foreconomic, environmental, and technical reasons, land treatment ofwastewater is becoming recognized as a viable alternative tostream discharge or even “advanced” wastewater treatment (Syers andIskander 1981). secondary sewage effluent often has a high Pcontent, predominantly orthophosphate accompanied by lesseramounts of organically—bound forms. The organic forms become theavailable pool of orthophosphate as soil organic matterdecomposition proceeds (McKimm et al., 1982). This makes sewageeffluent an important source of P on irrigated soils.33Table 2.5 Nitrogen transformation and utilisation inwaste effluent—irrigated forestsApplication rates____________________Soils Plant Leached LeachateVegetation W.W. org.N inorg.N storage uptake nitrate-N nitrate-N(nun/week) (kg/ha/yr) (mg/L)Pacific Northwest RegionPoplar 50 100 200 134 200—300 50 10Douglas fir 50 100 200 96 150—200 87 14YoungDouglas fir 50 100 200 175 125 8matureGreat Lakes RegionPoplar 35 25 30 100 25 12Poplar 70 50 60 100 50 25Mixed hardwoods 50 48 32 30 51 2Mixed hardwoods 50 48 147 50 146 5Mixed hardwoods 72 90 20 20 40 20 2Redpine 25 35 5 5 1Red pine 50 120 20 60 50 5Northeastern RegionWhite spruce 50 100 180 30 200 50 5Mixed hardwoods 50 100 180 10 84 200 15Mixed hardwoods 50 —---548---- 25Mixed hardwoods 25 -—--241---- 10Southeastern RegionMixed hardwoods 76 150 150 50 50 200 9* Soil storage includes volatilized N; W.W. = Wastewater;Org.N = Organic—N; Inorg.N = Inorganic-N;(After Brockway et al. 1986)34The amount of P added to the soil through sewage effluentirrigation is usually not excessive. However, highloads of P aresometimes added, especially when the soil is used for disposalpurposes. Excessive levels of available P may result in nutrientimbalances, such as Cu, Fe, and Zn deficiencies (Ryden and Pratt1980). Application of P to the soil, as fertilizer or ineffluent,results in an immediate rise in the level of water—solubleP in thesoil. However, due to adsorption and precipitation reactionstaking place in the soil, the level of soluble P declines rapidlywith time. Phosphorus uptake by plants also reduces the level ofsoluble P in the soil, but usually at a much lower rate. The actuallevel of water—soluble P in soil is usually very low, and themovement of P through the soil is restricted. Consequently, soil Pcompounds are usually considered immobile and P leaching and runoffhave been considered negligible. However, the transport of evensmall quantities of P can induce eutrophication insurface waters(Taylor and Kilmer 1980; Avnimelech 1984). Taylor andKilmer (1980)concluded that 0.03 ing P/1 is sufficient to cause eutrophicationin water. Some of the general interactions and processes relevantto the chemistry of P in the land treatment of wastewater are shownbelow (Figure 2.1.).Figure 2.1. General interactions and processes relevant to thechemistry of P in the land treatment of wastewater (After Syers andIskandar 1981).INPUT SOILBEACTION/STORAGE - LOSSES352.7.2.1 Phosphorus concentrations and forms in soilsThe level of P in soils varies greatly, ranging between0.2and 0.8 g/kg dry soil. Plant available P comprises only a smallfraction of the total P present. The concentration ofwater-soluble P is 0.03 - 3 mg/kg dry soil (Ryden and Pratt 1980).Typical levels of P in the subsoil solution of unfertilized soilrange from 0.001 to 0.1 mg P/L (Hook 1983). The application ofsecondary effluents in which the concentration ofP (mainlyorthophosphate) is 4 — 16 mg/L, may result in P penetration intosubsoil layers. However only small changes in the P concentrationin subsoils of many fields irrigated with secondary effluents arereported (Hook 1983). With proper management, many soils have highcapacity for removing P from wastewater, often reducing itto lessthan 0.1 mg/L (Iskandar et al. 1976).Soil P comprises organic and inorganic fractions, consistingof compounds characterised by different solubility and availabilityfor various reactions, and with specific potential contributions tothe pool of labile or available P in the soil. The percentage ofeach P fraction varies greatly. The organic fraction is5-90% ofthe total P, with the higher percentages being typicalof organicsoils (Dalal 1977; Parfitt 1978; Syers and Iskandar 1981; Mengel1985)The principal inorganic P forms in soil are Ca ortho—phosphate, adsorbed orthophosphates and occludedphosphates(Lindsay 1979; Mengel 1985) The formation of Ca phosphates ispromoted under alkaline conditions in the presence of ahigh Caconcentration. Since the pH and the level of Ca incalcareoussoils are high, Ca phosphates are predominantly stablecompoundsin these soils. The different Ca-phosphate compounds found in36soils are characterized by specific solubility and availabilitylevels. The order of solubility of the common phosphate ion isH2P04 > HPO2 > PO4 . The formation of stable phosphate compounds(tricalciumphosphate and apatite) is favoured at high pH, while Aland Fe phosphate are formed at low pH. Phosphorus transformations in soilsSubstances containing P such as fertilizer and sewageeffluent, when added to the soil soon become an integral part ofthe P cycle in the soil. Fertilizer P, consisting of soluble P,becomes part of the labile P in soils. Effluents, depending on thechemical properties of the P they contain, may also contribute tothe pool of fresh organic P. The labile P is available to plantsand is therefore immobilized in plant materials and throughmicrobial activity as organic P. Some of the plant P, such as woodand bark P is removed from the field while the rest of it isreincorporated into the soil, finding its way into the pool offresh organic P. Decomposition of soil organic matter releases Pback into the pool of labile P. The rate of this process dependson the nature of the soil organic matter, and on soil conditionse.g., pH, moisture, temperature and aeration. The labile P peakconcentration, which occurs immediately after the addition ofsoluble P to the soil, declines within a few hours or at most,within a day or two, as P is being transformed into other forms,mainly by binding to the pools of active and stable inorganic P.The relative proportions of the labile, active and stableinorganic—P forms are constant providing a constant supply of P asit is taken up by the plant (Jones et al 1984).372.7.2.3 Boil process affecting P movementThe predominant processes involved in the transformation oflabile P to less soluble forms are precipitationand occlusion ofinorganic P. The formation of insoluble Ca—phosphate compoundsis the main process responsible for the reductionin the level oflabile P in calcareous soils. The high concentration of Ca and thehigh pH characteristic of these soils promotethe process.Sorption processes are often the major explanation for theremoval of labile P by noncalcareous soils mainly on Fe- and Al-oxides (Ryden and Pratt 1980). This is especially so in the case ofsewage effluent in which the level of soluble P is usually muchlower than that near fertilizer granules in the soil. In spite ofthe great differences between soils and their capacities to retainP, the nature of retention reactions is remarkably uniform, andtheir extent can be estimated from relatively simple relationships(Broadbent and Reisenauer 1988). Ryden andPratt (1980) haveutilized this characteristic in developing amodel for predictingthe useful life of a field filtering system.Sorption isotherms have been used todescribe therelationship between the amount of P sorbed and that remaining insolution at constant temperature. A typicalLangmuir sorptionisotherm is shown in Figure 2.2.The Langmuir equation has been used extensively to measure Psorption on soils, and diversified experimental results have beenobtained for different soils (Syers and Iskander 1981). Even withina soil profile, the ability of individual soil horizons to sorbadded P can differ considerably (Figure 2.2.).38.200 1el+150 -FuaI P Conc.itroti. (mc £)Figure 2.2. Sorption of added inorganic phosphate byfive horizonsof Miami silt loam from 0.1 M NaC1 (After Ryden et al. 1972) (3)m 1+KCX weight of adsorbate, i.e., P.m = weight of absorbent, i.e., soil.K constant related to the affinity of adsorbent.C = equilibrium solution concentration of the adsorbate.1, maximum quantity of adsorbate that can be adsorbed.A procedure for using sorption isotherm data toestimate Pretention by soils is suggested by Loehr (1977). An importantconsideration discussed is the possibility of slow reactionsbetween P and cations present in the soil whichmay “free up”previously used sorption sites for additional P retention.Calculations involving sorption isotherm data, which ignore these39reactions, generally underestimate P retention. According to EPA(1981) actual P retention at an operating system will be at least2 — 5 times the value obtained during a 5-day sorption testintroduced by Fox and Kamprath (1970).However because of many uncertainties involved and the lackof standards for acceptable groundwater phosphate levels, sitesshould be monitored frequently, particularly as P additionsapproach the estimated capacity (Broadbent and Reisenauer 1988). Effect of irrigation with sewage effluent on soil Pand P movement in soil profilesPhosphorus movement through effluent—treated soils has beenstudied under different conditions (Sawhney 1977, Lance 1977,Nagpal 1985).The actual capacity of soil to adsorb P is often much greaterthan that predicted by laboratory tests. Alternate drying andwetting restore the adsorption capacity of soils (Ryden and Pratt1980), and precipitation and transformation processes in soilsalso contribute to this discrepancy. Nagpal (1985) summarized theresults of various column tests subjected to near—continuousleaching under saturated and unsaturated conditions as follows:(1) the P added is initially sorbed by the soil; (2) breakthroughof P occurs after the sorbed quantity of P is equivalent to thatsorbed by the soil after 200 hours of reaction time in a batchtest; (3) the concentration of P in the leachate increasessteadily with time after breakthrough and reaches the value ofthat in the effluent.The movement of P through the soil has been extensivelystudied in the field , especially in relation to high rates of40effluent application used for recharging groundwater (Kardos andHook 1976; Sommers et al. 1979). At typical slow—rate wastewaterapplication to forest ecosystems, nearly complete retention of Pcan be anticipated, leading to high renovation efficiency (McKimmet al. 1982). The P added through sewage effluent is removed,sometimes almost completely, by the top layer of the soil.Nevertheless, combinations of high-rate effluent application,especially of P-rich effluent, with soils having low P adsorptioncapacities may result in increased concentration of P below theroot zone of plants (Feigin et al. 1991). Murrmann and Koutz (1972)suggested approximately 4 to 6% organic matter and clay as aminimum to maintain soil renovation capacity for wastewater.Longevity estimates for P removal through chemical precipitationand adsorption exceeding 100 years have been reported forwastewater sites in Washington, Michigan and Pennsylvania (Brockwayet al. 1985). One may, nonetheless, expect disparity betweenempirical data and such theoretical predictions.Wastewater-applied P is largely retained in the surfacemineral soil (Harris 1979). As much as 34* of that applied has beenreported to have been taken up by poplar plantations in the PacificNorthwest (Cole and Schiess 1978) and Great Lakes Regions (Urie1979). Broadbent and Reisenauer (1988) mentioned that only smallamounts, less than 3% of that added annually have been found indrainage waters. Soil P tends to become less soluble over time.This process, in addition to plant uptake, tends to increase theperiod during which a forest site may function as an effectiverenovator for P (Brockway et al. 1986).Phosphorus renovation has been no problem in the short-termstudies for which records are available. Exhaustion of P retention41was suggested in a sequence of measurements in sandy loam(Hook et al. 1973) and loamy sand soils (Harris 1979). Soinmers etal. (1979) studied the status of inorganic P in effluent irrigatedsoils in Pennsylvania. Most of the added P was found in the toplayer (0 — 03 in) of the soil but also a significant quantity of Ptravelled into deeper layers of the sandy loam soil during theexperimental period. They found that the retention of P was higherin the clay—loam soils. Hook (1983) reviewed available data onmovement in wastewater—irrigated soils. Relevant field studiesfound little evidence of P penetration into subsoil.Latterell et al. (1982) studied the long—term effects ofeffluent irrigation on the status of P in soils in Minnesota. Theyfound that after five years of irrigation, the concentration oforganic P in the upper 15 cm of the soils treated with effluentwas twice as high as those of the control plots. Phosphorus uptake by forest cropsRyden and Pratt (1980) reviewed current models for predictingP removal by soils. They concluded that the main limitations ofavailable models are due to the following factors (1) the greatspatial and temporal variabilities in hydraulic conductivity offield soils; (2) similar variability in P sorption capacity; (3)lack of data on the soil acidity—alkalinity level; and (4) lack ofinformation on the effects of wastewater due to its Al, Fe and Cacontents. Since P reactions in soils cannot be predicted frommeasurement of simple soil properties that can be mapped in thefield or measured quickly in the laboratory, extensive laboratorywork is necessary to obtain the relevant information. Ryden andPratt (1980) have therefore suggested a simple practical empirical42model that can be used successfully to predict P removal fromeffluent by the soil. This model predicts the longevity oftreatment sites with respect to P removal. The Ryden—Pratt model isgoverned by the following equation:= ‘ ‘t = time in years for the P front to reach a given soildepth.S, = sorption capacity of the volume of soil above thisdepth kg P/ha.I,, = Input of P kg/ha/yr.= P removed in harvested crops kg P/ha/yr.Inaccuracies in this model are due to the invalid assumptionof abrupt boundaries between the different soil layers, variationsin effluent application rate, soil texture, infiltration,percolation and evaporation.2.7.3 CationsCations imported with wastewater disposal are conservative andwill remain at the application site unless they are leached fromthe system (Zasoski and Edmonds 1985).Potassium is an essential element for organisms, and is takenup by plants in large quantities, similar to, or even greater thanthose of N. The level of K in sewage effluent varies greatly,typical concentrations being 7-20 mg K/L. Irrigation with sewageeffluent often does not satisfy plant needs for K, especially when43the level of available K in soil is low.Potassium depletion on sites irrigated with wastewater may bea problem where plant uptake of K increases or when effluent Nconcentrations greatly exceed those of K. Analysis of tree foliageindicates that leaves typically accumulate less than half as muchK as N, suggesting that K deficiencies induced by imbalancedwastewater nutrient composition are quite unlikely (Feigin et al.1991). The concern in land treatment is not with respect to removalof K but rather with respect to the potential for a deficiency andthis deficiency in turn affecting the removal of N or P by thecrop. Each crop has a specific ratio of nutrient requirements(e.g., N:P:K) to optimize growth or from a treatment point of viewto optimize removal of N or P. If the proper balance is notmaintained, removal of N or P will be less than expected. Ingeneral there is an excess of N in municipal wastewaters withrespect to K for most agricultural and forage crops. Proportion ofN:P:K in a typical municipal wastewater is 6:1:2 respectively (Reedand Crites 1984). U.S. environmental Protection Agency (EPA) (1981)has developed a relationship for soils having low levels of naturalK to estimate K loading requirements:1Cr. • _i .0.911.. . ()where = annual K needed (kg/ha).U = annual crop uptake of N (kg/ha).= annual wastewater loading of K (kg/ha).When higher levels of K are present in sewage effluent, itbecomes an important source of the element. Application of largequantities of such effluent results in the addition of considerable44quantities of K to the soil, but K overdose is unusual whenstandard quantities of sewage effluent are used for irrigation(Feigin et al. 1991).Potassium applied to forest soils during wastewater irrigationis adsorbed by clay minerals but may be leached from the profileunder conditions of high amounts of Na and ammonium cations (McKixnmet al. 1982). Therefore the retention of added K depends to a greatextent on the CEC of the soil. The greater the CEC, the less Kmoves through the soil profile. Coarse—textured soils allow Kleaching, while soils rich in clay retain K. The magnitude ofleaching loss may be related to irrigation rate. In Pennsylvania,exchangeable K levels decreased in the upper metre of soilbeneath an old field and mixed hardwood forest that were irrigatedfor eight growing seasons with 5 cm of wastewater per week. Beneatha nearby hardwood forest irrigated with 2.5 cm of waste effluentper week, soil exchangeable K levels either increased or remainedunchanged from controls (Sopper and Kardos 1973).Sodium, Ca, and Mg delivered to forest sites with irrigatedwaste effluent will tend to exchange with cations on the soilexchange complex. The wastewater levels of those cations willinfluence establishment of a new equilibrium of soil cations, thesolution leached from soil being adjusted accordingly. Renovationefficiencies of 85% and 24%, respectively, for Ca and Na reflectthe tenacity with which each is held in the soil (McKimm et al.1982). Like K, Ca and Mg are increasingly leached from the profileunder the expanded presence of Na and ammonium ions. Totaldissolved salts remain relatively unchanged in the soil solution,normally at concentrations that do not adversely affect plants orsoils in the humid climates of forested regions (Brockway et al.1986).452.7.4 Trace elementsTrace elements are usually present in low concentrations innatural systems. Certain of these chemicals are especiallyimportant in waste—treated soils. Much of the information on thetrace elements originates from soil—plant systems treated withsewage sludge, which are the sources of many of the data presentedand discussed below. Since both sludge and effluent are derivedfrom the same source (raw sewage), carefully selected data can besuccessfully adopted for fields irrigated with sewage effluent.Page (1974) monitored the following trace elements asimportant components of sewage sludge: Ag, As, B, Ba, Cd, Co, Cr,Cu, Hg, Mn, Mo, Ni, Pb, Se, Sn, V, and Zn. Certain trace elementsare heavy metals, with a density greater than 5 g/cm3, although bycommon usage other metals are also included in this list (Tiller1989).Trace elements participate in many of the biochemicalprocesses that greatly affect plants and animals, including humans.The following trace elements are essential for plant developmentand growth (and are therefore named micronutrients): Fe, Mn, Zn,Cu, Mo, and B. Those required by animals are Mn, Cu, Zn, Fe, Mo,Se, I, Co. F, Cr, Ni, V. Sodium, Cl, CD, V and Ni are alsomentioned as being essential for certain plants (Tiller 1989). Onthe other hand, other trace elements have been shown to benonessential to plants and animals. Both the biologically requiredand the other relevant trace elements become toxic when present inconcentrations exceeding certain threshold levels of theiravailable forms. The margin between recommended (or acceptable)and toxic concentrations is often narrow, as in the case of B. Thehealth hazard posed by excessive levels of trace elements in46soils , and consequently in the tissues of plants, animals andhinuans consuming the plant materials, is therefore of great publicconcern (Allaway 1977, Purvis 1985). Movement of trace elements tothe groundwater is also considered as a serious threat under theseconditions.The quantities of trace elements added to the soil depend onthe origin of the wastewater used. The concentration of traceelements in sewage water varies greatly (Thomas and Law 1977;Page et al. 1981). High concentrations of trace elements are foundin industrial sewage effluent, especially in raw sewage, whilethe levels in domestic effluents and advanced—treated sewageeffluent are very low and negligible, respectively.Some trace elements are hazardous to organisms, while thetoxicity of others is low. This is the result of their biochemicaleffect on living organisms, their physicochemical characteristics,and the forms and actual quantities added to specific soil-plantcombinations. Cadmium, No, Ni, and Zn are considered morepotentially toxic than other elements applied to soils treatedwith wastewater. For various reasons, including their presenceat low level in wastewater, Mn, Fe, Al, Cr, As, Se, Sb, Pb and Hgare categorized as posing little environmental hazard (Page et al.1981). Boron is also mentioned as a potential hazard if added in anuncontrolled manner.As noted above, the quantity of trace elements added tosoils by means of sewage effluent irrigation is generally low.Bower and Chaney (1974) concluded that, at applications rates toavoid nitrate pollution, greater amounts of heavy metals can beadded to the soil in one year with sludge than may be added in acentury of effluent irrigation. Consequently most research on47trace elements in soils treated with waste dealswith sludgeapplication rather than with effluent irrigation.Despite their low content, the level of trace elementsis animportant characteristic of secondary effluent, due to itsextensive use for irrigation and groundwater recharge (Thomas andLaw 1977). According to Page and Chang (1985), althoughit may takea century before trace element levels in wastewater irrigatedsoils reach currently proposed upper limits, thepotentiallyharmful effects in the future should not be ignored. Since mostof the trace element material tends to accumulate inthe soil,long—term irrigation may substantially increase theirlevels intreated fields. Furthermore, owing to the great differences amongeffluents, information on the trace element levels in any effluentused for irrigation must be obtained and their levels in soiland plant tissues monitored. In addition, basic information ontrace element—soil—plant relations should be consulted. Themovement of trace elements in soil profiles has receivedconsiderable attention, since even slow transport through soil andsubsoil material may result in an increased content of traceelements in the groundwater. Trace elements reactions in soilTrace elements are found in sewage effluent bothin thesuspended solids and in the liquid fractions. Those associated withthe suspended solids accumulate on the soil surface as theeffluent infiltrates into the soil, while those dissolved in theliquid component penetrate into the soil. Thetrace elementsderived from both fractions interact with soilcomponents. Thetrace elements reaching soil—plant systemsparticipate in48different soil reactions (Page et al. 1981).Many studies have demonstrated the high capacity of soils toretain trace elements. McBride (1989) considered the followingprocesses as determining the solubility of heavy metals in thesoil: (1) ion exchange on layer silicates; (2) chemisorption onmineral surfaces; (3) reduction, precipitation and solid solutions;(4) redox processes, taking into consideration oxidation ofmetals, metal oxides and dissolution of metals by organicmaterials; (5) metal adsorption by organic matter; and (6)speciation. The soil pH is also a determinative factor for traceelement solubility in soils. Page and Chang (1985) report that ingeneral the solubility of cationic trace element species increasesand that of anionic ones decreases with decreasing pH. Many fieldstudies have shown that, in general, many metal elements are muchmore soluble under acid conditions and their solubility declineson addition of alkaline materials (such as lime) (Zasoski andEdmonds 1985). The presence of organic matter in soil greatlyaffects the solubility of trace elements (McBride 1989). Manygreenhouse and field studies have been carried out during the lasttwo decades to elucidate the effect of sewage sludge, as well asother wastes, on the level of trace elements in soils. Korte etal. (1976) found that the most useful information for predictingsoil effectiveness for trace element retention related to soiltexture, soil surface area, and the content of hydrous oxides andfree lime. Soil clay has often been considered as a major factordetermining trace element solubility (Williams et al. 1980).The movement of trace elements in soils is usually very low,and most of the added material accumulates in the soil layer intowhich the relevant waste materials are incorporated. Williams et49al. (1980) reviewed relevant literature and noted that in mostcases the trace elements added through different wastes were eitherretained in the top soil layer or were moved a few centimetresbelow the treated layer.Important information on trace element accumulation andmovement in soil profiles was obtained from the long—term Werribeeexperiment in Australia. Most of the elements accumulated in thetop layer of a clay loam soil irrigated for 80 years with sewageeffluent, having (in 1979) the following trace element content (inMg/L units): Cd 0.015; Cu 0.35; Cr 0.40; Pb 0.30; Ni 0.15 and Zn0.8. Despite the considerable increase in trace elements in thesoil, except for Pb and Zn, the levels remained within the normalrange (Evans et al. 1979).Dawdy and yolk (1983) concluded that, although some studieshave noted movement of trace elements to layers below the soilsurface or depth of incorporation, it appears that only Zn hasthe potential to move in soils. Movement of heavy metals insoils will occur in sandy, acid , low—organic matter soils,subjected to heavy rainfall or irrigation. Open channels or cracksincrease trace elements movement in soil but elsewhere suchmovement is usually limited.The effect of irrigation with treated sewage effluent wasstudied in a pasture near Christchurch, New Zealand (Quin and Syers1978). The metal levels in the effluent of domestic origin waslow (the concentration of Cd <0.0001 mg/L, that of Cr, Ni, and Co<0.001, that of Cu and Pb 0.001, and that of Zn and Mn 0.015mg/L). The levels of 0.1 N HC1 extractable metals (Zn, Cu, Coand Mn) in the soil were slightly higher after 16 years ofirrigation. They concluded that the effluent application of 840mm50effluent/year can be continued indefinitely without causing ahazardous heavy metal buildup.Removal of trace elements from solution is nearly complete insoils suitable for slow rate systems (EPA 1981). Performance datafrom selected slow rate systems are presented in Table 2.6.Table 2.6 Trace element behaviour during slow rate landtreatment (after EPA 1981)Element EPA drinkingwaterstandardRaw municipalwaste—waterMaskegon,’MichiganMelbourne, bAustraliain underdrainsin underdrainsPercolate removal Percolate removal(mg/L) (mg/L) (mg/L) (%) (rng/L) (%)Cd 0.01 0.004 — 0.14 0.002 90 0.002 80Cr 0.05 0.02 — 0.7 0.004 90 0.03 90Cu 1.0 0.02 — 3.4 0.002 90 0.02 95Pb 0.05 0.05 — 1.8 0.050 >40 0.01 95Mn 0.05 0.11 — 0.14 0.26 15 —— ——Hg 0.002 0.002 — 0.05 0.002 0.0004 85Zn 5.0 0.03 — 83 0.033 95 0.04 95a. Data represents average annual concentrations (1975) foundplaced at a depth of 1.5 m below the irrigation site.b. Data represents average annual concentrationB (1977) foundplaced at depths of 1.2 to 1.8 m below the irrigation site.c. Percent removal was not calculated since influent and percolate valuesare below lower detection limits.51A relatively small amount of trace elements applied through atypical slow rate wastewater application is removed by crops.For a forage crop the following levels (in %) have been obtained:As 5; B 1.25; Cd 2.5; Cr 0.5; Cu 3.75; Hg 0.55; Mo 5; Ni 6.25; Pb1; Se 2.5; Zn 8.3 (Page et al. 1981). Beneficial and hazardous effects of trace elementson plants and animalsThe addition of trace elements by means of effluentirrigation can be beneficial under certain circumstances. Thus, themicronutrient deficiencies occurring under various soil—plantconditions, especially in calcareous soils, can be corrected byadding mineral or chelated trace element substances. Since sometrace elements are required by animals, their addition throughplants irrigated with sewage effluent can be considered asanother advantage obtained from wastewater use. However, the mainconcern today is the danger of accumulation of excessive levelsof trace elements leading to toxicity and hence to health andenvironmental hazards (Purvis 1985).There is ample evidence showing that trace elements mayaccumulate in plant tissues, but plant properties differ greatlyand the effect of soil conditions is often decisive. Furthermore,the distribution of trace elements within plant organs alsovaries greatly among plant species. Since in most casesaccumulation of trace elements in effluent—irrigated soil,especially with advanced-treated effluent, is slow and small, noserious accumulation in plant tissues is anticipated after shortirrigation periods (Feigin et al. 1991).52Many reports have shown that the presence of high levels oftrace elements in the soil may result in a similar situation inplant tissues. In other cases, the levels of trace metals in cropconstituents remained low, even though large quantities of wastesrich in trace elements were added to the soil. This discrepancyresults from differences in soil conditions (e.g., pH) and theproperties of plants grown (Feigin et al. 1991).2.7.5 Suspended solidsSuspended solids in secondary effluents are mainly ofbiological origin. Their concentration and composition depend onthe level of treatment and particularly on the degree ofseparation of sludge from the treated sewage in the finalsedimentation process. Turbidity in excess of 20-30 mg/L may befound in over— or under—loaded systems. Suspended particles insecondary effluent leaving the treatment plant contain variousmicroorganisms, such as bacteria, protozoa, rotaria andphytoflagellata, ranging in size from colloidal to several hundredmicrons in size. Organic and mineralized flocs of 1 mm or evenlarger in size as well as clay particles and other inorganiccolloidal matter are also present. In general, suspended matter insecondary sewage effluent used for irrigation does not have anyadverse effect on soil, plant or environment. In some cases,though, with effluents of high organic and nutrient content usedfor surface flood irrigation, development of microbial growth onthe soil surface may reduce the soil infiltration rate and causeaeration problems (Zasoski and Edmonds 1985).532.7.6 PathogensAlthough pathogens are known to move rather large distancesthrough soils in some circumstances, there is evidence thatmovement is limited in most soil conditions (Zasoski et al. 1984)unless the soil is extremely coarse in texture. Consequently thethreat of pathogen movement to groundwater is likely to be low atslow infiltration sites (Zasoski and Edmonds 1985).2.7.7 OrganicsThe quantity and type of organics applied in wastewater areusually different from those in the soil before application. Likepathogens, organics are not conservative and can be chemically orphotochemically degraded, decomposed, or altered by organisms inthe soil or by organisms imported with wastewater. In addition manyof the imported organics can be adsorbed and immobilised by thesoil (Kowal 1983). The large number of organic compounds that canoccur in wastewaters does not allow for generalisation, however themore complex the molecule, the greater the number of condensedrings, and the more halogenated, the more difficult is thebiodegradation. The organics found in wastewater generally increasesoluble carbon in the soil and add to the native organics. Overcash(1983) reviewed the fate of organics in soils and concluded thatbecause of adsorption by the soil and decomposition reactions,little leaching would occur.2.8 Site selectionProper site selection for wastewater irrigation can reduce orprevent pollution problems (e.g., contamination of groundwater) andcontribute greatly to a better use of effluent water and nutrients.54The general criteria in selecting acceptable sites for landtreatment of wastes are minimization of migration or transportationof pollutants from the place of waste deposit and maximizingpollutant biodegradation, retention and stabilization (Fuller andWarrick 1985). Site properties affect planning, design andmanagement operations necessary for proper utilization of sewageirrigation for irrigation. The main site considerations aretopography, soils, geology, groundwater and climate. The selectionof sites for wastewater application are discussed by Hall et al.(1976), Fuller and Tucker (1977), Witty and Flach (1977), Crites(1985), and Fuller and Warrick (1985), among others.2.8.1 TopographyThe topographic variables that are important in the selectionand design of an irrigation system are slope and relief. A steepslope increases runoff and erosion and causes difficulties incultivation. Relief, which is the difference in elevation over aland surface, affects pumping demands and water distributionuniformity.2.8.2 Soil PropertiesTexture, structure and soil depth are the main relevantphysical parameters. Texture is the most important soilcharacteristic due to its effect upon the hydrologic regime, soilrenovation capability, crop production, and total land—treatmentsystem—management. Fine—textured soils do not generally drainwell; consequently, they retain large quantities of water for longperiods, which enhances development of anaerobic conditions. Mediuito light textured soils (barns, sandy barns, or loamy sands) can be55preferable for land application systems. Although soils with highsand content usually have the higher infiltration and percolationcapacities, soils high in clay can provide better nutrient removaland wastewater renovation as effluent filters through the soilprofile. Plant roots help improve drainage, soil structure andtilth. Crop removal of nutrients from the soil chemical complexprovides continuing renovation capacity (Sutherland and Myers1982).Stable soil structure ensures proper drainage and aeration.Unstable soil structure may result in crust formation followed bya severe reduction in infiltration rate. Spray irrigation withlarge water drops, and alternate application of water having highand low salinity and SAR levels may result in crusting. Certainmedium—textured soils (e.g., bess) are especially prone to crustformation. Depth of soil is also an important factor in renovationof wastewater. Kleiss and Hoover (1988) suggest that 90 cm isaminimum thickness of natural soil required, since it is deep enoughto allow normal root development and the residence time of thewastewater in the active soil zone is sufficiently long. The sameauthors state that maximum slope should not exceed 30%. The deeperthe soil, the steeper the slopes that can be used.The design of an irrigation system and its operation shouldtake into account the infiltration rate (IR) and the hydraulicconductivity (HC) or permeability of the soil. The hydraulicconductivity is the rate of water movement through the soil profileby gravity, capillarity and other driving agents. The HC varieswith the texture of the soil. The saturated HC of sandy soils ischaracterized by high values (10-2 cm/sec) and of clay soils, bylow values (10 — i0 cm/sec). Soils with a saturated HC of <l056cm/sec are considered impermeable. The HC may vary within the soilprofile.The infiltration rate — the rate at which water enters theground — depends on the soil texture and structure, initial watercontent and the rate of water application. At high applicationrates, or when ponded water enters the ground, the IR for a soilvaries inversely with the initial water content, and decreaseswith time, approaching a steady state minimum rate close to thesoil saturated HC. When IR is lower than the application rate,ponding and runoff occur (Reed and Crites 1984). Typical IR valuesare given in the following table (Table 2.7.).Table 2.7 Typical steady infiltration rate of various soil typesSoil type Infiltration rate (mm/hr)Sand > 20Sandy loam 15 — 10Silty loam 10 — 6.5Clays 7.5 — 2(After Reed and Crites 1984)It is recommended that the IR be measured on test field plotsirrigated with effluent. Soils having an IR <10 mm/hr are suitablefor surface irrigation, while those with an IR of 10-50 mm/hr orhigher are suitable for sprinkler irrigation at either low or highapplication rate (Feigin et al. 1991).The soil chemical characteristics that influence siteselection for effluent irrigation include pH, electrical57conductivity (ECj, exchangeable Na percentage (ESP) and cationexchange capacity (CEC). Other relevant factors to be taken intoaccount are organic matter, boron and CaCO3 content. At an ESP >10%with low salinity irrigation water, clay dispersion may enhancecrusting, followed by a reduction in the infiltration rate and pooraeration.The HC of the soil depends on the levels of Na and total saltof the percolation solution. Clay dispersion occurs at low saltconcentration. The negative effect of Na can be reduced orprevented by the presence of sufficient electrolytes released tothe soil through dissolution of primary minerals or lime(Shainberg and Letey 1984).2.8.3 Geologic FactorsThe geology of the underlying strata affects groundwatercontamination, especially where shallow soil overlies a sandysubsoil. Fractured rock and geologic discontiriuities mayfacilitate transport of percolating effluent to unknown locations.2.8.4 GroundwaterGroundwater quality, depth, and direction of flow are usuallyconsidered when selecting an irrigation site. Aquifer rechargeareas should be evaluated for slow rate land treatment (Sutherlandand Myers 1982). The highest water table level should be no lessthan 90cm beneath the land surface during peak irrigationapplications (Kleiss and Hoover 1988). From the adequacy point ofview, groundwater depths greater than 2.5iu indicate the existenceof good drainage conditions. High and fluctuating water tables cankill large sections of a plant’s roots and cause much stress58(Feigin et al. 1991).The quality of groundwaters in the region can play animportant role in determining the type of treatment, and in someinstances the overall feasibility of wastewater systems utilizingland disposal. If groundwaters already contain large amounts ofparticular chemicals, then pretreatment of the wastewater to removethese chemicals may be necessary in order to keep the totalconcentrations below critical levels (Lee 1976).Some pollutants originating from sewage effluents are eithernot retained or are not inactivated by the soil, and the movementof others depends on soil properties. Dilution of such material inthe groundwater can reduce the severity of the problem (Feiginet al. 1990). Nitrate-N is the parameter of great concern andconcentration of organic and ammonia N are also determining factors(Reed and Crites 1984).2.8.5 Climatic factorsLocal climate may affect: 1) the water balance and thus theacceptable wastewater disposal rate, 2) the length of the growingseason, 3) the number of days per year that a land treatment systemcannot be operated, 4) the water storage capacity requirement, and5) the amount of stormwater runoff. For this reason localprecipitation, evapotranspiration, temperature, and wind valuesmust be determined before design criteria can be established.Whenever possible, at least 10 years of data should be used toobtain these values. Data requirements for planning purposes aresummarized in Table 2.8.59Table 2.8 Summary of climatic analyses.Factor Data required UsePrecipitation Annual average Water balancemax. and mm.SeasonaldistributionRainfall storm Intensity. Runoff estimateDurationStorage. TreatmentTemperature Days with average Efficiency.Growingseason.Wind Velocity. Duration Cessation ofsprinklingEvapo— Annual. Monthly, Water balancetranspiration AverageAtter Reed and Crites 1984).2.9 Idea]. sitesHall et al. (1976) suggested the following site criteria asideal for wastewater utilization:1) Landscape: A closed drainage system, preventing pollutant fromwastes reaching adjacent fields. It is possible to block opendrainage systems (modified closed systems) by heaping small ridgesacross basin outlets. Crites (1985) recommends a maximum slope of15% for cultivated agriculture and 15%-20%, or greater if localconditions allow, for noncultivated fields (e.g., pasture).Crites mentions that woodland areas having steep slopes (15%-30%and even more) were successfully irrigated by sprinklers.Thepresence of impermeable horizons in the soil (e.g., clay pans,shales, lime or silica hardpans) restrict water movement to deepersoil or subsoil layers and become a problem where renovationofgroundwater is the goal.602) Parent Material: A medium-textured soil material with relativelyhigh pH (6.5-8.2) and/or high levels of free carbonates. Bedrockor unconsolidated strata (when present) should be free of coarselayers and should be at least 0.9—1.2 m below the soil surface.3) Soils: A high infiltration capacity for the upper soil andmoderate subsoil permeability, no restrictive layer to a depth ofat least 0.75 in, with good drainage conditions and a moderatelyhigh water—holding capacity (15%-20% by volume). Information onsoils, geology, hydrology and topography as well as site visits andtests are important for successful planning of the system. Soilsurvey maps and equivalent data can be extremely valuable in thechoice of sites suitable for effluent irrigation.2.10 Irrigation schedulingOne of the important aspects of effluent water management isthe availability of reliable information on crop irrigation waterrequirements. Municipal effluent is continuously supplied by theplant, regardless of irrigation needs, and it must be adjusted, atleast partially, to irrigation water supply. Furthermore, effluentmay contain potentially hazardous constituents , which may causesoil and groundwater pollution, and may also directly affectplant growth. Consequently, it is critical that the quantity ofwater applied does not exceed the consumptive use and leachingrequirements of the irrigated crop.2.11 Crop water requirementsCrop water requirement may be defined as “the depth of waterneeded to meet the water loss through evapotranspiration (ET) of ahealthy crop, grown under nonrestrictive conditions and achieving61full production potential” (Doorenbos and Pruit 1977).It is the minimum amount of water which results in maximum yield inthe crop—water production function, which relates to ET.2.11.1 Estimation based on direct measurementsThe best way of obtaining reliable water requirement valuesfor a crop under a specific set of environmental conditions andcultural practices is by evaluating its water production function.Such functions may be obtained empirically by applying irrigationtreatments with various known water quantities to the crop in thefield plots, and measuring yield and changes in soil watercontent, before and after each irrigation (Shuval et al. 1986).Another direct method is the use of drainage or weighinglysimeters placed in large fields with a single crop. Weighinglysimeters provide a closed system in which all the components ofthe water balance can be measured. If properly designed andplaced they provide precise estimates of ET.2.11.2 Estimation based on climatological factorsThe dominant factor controlling the loss of water from cropand soil surfaces (evapotranspiration) is climate. The importantclimatic variables are radiation, temperature, humidity and windspeed.The potential ET (Er) in a given area may be computed frommeasurements of climatic variables . The potential ET representsthe upper limit or maximum ET that occurs under given climaticconditions within a field having a well—watered crop (Doorenbosand Pruit 1977).There are numerous approaches for estimating Ep from62climatological data. The approaches increase in complexity asgreater accuracy is desired.To use the values calculated from climatic variables, theyneed to be converted to crop ET (Es) by using a crop factor K.Thus E =Item (1974; 1978) has estimated potential evapotranspirationof deciduous and coniferous stands (on water saturated soil) to beabout 2.5 and 1.5 times the evaporation of an open water surfaceunder identical meteorological conditions, respectively.2.11.3 Selected methods of estimating of evapotranspirationIn this section, the discussion will be limited to themodified Penman equation (Penman 1963), which is one of the mostcomplete methods for calculation of ET (Hansen 1980), and theclass—A evaporation pan, both of which were used in this study todetermine wastewater irrigation amounts.The Penman method, first introduced in 1948 and latersimplified, was the first of several combination equations.Combination equations are derived from a combination of energybalance and mass transport or aerodynamic term. The AmericanSociety of Agricultural Engineers (ASAE) report shows that thecombination methods are the most accurate methods for a very widerange of climatic conditions. The accuracy of combination methodsresults from the theoretical basis of the methods. Estimatesobtained with a combination equation are reliable for periods of 1day to 1 month. With modifications, reliable hourly estimates arepossible (Burluan et al. 1980). More details of this method arediscussed in the Materials and Methods section.The use of the US Weather Bureau Class-A Evaporation Pan is63the simplest indirect approach to measure evaporation from a bodyof water. For the measurement to be applicable, the pan must bestandardized and properly sited near the area of interest. Despitesome obvious differences between pan evaporation and cropevapotranspiration conditions, such as reflectivity of solarradiation, heat storage in the pan during the day which inducesnight evaporation, and wind effect, the Class—A evaporation panprovides reasonable estimates of ET. Calibration of panevaporation (E0) against crop ET (Eu) and determination of panfactor (K0) are required for each specific area (Hansen 1980).2 • 1.2 Irrigation-fertilization InterrelationsIrrigation with treated effluent involves addition of bothwater and nutrients to the soil-plant system. Optimization ofwater application in accordance with economic and environmentalconsiderations also affects crop nutrition, since the amounts ofdifferent substances added are also influenced. The distributionof nutrients contributed by sewage effluents during theirrigation season also differs from that of nutrients supplied byfresh water amended by fertilizer (fertigation) since witheffluent, nutrient quantities cannot be directly controlled.Furthermore, effluents containing considerable quantities of Nmay cause nutrient buildup in the soil during sensitive growthperiods e.g., harvest time periods (Feigin et al. 1991).Appropriate irrigation—fertilization management enhancesefficient use of nutrients by crops resulting in high yields,reduced expenses on fertilizer, decreased water pollution hazardand mitigation or prevention of physiological disorders due toexcessive concentration of nutrients in the root zone (Hanks et64al. 1983).2.12.1 Nitrogen managementThe role of N in the maintenance of soil fertility andconcern in pollution of surface water and groundwater has led to Nmanagement becoming the subject of many studies and discussions.Numerous publications deal with irrigated soils in general, whileothers discuss specific aspects of effluent—irrigated sites.Appropriate application of N to crops should be based onminimum damage to the environment and understanding of the water,soil, climate and other components of the relevant system,supplemented by data from soil and plant analyses. The availableN derived from sewage effluent replaces equivalent or similaramounts of fertilizer. Different soil and plant analytical methodshave been suggested for determining the actual quantities offertilizer necessary under specific site conditions.Plant tissue analysis, yielding the N concentration inspecific plant parts, is used for fertilizer decision—making. Thismethod helps to determine the nutritional status of the plantand, if necessary, indicates the time, quantity and mode offertilizer application.Soil testing is a valuable tool for assessing N requirementsunder various conditions and is used in effluent—irrigated sites.Various chemical and biological soil testing methods have beensuggested for predicting the potentially available N in the soil.Residual mineral N in the soil is similar in availability tostandard fertilizer N. Under conditions of negligible N lossesthrough leaching or denitrification, the level of N03-N in soilnear crop planting time is considered as available for the crop65(Goh and Haynes 1986). Some models using soil and meteorologicaldata have also been proposed. The N balance principle has been usedfor predicting the N fertilizer requirements of crops (Stanford1973, Frissel and van Veen 1981). Meisinger (1984) presented the“whole crop N balance” model, which includes within itsboundaries both the above-ground portion of the plant and theroot zone component of the soil:Nf + N1 NCh — N — N, — Ng = + N (6)in which N1 is fertilizer N input, N comprises various N sources(e.g., rainfall and/or irrigation), NCh is N removed in harvestedcrop, Ne is N lost by erosion, N, is N lost by leaching, and Ng isgaseous N losses (volatilization and denitrification). The N andN8 are the changes in the soil organic and inorganic N content,respectively.Usually N uptake efficiency of effluent N is similar to thatof standard fertilizers, especially when effluent is used forextended periods. However, lower efficiency may occur when leachingis required to prevent salinity buildup or when denitrification isincreased as a result of reduced aeration caused by effluents withhigh COD or BOO levels. Losses through NH3 volatilization may occurin alkaline soils (Feigin et al. 1981).2.12.2 Phosphorus, potassium, calcium, magnesium andsulphate managementMost data obtained from low-rate effluent application show anincrease in soil P, but do not indicate problems resulting fromexcessive P buildup. Phosphorus applied in the effluent willconcentrate in the top layer and will usually not be availableuntil it is incorporated into the soil or otherwise transported66into the main root zone. Under drip irrigation, the roots of cropsare concentrated within the continuously maintained wet zonewhere the concentration of P is high and is more readily availablefor the growing crop than under sprinkler irrigation.Although chemically greatly different from P, K movementwithin the soil profile is also slow. Potassium availability tocrops depends on its presence within the active root zone of theplant.Calcium and Mg are often present in large quantities ineffluent. In addition to their positive effect on soil quality theyare important nutrients.Sulphate is also important for plant growth, since S is oneof the essential nutrients. The presence of SO4 in effluent can betherefore advantageous in S deficient soils (Feigin et al. 1991).2.13 Biomass productionUnder the pressure of a worldwide crisis in nutrition, rawmaterials and energy, a new field of research has evolved topromote the production of economically convertible biomass rapidlyand effectively using modern biotechnological methods(Schwarzenbach and Hegetschweiler 1982).According to Webster Dictionary (1986) biomass is defined as“the amount of living matter in the form of one or more kinds oforganisms per unit of area of habitat or as weight of organisms perunit volume of habitat”. Biomass has potential use as food, as rawmaterial for economically important products and as an energysource. One of the aims of this new research is to find suitableorganisms producing the greatest quantity of economicallyconvertible biomass rapidly under well—adjusted conditions67(Scwarzenbach and Hegetstchweler 1982). This biomass can beconverted to energy by direct combustion or to gaseous or liquidfuel before burning. Such fuel can be used domestically, fortransportation, and by industries and public utilities. Wood andother parts of the tree contain complex, useful molecules. Usingthese as solid materials or as chemicals may be their best use(Schneider 1977).The largest part of global biomass is in forest trees.According to FAO (1979) less than half of annual forest biomassgrowth is used to satisfy human needs.Worldwide demand for wood products is increasing; at the sametime society is placing more diverse demands on forested land.Recreation uses of forest land and even their medicinal use istaking precedence over wood production in some areas. Large areasof prime hardwood forests are being converted to other uses, forexample, agriculture, urban and industrial development and utilityrights—of—way. These factors have motivated foresters to seekmethods of maximizing production on lands that are available forforestry purposes (Wittwer and Stringer 1985). Most of these landsare least in demand for agriculture, e.g., abandoned farmland,semi— or unutilized coppice forest, sedge— or cane—growingcoastal or riverine areas, saline soils, mountain slopes, dryareas, strip-mine, and other types of wasteland (Siren 1982). Insuch conditions, a key to maximum biomass production is rapidestablishment and early utilization of the growing capacity of thesite. Optimised conditions for nutrients, water, and tree growingspace will be required for maximum yield. This can be accomplishedin short—rotation intensively cultured forest plantations by usingclose spacings and high tree densities (Sopper and Kerr 1980).68Biomass plantations are of genetically improved, fast growing,usually broad—leaved trees that are intensively managed, with theshortest possible time-lapse between planting and cropping (2-10years), of a maximum of woody biomass for energy or chemistry,where Schneider’s (1977) “minirotation” and Young’s (1964)“complete tree” concepts are used.Cannell and Smith (1980) have reviewed yields resulting fromuse of silvicultural systems. Species—site relationships, rotationage—stand density interactions and cultural treatments exert stronginfluences on biomass production. Important attributes of suitablespecies include: a) rapid juvenile growth; b) efficient dry-matterproduction in terms of water and nutrient inputs; C) crowncharacteristics to maximize interception of solar radiation; d)ease of regeneration by coppicing (Fege 1981).2.13.1 Short rotation intensive culture forestryShort rotation intensive culture (SRIC) forestry is asilvicultural system that incorporates close spacing, intensivecultural techniques, and short cutting cycles. The intent is toobtain the best production at an economically competitive cost(Mitchell 1990). Relevant to this concept are numerous harvestsresulting from coppice stands (Geyer and Melichar 1986).Short—rotation intensively cultured hardwood plantations havegenerated much interest because they yield more fiber than nativehardwood stands under similar rotation periods (Hansen and Baker1979). There are now several programmes around the worldinvestigating the production of woody biomass for pulp and fuelusing short-rotation coppices (Cannell et al. 1988).Advantages of SRIC include: a) potential for complete69mechanization from establishment to harvest; b) excellentopportunity for rapid genetic gain by selection and breedingfollowing clonal propagation; c) reduced investment time; and d)better utilization of land area (Bowersox et al. 1979).The species which are frequently studied and used for biomassand energy plantations in temperate climates are: Hybrid andselected clones of various poplar species (Populus sp.), willows(Salix sp.), alders (Alnus sp.), elms (Ulmus sp.) eucalyptus(Eucalyptus sp.) hornbeam (Ca.rpinus sp.) (Schwarzenbach andHegetschweiler 1982). A more extensive survey of species suitablefor wood production is presented by Burley (1978), Howlett andGamach (1977) and Lavoie and Vallee (1981). Each of these specieshas a preferred range of sites on which growth is at a maximum. Ofthe above mentioned species, poplars occupy a unique position inbiomass production, short rotation intensively cultured forestryand agroforestry because of their characteristics. Stand ManagementResearch results from numerous SRIC tests show thatsuccessful establishment, (i.e. low mortality and rapid earlygrowth) requires quality planting stock, thorough site preparation,and effective weed control. These efforts require a larger energyinput than traditional culture of naturally regenerated foreststands (Bowersox et al. 1979). For example, successful andconsistent establishment of hybrid poplar under most conditionsrequires 1) fall application of a contact herbicide followed byploughing and disking, 2) spring disking and application of a preemergent herbicide at the time of planting and 3) on some sites,post-planting cultivation or application of a contact herbicide70during the middle of the first growing season (Hansen 1983).Effective weed control is critical to success in establishinghardwood trees. The appropriate weed control measures and thefrequency of implementation is directly related to tree spacing,and is influenced by site quality and stand management practices.Denser spacings will not usually require weed control beyond thefirst growing season because the closely spaced trees will shadeout competing vegetation, whereas wider spacings may require weedcontrol for several years beyond the first growing season.However, the apparent advantage of denser spacing is not withoutcosts. Nutrient depletion is highly correlated with spacingdensity, and may therefore result in a lower productivity in thelong—term. Denser spacings will require higher levels of nutrientamendments to maintain soil productivity. Denser spacings alsoincrease establishment costs (Perlack et al. 1986). Pests and diseasesBecause of dense spacings and monocultures, SRIC biomassplantations are prone to serious risk from pests and diseases.Conditions favouring rapid tree growth can encourage pathogen andinsect infestations. To minimize these risks, pre—establishmentplanning must consider the choice of a healthy and disease—tolerantplanting stock, and maintenance activities should includemonitoring for disease development and incorporation of pestmanagement practices (Perlack et al. 1986).712.13.1.3 Rotation AgeThe determination of an optimal rotation age for SRIC biomassplantation is constrained by some basic biological andenvironmental relationships. The species, site quality, standmanagement practices, and the end—product influence the plantingdensity. The planting density, in turn, affects the rotation lengthand, hence, the total yield of the biomass plantation (Perlack etal. 1986). In general, denser spacings will dictate shorterrotations. Cannell and Smith (1980) reviewed the literature onminirotation systems and yields attained in these systems. BRIC and AgroforestryAs rotation lengths shorten and management intensifies, treeplantations become similar to conventional agronomic systems(Hansen et al. 1983), and differ from forestry methods. If weaccept Raitanen’s (1978) definition of agroforestry , i.e., “theapplication of the principles and procedures of agriculture to thegrowing of forest trees”, then each SRIC plantation may as well beconsidered an agroforestry plantation.Fast growing material is very demanding of site, so eithervery good sites are used or they need to be ameliorated to somedegree (Mitchell 1990).Nutrient amendments directly affect the growth rate (energyquantity) and chemical composition (energy quality) of woodybiomass crops. In general, fertilization seems to be required foroptimim biomass productivity. Its level and application schedulewill depend on species, site climatic conditions, and the nutrientcomposition of the soil prior to planting. The appropriate levelof fertilization will be dictated by the economics of yield72response (Perlack et al. 1986).The accelerated harvesting of the SRIC plantations atintervals of 4-8 years may rapidly deplete the site of plantnutrients and require fertilization to maintain maximum production(Sopper and Kerr 1980). Nitrogen is the nutrient most likely tolimit growth of SRIC plantations, and N fertilization has beeneffective in increasing yields. However, N fertilizer isexpensive, and recovery of applied fertilizer N in plantation treesrarely exceeds 20%. Aside from tree uptake, both native andfertilizer N can be immobilized in the soil, absorbed by vegetationother than the trees, leached below the rooting zone, or convertedto gaseous forms and lost (Baker and Broadfoot 1976).Maximum efficiency in biomass production in SRIC woody cropsrequires a level of N fertilization that achieves a balance betweenmaximum growth and minimum nitrate level leaching into groundwater(Tschaplinski et al. 1991). Determining optimum fertilization rateand timing to maximise tree growth and minimise fertilizer losseswould require fertilizer trials on a massive scale (Hansen etal.1988). In addition, annual biomass production will be greatlyinfluenced by rainfall and therefore may require irrigationtoassure maximum production. As a result, the need to irrigateandfertilise might increase forest biomass productioncostsconsiderably. Economic evaluation of production costs forsilvicultural energy farms showed that the two primary productioncost items were fertilization and irrigation, accounting forup to40% of the total forest biomass production cost. A possibleeconomic solution to these two requirements (irrigationandfertilization) to maximize biomass production, might be to utilizetreated municipal wastewater. The forest plantation could benefit73from the nutrients and water in wastewater, which might increasebiomass productivity and shorten rotation periods, and at the sametime provide a land treatment system for the renovation of theurban wastewater. This symbiotic relationship might make bothsystems more cost-effective (Sopper and Kerr 1980). The viabilityof SRIC and wastewater regimes will depend largely on the distancebetween the treatment plant and the plantation. In some cases, thecomposition of the wastewater may preclude its use with SRIC(Perlack et al. 1986).If high yielding, irrigated plantations can be grown onsufficiently large scale (such as proximity to, and utilising theeffluent from large metropolitan areas) then the production fromsuch zones can be used to offset existing production elsewhere.Natural forest resources can potentially be released forrecreational and conservational purposes, and conflicts in resourceuse can be reduced. More directly, the planting of large areas offorest on effluent disposal areas can significantly improve thelandscape and, with careful planning, create or recreate manynatural elements which do not at present exist in the area. suchconsiderations can operate at many scales from single productionplant to a significant sub-region around a city (Edgar and Stewart1979). Wastewater Irrigation and Intensive Forest CultureCombination of intensive forest culture with wastewaterirrigation represents an ideal solution for wastewater disposal.Forest stands of rapidly growing trees and understorey flora mosteffectively remove nutrients from wastewater, as opposed toeffluent disposal over grass and even natural forest stands.74Irrigation of forest plantation is likely to result in a usefulproduct and increased service. From the effluent disposalstandpoint, the intensive plantation has several advantages: 1)requires large amounts of water and nutrients, 2) has a largeevaporation area (Papadopol 1984), and 3) has a relatively uniformspacing, thus it is possible to mechanize planting, tending andharvesting operations.Hybrid poplars appear to be the most suitable species for therenovation due to the following characteristics:1) Relatively easy establishment2) Indeterminate growth3) Rapid juvenile growth4) High total photosynthetic production5) Relatively full utilization of growing season by meristems6) High evapotranspiration rate (FAO 1979).Hybrid poplars and eastern cottonwood (Populus deltoidesBartr.) have been tried in several regions and they comparefavourably with corn and forage grasses with regard to wastewaterrenovation (Brockway 1982, Papadopol 1984, Stewart et al. 1986).The major rationale for planting poplars is to exploit theiramazing potential to produce wood. Hybrid poplars will increase inheight and diameter faster than any other tree adjusted totemperate North America (Dickman and Stuart 1983). This particularcharacteristic makes them desirable “wastewater disposal” species.A significant amount of nutrients taken up by tree are transformedinto woody biomass. In contrast to foliage, which eventuallyreturns to the soil as litter and releases its nutrients into thepercolating water after decomposition, woody biomass remains at theplantation until it is harvested and is removed from the site.752.13.2 Poplar CulturePoplars have long been cultivated in widely different regionsof the world. In the East, their cultivation would appear to datefrom very early times. Because of the value of the trees and theproven ease of propagating them by cuttings, people came graduallyto plant them near their homes and around their fields or as rowsbeside ditches, roads and water points. This is still happening onthe high plateaus of the Near East and around the shores of theMediterranean. In Europe too, there are countries wherepoplargrowing has a very long history, but it is chiefly since the 18thcentury, when North American poplars were imported to hybridizewith native European poplars that the cultivation of poplar beganto expand. Throughout the 19th century and at the beginning of the20th century cultivation made rapid strides (FAQ, 1979). Inseveral European countries, in the Near East, as well as intemperate regions throughout the world, interest in poplars isgrowing. Efforts are being made to cultivatethem morescientifically over wider areas, and to introduce them into regionswhere they are as yet only slightly known, or evencompletelyunknown (FAQ, 1979).In addition to its traditional timber, land reclamation andlandscaping values, poplars are becoming a potentialsources ofother products. Published results are already available in thefield of pulp and paper (Laundrie and Berbee 1972, Neuman 1976,Crist et al. 1979), food production (Anderson andZsuffa 1977,Dickson and Larson 1977, Anderson, 1979, Chen et al. 1979, Perlacket al. 1986), energy (Love and Overend, 1978, Siren 1982) andchemical feedstock (Lora and Wayman 1979).76New and diversified poplar markets and needs for poplar treesare developing in North America and around the world (Zsuffa etal. 1979).The genus Populus occurs interspersed throughout all theforests of the temperate and cold regions of the northernhemisphere. In certain localities small uniform blocks or tractscan develop naturally although rarely where there is seriouscompetition with other major species as components of the forest(FAO 1979).There are five sections of genus Populus. These are: Turanga,Leuce, Leucoides, Tacamahaca and Aigeiros. The first threesections contain species of major use in Canada’s poplarprogrammes.Poplars are distinguished by features that even if common toquite a number of cultivated plants, are decidedly originalcompared with how other wood-producing species behave. Thesefeatures are:1. Hybridization is frequent between trees of different speciesand of complementary sexes.2. They are reproduced primarily by vegetative processes and notfrom seeds (FAO 1979). Hybridization of PoplarsThe ease of hybridization in poplar allows combinations ofspecies characteristics. Thus, breeding results in interspecifichybrids, which possess improved site adaptability, pest resistance,cold hardiness, and biomass qualities (Anderson et al. 1983).There are several poplar hybridization projects in Europe,America and Asia. There has been so much hybridization between77species and the hybrids have been distributed so widely that it isdifficult to locate a tree typical of a pure species in thearboretum and park collections of the United States and Europe(Wright, 1976). In Canada F.L. Skinner, famous breeder of theprairies, was the first to produce new poplar varieties by means ofhybridization and selection in the early thirties (Heiluberger atthe Petawawa Forest Experiment Station in Ontario (Armson andSmith, 1977). Very extensive work on clonal development andevaluation has been reported since the 1930’s. It has involvedselections of native species, exotics and hybrids. In addition todomestic selections many foreign hybrid poplar clones, especiallyof European origin and imported from U.S.A., have been screened forgrowth, tolerance, and resistance in Canada (Roller 1970; Hubbes1971, Linguist et al. 1979, Zsuffa 1979a, Zsuffa 1979b, Blom 1981,Popovich 1982, van Oosten 1990).In Washington State Heilman and Stettler (1986, 1990)produced numerous clones of hybrid poplars by crossing the nativeblack cottonwood (Populus trichocarpa Torr and Gray) with easterncottonwood (P. deltoides Bartr. and Marsch.). These geneticallyimproved, fast growing clones were suitable for short rotationbiomass culture. Productivity of some of the best hybrids averagedmore than twice the mean for Black Cottonwood or ‘Robusta’ hybridand were significantly higher than those of the best nativeclones tested (Table 2.10) (Heilman and Stettler 1986). Some ofthese clones were planted in Vernon B.C. where they showed anexcellent performance and very good adaptation to climaticconditions (Carlson 1988, personal communications).78Table. 2.9 Comparison of mean annual dry weightproduction between different clones(kg/ha/year).Year 1 Year 2 Year 3P. tn chocarpa 1.40 9.90 10.30P. x robusta 0.30 4.70 9.40P. trichocarpa xdel toidesclone #5 1.40 9.90 20.10clone #8 0.50 4.10 10.70clone #11 0.80 8.60 19.50(After Heilman and Stettler, 1986).Most commercial strains of poplar are reproduced auto—vegetatively by their seedlings, whips, root cuttings or stemcuttings. The choice depends on the management system and speciescharacteristics.Stem cuttings are the cheapest and most flexible plantingstock (Anderson et al. 1983). But difficulties are encountered withthis method in the case of certain cultivars of section Leuce andof the section Leucoides, and also exceptionally, with some clonesof section Aigeiros. As a general rule, cuttings should have alength of 20 cm and a diameter at midpoint of 10-20 mm (FAO 1979).Cuttings are produced in cutting orchards or stool beds. A cuttingorchard with 1 in x 1 in spacing produces an average of 30 cuttingsper stump (Hansen et al. 1983). Stem cuttings are mostly used forininirotations, while short—rotations are established either by stemcuttings, one year rooted cuttings, or whips (Anderson et al.1983).79The time and method of planting influences the survival andinitial growth as well as the economics of energy plantation.Planting is completed during the early spring when the temperaturesare low (0—10 °C) and the moisture levels are at, or near, fieldcapacity. These conditions are excellent for the development ofcallus and initiation of roots (Raitanen, 1978). Nutrition of poplarsThere is an enormous literature on fertilization, nutritionand nutritional requirements of Poplars species and their clones.However, this literature is scattered and only few researchers havemade an attempt to collect and published this data in one article(FAQ 1979; Dickman and Stuart 1983).Poplars are luxuriant users of soil nutrients. For example,according to Switzer et al., (1976) 16-year-old Aigeiros poplarssuch as eastern cottonwood contain more than twice as much N, P, K,Ca, and Mg combined, as do equivalent—aged southern pines e.g.loblolly pine and slash pine. McColl (1980) concluded that theannual uptake of nutrients in aspen stands is considerably higherthan in many other broad—leaved stands.Poplars are able to take up and remove a considerable amountof nutrients from soil and then return them through litter(Yakushenlco, 1985). Francis and Baker (1981) have calculatednutrient uptake by eastern cottonwood (Populus deltoides Bartr.)during four years after establishment of a plantation(Table2.10.). This characteristic of poplars has made themsuitable species for their implementation in wastewater and sewagesludge disposal sites.80Table 2.10 Nutrient content per tree in years 1 through 4in a cottonwood plantation (g/tree)N P K Ca MgYear: 1 20 1 17 1532 64 8 47 97 143 108 15 80 175 234 117 18 107 107 34(After Francis and Baker 1981).Quantities of nutrient accumulation in the poplar standsandplantations in decreasing order are Ca>> N> K> Mg> P (Switzer etal. 1976). Although the uptake of Ca is very high,it isimmobilized most (Gosz 1984). Thus, it is N which plays a moreimportant role in poplar nutrition. Switzer et al. (1976) foundthat natural stands of Aigeiros poplars in the Mississippi Valleyaccumulate nutrients through age 12, when maximum levels for allnutrients are reached. In contrast, the accumulationof nutrientsin the unthinned plantation at this age is only 40%-60% of thenatural stands. Maximum levels for nutrients inunthinnedplantation stands occur by age 20. Total nutrient accumulation forboth stands is almost identical at age 20.Foliar analysis is a well established method used toassistdiagnosis of mineral requirements in agriculture andforestry,since the leaf is the focal point of plant functionsand is arelatively sensitive indicator for those mineralelements thatdirectly affect photosynthesis. In addition it isa convenientportion of the plant to sample (van den Driessche 1974). The81knowledge of standard values of nutrients in the foliage and otherlimbs of poplar clones is still far from perfect. Further researchneeds to be pursued and indeed to be specially intensified at theregional level to compare levels of mineral nutrition toproduction, clone by clone. Useful guides to fertilizer needs mightthen become available.Seasonal changes in nutrient concentrations of poplars formedthe subject of several studies. Tew (1970), Verry and Timmons(1976), Coyne and van Cleve (1977), James and Smith (1978) andMcColl (1980) have studied seasonal nutrient variation of tremblingaspen (Populus tremuloides Michx.) while Smirnov and Semenova(1972), Baker and Blackmon (1977) and Heinemann and Hennessey(1982) carried out the same studies on eastern cottonwood (Populusdeltoides Bartr.) and black poplar (P. nigra L.). Some data is alsopresented by FAO (1979) on seasonal changes of nutrients in hybridpoplars. All these studies agree that, in poplars, concentrationsof foliar N, P, K, and S are usually high at the time buds open,diminish during the spring, level of f through the summer anddecrease before leaf fall; the variations are reversed in the caseof Ca i.e., concentration of this element in foliage increasesuntil the litterfall. Concentration of Mg in leaves also increasesslightly by the end of the growing season.Verry and Timmons (1976) also studied seasonal variations ofsome micronutrients and trace elements in the foliage of aspen (P.tremuloides). They found that the concentration of B in foliage didnot change significantly from May to September. Concentration of Fedecreased from May to mid June; and after that it increasedconstantly up to the end of growing season. Concentrations of Znand Al at the end of September were significantly higher than in82May, while the concentration of foliar Cu generally declined overthe season.Nutrient changes in other components of poplars follow thereverse direction to those in the leaves. James and Smith (1978)report that concentrations of N and P in twig bark of aspen (P.tremuloides Michx.) decreased from April to a minimum in May andthereafter increased to a maximum in September. Changes in Mg andK followed a similar pattern, but the lowest concentration occurredin June and July respectively, while concentration of Ca increasedto a maximum in May and after that decreased constantly untilSeptember. Mean Ca concentration at the end of growing season was75% of that in May.As regards position on the tree, Coyne and van Cleve (1977)and van Coyne and Oliver (1981) found that foliar N concentrationin aspen increased with canopy height, while concentration offoliar P, K, and Ca did not change with canopy position.Concentrations of these elements showed considerable differencesdue to leaf position on a twig. Although Verry and Timmons (1976)found that concentrations of N, P, Mg, Na, Zn, Mn, Fe, Al, Cu, andB were not significantly different between crown positions.White and Carter (1970), and Carter and White (1971) comparedconcentrations of nutrients in the foliage of a 6—year old easterncottonwood stand in lower Alabama. They found higher N and Pconcentrations in the foliage of the upper crown, while Mg and Catended to be less in the upper foliage. These trends are in generalagreement with a later published study for hybrid poplars by FAO(1979).Bowersox et al. (1979) observed significant differences inmacronutrient concentrations (Table 2.12) among seven poplar83hybrids grown under similar conditions. They concluded thatparentage selection may influence nutrient budgets of theplantations and potential yield of chemical products from biomass.Heilman and Stettler (1986) stated that N—use efficiency ofclones of P. trichocarpa x deltoides was significantly lower thanblack cottonwood (P. trichocarpa). These clones also showed a rapiddecline in N concentration in both bark and wood with tree age.Table 2.11 Selected nutrient concentrations of seven populushybridsClone P K Ca Mg(g/kg)NE—49 0.7 3.70 4.60 0.6NE—245 0.8 3.10 5.70 0.6NE—252 0.7 3.00 6.40 0.5NE—279 0.9 3.70 7.10 0.5NE—302 0.9 3.70 5.50 0.6NE—350 0.8 3.70 5.70 0.6NE—388 0.9 3.50 6.30 0.5Avg. 0.8 3.50 5.90 0.6(After Bowersox et al. 1979)Age is another factor which determines concentrations ofnutrients in different parts of trees. Shelton et al. (1981) foundthat the effect of plant age is most apparent in the concentrationof N, P, and K in the stemwood of eastern cottonwood.Concentrations of these nutrients in stemwood decline with increasein age.84The change in concentrations of nutrients in poplars can bedue to meteorological elements, such as average daily airtemperature and solar radiations (Sxnirnov and Semenova 1972).Gladysz et al. (1983) concluded that microclimatic conditions exerta stronger influence upon the concentration of some nutrients suchas N, P, and K than the genetic properties of poplar clones.Physiological disorders can appear when there are insufficientamounts of certain nutrients to satisfy the poplars’ needs; thewarning signs are generally changes in the colouring of leaves.Under natural conditions it is unlikely that any one essentialplant nutrient would be completely lacking, while plantation treesgrowing on lands formerly devoted to other crops may show one ormore deficiency symptoms if the nutrients in the crops were notreplaced by subsequent fertilization. Under these conditions,macronutrients would be removed in the largest quantities anddeficiencies of these would probably be apparent first. Deficiencylevels of poplars are not well—studied; the following values may beregarded as appropriate orders of magnitude, as proportions of drymatter (Table 2.13). FertilizationIn poplar plantations, the purpose of applying fertilizers isto maintain the soil fertility. This means both compensating forthe loss of mineral elements resulting from the removal andtransplanting of plants, and at the same time maintaining a properlevel of biological activity. That is why fertilization in thenursery must involve both application of mineral fertilizers and oforganic matter in the form of animal manure or manure crops (FAO1979).85Table 2.12 Composition of Deficiency levels of some nutrients inthe foliage of poplars from different sources (g/kg)N P K Ca MgPopulus sp.(1) 22.0 3.0 10.0 — 1.2Populus sp.(2) 22.0 — 14.0 — 2.0P. deltoides (3) 30.0 3.0 12.0 — 2.0P. deltoides (4) 20.0 1.7 13.0 23.0 1.8P. euramericana [I—45/51](5) 25.6 18 12.7 11.0 3.9P. trichocarpa(6) 25.0 - - - -1) FAO 1979, 2)van der Meidn 1962, 3)Bonner and Broadfoot 1967,4) White and Carter 1971, Blackmon and White 1972, 5) Kim and Leech1986, 6) Heilman 1985.The role of fertilization in the plantation is twofold. On onehand, an application of a selected mineral fertilizer at thetimeof planting can improve the chances of rooting and in some measureserve as a preventive against parasites like Dotchirhiza populeawhich attack plants of poor vigour. Generally, this meansapplyingmineral fertilizers containing P, the element promoting rootdevelopment, and N. On the other hand, fertilizationin theplantation can serve as a palliative against a relative poorness ofthe soil in certain elements. Numerous field trials have beencarried out to determine the best formulae. The variance in theresults may be explained by differences in fertility of thesiteswhere the experiments were conducted (FAO 1979). Fertilization86should be done only if soil or foliar analysis indicates nutrientdeficiencies, because a response to supplemental nutrients wfll notoccur on highly fertile sites, and the high investment will bewasted (Blackmon 1977). Fertilization will not affect all poplarclones in the same way (Baker and Randall 1975), so nutrientadditions should be tailored to clonal requirements. Furthermore,in a mixed clonal planting the overall stand response may be morecomplex than in pure clonal planting, and probably not as great.Nitrogen is the most limiting nutrient on most poplar sitesand fertilization with this element generally stimulates thegrowth. Weeds are the major N sink the first few years in poplarplantations and trees are most likely to be nutrient deficientduring the years prior to canopy closure (Miller 1983). Hansen etal. (1988) suggest that if weeds are eliminated, N fertilization isnot necessary on moderately fertile soils. After canopy closure, Nfertilization may be greatly reduced or even eliminated. Authorsalso suggested that N fertilization of about 112 —168 kg/ha/yearmay be a good first approximation in the absence of specificlocal data for young poplar plantations.Blackmon and Broadfoot (1969) obtained greater growth afteradding N to infertile acid alluvial soil. A 200% growth increasefor trees fertilized with N was reported by Blackmon and White(1972). In further research, they also noted that responses ofpoplars to N fertilization are most likely to occur when the soilcontains less than 1100 kg/ha total N. Garbaye and Leroy (1974)reported that surface application of N for three successive yearsafter planting produced a 43% increase in diameter. Blackmon (1977)concluded that eastern cottonwood growth can be stimulated byfertilization with 168 kg/ha N as ammonium nitrate. Fertilization87with N approximately doubled leaf biomass, mainly due to increasesin leaf numbers of trembling aspen (Coyne and van Cleve 1977). VanCleve and Oliver (1982) reported that application of NH4 at thedosage of 111 kg N/ha resulted in 9% increase in specific leaf areaof poplars. According to Menetrier (1979), P seems to be of theutmost importance of unrooted cuttings to get a good start.Czapowskyj and Safford (1979) also report that application of Pincreased growth of bigtooth aspen.Addition of P and K have also been beneficial. Chardenon(1960) found that on slightly acid soils, addition of K increasedthe growth of poplars. Van den Meidn (1962) and Chardenon (1960)asserted that K should always be applied with N. White (1969) founda strong relationship between height growth and extractable K. Vanden Burg and Schoenfeld (1978) also mentioned a close relationshipbetween K and annual height increment of poplars.Most of the researchers have used combinations of N, P, and Kin their experimental plots to determine the effects of theseelements on growth of poplars.Many workers have obtained increased height and diameter afterapplying a combination of N,P, and K to poplar plantations (Hitier1947, Karlsberg 1954, Gunther 1957, Jobling 1960, Fritzche andKremmer 1961, Bhagwat 1967, Carter and White 1971). Otherresearchers report increase in wood specific gravity and fibrelength (Bhagwat 1967) or gains in wood weight Fritzsche and Kremer(1961) due to application of N P K fertilizers. Addition of NPKfertilizers also decreased losses from diseases in poplars (Leroy1969). Bonner and Broadfoot (1967) showed that cottonwood grew bestwith nutrient solutions containing 100, 70, and 100 mg/L N, P, andK, respectively under greenhouse conditions. However, fertilization88with N P K seems to be beneficial only on poor soils that have beenimpoverished by agronomic cropping (Frison 1974). Deol and Khosla(1983) obtained a significant increase in total biomass,treeheight, collar diameter and fibre length of P. ciliata Wall.exRoyle saplings after application of NPK fertilizer in the spring.Application method of the fertilizer also seems to affect thegrowth rate. Lavezzini (1957) recommended that NPK in combinationwith manure be placed in the planting hole, while Leroy (1969)found that placing NPK in bands around poplar trees increased theyield.Because of rapid growth and relatively high nutrientconcentrations in their tissues, poplars not only require highlevels of soil N, P and K, but also require soils with highbasestatus and ample micronutrients (Baker and Broadfoot 1976).Berneoud and Bonduelle (1971) reported that reaction ofpoplars to Ca and Mg was unpredictable and variable. The sameresearchers mentioned later that application of Mg did notaffectgrowth of 1-214 poplars, which confirm conclusions ofLiekens(1960) concerning the importance of Mg. Carter and White(1971)recommended mineral value of 1000 mg/kg exchangeable Ca forpoplarplantations.On sites suitable for growth of poplar, deficiency of traceelements is all but unknown, except copper deficiency. Lime inducedchiorosis (iron deficiency) may occur in balsam poplars andbalsam—hybrid poplars on calcareous soils. No dependable methodsare yetknown for determining the available amount of trace elements in thesoil, but leaf analysis can provide necessary information(Van denBurg and Schonenfeld 1978).89Vsevolozhskaya et al. (1963) report that addition of Cu to NPKfertilizer had positive effect on growth of Populus deltoidesBartr. Berneoud and Bonduelle (1979) also report a favourableeffect of Cu on the growth of P. euramericana (1-214). Boil pHSoil pH is important for nutrient availability in that manyelements are fixed in the soil and unavailable for plant absorptionwithin certain pH ranges. Most nutrients are available to poplarswhen pH is near neutral (Baker and Broadfoot 1976). Manyresearchers agree that poplars grow best when pH ranges from 5.5 to7.5 (Schreiner 1959, Capel and Coffman 1966, Gyarmatine-Proszt1971, Carter and White 1971). Van den Burg and Schoenfeld (1978)report that the optimum pH range for balsam poplars is smaller thanfor euramerican poplars (pH, 5.0—5.5). It is not recommendedtoplant poplars at pH lower than 4.5 (Baker and Broadfoot 1976). Onstrongly acid soils, large doses of lime are required, with orwithout fertilization, to increase soil pH. LimingChardenon (1961) recommended application of N together withliming to acid soils with loamy texture, when poplars are planted.Carter and White (1971) recommended heavy application oflimebefore planting poplars. Kaszkurewicz (1973) recommended 6.7 Mg perha of lime to strongly acid (pH=4.0) silty clay. CzapowskyjandSaf ford (1979) found that lime stimulated growth of tremblingaspen; after application of N and P together with lime, bigtoothapsen grew 7 times as fast as control.902.13.2.6 Soil TextureResponse of poplars to fertilizers is largely dependent onsoil texture. Chardenon (1960) concluded that poplars grew bestwhen planted in sandy soils and fertilized with N, P and K plusliming. Frison (1974) reports that two-year—old saplings of Populuseurainericana (1-214) planted in sandy soil did not showsignificantly more growth after application of N fertilizer. Thesame species showed significant increase in height and basaldiameter when planted in sandy-loam soils and treated with the samelevel of N fertilizer. Blackmon (1977) found that cottonwoodplanted on medium-textured soils responded significantly to Nfertilizer application.Krinard and Kennedy (1980) found that eastern cottonwood canbe planted and grown on clay soils, however their yields may beslightly more than half that on medium-textured soils. Dickman andStuart (1983) concluded that on dry sandy soils, where water is themajor limiting factor, fertilization does little good.Fertilization can often provide supplementary nutrients;however, some of the soil-site properties that influence the nativefertility and nutrient availability include soil age, geologicsource and mineralogy, depth of topsoil, organic matter, pH andpast use.Geologic source and mineralogy strongly influence inherentfertility. Soils, derived from parent material with high nutrientcontent are obviously more fertile than those formed from materiallow in nutrients. Likewise, soils with relatively high proportionsof clay minerals that contribute to good cation exchange usuallyhave good fertility.Organic matter is a potential source of soil nutrients and91also serves as part of the soil—nutrient exchange complex.Intensive agronomic tillage and cropping often reduce the amount oforganic matter in the soil and deplete the nutrient reserve(Blackmon and White 1972).A soil’s nutrient content declines with age because of theleaching of soluble elements from the surface layers. Increasedprofile development indicates leaching and thus aging. Young soilsdeveloping on floodplains are usually fertile because of thedeposition of recent alluvium. Table 2.14 shows some factors thataffect the productivity of soils for poplars. SRIC Poplar Plantations and FertilizersThe complete removal of the biomass and frequent harvestingperiods in the energy plantations can accelerate the nutrient drainfrom the site.Minirotations result in substantially higher nutrient demandsbecause of high biomass production, more frequent harvests andlarger proportion of the nutrient rich tissues in biomass. Thenutrient drain is particularly acute when foliage is harvestedtogether with stem biomass. Since foliage of poplar contains crudeproteins in the range of 13%-24% (Chen et al. 1979, Hansen andBaker 1979), N deficiencies may appear after repeated harvests(Anderson et al 1983).The scientific evidence of nutrient depletion and its impacton soil productivity after repeated biomass harvests is scarce.Young (1980) notes that the natural loss of nutrients due toleaching may exceed the amount tied up in the production of newbiomass each year in forests. Usually, in regular forests the treesare able to find the necessary nutrients. However, lands considered92for SRIC plantations may show deficiencies. A continuous monitoringof nutrient availability is needed in a SRIC plantations to. avoidthe possibility of decreased productivity . Since commercialfertilizer tends to be limited to agricultural uses, restoration ofsoil fertility in biomass plantations should be done by otheralternative fertilizers. One way is to “fertigate” (fertilise +irrigate) poplar plantations with municipal or industrialwastewaters.Table 2.13 Some of the best and worst conditions of soils forpoplarsBest conditions Worst conditionsUndisturbed site for not less Recent intensive cultivationthan five years. for more than 20 years.A—horizon (topsoil) more than A—horizon absent or less than15 cm. Young and well- 8 cm. Old highly leacheddeveloped profile, profile.Organic matter more than 3%, Organic matter less than 3%especially in sandy soils.Source of basic (calcareous) No basic parent material inparent material in rooting rooting in rooting zone =5.5 —7.5. pH in rooting zone less than4.5 or more than 8.5.Silty or loamy texture. Clayey or sandy texture.(After Dickman and Stuart 1983).932.1.4 Foliar analysisThe use of foliar analysis in studies of nutrient status andfertilizer response is based on the assumption that a quantitativerelationship exists between plant growth and the level of one ormore mineral nutrients in the foliage. This functional relationshipis commonly referred to in forestry as a response curve (Armson1973).Typically, the yield response of a plant species to increasinglevels of nutrient availability shows distinct phases (Figure 2.3).Yields may increase sharply with initial inputs and level off whengrowth is not limited by the nutrient in question. Nacy (1936)held that the central concept in interpreting this curve was thatthere was “a critical percentage of each nutrient in each kind ofplant, above which there is luxury consumption and below whichthere is poverty adjustment, which is almost proportional to thedeficiency until a minimum percentage is reached”. Thus in Figure2.3, AB corresponds to the minimum percentage, BC the povertyadjustment, and CD the luxury consumption range. Point C isdescribed as the critical percentage or critical level (or“optimum range” where greater variation exists) of that nutrientfor that species in question, beyond which no additional growthresponse can be obtained. The decline in growth (DE) signifies“toxicity” and is associated with excess nutrient supply. Figure24. depicts the interrelationships between crop yield, plantnutrient concentration and soil nutrient supply. In this figure,increased soil nutrient supply can induce either positive ornegative response in yield , but only positive responses inplant tissue concentrations; the latter may obscure diagnosticinterpretations, as will be discussed later.94The existence of response curves has been demonstrated innumerous forest stands (Mitchell 1939, Leyton 1958, Everard 1973,Tamm 1974). In theory, knowing critical levels for a number ofnutrients allows prediction of the growth response that might beobtained by fertilization. In practice, however, use of criticallevels needs careful consideration and interpretation since bothexternal (environmental) factors and internal (genetic-physiological) factors may modify tree nutrient status (Goodal andGregory 1947, Leaf 1973). The reliability of such simpleapplications depends on similarities between the candidate standand the reference stand(s) from which the critical levels wereexperimentally derived. Armson (1973) has warned that the “greatestunreliability of comparative values may be expected when valuesare extrapolated from one growing location to another or from atree or stand at one stage of development to another of adifferent age class or stage of development”.In many instances, critical levels or optimum nutrient rangeswere not determined by controlled fertilization field experimentsbut by greenhouse and solution cultures. It is questionablewhether values thus established can be applied to analyses fromnatural forests or plantations, or even nursery seedlings, withoutsubjective modification (Swan 1971).2.14.1 Expression of nutrient compositionNormally, only part of the plant is sampled when analysis isundertaken for diagnostic purposes. The level of nutrients isexpressed as concentration, usually a percentage of tissue dryweight.. Plant nutrient composition may be expressed asconcentration or absolute content in tissue. The distinction is95obvious (Farmhood and Peterson 1968), but the two terms often havebeen used synonymously, and at times erroneously. Surprisingly,studies of nutrient relationships and fertilizer responsegenerally make use of foliar concentration, rather than totalcontent (van den Driesche 1974), although there are frequentexceptions. The implicit but largely untested assumptions are thatconcentration alone correlates best with growth response, and thatconcentration alone sufficiently reflects the degree of nutrientadequacy or deficiency.Thus, relationship between plant growth and nutrientconcentration in the deficiency range of the limiting nutrient areoften regarded as positive and unequivocal (Figures 2.3 and 2.4).Under conditions of low nutrient supply, however, it is possiblethat negative relationship may occur, as has been demonstrated byIngestad (1964) with birch (Betula verrucosa Ehrh.) seedlings, andby Ebbel (1972) with foliage tissue of Douglas fir [Pseudotsugamenziesii (Mirb.) Franco.). This phenomenon is described as the“Steenbjerg effect” (1954). It results when a relatively largeincrease in dry matter dilutes a limited amount of nutrient inplant tissue (Munson and Nelson 1973).The fact that the correlation between growth and theconcentrations of nutrients is negative over one range and positiveover another may confuse diagnostic interpretation. This situationcan be remedied by expressing nutrient composition in terms of theabsolute nutrient content per unit of seedling, root, needle orfascicle. Such expression better reflects uptake in the portion ofthe plant of interest (Armson 1973).Interactions between nutrients also may confound diagnosis. Achange in the concentration of one element is sometimes accompanied96by change in concentration of others (Chapman 1967). Suchinteractions may be either positive (synergisms) or negative(antagonisms), but hinder simple interpretation of plant nutrientstatus (van den Driessche 1974). Attempts to rationalize N-P and N-K interactions have been made by examining N/P and N/K ratios(Waring 1972).A graphical technique which helps recognize and interpret someof the complex relationships of nutrients in foliage was employedby Krauss (19 67) and subsequently by Heinsdorf (1967), Weetman(1971), Weetman and Algar (1974) Ti!niner (1979) and Timmer and Teng(1990). Although little known, and at first glance somewhatdifficult to comprehend, the approach is effective for interpretingdata of this type. Concentrations and content per unit leaf weightare represented in a single display (Figure 2.5.). Inferences ofspecific dilution, concentration and antagonistic or synergisticeffects can be made by observing the extent and direction ofchange in three parameters. This graphical technique forms thebasis of a foliar diagnostic system that is used in this thesis andwill be discussed later in more detail in the section of materialsand methods.2.14.2 Choice of sample tissueA critical factor in using plant analysis for nutrientdiagnosis is the selection of sample tissue which best reflectsthe nutrient condition of the entire plant. Foliage is thecomponent most commonly analyzed, presumably because foliarconcentrations most readily reflect variation in nutrient supply.Furthermore, leaves are often well correlated with other treeresponse parameters (Morrison 1974).Figure 2.4. Schematic relationship between crop yield, nutrientconcentration and available nutrient supply (fromTimmer, 1979).C DEBA97-jw>-NUTRiENT CONCENTRATiONIN TISSUEFigure 2.3. Generalized representation of yield as a function ofnutrient concentration in tissue of plants (AfterTiinxner, 1979).OPTIMUM YIEONE OF WXUPYDNSUMPTIONZONE OF POVERTYADJUSTMENT ç)/MINIMUM cRrncAL LEVELPERCENTAGE OR/ OPTIMUMI# OPTIMUMSUPPLYNUTRIENT SUPPLYI98z[81.6IA1.2I.0g /1000 NEEDLES16 18 20240 300 360 420 480mg N /1000 NEEDLESFigure 2.5. Relationship between N concentration, N content,and dry weight of current needles of black spruce3 years after fertilization (From Weetman and Algar1974).The usefulness of foliar analysis as a diagnostic tool dependson the degree of correlation with future growth response (Morrison1974). Thus, relationships between leaf characteristics other thannutrient concentration and growth should be examined as possiblepredictors of growth. Dimensional measures such as size, biomassand surface area of leaves are major factors determiningphotosynthetic productivity and tree growth response (Kozlowski andKeller 1966). In fact, dry weight and total surface of leaves havebeen found to correlate well with growth responses in severalfertilization trials. It may well be that an integrated approachinvolving some of these parameters may prove more successful inimproving the precision and reliability of tree nutrient statusdetermination techniques based on foJ.iar nutrient concentrationalone.V CONTROLA N200N1I NP100D N200 PK0 N200 K100993. Materials and methods1003.1 Site characteristics3.1.1 Location and climateVernon, located in the Interior of British Columbia in theOkanagan Valley (Latitude = 50°14’N, Longitude = 119°17’W,Altitude = 500 m) has one of the mildest climates in Canada(Kelley and Spilsbury, 1956). Summers are warm with coolnights and winters are mild with subfreezing periods.Average rainfall based on 27 years of data to 1948 was396 mm/yr. For the period 1972 to 1983 this average increased to41.9 cm/yr. Mean daily temperature and monthly averageprecipitation for the period 1972 to 1983 are presented inTable 3.1.Table 3.1 Mean daily temperature (M.D.T.) and monthly precipitation (M.P.) for Vernon B.C. (Average of 30 years1951—198 0’)Month M.D.T. M.P. Month M.D.T. M.P.(C°) (nun) (C°) (nun)January -4.8 32.8 July 20.0 25.6February —1.1 24.8 August 19.3 33.1March 2.5 20.7 September 14.2 27.2April 8.0 19.2 October 7.9 23.8May 12.8 31.6 November 1.1 30.1June 16.68 33.1 December 2.3 45.71 Environment Canada 1984101The growing season is relatively short (175 days early Mayto October) for the northern Okanagan Valley. The prevailingwind is from the southwest (except in July) with an averagevelocity of 2.8 rn/s. In July the wind prevails from thenortheast averaging 3.1 rn/s. These winds are warm and light butare occasionally strong in the spring and fall (Kelley andSpilsbury 1956). A simple method of expressing aridity of aregion by showing the relationship of temperature to rainfallwas used by Bagnoles and Gaussen (1953). This method isdemonstrated in the pluviometric graph (Figure 3.1.). Months ofthe year are shown on the horizontal axis of the graph.Temperature (C°) and monthly rainfall (mm) are shown on thevertical axis. The scale of the temperature axis is double thatof precipitation axis. The shaded area between the precipitationcurves (dashes) and the temperature curves (solid) are drymonths. The more widely this shaded area is spread, the morearid the locality (Goor and Barney 1968).3.1.2 Geology and TopographyThe research site was established in the Vernon Commonagearea, south of Bench Row Road, located 4.5 km south of Vernon(Figure 3.2). This is a rectangular piece of land (275 m x 200in) with an approximate area of 5.0 ha (13.6 acres) (Figure 3.3).The general slope of the land is 8.5%, north facing.0010E-zE-060020U1028020 II/I//////40-10Jon F I’er A4x Mey J.r JJ A Sep Oct Nov Dec ..vI IPREC.TEMP.MONTHSFigure 3.1. Pluviometric diagram of Vernon B.C.-a 0 0 0‘-3 C,)00C)(D0“3U,4w—Ao—e0g2.mL:i0-.g‘-3 z zII104s\\\\N\\\\\\\\\\\\\\____ __\__\ \__....,)\ \ \\\c\_\:___T\ \.(hH’.4:*:zzr1iI )L1 .1.Scale: 1:1250aITt.\\\I0(S.00%4z-5 C.,-4 -Figure 3.3. Topographic map of the project site105The site had been under wastewater irrigation for seven yearsbefore this study began (Jackson 1989, personal communications).3.1.3 SoilsThe soil parent material is composed of sandy glacialoutwash. At depths lower than 100cm, soils contain a calciumcarbonate layer (Wittneben 1987) which is very desirable for theproject, since this layer can immobilize leached P in percolatewater.Little data are available about the lower soil layers ofthe site. Drillings along Bench-Row Road, at the foot of theslope, have shown that glacial till is encountered at depthsgreater than 6.0 in. It is important for further research to knowwhether or not there is a water—impermeable stratum at lowerdepths.The soil of the site belongs to the Black Chernozemic orderwhich represents the local soils (Clayton et al. 1977).Wittneben (1987) has identified the soil series as Armstrong.Armstrong series (After Kelley and Spilsbury 1956):Horizon Depth DescriptionA1 0-20 cm Black sandy loam, well mattedwith grass roots, fine grainedstructure, loose and friable. pH7.2106B1 20-45 cm Black shading to dark brown sandyloam compact and weakly columnar.Scattered fine gravel. pH 7.3.B2 45—80 cm Brown sandy loam, compact andstructureless. pH 7.4B3 80—110 cm Brown loamy sand, loose, porousand limy, sometimes slightlycemented with lime accumulation.pH 8.3C 110 cm< Greyish brown shading to greystratified medium to coarse sand,slightly compact, with layers ofgrit or fine gravel. Limy in theupper part. pH 8.6.In 1987 two pits were dug at the site and soil profile wasdescribed.107Soil Profile Description (After Witneben 1987):Pit no. I.Terrain classification: Sandy gravel blanket overlaying amorainal blanketSoil moisture subclass: SubhumidSoil drainage: WellPerviousness: ModerateFree water: AbsentFlood hazard: NoneWater table: Not observed at the time of sampling (October1987)Effective rooting zone: 50 cm, without any root restrictinglayer.Carbonate accumulation zone: 100 — 130 cm.Salinity: NoneSoil name: ArmstrongAssociated soil: NahunHorizon DepthAh 0 -30 cm 30 - 36 cm thick. Horizon boundaryclear and smooth (2—5 cm). Coarsefragment: 2% rounded gravel. Texture:Sandy loam. Structure grade: Week tomoderate. Primary structure:very finegranular.Moisture consistence: veryfriable. Colour: Aspect=Matrix moistHue=lOyr 3/2. Roots: Few, very fine,vertical in pad.108Bm 34 —71 cm 35 — 40 cm thick. Soil boundary clearand smooth (2—5 cm). Horizon surfaceplane. Coarse fragment: 25% — 17%rounded cobbles. Texture: Sandy loam.Structure grade: Weak. Primarystructure: Medium sub—granular blocky(10—2 0 mm). Moisture consistence:veryfriable. Colour: Aspect=Matrix moisthue=lOyr 6/4. Roots: plentiful, veryfine, vertical in pad.C 71 - 101 cm Horizon boundary: Abrupt (2 cm <) ardwavy. Coarse fragment description: 15%(10% rounded gravel, 5% roundedcobbles). Texture: loamy—sand.Structure grade: Weak . Primarystructure: Medium subangular blocky (0—20 mm). Moisture consistence: veryfriable. Colour: Aspect=Matrix moistHue=lOyr 6.5/3. Roots: Very few, veryfine, vertical.Ck 101 cm < Coarse fragment description: 11% (8%sub-angular gravel, 3% sub—angularcobbles). Texture: loamy—sand.Structure grade: Weak. Primarystructure: Fine subangular blocky (5-10109mm). Moisture consistence: veryfriable. Colour: Aspect=Matrix moistHue=lOyr 6/2.5.Pit no. 2Terrain classification: Sandy gravel blanket overlayinga morainal blanket.Soil moisture subclass: HumidSoil drainage: WellPerviousness: ModerateFree water: PresentFlood hazard: None. Water table: 185 cm.Effective rooting zone: 50cm, without any root restrictinglayer.Carbonate accumulation zone: 98 cm.Salinity: NoneSoil name: ArmstrongAssociated soil: NahunAh 0 — 38 cm 36 - 40 cm thick. Horizon boundary:Abrupt and smooth (2-5 cm). Horizonsurface: Plane. Coarse fragment: 4%rounded gravel,1% rounded cobbles.Texture: Loamy. Structure grade: Weakto moderate. Primary structure: Finegranular (1—2 mm). Moisture110consistence: very friable. Colour:Aspect=Matrix dry Hue=lOyr 2/1. Roots:Few, very fine, vertical in pad.Bm 38 —70 cm 30 - 35 cm thick. Horizon boundary:Abrupt and wavy (2-5 cm). Coarsefragment: 15% rounded gravel 5% roundedcobbles. Texture: Sandy loam. Structuregrade: Week—moderate. Primarystructure: Fine to medium sub—angularblocky (5-2 0 mm). Moistureconsistence: Very friable. Colour:Aspect=Matrix dry hue=lOyr 4/3.5.Roots: Few, very fine, vertical in pad.BC 70 - 98 cm 24 - 34 cm thick.Horizon boundary:Clear and wavy. Coarse fragmentdescription: 10% (7% sub-angulargravel, 3% sub—angular cobbles).Texture: Loamy. Structure grade: Weakto moderate. Primary structure: Finesubangular blocky (5—10 iiun). Moistureconsistence: Friable. Colour:Aspect=Matrix dry. Hue=lOyr 5/3. Roots:Few, very fine, vertical, matrix.111CCa 98 - 115 cm 15 20 cm thick.Clear and wavy. Coarsefragment description: 10% (8% sub-angular gravel, 2% sub—angularcobbles). Texture: Sandy—loam.Structure grade: Moderate. Primarystructure: Fine to medium angularblocky (5-2 0 mm). Moisture consistence:friable. Colour: Aspect=Matrix dryHue=lOyr 5.5/2.Ck 115 cm< Coarse fragment description: 12% (10%sub—angular gravel, 2% sub—angularcobbles). Texture: Sandy—loam.Structure grade: Moderate. Primarystructure: Medium angular blocky (10-20mm). Moisture consistence: Friable.Colour: Aspect=Matrix dry Hue=5yr5/2.5.Sandy-loam to loamy-sand texture gives this soil highinfiltration rate which makes it suitable for irrigation.Presence of carbonate layer at the depth of 1 in increases thissoil’s capacity to sorb P added through wastewater irrigation.1123.2. Sewage effluent and groundwaterThe sewage effluent used at the study area comes from theCity of Vernon Sewage Treatment Plant. The plant employs bothprimary and secondary treatment. The chemical composition of theeffluent varies from day to day. During the non—vegetativeseason i.e., from mid—October to May , sewage effluent is storedin a lagoon located 7 km south of Vernon. Storing wastewatersignificantly reduces concentrations of N as a result ofdilution, absorption by aquatic plants anddenitrification/volatilisation.3.3 Selection of poplar clonesPoplar saplings established in the Kalamalka nurserycomprised a rich collection of poplar clones collected fromdifferent sources and origins. Those saplings had been irrigatedwith the same wastewater that was supposed to be used in thepilot project. Thus, it was possible to determine the reactionof different clones to wastewater and the local conditions.Field observations showed that the following 14 clones hadbetter performance than the other clones. These clones wereselected for the plantation.113Clones imported from Ontario:NM—i Populus nigra x maxirnowicziiNM-2 P. nigra x rnaxirnowicziiNM—4 P. nigra x maxirnowicziiDTAC-8 P. deltoides x trichocarpaDN-54 P. deltoides x nigraDN-152 P. deltoides x nigraFrom Scott Paper Co. Chilliwack, B.C.1—214 P. euramaricana*Clones imported from Washington State, U.S.A.50—178, 52—234, 53—242, 58—286, 44—132, 44—135, ii.All these clones were of the of P. trichocarpa x deltoides.parentage.3.4 Experimental design and field layoutSince the site was not topographically uniform and a slopegradient existed, the most suitable experimental designselected was randomized complete block design (RCBD) with tworeplicates (Steel and Torrie 1980).Originally, the experimental design incorporated a split-split-plot layout with two blocks (Blk=2 ha, 100 m x 200 meach). In each block two irrigation levels were randomized tothe main plot unit (MPU=l ha, lOOmxlOOm each). Two tree spacingswere randomised to each sub-plot unit (SPU = 0.5 ha, 50 m x 100in). Each poplar clone was planted in a 25 in x 12.5 in = 312.5 in2114area within each sub-sub-plot unit (SSPU). Two remaining SSPU’sin each SPU were planted with a mixture of leftover clones dueto shortage of cuttings. (Figures 3.4 and 3.5).3.5 Calculation of the total number of treesTotal number of trees planted:Each SPU with 1.5 in x 1.5 in spacing contained50 in x 100 in / 1.5 in x 1.5 in = 2222 trees.Each SPU with 2 in x 2 in spacing contained50 x 100 / 2m x 2m = 1250 trees.Total number of trees in wastewater irrigation:(2222 + 1250) 4 = 13888.Due to scarcity of freshwater, field layout of the freshwater(control) blocks was limited to 1.5 in x 1.5 in spacing.Freshwater block = 25 in x 87.5 in = 2187.5 in2 = 0.219 ha.Number of trees per block = 25 in x 87.5 in / 1.5 in x 1.5 in = 972Total number of the control trees = 1944Total No. of trees in the project = 13900 + 1944 = 15844Figure 3.4. Distribution of poplar clones in sub-plotsCl)C)C.)CD331-CCDC)rt(0r’3-1-CCDC)(0U,xI-,U,-‘I-CCD“In-‘C)NM—i DN—152 44—132 58—286NM—2 NM—4 11 50—178115DN—54 .1—214 53—242 52—234DTAC-8 Mix 0. 44-135 -Mix W.Mix 0. DTAC—8 50—178 44—135DN—54 DN—152 Mix W. 53—242NM—2 NM—4 11 58—284NM—i 1—214 44—132 52—234Mix W. 52—234 DTAC—8 1—214ii 50—178 DN—54 Mix 0.4- -44—132 44—135 NM—i DN—15258—286 53—242 NM—2 NM—4.11I,xI-,UI1--i0<1-3UI0<UI1-30<1-3I-’.UIJI-..U)11 53—242 Mix 0. - NM—i58—286 44—135 DTAC—8 DN—1524 —Mix W. 50—178 1—214 DN—5452—234 44—132 NM—4 NM—2IDN—54 1—214 ii 50—178Mix 0 DTAC—8 Mix W 44-1324NM—2 NM—i 52—234 58—286NM—4 DN—152 53—242 44—13552—234 58—286 DN—54 NM—i50—178 53—242 Mix 0. NM—211 Mix W. DN-152 NM-444—132 44—135 DTAC—8 1—214GrassNM—2 DN—54 : 53—242 44—132NM—i 1—214 52—234. 44—135.4 —DTAC—8 Mix o.: 58—286; 50—178NM-4 DN-152 Mix W. iiI 4-11 53—242 DN—152 NM—4Mix W. 52-234 NM-i DTAC-844—135 44—132:. NM—2 . 1—21450—178 58—286; Mix 0. DN—54J IGrass! I — — —z . :c, I-I-Z . !Z . I1 I I I I-.-)1--3 I-’ —‘ 1-.) I; 1.3 ;U1 1.3 .Lfl1-3— ! —; z -. I-I: . z :1-.):i I I 1-.): 1-3 ;l— I—’ 1.i I-’:I- U I...) .1.R 1-3—Z--M.P.U. = Main plot unit 116S.P.U. = Sub plot unitS.S.P.U. = Sub sub plot unit1.1.- . 4. --04 -F ..1. . .I . iS.P.U. -s.S.P.U— — — —1—z-.Figure 3.5. Field Layout of the project site._____j_____ __________1173.6 Establishment of the plantationIn October 1987 grass was killed with 2% Glyphosatesolution then the land was ploughed to the depth of 30-40cm. InMarch 1988, Simazine was applied to the site in order to preventregrowth of the previous vegetation from seed. In May 1988 solidset sprinklers of Nelson F-33 model with a capacity of 19 litres(5 Us gallons) water per hour mounted on 2.5 m tall risers wereinstalled at the site at a spacing of 12 m x 18 m ). “Homemade”suction lysimeters were installed at the centre of each sub—sub-plot (Nutter et al. 1979) to a depth of 80cm. Below thisdepth a layer of gravel and rocks made installation impossible.Soil around the lysimeters was compacted and a layer ofbentonite was applied to prevent leakage of irrigation water tothe base of the suction lysimeters.Unrooted poplar cuttings of 25-30 cm length and 1.5-2.5 cmdiameter were harvested in January 1988 and freezer—stored at—2°C. The cuttings were then soaked in water for 24 hours priorto planting. Planting started in mid-May and lasted one week.Cuttings were planted by hand.3.7. IrrigationTwo wastewater irrigation treatments were applied.Wastewater treatment 1 was determined on the basis of cropwater requirement rate, i.e., local potential evapotranspirationrates. Potential ET rate was calculated using the modified118Penman method (Hansen 1980). This method was selected because ithas made the most complete theoretical approach showing thatpotential evapotranspiration is inseparably connected toincoming energy. The local weather station was near the projectsite, and provided accurate meteorological data required for thecalculation of ET with the Penman model. Mean hourly netradiation and mean hourly global solar radiation were obtainedfrom the meteorological station in Summerland, B.C.The formula estimating the potential evapotranspiration(consumptive use) is as follows in the modified form:EtpAY(Rn+G)1A’4.Y(15.36)(wi+w2)(es_ea) (1)reference crop potential evapotranspiration, well—wateredalfalfa in cal/cm2/day.= slope of saturation vapour pressure—temperature curve in(mbar/°C). For T >-23°C:A=33.86[O.05904(0.00738T4-0.8072)7—0. 3 2] (2)7 = psychrometric constant.= net solar radiation (cal/cm2/day).G = soil heat flux (cal/cm2/day).u2 = wind movement (km/day) at 2 m above ground surface.e1 = saturation vapour pressure, mean of values obtained atdaily maximum and minimum temperatures in mbars.119w1, w2 = wind term coefficientsY=Cpo62AC = 0.240.P=1013—0.1055EL (4)P = atmospheric pressure at a given elevation (mbar).EL = elevation (m).= latent heat of water (cal/g).A=595—o.55T (5)T = mean air temperature (°C)Rfl=0.77R$Rb (6)= incident (incoming) solar radiation (cal/cm2/day).Rb = outgoing solar radiation (cal/cm2/day).The 0.77 value is obtained by assuming a reflectivity of0.23 for a green growing crop.120a.R(7)where:Rb=(al+bl/)11.71x1O8TfT)(8)a, b, a1 and b1 = constants (see Table 3.2)R = net outgoing solar radiation (cal/day).R, = clear day solar radiation (cal/day). If actualrecords are not available, R80 values may be estimated fromthe table of total daily solar radiation at the top ofatmosphere.Rs=KT.RA. 1/2 (9)R = global solar radiation (cal/day).RA = extraterrestrial radiation (cal/day).TD = temperature difference (TxTmm) (°C).KT = calibration coefficientR5(10)121S = percent of possible sunshine.ea = mean actual vapour pressure (mbar).ea=33.8639[(O.00738T+O.8072)—O.000019(1.8T+48)+O.001316).(11Ta = maximum daily temperature (°K)Tb = minimum daily temperature in (°K)T = mean temperature = (T + Tj/2An empirical equation for estimating the soil heat flux is:G9.1(7,r) (12)Tpr = mean air temperature for previous 3 days when dailyestimates of E, are required.T = mean air temperature for the current time period, i.e.mean air temperature of the particular day for which E.g, isrequired.Estimate of the wind movement at 2 in when the anemometer is ata height Z:u2=u(.)0.2 (13)u= wind movement at height Z (km/day)Z = height of anemometer above ground (in).122E (cal/cm2/d y.i0)E(mm/day)=A(ca1/g)(14)Estimates of actual crop consumptive use are calculated fromby use of a crop coefficient which relates growth stage back tothe reference crop.ET=k0*E (15)ET = estimated crop consumptive use (mm/day).K0= crop coefficient from Hansen (1980).Table 3.2 Constants used in modified Penman method forcalculation of ETp in Vernon, B.C.KT 0.16 for Seattle and TacomaEL 520 m elevation of Vernon B.C.a 1.15 for semi—arid regionsb —0.15 ,, , ,a1 0.39 ,, ,,b1 —0.05 , , , , , ,0.75w2 0.01151.0123Table 3.3 Calculation of ET in Vernon B.C. using Modified Penman MethodMay Jun. Jul. Aug. Sep. Oct.T (°C) 12.80 16.80 20.00 19.30 14.20 7.90T (°C) 18.90 22.80 27.00 25.80 19.80 11.90T, (°C) 6.70 10.80 13.00 12.80 8.60 3.70TD (°C) 12.20 12.00 14.00 13.00 11.20 8.20T (°K) 291.90 295.80 300.00 298.80 292.80 284.90Tb (°K) 279.70 283.80 286.00 285.80 281.60 276.70RA1 (cal/day) 15.78 17.08 16.38 14.05 10.83 7.31R2 (cal/day) 519.31 556.10 574.69 475.42 341.61 198.48S3 (%) 51.00 51.00 64.00 62.00 54.00 39.00(cal/day) 727.18 778.70 718.37 603.78 468.87 317.81e (mbar) 21.83 27.75 35.64 33.20 23.09 13.94e (mbar) 9.83 12.86 14.99 14.79 11.19 7.97e (mbar) 14.79 19.14 23.38 22.39 16.20 10.67e8 (mbar) 15.83 20.36 25.31 24.00 17.14 10.96e1—e 1.04 1.22 1.93 1.61 0.94 0.29R, (cal/cm2/day) 154.87 141.82 128.37 131.53 150.71 165.25Rb (cal/cm/day) 103.96 95.20 98.84 99.37 103.67 93.89Rb(cal/cm2/day) 295.91 333.00 343.67 266.70 159.37 58.94u13 (km/day) 316.8 326.40 288.00 270.00 259.20 256.80u2 (km/day) 217.87 224.44 198.06 189.81 178.26 176.61w1+w2u 3.26 3.33 3.03 2.93 2.80 2.78(mbar/°C) 0.97 1.19 1.42 1.35 1.04 0.75X (cal/g) 588.81 586.83 585.09 585.56 588.12 591.207 — 0.63 0.63 0.63 0.63 0.63 0.63Etp (cal/day) 195.18 233.31 264.19 214.80 122.84 31.74Etp (mm/day) 3.31 3.98 4.52 3.68 2.09 0.54Etp (mm/zonth) 102.76 119.27 139.97 113.72 62.66 8.05‘. Doorenbos and Pruitt (1977).2 Samani and Pessarakli (1986).. Chilton (1981)124In this research the value of the crop coefficient (I() wasassummed to be 1.0. Based on the ET data and mean monthlyprecipitation values, mean monthly irrigation rates fortreatment 1 (wastewater irrigation) and control (freshwaterirrigation) were determined. An additional 10%ET and 20%ET ofthe irrigation rate were added as leaching requirement (LR)(Oster and Roades 1988) and application efficiency (En) for solidset sprinklers (Smith et al. 1988), respectively. Treatment 2(wastewater irrigation) was chosen to be two times treatment 1in 1989 and 1990, for the facility of calculations (Table 3.4).Table 3.4 Calculation of mean monthly irrigation rates fortreatment 1 and control.Months ET Precipi- Net ET 1+LR/100 100/Eu Treatment 1tation andControl(a) (b) (c=a—b) (d) (e) (f=c x d x e)(mm) (mm) (mm) (mm)May 105.40 31.60 73.80 1.10 1.25 101.48Jun. 136.80 33.10 103.70 1.10 1.25 142.59Jul. 141.36 25.60 115.80 1.10 1.25 159.23Aug. 108.50 33.10 75.80 1.10 1.25 104.23Sep. 58.50 27.20 31.30 1.10 1.25 43.04Oct. 9.30 23.80 0.00 — — 0.00Total 599.86 174.40 399.96 — — 550.13b. After Environment canada 1984LR. Leaching requirement = 10%Eu. Unit application efficiency for distribution system = 80%for solid set sprinkler system (Smith et al. 1988).125A class ‘A’ Evaporation Pan (model EL-506, height=25.4 cm,diameter=122 cm) was installed at the site in order to comparethe calculated potential ET values with those of the pan.Evaporation values were measured on a daily basis. On rainy daysprecipitation values were either directly read from a rain gaugeinstalled at the site or were obtained from a weather stationlocated nearby. Precipitation values were subtracted from dailywater level readings of the pan.3.8 TendingIntensive weeding throughout the first growing seasons wascarried out in order to increase survival and growth of therooted cuttings (trees).At the beginning of the second growing season plots whichhad the highest mortality rate were replanted with rootedcuttings obtained from Kalamalka Forestry Centre.3.9 Sampling and field measurementsDuring the project period, soils plant biomass, groundwaterand wastewater were sampled and analyzed for some of theirchemical components. Nondestructive sampling was carried out todetermine tree height and diameter.3.9.1. Soils samplingSoil samples were collected from sampling points which werelocated randomly within each SSPU at the end of each growing126season. Care was taken to avoid placing the sampling point in anatural depression, within 60 cm of a tree or in an area wherevegetation might prevent effluent from reaching the ground.Pits were excavated with a shovel and soil was sampled from fourcorners of the pits from two depths of 0-30 cm and 30—60 cm. Determination of infiltration ratesInfiltration rate of the soil was determined with a double-ring infiltrometer. The purpose of this test was to determinethe maximum amount of effluent that could be applied in oneapplication with no surface runoff. Steel cylinders werecarefully pushed into the soil to depth of about 10 cm. Lateralflow of water was minimized by means of the ‘buffer’ zoneprovided by the outer ring. Cylinders were filled with water andthe decrease in water level inside the inner cylinder wasmeasured at half minute intervals until the infiltration ratedecreased with time and approached a steady—state value.3.9.2 Water and wastewater samplingContainers where water or wastewater samples werecollected were treated with a few drops of toluene to suppressmicrobial activities. Wastewater was sampled on a weekly basisstarting from the beginning of May up to the end of September ormid—October of each year 1988—1990. Wastewater samples wereimmediately sent to the U.B.C. Soils Department Laboratory foranalyses.127Percolate water from suction lysimeters was collected atintervals of 2 or 3 weeks during each growing season. Suction of80 centibars was applied to lysimeters. After 24 hours water waspumped from the lysimeters into containers. The containers weresent to the laboratory for analyses. Chemical analysis of thepercolate water provided data covering leaching of the nutrientsfrom the experimental site.3.9.3 Plant samplingAt the end of the first growing season (Oct. 1988) 10% ofthe trees were selected randomly for measurement of height,diameter at breast height (dbh) and basal diameter (bd). Thesevariables were measured on each of the selected trees at the endof each of the three growing seasons; 1988,1989 and 1990.Height was measured with a direct-reading height pole. Basaldiameter was measured with callipers.From each SSPU one tree was selected randomly and was cutfrom its base at the end of each of three growing seasons.Height and bd of each tree was measured. Leaves were separatedfrom the woody parts and were stored for further measurements.Tree trunks and branches were cut into pieces and were stored.At the same time ground vegetation was sampled at each SSPU andgrass was cut from 1 in x 1 m quadrats established in grassplots. Leaf area was measured with a LICOR Conveyer Belt AreaMeter (Model LI 3100).128Tree parts and ground vegetation and grass were dried in adryer at 75°C until no loss of weight was observed in selectedsamples. All samples were weighed with an electric balance.3.1.0 Laboratory analyses of soilsSoil samples were prepared for determination of certainchemical properties such as Total—N, plant available P, K, Ca,Mg, Mn, Mo, Cu, Fe, Zn, Na, electro—conductivity, total carbonand organic matter and pH.Some physical properties of the soils, such as infiltrationrate and bulk density were calculated.Soil samples were air—dried at room temperature (20°C) untilno loss of weight was observed in selected pre—weighed samples.The soil samples were crushed by hand and were sieved througha 2.0—mm stainless steel mesh sieve. The remaining gravel wasweighed and discarded.Soil pH was measured in water and in 0.01 M Cad2, using aglass electrode pH meter. For this purpose 10 ml of distilledwater or Cad2 was added to 10 g of soil suspension, stirredseveral times, and left for an hour.The hydrometer method (Lavkulich 1981) was used todetermine particle size of the soils.Bulk density of the soils was determined by excavatinglumps of soil weighing approximately 1.0—1.5 kg. These soillumps were placed in soft plastic bags. Air was pumped out ofthe bags. The samples were immersed in a volumetric container129filled with water. Volume of the lumps was measured from thevolume of displaced water. Later the lumps were dried in a dryerat 105°C and weighed. Bulk density was determined by division ofdry weight by the volume of each lump.Total carbon concentration of the soils was determined byCombustion CO2 Analyzer (Leco). Organic matter concentration wascalculated by multiplying total carbon values by the factor1.724 (Jackson 1958).Total N was determined using semi-micro Kjeldahl digestionfollowed by colorimetric determination using the Autoanalyzer(Lavkulich 1981).Plant available P, K, Ca, Mg, Na, Al, Mn, Zn, Cu, and Fewere extracted using the Mehlich #3 soil test extractant(Mehlich 1984).All nutrients except P were analyzed by Flame AtomicAbsorption (Perkin Elmer Model #3026). Phosphorus concentrationwas measured by Gilford Transmission Spectrophotometer at 660nanometres.Phosphorus sorption test was carried out to obtain data forplotting P sorption isotherms in order to predict capacity ofthe soils to hold P added by application of sewage effluent. Forthis purpose a procedure suggested by Fox and Kamprath (1970)was applied. Three-gram samples of soil were placed in 50 mlErlenmeyer flasks; 30 mL of 0.O1M Cad2 containing differentamounts of P as Ca(H2P04) (2,5,10,15,30,60 and 90 mg/L) wasadded per flask. Two drops of toluene were added per sample.130Samples were shaken in a reciprocal shaker for a 30—minuteperiod twice daily for six days at room temperature. Aftercentrifugation in a super—speed centrifuge, P was determined inthe supernatant with Gilford Transmission Spectrophotometer at660 nanometres. Phosphorus which disappeared from solution wasconsidered to have been sorbed.Concentrations of the remaining P in each flask(equilibrium solution) were plotted against concentration ofsorbed P.3.11. Laboratory analyses of waterColorimetric method was applied for determination ofnitrate/nitrite and ammonium contents of water samples.Total N was determined using semi-micro Kjeldahl digestion.followed by colorimetric determination using Autoanalyzer(Lavkulich 1981).Concentrations of soluble P, K, Ca, Na, Mg, Mn, Zn, Cu, andFe, were determined directly by ICP after a few drops of nitricacid was added to the samples.Water pH was measured, using a glass electrode pH meter.3.12 Laboratory analyses of plants and measurementsIn 1988/89 whole dried wood samples were crushed manuallyto an approximate size of 2 x 2 x 2 cm then ground in a StandardModel Wiley Mill (Arthur H. Thomas Co., Philadelphia, Pa.).Later, the same samples were ground with a smaller Wiley Millusing a No.60 mesh (Jackson 1958).131In 1990 due to the large volume of wood, 3—cm thick sliceswere taken every 30 cm along each tree trunk. These wood sliceswere treated with the same procedure mentioned above.Dried leaf and ground vegetation were ground in a Wileymill and sieved through No.60 mesh.The wet digestion method of Parkinson and Allen (1975) wasused for the determination of total N, P, K, Ca, Mg, Na, Mn, Zn,Cu, and Fe in plant tissue. N was measured by colorimetricanalysis (phenol-hypochlorite method) by the TechniconAutoanalyzer II. The elements P, K, Ca, Mg, Mn, Zn, Cu, and Fewere measured using inductively coupled plasma emissionspectroscopy (ICP Jarrell Ash Atom Comp Series 1100) on theoriginal digests.3.13. Statistical analyses and graphicsAll the data were summarized using the Statistical AnalysisSystem (SAS) programme (version 6.03) PROC MEANS (Goodnight1979). The general linear model procedure (PROC GLM) was used totest the relation between the dependent variable (nutrientcontent, tree height and weight, etc.) and the independentvariable (treatment) for each component (soils, percolates,etc.). Tests for significant differences between sample meanswere conducted using the SAS version of Duncan’s multiple rangetest. The level of significance was fixed at 1% and 5% for alltests.systat/Sygraph statistical package (version 5.3.) was usedto draw histograms, graphs and regression curves.1323.14 Foliar diagnosis systemTo facilitate interpretation, changes in leaf weight,concentration and content are displayed in a single graph foreach element by the technique first employed by Krauss (1965)and later by Heinsdorf (1967), Weetman (1971), Weetman and Algar(1974), TilTuner (1979) and Timxner and Teng (1990). By plottingfoliar concentration of a given element on the y—axis andabsolute content per unit leaf on the x—axis the series ofdiagonal lines from the origin represents unit increases inneedle weight (Figure 3.6). Given data from control (0 symbolin Figure 3.6) and treated plots, for example, any pointsfalling in the sectors above or below the dotted line indicatea loss or gain, respectively, in leaf dry weight in comparisonto the control. The direction and magnitude of the resultingchanges in all three parameters can be described by a singlearrow (Figure 3.7.) which forms the basis of the followingfoliar diagnostic system.UNIT NEEDLE WEIGHT, mg/needleResponse inDirection Needle Nutrient Possibleof Shift weight Conc. Content interpretation DiagnosisA + - + Dilution Non-limitingB + 0 + Sufficiency Non-limitingC + + + Deficiency LimitingD 0 + + Luxury consumption Non-toxicE - ++ ± Excess ToxicF — - - Excess AntagonisticFigure 3.7. Directional relationships between foliarconcentration and absolute content of an elementfollowing treatment such as fertilization.z0133Figure 3.6. Schematic relationship between concentration andabsolute content of leaves. The area within the enclosedrectangle is examined in figure 3.7.(After Timmer 1979).Elementconcentration(% dry weight)134A shift towards A (arrow in Figure 37) signifiesdecreasing concentration but increasing leaf weight and content;hence, the supply of the nutrient has been diluted byadditional growth (false antagonism), suggesting that thespecific nutrient is not the major limiting nutrient, unlessassociated with the “Steenbjerg effect” (1954). The boundarycase is represented by an outward horizontal shift (B), wherebyweight and content increase without change in concentration.This horizontal shift may be analogous to Macy’s (1936)“minimum percentage” (Figures. 2.3 and 2.4) range resulting fromnutrient transport into the foliage just sufficient to keeppace with shoot or leaf expansion or redistribution within theplant. In contrast to A, an outward shift towards C denotesincreases in both nutrient concentration and leaf weight. Foran added nutrient, this implies that the initial level waslimiting, and the sector between radii B and D would correspondto Macy’s (1936) “poverty adjustment” zone (Figures 2.3—2.4).For non—added elements, it would illustrate a synergistic effectof the ion applied (Smith 1962).Movement towards D, resulting from increased accumulationwithout any gain in leaf weight, may be interpreted as luxuryconsumption (Figs. 2.3 and 2.4) by the foliage sampled. Movementin the direction E results from a concentration increasecombined with reduced leaf weight. This is a strong indicationof toxic accumulation (Figs. 2.3 and 2.4), unless associatedwith some other growth constraint. A shift towards F, in reversedirection to C, involving depression of both nutrient135composition and dry weight in needles would signify deficiencyinduced by treatment, or true antagonism (Cain 1959). It mayalso describe the nutrient drain imposed by heavy fruitingtriggered by fertilizer application or transfer of storedelements to shoots before senescence in deciduous tress.3.15 Determination of leaf weight units in figures 3.6and 3.7Assume you know leaf concentration in per cent and unitleaf dry weight in mg.—Slope of line for unit needle dry weight:1. To obtain the 1st point:multiply 2.5% (concentration) x 3 mg (needleweight) = 0.025 x 3 ing x 1000 ug / 1 mg= 75 ug foliar content.follow dashed lines in ink. Plot point intersectedby 2.5 % and 75 ug. This is 3 mg.2. To obtain 2nd point:multiply 2.0% (concentration) x 3 mg= 0.02 x 3 mg x 1000 ugh mg= 60 ug foliar content.Plot point intercepted by 2.0% and 60 ug.This is 3 mg.Connect the two points and extend lines as far as needed ongraph. Note the slope for each line is different. After you havecalculated each line for unit needle dry weight, then plot yourdata.1364. Results and DiscussionThe objectives of this study are to test the hypothesisoutlined in the Introduction by:1. Determining which of two wastewater irrigation levels can beused for the first three year period in the duration of thehybrid poplar plantation so that groundwater contamination isminimal.2. Determining uptake rates of macro— and micro—nutrients (N, P,K, Ca, Mg, Mn, Zn, Cu, Fe) and Na by tree foliage and woodybiomass.3. Determining how much of the nutrients added by wastewaterirrigation is a) leached down to groundwater, and b) retainedby the soil-plant system (i.e., the “living filter”).4. Determining the effects of wastewater irrigation on theconcentration of particular nutrients in soil solution and insoil.5. Determining the effect of wastewater irrigation on biomassproduction and growth of the poplars.6. Determining the nutritional status of the poplars during thethree—year period.137In this research, data was collected from subplots of 1.5m x1.5m tree spacing only. The effect of tree spacing on biomassproduction is beyond the scope of this research.4.1 Chemical quality and application rates of wastewater, andnutrient inputIn this section the chemical quality of the wastewater usedfor irrigating the poplar plantation, the amount of water applied,and the amount of nutrient input to each treatment are discussed.The mean concentrations of inorganic constituents and relatedcharacteristics of wastewater used for irrigation at the plantationare shown in Table 4.1.The ammonium, nitrate, and total N concentrations in thiswastewater exhibited annual periodicities. These fluctuationscoincided with the periods of highest rainfall in the region andmay be attributed to primary dilution by rainwater.The intent was to irrigate control and treatment 1 withmonthly ET plus 10% for leaching and 20% for applicationefficiency, (Table 3.4) and for treatment 2 and grass plantationto apply twice that amount. Variations in actual application rateoccurred because of occasional rainy days when no irrigation wasapplied or some extremely dry days when some additional water wasadded to daily irrigation amounts. High amounts of water andwastewater were applied during the first two months ofestablishment in 1988 to encourage sprouting and growing of thecuttings (Table 4.2). It was not possible to keep the proportion oftreatment 2 to treatment 1 at exactly 2 because of occasional138Table 4.1 Some properties of the applied municipalwastewater and freshwater’Wastewate Mi.ricipaL RecoendedFresh- maxim.in1988 1989 1990 water2 concentrationfor irrigation3pH - 6.9 10.2 2 7.5 [0.2) 7.7 [0.2) 7.7 6.5 8.5E.C. (dS/m) 0.73 [0.03] 0.81 [0.03] 0.82 [0.05) 0.40 0.70 - 3.0BOO (wçft) 10.0 [1.9) 10.8 [1.4] 11.4 [2.9]TDS4 (rag,’L) 469.0 [23] 520.0 [21] 524.0 [29] 248 450 - 2O0OSS° (mg/L) 6.4 [5.6) 5.9 [3.6) 8.4 [9.0] - <50NH4-N (mg/L) 4.0 [2.1] 4.3 [2.0) 4.7 [2.6] <5N03-N (mg/L) 5.5 [2.3] 6.0 [1.8) 6.3 [3.2] 0.07 <5TOTAL-N (ir/t) 12.00 [5.3) 13.4 [7.6] 13.15 (4.2) 0.1 5 - 30ORTHO-P (w/L) 5.9 [1.0] 6.6 [0.7] 6.50 [1.6) - -TOTAL-P (/L) 6.2 [2.2) 7.2 [1.0) 6.7 [3.9) 0.03 -K (e/L) 17.4 [4.2) 18.6 [3.7] 20.1 [5.7) 4.6Ca (/L) 43.2 [9.1) 48.8 [6.1] 47.1 [14.1) 29.6 0 - 4008Mg (/L) 18.4 [3.3] 198 14.5] 21.0 [2.9] 17.8 0 - 60°Na (/L) 68.8 [13.2) 70.0 [13.1] 82.9 (16.3) 14.9 0 - 9008Cu (mg/L) 0.04 [0.0] 0.03 [D.01] 0.06 [0.01) 0.20Fe (a/L) 0.09 [0.02) 0.07 [0.02) 0.14 [0.1) 0.04 5.0Mn (/L) 0.03 [0.01) 0.04 [0.01] 0.04 [0.02) <0.01 0.2Zn (mg/L) 0.05 [0.02] 0.05 [0.01] 0.07 [0.01) 2.0No (mgft) 0.00310.00) 0.03310.00) 0.003(0.0006) 0.01B (./L) 0.15 [0.04] 0.13 [0.05] 0.20 [0.04) 0.7AL (./L) 0.04 [0.07) 0.04 [0.03) 0.06 [0.13) 5.0As (.‘IL) 0.01 [0.01] 0.01 [0.00) 0.01 [0.01) <0.01 0.1Pb (/L) 0.01 [0.0) 0.01 [0.0) 0.01 [0.0) 0.003 5.0Cd (wç/L) <0.00110.0] <0.001(0.0) ‘0.00110.0) 0.01WI (icIL) <0.001 <0.001 <0.001 0.2SAR° 2.2 2.1 2.6 0.6 <6.0. VaLues are means of 23 determinations, with standard deviations in brackets.2 VaLues were obtained froni the City of Vernon.. After Westcot and Ayers 1988.. TDS totaL dissoLved soLids.8 ss g suspended soLids.. BAR = Sodius adsorption rate.‘. SLight to moderate degree of restriction on use.‘. UsuaL range in irrigation water.139waterlogging problems in certain locations in treatment 2. Theproportions from 1988 through 1990 were 1.27, 1.74 and 1.85.Wastewater was applied for three growing seasons starting onMay 1st and ending on mid-October of each year from 1988 to 1990.Table 4.2 Annual (growing season) application of wastewaterand freshwater irrigation to irrigation plotsYear1988 1989 1990 Total(mm)Control1 598 401 514 1513Treatment 1 598 401 514 1513Treatment 22 762 698 952 2412. Control plots were irrigated with freshwater.2• Grass plots were treated similarly.The effluent irrigation provided substantial amounts of macronutrients to the soil-plant system (Table 4.3).There were significant variations in nutrient composition frommonth to month. They were primarily caused by changes in effluentquality and nutrient concentrations at the treatment plant and byvariations in the irrigation schedule.140Table 4.3 Annual (growing season) input of some nutrientsto wastewater irrigation (kg/ha)Nutrient Irrigation1988 1989 1990Treatment1 2 1 2 1 2NH4—N 24.0 31.0 17.0 30.0 24.0 44.5N03—N 33.0 42.0 24.3 42.0 32.0 60.0TOTAL—N 72.0 91.0 54.0 94.0 68.0 125.0ORTHO—P 35.0 45.0 27.0 46.0 33.0 62.0TOTAL—P 37.0 47.5 29.0 50.0 34.0 64.0K 104.0 133.0 75.0 135.0 103.0 191.0Ca 258.0 329.0 196.0 341.0 243.0 449.0Mg 110.0 140.0 80.0 139.0 108.0 200.0Na 412.0 524.0 281.0 489.0 426.0 789.0Cu 0.24 0.30 0.12 0.21 0.31 0.57Fe 0.54 0.68 0.28 0.49 0.72 1.33Mn 0.18 0.23 0.16 0.28 0.20 0.38Zn 0.30 0.40 0.20 0.35 0.36 0.66141.4.2 Nutrient losses to percolationRenovation and retention capabilities of each test plot arebest determined by comparing total nutrient application (input)with leaching losses. Leaching losses were determined by analyzingsoil—solution samples collected from suction lysimeters at a depthof 75 cm in treatment plots.Results of the regression analysis of nutrient inputs(nutrient contents in wastewater) and outputs (nutrientconcentration in soil—solution) are presented in Table 4.4.When the result of regression analysis was not significant,nutrient input rates did not affect its concentration in soilsolution, i.e., the nutrient either had been taken up by theplants or had been immobilized by the soil. On the other hand, whenthe result of the analysis was significant, effect of nutrientinput on its concentration in soil solution was significant, i.e.,a part of the nutrient added through wastewater irrigation had beenleached to the depth of 75 cm where the lysimeter is installed.4.3 Volume of soil solution and percolateTo obtain the total amount of nutrient in soil solutionpassing through the 75—cm depth, where the suction lysimeters wereinstalled, we needed total volume of water which passed throughthat depth. For this purpose, total potential evapotranspirationduring each growing season (Appendix A) was subtracted from the sumof irrigation water and precipitation during that period (Table4.5). Multiplying this volume of water by concentration of eachelement in soil—solution gives total quantities of unretainednutrients.142Table 4.4 Results of regression analysis between nutrientinputs and outputs (Jul. 1988 — Sep. 1990)p R2Nutrient Treatment1 2 1 2N03—N 0.01 0.05 0.78 0.35NH4—N 0.60 0.88 0.03 0.00Total—N 0.01 0.05 0.76 0.34Total—P 0.50 0.05 0.06 0.33K 0.01 0.05 0.56 0.37Ca 0.90 0.60 0.00 0.03Mg 0.03 0.70 0.40 0.01Na 0.30 0.82 0.10 0.01Mn 0.40 0.35 0.06 0.1Zn 0.08 0.40 0.30 0.06Cu 0.50 0.90 0.05 0.01Fe 0.13 0.30 0.20 0.11143Table 4.5 Calculation of volume of soil solution passingthrough the 75cm depth of soil from May 1to Oct. 15Year and Precipi— Irriga— Evapotrans— Estimatedtreatment tation tion piration volumeof soilsolution[a) [bJ [c) [d=a+b—c)(m3/ha)Control1988 2090 5984 5460 26141989 2100 4012 5530 5841990 2410 5144 5380 2174Treat. 11988 2090 5984 5460 26141989 2100 4012 5530 5841990 2410 5144 5380 2174Treat.21988 2090 7617 5460 42471989 2100 6982 5530 35521990 2410 9519 5380 65491444.4 Effect of wastewater irrigation on soilsThe research site was under wastewater irrigated grassplantation for seven years prior to this research. Irrigation rateof the grass plantation was about 61 cm (24 in) per growing seasonwhich most likely affected the original properties of the soilthrough addition of different nutrients and other chemicalsubstances to the soil. Estimated macro— and micronutrient inputrates during seven years of wastewater irrigation and some chemicalcharacteristics of the soil at the beginning of the project arepresented in Table 4.6. Some physical properties of the soils areshown in Table 4.7.It was calculated that soil infiltration rate was 10.80nun/hour (Figure 4.1). This value was 69% higher than the capacityof sprinklers to supply wastewater to the site (i.e., 6.4 nun/hr.)However some precautions were taken in timing of irrigation. Thesite was irrigated at discrete intervals during the day dependingon irrigation level. No surface runoff was observed during thewhole project period.To study the effects of wastewater on nutrient concentrationsof the soils, analysis of variance was carried out for eachirrigation treatment separately.The quantity of micronutrients added to soils by means ofwastewater irrigation is generally low. At pH 7-7.5 mobility ofmicronutrients in soil is low and addition in small quantities ofthese elements for three years would not have a significant effecton their concentration in soil. Richenderfer et al. (1976) observedsome significant increases in soil micronutrients after irrigatinga hardwood forest with wastewater for 10 years.145Values are means of 65 determinations, with standarddeviations in brackets.Cation exchange capacity.Table 4.6 Baseline data for nutrient concentrations in twodifferent layers of soil’and added nutrientsthrough 7 years of wastewater irrigationAddedSoil depth (cm) nutrientsthroughwastewater0-30 30-60 irrigation(kg/ha)pH 7.1(0.2) 7.2(0.3) —CEC (meg/bOg) 13.7(3.8) 9.8(3.7) —EC (nunhos/cxn) 0.44(0.24) 0.41(0.22) —Total—N (g/kg) 1.5(0.4] 1.0(0.5) 550P (mg/kg) 111.4(32.6] 63.6(21.3] 285K ,, 296(92.9] 250(60.1] 810Ca ,, 2389(978] 2494(1382) 1960Mg ,, 252(59.9] 192(110) 853Mn ,, 67.5(13) 46.5(20) 2.0Zn ,, 4.30(2.9) 2.1(1.3] 2.5Cu ,, 3.3(1.0] 2.9(1.1] 2.0Fe ,, 178(59] 132(45) 4.5Mo ,, <0.001 <0.001 —Na ,, 128(55) 120(46] 3158Al ,, 706(77) 671(98) 50Cd ,, 0.03(0.003) 0.02(0.004] 1.0Ni ,, 0.091(0.03) 0.14(0.01] 1.0Pb ,, 1.56(0.8) 0.45(.05] —Cr ,, <0.0001 <0.0001 —As ,, <0.0001 <0.0001 —1.CEC.EC. Electroconductivity146Table 4.7 Some physical characteristics of the project soilsSoil depth (cm)0—15 15—30 30—60Particle size (% by volume)More than 25 mm 3.50 3.50 20.002 to 26 mm 17.50 17.67 20.82Prtic1 size (% by weight in the < 2 rim fraction)Sand 66.90 67.60 70.95Silt 16.10 22.80 19.25Clay 17.00 9.60 9.80_______Sandy loam Sandy loam Sandy loam___ ______1.33 1.33 1.64___ __13.28 13.28 —1• Percentage by dry weight of the whole soil.Texture:Bulk density (g/cm3)Field capacity: (%)134730 I IC?100 I0 20 40 60 80 100Elapsed time (mm.)Figure 4.1. Infiltration test results (mean of 20 samples).1484.4.1 Soil pHSoil pH in the 0—30 cm and 30-60 cm layers of soil did notchange with time (p>0.05) in control and treatment 1. In treatment2 it increased from 1988 to 1990 (p<0.05) (Table 4.8).4.4.2 Soil organic matter (0.14.)Organic matter concentration in soil did not change from yearto year in control, treatments 1 and 2 (Table 4.8).4.4.3 Soil C/N ratioSoil C/N ratio did not change during the three years of thestudy (Table 4.8). However there was a trend toward increase in alltreatments in the 0—30cm and 30—60cm layers of soil.4.5 Effect of wastewater irrigation on poplar growthFourteen different clones were planted in separate sub—plots.The rationale behind the selection of different poplar clones andorigins was twofold: 1)to avoid the risks of monoculture, and 2) tostudy the performance of different clones under wastewaterirrigation. By selection of fast growing clones with high foliarand woody biomass production it is possible to increase waterconsumption and nutrient uptake rates by a tree plantation andthus raise efficiency of the plantation as a living filter.At the end of each growing season two trees were selectedrandomly from each sub—plot and cut for measurements of woodybiomass, foliar biomass, total height, diameter at breast height(dbh) and basal diameter (bd).149Table 4.8 changes in soil pH, Organic Matter (O.M.),and C/N ratio resulting from irrigationtreatmentspH O.I4.(%) C/NSoil depth (cm)0—30 30—60 0—30 30—60 0—30 30—60Control1988 7.1[.1) 7.2[.1J 3.4[.8] 2.2(1] 12(1.4] 13(4.0)1989 7.1[.1] 7.6(.4) 3.3(1) 2.3(1) 13(3.0] 15(4.5]1990 7.2[.2] 7.4[.4) 2.8[.6) 1.7(.5) 13(3.0) 13(2.0]Treat.11988 7.3[.3) 7.2[.4] 3.1[.5] 2.3[.5] 10[2.5] 15(2.0)1989 7.4[.2) 7.4[.4] 2.9(1] 2.0[.5] 12(3.0] 15(5.0)1990 7.6[.3) 7.6[.S] 2.6[.7] 1.6[.4) 12[3.0) 14[3.5]Treat.21988 7.0(0.1] 7.0[.1) 3.6(1] 2.0[.5] 14(2.0 13[1.0]1989 7.2(0.2) 7.3[.2) 3.1[1] 1.9[.8) 14(3.0) 15(5.0]1990 7.0(0.2) 7.0[.2) 2.6[.5] 1.9[.6] 16(3.0) 15(4.5)‘. Values in the brackets are standard deviations.150These data were used in a stepwise elimination technique todetermine the most significant regression equations for estimationof woody and foliar biomass from tree height, dbh and bd for eachirrigation treatment (Table 4.9). These equations were used tocalculate wood and leaf biomass of the 10% of the plantation whichwas sampled undestructively for measurements of tree height, dbhand bd, at the end of each growing season. This procedure increasedthe precision of the estimation of wood and leaf biomassproduction of the whole plantation. During the first growing seasonsome young trees were killed by excessive application of Simazinein some areas, while in other areas its insufficient applicationresulted in sudden flush of weeds which suppressed growth of youngtrees. Close spacing of the trees and steep slope of the sitediscouraged use of any mechanical means to remove the grass. As aresult, mortality of the trees reached a high level. In the secondyear (1989) some plots were replanted. In 1990 rodents girdled thebase of some trees. Later, these damaged trees were broken by wind.At the end of the third year 35% of the whole plantation survived.Clones 58—286 and NM—2 were excluded from the research becausemost of the mortality caused by the rodents was localized in thesub—plots where these clones were planted (Photo 4.1). Generally,tree mortality happened in patches. Spacings of the surviving treeswere not seriously affected, therefore it was possible to calculatepotential biomass production of the whole plantation, i.e., biomassproduction under no mortality conditions (Photo 4.2). Out of theremaining 12 clones five were selected and were studied for theirgrowth response to different wastewater irrigation treatments.These clones were: 52—234, 44—135, DN—152, 1—214 and NM—2.151:‘‘‘a- - V.—VPhoto 4.1. Damage caused by rodents.f__ c-:!_LI/ : ,—It_*•_ •;:p —— % .:.-.-Ha-A:----- -Photo 4.2. A bird’s-eye-view of the project site. Thenarrow strip at the left side of the picture is thecontrol, separated with a grass strip from treatment 1.r152Table 4.9 Regression equations for estimation of wood bioniass(Wb), leaf biomass (Lb) and total leaf area (TLA)p2 C.V. OF p Regression EquationWoody biomass (g)ControL:1988 0.82 9.52 9 0.0003 WB 3.74 • 12.47bd1989/90 0.97 15.52 19 0.0001 WB = -261.18 + 0.OlHt2Treatment 1:1988 0.95 16.74 23 0.0001 WB = -6.61 + 23.49bd1989/90 0.91 29.88 79 0.0001 biB = -1174 + 799.lódbh2 + o.Oo4Ht2Treatment 2:1988 0.86 26.98 20 0.0001 biB = 79.89 + 0.002Ht2 - 147.45bd + 58.70bd21989/90 0.93 25.82 77 0.0001 biB 259.61 • 162.29dbhLeaf biomass (g)Cant rot:1988 0.76 27.91 9 0.0010 LB = -17.80 + 51.83bd21989/90 0.89 23.27 19 0.0001 LB = 161.45 + 41.81h2Treatment 1:1988 0.89 22.20 20 0.0001 LB = -49.28 + 80.59bd2 - 0.OOlHt21989/90 0.81 37.73 76 0.0001 LB = -235.54 + 293.94dbhTreatment 2:1988 035 31.4 21 0.0001 LB = 157.38 • 104.49bd2 - 233.Slbd1989/90 0.85 34.28 75 0.0001 LB = -283.12 + 374.T9dbli - D.008Ht2TotaL Leaf area Cm2):ControL:1988 0.82 15.95 9 0.0003 TLA = -136.43 + 0.34Ht21989/90 0.91 21.36 19 0.0001 TLA = 5012.03 + 0.32Ht2Treatment 1:1988 0.83 26.19 22 0.0001 TLA = -5287.21 • 8634.92bd - 726.28bd1989/90 0.84 32.95 75 0.0001 TLA = -29114.06 • 35725.2ldbh - 433.6&k*2Treatment 2:1988 0.84 22.82 23 0.0001 TLA = 7398.63 + 5792.29bc1 - 10407.89bd1989/90 0.81 34.68 75 0.0001 TLA = 3288.33 • 49617.9lthi - 176.2OHtHt = height (cm); dbh = diameter at breast height (cm);bd = basal diameter (cm)153Despite the fact that the site was under wastewater irrigationfor seven years before the project started (Jackson 1989) and thesoil was quite fertile, at the end of the first growing seasonheight, basal diameter, foliar biomass, woody biomass, and totalleaf area showed a positive response to wastewater irrigation(Photos 4.1 and 4.2).4.5.1 Woody biomassIn 1988, mean woody biomass of all 12 clones in treatments 1and 2 was greater than control (p<0.05), although there was nodifference between treatment 1 and treatment 2 (Figure 4.2).In 1989, mean woody biomass of all 12 clones in treatments 1and 2 was greater than control. Treatment 2 produced more woodybiomass than treatment 1 (p<O.O5).In 1990, mean woody biomass of all 12 clones in treatments 1and 2 were 23% and 38% greater than the control, respectively(Table 4.10). Of the 5 selected clones, 44—135, 52—234 and DN—152produced more woody biomass on treatments 1 and 2 than on control.Wastewater irrigation did not affect woody biomass production ofclone NM-2 and had a little effect on woody bioinass production of1-214. In treatments 1 and 2, clones 44—135 and 52-234 producedmore woody biomass than the other clones (p<O.05).4.5.2 Leaf biomassIn 1988, leaf biomass on treatments 1 and 2 were greater thancontrol (p<O.O5) However treatments 1 and 2 were not different(p>O.O5) (Figure 4.3).154Photo 4.3.Basal diameter of a typical tree (Oct. 1990).Photo 4.4. A typical poplar stand (Oct. 1990).1.558192 I4096204810240 25616 0 CONTROLv TREAT_i8 D TREAT_21988 1989 1990YearFigure 4.2. Effect of irrigation on total woodbiomass (all 12 clones).2048 I1024512 -2560128840 CONTROLv TREAT_I16 1 D TREAT.21988 1989 1990YearFigure 4.3. Effect of irrigation on total leafbiomass (all 12 clones).156Table 4.10 Woody bioniass (Wb) growth response of 3-year-oldpoplar plantation to wastewater irrigation 1Clone Control Treat.1 Change Treat.2 Change(g) (g) in Wb(%) (g) in Wb(%)2All—clones 3726(332] 4588(413) 23 5153(518) 3844—135 4911(872] 7473(1052] 52 7587(791] 5552—234 3550(401) 4865(786] 37 7020(689] 98DN—152 3108(257] 4173(757) 34 4529(920] 451—214 2994(128) 3030(257) 1 3833(606) 28NN—2 4071(2133] 4015(1012] —1 4006(561] 2. Values are means of 4 observations of each clone.2 Standard deviations are indicated in brackets.157In 1989, the mean leaf biomass of all 12 clones was notaffected by wastewater irrigation significantly (p>O.05).In 1990, Treatments 1 and 2 produced 46% and 69% more foliagethan control, respectively (p<O.05) (Table 4.11).Of the five clones, 44-135, 52—234 and DN—152 produced more leafbiomass at wastewater treated plots. Clone NM—2 produced lessfoliage on treatment 2 plot than on treatment 1 and control. Clone44—135 produced more leaf biomass than the other clones under allirrigation treatments.4.5.3 Total leaf area (TLA)In 1988, mean TLA in treatments 1 and 2 was greater thancontrol (p<0.O5), while there was no difference between treatments1 and 2 (Figure 4.4).In 1989 wastewater irrigation did not affect mean TLA of 12clones significantly.In 1990, mean TLA of all 12 clones was 19% greater than thecontrol in treatment 1 and 58% greater than the control intreatment 2 (p<0.05) (Table 4.12). Each of the five clones had agreater TLA in treatment 2 than the control. Total leaf area ofclones 44-135 and DN-l52 was greater than the other clones underwastewater irrigation (p<0.05).158Table 4.11 Leaf bioinass (Lb) growth response of 3—year—oldpoplar plantation to wastewater irrigation1Clone Control Treat.1 Change Treat.2 Change(g) (g) in Lb(%) (g) in Lb(%)212—clones 1039[286J 1517(147) 46 1758(241] 6944—135 1429(49) 1444(51) 1 1681(86) 1852—234 1048(170] 1191(233) 14 1230(263] 17DN—152 979(193) 1147(159) 17 1240(231) 271—214 725(25) 877(57) 21 1153(310) 59NM—2 1016(386] 1047(427) 3 1104(62) 8Values are means of 4 observations of each clone.2 Standard deviations are indicated in brackets.I32.00016.0008.0004.0002.0001.0000.50002500.1251988 1989 1990Figure 4.4. Effect of irrigationarea (all 12 clones).o CONTROLv TREAT_Io TREAT_2”on total leaf159Figure 4.5.growth (all 12 clones)Year4)NE4)4)1024 -51225612864 -O CONTROLv TREAT_i0 TREAT_21988 1989 1990YearEffect of irrigation on tree height160Table 4.12 Total Leaf area (TLA) growth response of 3-year-oldpoplar plantation to wastewater irrigation1Clone Control Treat.1 Change Treat.2 Change(in2) (in2) in TLA(%) (in2) in TLA(%)2All—clones 12.1(3.7] 14.4(4.5] 19 19.1(3.9) 5844—135 16.O[3.1] 17.0(3.9) 6 19.3(3.7] 2152—234 11.3(0.5] 12.0(1.5] 6 12.3(0.6) 9DN—152 10.9(1.5] 15.2(0.8) 40 19.4(4.0) 781—214 8.1(1.2] 8.9(0.3] 10 14.8(5.8) 83NN—2 13.9(3.1) 13.4(2.5] —4 9.4(1.9) —30. Values are means of 4 observations of each clone.2 Standard deviations are indicated in brackets.1614.5.4 Tree heightIn 1988, treatments 1 and 2 were taller than the control(p<0.O5), although there was no difference between treatment 1 andtreatment 2 (p>0.05) (Figure 4.5).In 1989, mean tree height of the 12 clones was not affected bywastewater irrigation (p>0.05).In 1990, mean height of all 12 clones in treatments 1 and 2were 13% and 12%, respectively, greater than the control (p<0.05)(Table 4.13). The difference between treatments 1 and 2 was notsignificant. In clone 52—234, treatment 2 was taller than control(p<O.O5), while treatment 1 was not different from control. Clones44-135, 52-234 and DN-152 were taller than the other clones intreatments 1 and Basal diameter (bd)In 1988, treatments 1 and 2 were greater than the control(p<O.O5), while difference between treatments 1 and 2 was notsignificant (Figure 4.6).In 1989, treatment 2 was greater than treatment 1 and thecontrol (p<0.05), while difference between control and treatment 1was not significant.In 1990 mean bd of all 12 clones in treatments 1 and 2 was16% and 47% greater than the control, respectively (p<O.O5) (Table4.14). Of the five clones 44-135 and 52-334 had a greater bd thanthe other clones.162Table 4.13 Height growthplantation toresponse of three—year—old poplarwastewater irrigation 1Clones Control Treat.1 Change Treat.2 Change(cm) (cm) in ht (%) (cm) in ht (%)2All—clones 559 [43) 634 [28) 13 682 [57] 2244—135 669 [37) 820 [69) 22 851 [59) 2752—234 559 [35) 700 [17) 25 748 [33) 34DN—152 519 [77) 676 [88) 30 677 [21] 111—214 453 [38] 455 [80) 0.5 564 [85) 25NN—2 594 [71] 565 [71] —5 577 [16) —31. Values are means of 10% sampling of each clone.2. Standard deviations are indicated in brackets.1634)C)Figure 4.6.growth (allEffect of irrigation on basal diameterI I I16. I I1988 1989 1990O CONTROLv TREAT_iD TREAT_2Year12 clones).164Table 4.14 Basal diameter (bd) growth response of three-year-old poplar plantation to wastewater irrigation1Clone Control Treat.1 Change Treat.2 Change(cm) (cm) in bd(%) (cm) in bd(%)2All—clones 6.8 [1.0) 7.8 [1.3) 16 10.0 [1.1) 4744—135 8.1 [.59) 9.0 [1.0) 11 11.0 [0.1) 3752—234 7.2 [.41) 8.6 [0.6) 20 11.4 [0.1) 57DN—152 5.6 [.44] 7.1 [0.6] 27 7.9 [1.2] 421—214 5.8 [.68] 6.5 [0.7] 12 6.5 [1.5) 13NN—2 7.2 [.52] 7.6 [0.8] 6 6.1 (1.0) —15. Values are means of 10% sampling of each clone.2 Standard deviations are indicated in brackets.1654.6 Estimation of leaf area index, woody and foliar biomass perhectare and nutrient uptake rates by wood, leaves and grassLeaf and woody biomass production of the plantation showeda direct relation with nutrient addition during the 3 years ofwastewater application.At the end of the third year, annual woody biomass productionreached 3.9, 6.9 and 7.5 Mg/ha in control, treatment 1 andtreatment 2, respectively (Table 4.15). Assuming no mortality andthat other factors such as edge effect had a minimal influence onthe growth of the trees potential annual woody biomass productionwould be 11,000, 20,000, and 24,000 kg/ha for each treatment,respectively. Mean annual woody biomass production would roughly be4.6, 8.1, and 9.8 Mg/ha/year for control, treatments 1 and 2,respectively.According to Sopper and Kerr (1980), the range of woodproduction of a SRIC plantation is 11.2 - 29.1 Mg/ha/yr. Heilinanand Stettler (1985) and Stettler et al. (1990) reported that meanannual woody biomass production for a 3—year—old Populustrichocarpa x deltoides at a 1.2 in x 1.2 m spacing and with 15%mortality was 4.6 Mg/ha/yr. This value at zero mortality conditionswould be 8.6 Mg/ha/yr. At a 1.5 in x 1.5 in spacing woody biomassproduction would be 4.8 Mg/ha/yr which is very close to valuesobtained from the Vernon plantation under freshwater irrigation.According to Schiess and ‘Cole (1981) a 3—year—old wastewaterirrigated poplar plantation produced 11.6 Mg/ha/yr (8.6 Mg/ha/yrwhen adjusted to 1.5 in x 1.5 in spacing). This value also166corresponds with the values obtained for mean annual woody biomassproduction under wastewater irrigation in Vernon.Leaf biomass production does not play an important role innutrient removal from the site unless the whole tree is harvestedduring the growing season and removed from the site. However itslitter can increase organic matter of topsoil and thus hinder ordelay downward movement of heavy metals and nutrients intogroundwater (Schiess and Cole 1981).Table 4.15 Actual and potential woody, foliar and grass biomassproduction and total leaf area (TLA) of theplantationYear and Leaf Wood GrasB Totaltreatment weight weight weight leafarea(kg/ha) (kg/ha) (kg/ha) (m2/ha)Control1988 35 (100) 19 [54) 11500 300[1000]1989 429 (1225) 860 [2457) 7380 5000(14000)1990 1307 (3736) 3912 [11179) 3830 16000(47000)Treat. 11988 59 [1743 51 [150] 11500 l000[2000)1989 535 (1588) 1274 [3779) 7700 6000(18000)1990 2171 (6440) 6857 [20343) 3940 24000(72000)Treat. 21988 75 [244] 56 [180] 11500 1000(2000]1989 555 [1796) 1507 [4878) 7500 6000(20000]1990 2320 (7510] 7537 (24396] 3830 24000(78000). Numbers in brackets are the potential (zero mortality)values.167The same thing might be true regarding the undercanopy growth,grass in the case. However total leaf area (TLA) is a function ofleaf biomass. The growth of a tree is closely related to thequantity of water available during the growing season. Waterdeficits affect growth directly through their impact on cellelongation and indirectly through their influence on stomatalaperture. Since stomata are key in exchange of gasses by the tree,then the quantity of foliage should be linked with thetranspirational and photosynthetic potential of the tree (ChapmanKing et al. 1986). The relationship between available water andleaf area has been described by Grier and Running (1977). Gholz hasobserved a close relationship between total leaf area and aboveground primary productivity. However stands with large leaf areasdo not necessarily have large stemwood volumes. Results obtained byLaughton et al. (1990) suggest that by increasing tree foliage ortotal leaf area it is possible to increase evapotranspiration ofwastewater to 3-4 times greater than that of grass. Significantpositive relations were found in other studies between total leafarea (TLA) per ha and production of various crop plants. PotentialTLA/ha of the plantation is equivalent to a leaf area index of 4.7,7.2, and 7.8 in control, treatment 1 and 2, respectively. Inbroadleaved deciduous forests LAIs range from 3 — 14 (Zavitovski1976), while some hybrid poplars grown under intensive culturedeveloped LAIs of 16 - 45, depending on spacing (Isebrands et al.1977). Zavitovski (1983) reports LAI=5 for a three—year old Populus‘Tristis #1’ stand planted at 1.2 in x 1.2 in spacing.168Maximum gross productivity of a forest stand occurs at LIvalues in the range of 8—10 (Kramer and Kozlowski 1979). PotentialLAI in the Vernon plantation is within the mentioned ranges fordeciduous forests and close to the range stated by Kramer andKozlowski (1979).No analysis of variance was carried out for grass productionunder different treatments. However, in the control, dry biomass ofgrass per ha decreased from 11.5 Mg/ha in 1988 to 3.8 Mg/ha in1990 due to closure of tree canopy. Practically, it was notpossible to estimate how much grass would be produced at zeromortality (i.e., potential conditions) before closure of thecanopy.Total actual and potential nutrient uptake rates by the plantswere calculated by multiplying nutrient concentration in plantparts by the biomass of plant parts.4.7 Concentration of nutrients in the woody biomassConcentrations of N, P, K, Ca, Mg, Mn, Zn, Cu and Fe in woodybiomass did not change with irrigation treatments significantly.However the concentration of macronutrients in wood decreased overtime from 1988 through 1990 (p<0.05), while the decrease inconcentration of the micronutrients was not significant. This canbe attributed to decreasing quantities of chlorophyll in barktissue. During the first year, when the canopy was still open andthe bark was green tree stems acted like leaves, thereforeconcentrations of macronutrients in them were relatively high.169With gradual closure of tree canopy and growth of the trees thebark tissue lost its chlorophyll. Fast growth of wood tissue, whichcontains less macronutrients than the bark, also decreasedconcentration of the nutrients. Therefore, trees at age 3 yr tookup less nutrients per unit weight than in the first year, howeverfast growth of the woody biomass compensated for the decrease innutrient concentration.4.8 Nitrogen (N)4.8.1 Nitrogen in soil solution4.8.1.1 Nitrates (N03)At the soil depth of 75cm, nitrate-N was the predominant formof N. During the 1988 growing season it was not possible to detecteffects of wastewater irrigation on nitrate concentration of soil—solution because of the flush of nutrients caused by previouscultivation and disturbance of the site. Mean concentrations ofnitrates collected from control, treatment 1, and treatment 2 andgrass plots at the end of the growing season of 1988, were 33, 31,29 and 30 mg/L, respectively. At the following growing seasonthese values decreased to 12.3, 6.2, 6.7, 15.0 mg/L , and at theend of 1990 growing season they dropped to 0.44 0.70, 0.54, and0.86 mg/L . These values were well below the 10 mg/L establishedguideline of Environment Canada (1981) for drinking water. Thedecrease over time (1988—1990) suggests that the effect of sitecultivation prior to planting diminished at the end of the firstgrowing season. The higher the application rate of nitrates to each170of the plots the higher was the concentration of nitrates in therespective soil solution (Figure 4.7). Nitrate concentration of thecontrol plots remained low and was not affected by freshwaterirrigation. Regressions of the nitrate inputs (kg/ha) and nitrateconcentration (mg/L) in the soil solution of treatments 1 and 2were significant at 0.01 and 0.05 levels, respectively, i.e.,nitrate-N inputs affected soil solution quality. mmonium (NH4)Wastewater irrigation at neither level had a significanteffect on concentration of NH4 in soil solution (Table 4.4).However, NH4 in soil solution in control, and treatment 1 and 2 washigh in 1988, probably due to the initial disturbance of the site.The level of NH4 decreased in 1989 and remained low for the restof the research period (Figure 4.8). Low levels of NH4 in soilsolution might have many reasons. A part of the wastewater NH4might have been volatilized before reaching the ground. Anotherpossibility would be nitrification (Feigin et al. 1991). Total—NRegressions of total—N inputs with soil solutionconcentrations at the 75 cm depth for treatment 1 and treatment 2were significant at 0.01 and 0.05, respectively. This was mostlikely due to the effect of nitrate—N in soil solution.171N019881 1988.2 19891 19892 1989.4 1989.5 1989.8 1990.1 19902 1990.5 1990.4 1990.6Outputs of nitrate—N in controlNteE 100.0..,z1fto[rrr[[:,. :. :,. :.1988.1 19882 19891 19892 1989.4 1989.5 19898 1990.1 19902 1990.5 1990.4 1990.6Inputs and outputs of nitrate—N in treatment Ii1iiH1988.1 19882 1989.1 19892 1989.4 1969.5 1989.8 1990.1 19902 1990.5 1990.4 1990.6Inputs and outputs of nitrate—N in treatment 2C OUTPUT.• INPUTFigure 4.7. Comparison of the inputs (wastewater) and the outputs(soil solution) of N03 at different irrigation treatments. I I iii a___C OUTPUTI INPUT1720.100bLOOJ IIIII IIIE• 0.010-0.0011988.1 1988.2 1989.1 1989.2 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.5Outputs of ammonium in control100.00g 10.00-Niiiii1.00i0.10 • INPUT•; 001 19891 19892 1989.4 19893 1969.6 1990.1 19902 19903 1990.4 19903.Inputs and outputs of ammonium in treatment 1-NbLE I I IE. 10.0001.000?0.100N. 0.010OUTPUT• INPUT0.0011988.1 19882 19891 19892 1989.4 19893 1969.6 1990.1 19902 19903 1990.4 19903—Inputs and outputs of ammonium in treatment 2Figure 4.8. Comparison of the inputs (wastewater) and the outputs(soil solution) of NH4 at different irrigation treatments.173The control plot showed continuing decrease in total—N in soilsolution over the 3—yr period, while in treatment 1 and treatment2 the total—N concentration corresponded with fluctuations of Ninputs in 1988 and 1989. The trend was towards continuous decreasein concentration of total—N (Figure 4.9.) in the soil solution overthe 3—yr period. Mean annual concentrations of total—N in eachtreatment are shown as absolute values and percentages in Table4.16. In 1988 there was no established tree cover and the site wasdisturbed by cultivation. The poplar cuttings required one year ofestablishment, after which they developed a growth rate thatutilized part of the applied total-N.In 1989, mean annual N concentrations of soil solution in thecontrol, treatment 1, treatment 2 and grass plots were 36%, 20%,22% and 51% of 1988 respectively, while in 1990 these valuesdropped to 1.4%, 2.5%, 3% and 3% of 1988 (Table 4.16). The lowertotal-N concentrations of the poplar plantations for treatment 2 in1989 and 1990 were most likely due to utilization of total—N bythe poplars. In 1989, concentrations of total—N in treatments 1,and 2 were 52* and 54% of the control plot while soil—solutionunder the grass plot contained 30% more total—N than those of thecontrol plot. This may be attributed to tree uptake, rather thangrass uptake, plus retention by the soil.In 1990, concentration of total N in wastewater-irrigatedplots was higher thanthe control (Table 4.16). However higherconcentrations under grass plots suggest that total N was taken upby trees in treatment 1 and treatment 2 plots. These results agreewith those obtained by Schiess and Cole (1981).174‘1E 10.01.0C0.11988.1 19882 1989.1 1989.2 1969.4 1989.5 1969.6 1990.1 19902 1990.3 1990.4 1990.6Outputs of total—N in control1 100.0. io.o[ Ii II Ii 11C l.0- OUTPUT0.1 I INPUT1988.1 19882 1989.1 19892 1969.4 1989.5 1969.6 1990.1 19902 1990.3 1990.4 1990.8Inputs and outputs of total—N in treatment 110[100‘C.OUTPUT.- I I INPUT11988.1 1988.2 1989.1 19892 1989.4 1989.5 1969.6 1990.1 19902 1990.3 1990.4 1990.6C1Inputs and outputs of total—N in treatment 2Figure 4.9. Comparison of the inputs (wastewater) and the outputs(soil solution) of N at different irrigation treatments.175Table 4.16 Mean annual concentration of N in soil solutionat 75 cm depth under each irrigation treatmentwith percentage of establishment year concentration1YearTreatment 1988 1989 1990Control (mg/L) 36.O[11.O] 12.9[1.2) 0.5[0.2](%) 100 36 14Treat.1 (mg/L) 33.O[9.O) 6.7(3.0] 0.8(0.2](%) 100 20 2.5Treat.2 (mg/L) 32.0(9.0) 7.0(1.5] 0.9(0.4](Poplar) (%) 100 22 3Treat.2 (mg/L) 33.0(11.0) 16.8(1.3) 1.5(0.3](Grass) (%) 100 51 4.5. Values are means of 5 determinations, with standard deviationsin brackets.1764.8.2 Boil total—NThe concentration of total-N in the 0-30 cm layer of soil incontrol decreased with time from 1988 to 1990 (p<0.01). There wasno significant difference from year to year for treatments 1 and 2(Figure 4.10). In the 30-60 cm layer the total-N concentration didnot change significantly in any of the treatments. However therewas a trend towards decrease in concentration of this nutrient withtime.4.8.3 Foliar and wood NIn 1988 and 1989, concentration of N in foliage or wood didnot change significantly due to wastewater irrigation (Table 4.17).In 1990, concentration of N in treatment 2 was higher thanthe control. Treatment 1 and control were not different. Increasein foliar N as a result of wastewater irrigation has been reportedby many researchers. Brockway et al. (1986) have summarized someof these data (Table 2.3).4.8.4 Nitrogen uptake and removal efficiencyAt the end of the third year, woody biomass would take up20 kg N/ha/yr in treatment 1 and treatment 2, respectively (Table4.18). These values were only 30% and 16% of the N added bywastewater irrigation in treatments 1 and 2, respectively. At thepotential conditions, (i.e., with no mortality) these values wouldbe 88% and 52% of N inputs. The rest of the added N was taken upby the foliage and the grass which would eventually return to the020 I I I1770.15C.)700.10 -0.050.00 IBgBQ$Control TreaLl Treat2012 —___________ ____________________0.10c0.8I::0.02 -0.00Control TreaLl Treat2Figure 4.10. Effect of irrigation on concentrationof total-N in soil at 0-30 and 30-60 cm depths.178Table 4.17 Mean concentration of N in foliage and wood ofall clones under 3 irrigation treatments1 (g/kg)Foliage Wood1988 2Control 24.5(1.1] 13.7(2.5)Treat.1 21.7(0.9) 9.6(2.2)Treat.2 20.4(0.8) 11.2(1.8)1989Control 28.6(1.5) 10.6(2.6)Treat.1 28.5(1.0) 10.7(2.5)Treat.2 28.5(1.1] 11.8(2.7)1990Control 24.7(1.0) 5.1(0.8)Treat.l 28.1(1.2) 5.5(1.3)Treat.2 29.9(1.2) 6.0(1.2). Values are means of 4 observations of each clone.2 Standard deviations are indicated in brackets.179Table 4.18 Nitrogen uptake of wood and foliage comparedwith its inputs by wastewater irrigationYear ---Input Uptakeandtreat- Irrigation ----Wood---- FoLiage---- Grasment water(kg/ha) (kg/ha) (%)1 (kg/ha) CX) (kg/ha) CX)ControL1988 0.60 0.2 [1)2 28 [123) 1 [5) 166 [833) 180.6 301001989 0.40 4.6 [13) 1160 [32) 13 [38) 3520 [9500] 106.9 267501990 0.50 7.3 [20) 1460 [4174) 32 [92) 6400 [18400] 67.8 13558Treat.11988 71.6 0.4 [2] 0.5 [2) 2 [7) 3 [10] 180.6 2531989 54.0 6.8 [20) 13 [37) 13 [38] 24 [70] 111.5 2061990 67.6 20.1 [60) 30 [88) 61 [179) 69 [90] 69.7 103Treat .21988 91.10 0.4 [2] 0.4 [2] 2 [9] 2 [10) 180.6 1981989 93.8 6.8 [21) 7.2 [23) 10 [31] 11 [33) 108.6 1161990 125.2 20.3 [66] 16.2 [52) 68 [221] 54 [177) 67.8 54Percentage of wastewater input.2 NiNers in brackets represent nutrient uptake rates at zero mortaLity conditions.180soil (Steenvoorden 1988). McKim et al. (1982) reported that arapidly growing juvenile forest could store up to 300 kg N/ha/year.Under potential conditions, when the canopy is closed and there isno ground vegetation, the Vernon plantation would be able to storeup to 270 kg N/ha/year. Whole tree harvest at the age of threewould remove about 90% of the total N input during the past threeyears. Updegraff and Zak (1990) found that the annual increment ofa SRIC hybrid poplar plantation with a in x in spacing was 54 kgN/ha at the 3rd year of its establishment while N uptake rate ofthe Vernon plantation under actual conditions and at the same agewas 81 kg/ha/year.From 1988 to 1990, soil total—N content showed a trend towarddecrease in all three treatments (Table 4.19). Red and Nutter(1986) obtained a similar result from a 3—year old wastewaterirrigated forest site. One hypothesis that they suggested was thatinstallation of a drainage network at their site increased theaerobic depth of the soil, creating conditions favourable tonitrification. The nitrate thus formed would be leached into theanaerobic zone where conditions would be ideal fordenitrification because of the presence of a carbon source inwastewater. In the case of the Vernon plantation, disturbance ofthe upper soil horizons through cultivation night have beenresponsible for a similar effect. In 1990, removal efficiency of Nby the soil—plant system was as high as 97% and 95% in treatments1 and 2, respectively (Table 4.19). Nitrogen discharge of thesystem in 1989 and 1990 in both wastewater treatments was far lessthan the figures given by Brockway et al (1986) in Table 2.5.181.Table 4.19 Nitrogen removal efficiency by thesoil-plant systemYear Soil N Irriga— Soil Irriga— Soil Elementand at tion solu— tion golu— removaltreat— 0—60cm water tion water tion eff i—ment N N (content) (content) ciency[a] [b] (c=100—b/a*l00](kg/ha) (mg/i) (mg/i) (kg/ha) (kg/ha)Control1988 8500a 0.1 58.0 0.6 152 24001989 7500b 0.1 10.0 0.4 6 14001990 6500b 0.1 10.0 0.5 2 300Treat.11988 7600a 12.0 39.0 72 101 —401989 6560a 13.4 5.3 54 3 941990 6600a 13.2 1.0 68 2 97Treat.21988 6250a 12.0 30.6 91 130 —431989 5750a 13.4 5.8 94 21 781990 4540a 13.2 0.9 125 6 951. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching1824.9 Phosphorus (P)4.9.1 Soluble P in soil solutionRegression of P input with concentration of P in soil solutionwas significant at 0.05 level for treatment 2 but not significantfor treatment 1 which implies that P added by treatment 1 waseither utilized by the plants or was immobilized by the soil whileat the higher level of wastewater irrigation there was a surplus ofP which affected soil-solution quality (Figure 4.11.). However, thegeneral trend in all three treatments was toward decrease of Pconcentration in soil solution which suggests uptake of thiselement by plants and/or retention by soil (Table 4.20). The sharprise in P concentration at the beginning of the 1989 growing seasonin treatment 1, grass, and control coincides with the period inJune and July when less water was applied. Due to fluctuations insoil moisture some mineralization might have occurred whichreleased some soil P (Syers and Iskandar 1981). Concentration ofthis element in all treatments, including the control plot, at the75 cm depth was much higher than the desirable level of P forOkanagan Lake which is 0.03 mg/L (Jackson 1990). However, P is anelement which can be retained by soil at greater depths where acarbonate layer is present. Concentration of about 0.25 mg/L of Punder the control plot in 1990 was probably due to mineralizationof the organic matter, while higher concentrations of this elementunder treatments 1 and 2 and the grass plot, (0.52, 0.55, and 0.85mg/L , respectively) might be due to wastewater irrigation.183i.c I I I IiNI0.11988.1 1988.2 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.6Outputs of soluble—P in control-“bS ioo.o I I I I I I0.i It0[-e. I OUTPUT? • INPUT0.11988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 19903 1990.4 1990.6—Inputs and outputs of soluble—P in treatment 1“S15 100.0I’EiiIiiiiiii OUTPUT• INPUT1988.1 19882 1989.1 19892 1989.4 1989.5 1969.6 1990.1 19902 19903 1990.4 1990.6.Inputs and outputs of so]uble—P in treatment 2Figure 4.11. Compthson of the inputs (wastewater) and the outputs‘soil solution) of P at different irrigation treatments.184Table 4.20 Mean annual concentration of P in soil solutionunder each irrigation treatment with percentageof establishment year concentration’YearTreatment 1988 1989 1990Control (mg/L) O.4[O.2) 0.6[[0.2] 0.3[0.0)(%) 100 67 75Treat.1 (mg/L) 0.9[0.2) 1.0[0.2) 0.5[0.2](%) 100 ill 56Treat.2 (tng/L) 0.6[0.2) 0.5[0.l) 0.5[0.l)(Poplar) (%) 100 83 83Treat.2 (mg/L) 0.8[0.2) 1.0[0.2) 0.9[0.3)(Grass) (%) 100 111 112Values are means of 5 determinations, with standard deviationsin brackets.1854.9.2 Soil phosphorusThe concentration of plant-available P in the 0-30 cm layerdid not change during the three years in the control and treatment2, although there was a downward trend. In treatment 1 theconcentration of available P in 1990 was less than 1988 (p<O.O5)(Figure 4.12). In the 30—60 cm layer of soil the concentration ofavailable P in the control plot remained unchanged over the 3—yearperiod. In treatments 1 and 2 the concentration of available Pdecreased after 1988.When P is added to soils, most of it is in solubleorthophosphate form (Table 4.1). The orthophosphate anions bondchemically with surfaces of Fe and Al oxyhydroxides and will formprecipitates with Fe and Al when these are in solution. Thestrength of the bonds formed from surface and precipitationreactions varies. The weakest bonded ones are the most solublephosphates which readily equilibrate with the soil solution andbecome available to plants (Richenderfer et al. 1976, Ryden andPratt 1980). Decrease of concentration of available P in wastewater treated plots in both soil layers may be attributed touptake by the plants and reaction with the native and added Caand Mg which formed insoluble phosphates. As a result, concentration of available P in the 0-30 and 30-60 cm layers of soildecreased or remained unchanged.8070SE“ 50C•9 4030c1040Figure 4.12. Effect of irrigation on concentration of plant-available P in soil at 0-30 and 30-60 cm depths.60-186IC — — - W,yfl’,r,S,A,Ar,,’.,-’QBControl TreaLl TreaL2. 1-30C C-Control TreaLl Treat.21874.9.3 Phosphorus sorption capacity of soilsPhosphorus sorption isotherms (Figure 4.13) showed thecapacity of the soil to immobilize P. Isotherms of the upperhorizons (i.e., AjtBmi BC) started to level off when theconcentration of solution reached 120 mg/L . However the isothermsof C, C and C1 horizons continued to rise at a sharp angleimplying that sorption capacity of those horizons might be muchhigher. Calculations based on the obtained P sorption capacity(Table 4.21) showed that the soils of the project site from thesurface to a depth of 2.0 in are theoretically capable of sorbing asmuch as 17.7 Mg P/ha. Under wastewater irrigation amountsequivalent to treatment 2 in 1990 it would take at least 278 yearsto saturate the soils of the plantation site with P added throughwastewater irrigation.However, in practice there are some other factors such as uptakerates by the plants and soil pore size that might influencemovement of P in soil. It is known that large soil pores increasemovement of soluble P to lower horizons without being adsorbed bythe soil (EPA 1981).4.9.4 Foliar and wood PIn 1988 the concentration of foliar P was higher intreatments 1 and 2 than in the control. However the differencebetween treatments 1 and 2 was not significant (Table 4.22).In 1989 the concentration of foliar P in treatment 2 washigher than control and treatment 1, but the difference betweentreatment 1 and control was not significant.188o AHO BMACo CK* AHO BMo BCA X4o CKSoil *1o 20 40 60 60Equilibrium P concentration (mg/i)Soil *21005004000jaooJ2001000500400030020010000 10 20 30 40 50 60 70 60Equilibrium P concentration (mg/i)Figure 4.13. Phosphorus sorption isotherms of twotypical soil samples at the project site.189Table 4.21 Phosphorus sorption capacity of the project soilsHorizon Depth Maximum P particles Bulk Corrected P P storagesorption <2mm density sorption capacitycapacity capacity(cm) (mg/kg) (%) (g/cm3) (mg/kg) (kg/ha)a b c d e=b*c f=e*d*soil vol.Ab 0 — 36 316.00 76 1.33 240 1513B, 36 — 70 212.00 54 1.33 114.5 959C 70 — 105 500.00 53 1.64 265 2870Ck 105 — 200 794.00 50 1.64 397 12370Total = 1771217.7 Mg/ha190Table 4.22 Mean concentration of P in foliage and wood ofall clones under 3 irrigation treatments1 (g/kg)Clones: Foliage Wood1988 2Control 3.2(0.6) 1.9[.4)Treat.1 4.9(1.0] 1.7[.3]Treat.2 4.8(0.8) l.5[.3]1989Control 2.3(0.4) 0.8(.1]Treat.l 2.4(1.0) 1.O(.2]Treat.2 3.5(0.7] 1.O[.2)1990Control 4.9(0.7] 0.7[.1]Treat.1 6.3(0.6] 0.7[.1)Treat.2 6.1(0.7) O.8(.l). Values are means of 112 observations2 Standard deviations are indicated in brackets.1914.9.5 Phosphorus uptake and removal efficiencyPhosphorus uptake by the woody biomass at the end of the 3rdyear reached 12.2% and 7.6% of its input rates in treatment 1 andtreatment 2, respectively (Table 4.23). Potential uptake (i.e.,assuming no mortality) would be 36% and 24%. Foliage took up 30%and 17% of the input. Potential values would be as high as 88.7%and 54.9% of the input in treatment 1 and treatment 2,respectively. Cole and Schiess (1978) reported that a poplarplantation in the Pacific Northwest had taken up to 34% of theadded P. Grass had the highest uptake of 83% and 44% of the input.High wastewater P removal efficiency (Table 4.24) and decreasingsoil P content during the project period shows that some P wastaken up by the plants and probably a part of it had beenimmobilized by the soil. Hook (1983) stated that application ofsoluble P at 16 mg/L may cause small changes in concentration ofthis nutrient in percolate. Broadbent and Reisenauer (1986)mentioned that only 3% of the P added by wastewater was found inthe drainage water. Results obtained in this research supportstatements of these researchers.4.10 Potassium (K)4.10.1 Soluble K in soil solutionRegression analysis showed that there was a significantrelationship (p<O.01) between input rates and concentrations of Kin soil-solution samples in treatment 1 and treatment 2. Theoverall trend of K concentration in soil—solution under controlplots was towards a decrease (Figure 4.14.).192Table 4.23 Phosphorus uptake rates of wood and foliagecompared with its inputs by wastewaterirrigationYear ---Irçut- - Uptakeandtreat- IrHgation Wood Foliage ----Grass---ment water(kg/ha) (kg/ha) (%) I (kg/ha) (%) (kg/ha) (X)Control1988 0.18 0.02 [0.1)2 11.1 [56) 0.07 [0.3) 39 [178) 38.2 211111989 0.12 0.66 [1.8] 550.0 [1533] 0.98 [2.8) 816 [2325] 7.2 68081990 0.15 2.0 [5.6) 1320.0 [3760) 5.94 [17.0] 3960 [11313) 4.4 2900Treat.11988 37.3 0.06 [0.3] 0.2 10.7) 0.2 [0.7] 0.4 [2.0) 76.4 2051989 28.7 1.2 13.53 4.2 [12.3] 1.8 [5.4) 6.3 [18.8) 48.2 1651990 34.4 4.2 [12.4) 12.2 [36.23 ID.4 1308) 30.2 189.7) 28.6 84Treat .21988 47.5 0.1 [0.29] 0.1 [0.6) 0.2 [1.0) 0.5 [2.1) 76.4 1621989 50.0 1.3 [3.96) 2.5 [7.9) 1.4 [4.43) 2.7 18.9] 46.9 941990 63.6 4.8 [15.66) 7.6 [24.6) 10.8 [34.9] 17.0 154.93 27.8 44‘. Percentage of wastewater input.2 N*)ers in brackets represent nutrient itake rates at zero mortality conditions.193Table 4.24 Phosphorus removal efficiency by thesoil-plant systemYear Soil P Irriga— Soil Irriga— Soil Elementand at tion solu— tion solu— removaltreat— 0—60cm water tion water tion effi—ment (content) (content) ciency[a] [b] [c=100_b/a*100](kg/ha) (mg/i) (mg/i) (kg/ha) (kg/ha) (%)Control1988 140a 0.03 0.44 0.18 1.0 —4501989 130a 0.03 0.60 0.12 0.4 —2301990 llOa 0.03 0.25 0.15 0.5 —230Treat.11988 200a 6.23 0.87 37.3 2.0 951989 185a 7.16 1.13 28.7 0.7 981990 145b 6.68 0.52 34.4 1.0 97Treat.21988 320a 6.23 0.59 47.5 2.5 951989 270a 7.16 0.50 50.0 1.8 961990 275a 6.68 0.55 63.6 3.6 941. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.194The same trend was observed under treatment 1, treatment 2,and grass plots. In 1990, concentration of K slightly increased.Decrease in concentration of K in treatments 1 and 2 as compared tocontrol values (Table 4.25) can be attributed to absorption of thiselement by the plants that grew more vigorously on wastewaterirrigated plots. Potassium concentration values in 1990 show thatsoil solution under treatment 1 plots contained less K than thecontrol plot which had not received any K through irrigation. Atthe same time treatment 2 which received 2 times more K thantreatment 1 showed only 9% increase in K concentration. It islikely that most of the added K was absorbed by the plants withsome of adsorbed by the soil.4.10.2 Soil potassiumConcentration of K increased significantly in the 30-60 cmlayer of soil with time in treatments 1 and 2. Presumably the highmobility of this cation explains the increase in concentration inthe lower layer of soil (Figure 4.15). Red and Nutter (1986) andSopper and Kardos (1973) also observed similar results in forestsoils.4.10.3 Foliar potassiumIn 1988 wastewater irrigation did not affect concentrationof foliar K significantly (Table 4.26).In 1989 foliar K in treatments 1 and 2 was lower than thecontrol (p<O.05) but the difference between the treatments was notsignificant.In 1990 there was no significant difference between controland treatments 1 and 2.icco I INE 100101986.1 19882 1989.1 19892 1989.4 1989.5 1989.8 19901 19902 1990.5 1990.4 1990.6Outputs of K in control195NS1OI:I I I I I I I Iz• 100i: 101 OUTPUT. I I INPUT..). 1986.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.5 1990.4 1990.6Inputs and outputs of K in treatment 1.-Nbicoo I I I I* I1jtib I, I4) I S INPUT.1’Cl. 1988.1 19882 1989.1 19892 1989.4 1989.5 1989.8 1990.1 19902 1990.5 1990.4 1990.6Inputs and outputs of K in treatment 2Figure 4.14. Comparison of the inputs (wastewater) and the outputs‘soil solution) of K at different irrigation treatments.196Table 4.25 Mean annual concentration of K in soil solutionunder each irrigation treatment with percentageof establishment year concentration1YearTreatment 1988 1989 1990Control (ing/L) 287.0(69] 42.3(8] 40.0(8](%) 100 15 14Treat.1 (mg/L) 108.5(13) 22.0(2) 27.8(5](%) 100 20 26Treat.2 (mg/L) 151.7(11) 37.2(3) 44.0(3)(Poplar) (%) 100 24 29Treat.2 (mgfL) 109.0(13) 38.3(5) 34.0(6](Grass) (%) 100 35 31. Values are means of 5 determinations, with standard deviationsin brackets.40C) I I I I I I I I 197S.’300I:1ii.iControl Treat.1 Treat.2300 I IN.200 VL___ _Control Treat.1 Treat.2Figure 4.15. Effect of irrigation on concentration of plant-available K in soil at 0-30 and 30-60 cm depths.198Table 4.26 Mean concentration of K in foliage and wood of allclones under 3 irrigation treatments’ (g/kg)Foliage Wood1988 2Control 17.9[O.8] lO.O[.2]Treat.1 19.1[1.1] lO.O[.2)Treat.2 l8.5[O.7) lO.O[.2)1989Control 17.3[l.8) 3.5[.06)Treat.l lO.3[2.l] 4.1[.1)Treat.2 12.8[2.O) 3.9[.1]1990Control 17.4t2.2] 2.7[.07]Treat.1 17.9[3.4] 3.4[.l)Treat.2 17.6[4.7) 3.2[.l). Values are means of 112 observations.2 Standard deviations are indicated in brackets.1994.10.4 Potassium uptake and removal efficiencyContrary to the typical nutrient combination of North Americanmunicipal wastewaters, where the proportion of N, P and K is 6:1:2(Reed and Crites 1984) (i.e., there is a surplus of N with respectto K), in Vernon wastewater this proportion was 2:1:3, and theconcentration of K=17.5 mg/L was above the average value of 15 mg/Lmentioned by Reed and Crites (1984). As a result wastewaterirrigation added substantial amounts of K to the site that couldnot be taken up by the plants completely.In 1990, potassium uptake by the woody biomass was 21% and 13%of the inputs by wastewater in treatment 1 and 2, respectively(Table 4.27). Potassium uptake by the foliage was 37% and 22% andby grass was 136% and 72%. Under potential conditions all added Kwould be taken up by plant parts. Woody biomass would have taken60% and 40% of the added K in treatments 1 and 2, respectively. Inthe control plots there was an insignificant buildup of soil K(Table 4.28) despite a high level of K leaching into groundwater.It is likely that the source of K was decomposing litter andground vegetation. In treatment 1, K decreased probably due toleaching. In treatment 2 the content of soil K remained unchangedduring all three years. Therefore it can be assumed that the sourceof the leaching K was decomposing litter and ground vegetationwhile the added K compensated for K uptake by the plants.200Table 4.27 Potassium uptake of wood and foliagecompared with its inputs by wastewaterirrigationYear - - - Input- - - Uptakeandtreat- IrHgation Wood FoLiage Grassment(kg/ha) (kg/ha) (%) (kg/ha) CX) (kg/ha) CX)ControL1988 27.8 0.12 10.54)2 0.4 [2) 0.38 11.70] 1.5 [6) 292.77 10541989 18.6 2.88 [8.04) 16 [43] 7.59 [21.70] 41 1117] 69.50 3831990 23.9 9.61 [27.46) 40 [115] 22.65 164.74] 95 [271] 21.38 89Treat.11988 104.4 0.31 [1.37] 0.3 [1] 0.69 [3.09) 1 [3] 585.54 5621989 74.8 4.66 [13.36] 6 [18] 6.58 [19.53) 9 [26) 464.07 6181990 103.5 21.62 [64.15) 21 [62) 38.07 [112.94) 37 [109] 140.73 136Treat .21988 132.8 0.37 [1.64) 0.3 [1] 1.03 [4.59] 1 [4) 585.54 4401989 130.2 4.88 [15.35) 4 [12] 5.20 [16.84) 4 [13) 452.01 3481990 191.4 24.22 [78.38) 13 [41) 41.60 [134.65) 22 [70) 136.80 72Percentage of wastewater input.2 Wi.aiers in brackets represent nutrient LEtake rates at zero mortaLity conditions.201Table 4.28 Potassium removal efficiency by thesoil-plant systemYear Soil K Irriga— Soil Irriga— Soil Elementand at tion solu— tion solu— removaltreat— 0—60cm water tion water tion eff i—ment (content) (content) ciency[a] [b] [c=l00_b/a*100)(kg/ha) (mg/l) (mg/l) (kg/ha) (kg/ha) (%)Control1988 887a 4.64 287.0 28 750 —25801989 1495b 4.64 42.3 19 25 —301990 157Db 4.64 40.1 24 87 —260Treat.11988 1340a 17.44 108.5 104 283 —1701989 1330a 18.65 21.9 75 13 831990 144Db 20.11 27.8 103 61 41Treat.21988 1266a 17.44 151.7 133 645 —3851989 1106a 18.65 37.2 130 132 —11990 134Db 20.11 43.7 191 286 —501. Values with the saxne letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.2024.11 Calcium (Ca)4.11.1 Soluble Ca in soil solutionRegression of Ca inputs on concentration of soil—solution Cawas not significant (p>0.05). There is no clear pattern betweenfluctuations of Ca input and its concentration in the soil—solutionin any of the plots (Figure 4.16). Contribution of Ca by wastewaterirrigation to soil solution was negligible since these chernozemicsoils themselves contained quite high quantities of Ca (Table4.29)4.11.2 Soil calciumAlthough inputs of Ca through wastewater were higher than anyof the other nutrients, plant available Ca did not change from yearto year in any of the treatments in both the 0-30 and 30-60 cmlayers. Because the C horizon of the soils at the site is rich inCaCO3, addition of Ca would not have a noticeable affect on soil Ca(Figure 4.17). Increase in Ca and Mg may be due to the strongadsorptive power that soil colloids have for these cations.Calcium and H ions have approximately the same bonding strengthwith respect to soil colloids. If Ca is applied to the soil, thecation exchange reaction is reversed and H and a weaker bondedcation are replaced by a mass action of active ions. As a resultsoil pH increases (Richendorfer et al. 1975). However thequantities of these elements added during three years of wastewaterirrigation were not sufficient to increase soil pH at a significantlevel.203NC-NECN100010019881 1988.2 19891 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.6Outputs of soluble Ca in controlFigure 4.16. Comparison of the inputs (wastewater) and the outputs(soil solution) of Ca at different irrigation treatments.I I I I I I I I I INECNC—10001001011000100101988.1 19882 1989.1 19892 1989.4 1989.5 1989.8 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of soluble Ca in treatment 1OUTPUT• INPUTOUTPUTI INPUT19881 1988.2 19891 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of soluble Ca in treatment 2204Table 4.29 Mean annual concentration of Ca in soil solutionunder each irrigation treatment with percentageof establishment year concentration’YearTreatment 1988 1989 1990Control (mg/L) 254.0[9J 295.O[17) 204.0[37)(%) 100 116 80Treat.l (mg/L) 91.8[9J 95.5[12] 99.0[29)(%) 100 104 108Treat.2 (ing/L) 130.6[9) 151.O[18] 167.0[46](Poplar) (%) 100 116 128Treat.2 (mg/L) 88.0t3) 184.3[12] 94.0[27)(Grass) (%) 100 209 107‘. Values are means of 5 determinations, with standard deviationsin brackets.205b1200oSSC)0C?0S ioooC)C)0TreaLl20001500,1000C)4500C -- ‘-gf$ 9’Control Treat.1 Treat2Figure 4.17. Effect of irrigation on concentration of plant-available Ca in soil at 0-30 and 30-60 cm depths.)‘ø tgControl Treat.2ii ‘ii’12064.11.3 Foliar calciumIn 1988 and 1989, wastewater irrigation did not affectconcentrations of foliar Ca significantly (Table 4.30).In 1990, foliar Ca in treatments 1 and 2 were lower than incontrol (p<O.O5)4.11.4 Calcium uptake and removal efficiencyWoody biomass at the end of the third year had taken up 9% and6% of added Ca in treatment 1 and treatment 2, respectively. Underpotential conditions these values would not exceed 26% and 18% ofCa input rates (Table 4.31). Foliage had taken up 15% and 9% of theinput while grass took up as much as 26% and 13% of the Ca.Decrease in soil Ca content under control and treatment 1 plotsmight indicate uptake by plants and its conversion into plant-unavailable forms. Increase of soil Ca content in treatment 1 ismost likely due to its buildup.Because soil at the depth of 75 cm (where soil solution wascollected) contained high concentrations of Ca (Ck or C horizon),interpretation of calculated removal efficiency is not realistic.Comparison of Ca contents between treatment 1 and treatment 2 showsthat more Ca was leached down under treatment 2 (Table 4.32).207Table 4.30 Mean concentration of Ca in foliage and wood ofall clones under 3 irrigation treatments (gfkg)’Foliage Wood1988 2Control 14.3(1.5) O.94[.17)Treat.1 14.7(3.2) 0.63[.13Treat.2 14.4(1.9) 0.67[.141989Control 10.2(4.9] 0.62[.14)Treat.1 9.5(6.0] 0.58[.12)Treat.2 10.1(4.9] 0.55[.11)1990Control 23.4(2.1) 0.38[.10]Treat.1 18.5(1.6) 0.40[.12]Treat.2 17.1(3.9] 0.38[.10J. Values are means of 112 observations.2 Standard deviations are indicated in brackets.Table 4.31 Calcium uptake of wood and foliage comparedwith its inputs by wastewater irrigationYear ---Input Uptakeandtreat- IrHgation Wood FoLiage ----Grass---ment water(kg/ha) (kg/ha) (%) I (kg/ha) CX) (kg/ha) CX)Cont rot1988 177.1 0.11 [0.51)2 0.1 [0.33 0.32 [1.433 0.2 El] 68.70 391989 118.7 5.16 [14.58) 4 [12.3 4.98 [14.24) 4 [12) 11.13 91990 152.3 11.64 [33.25) 8 [22) 30.49 [87.13) 20 [57) 9.38 6Treat .11988 258.5 0.21 [0.92) 0.1 [0.4) 0.54 [2.41] 0.2 [1) 137.41 531989 195.9 6.50 [18.97) 3 [10] 5.02 [14.89] 3 [8] 74.32 381990 242.5 21.46 [63.65) 9 [26) 37.56 [111.42) 16 [46) 61.78 26Treat.21988 329.0 0.23 [1.04] 0.1 [0.3] 0.78 [3.46) 0.2 [1) 137.41 421989 340.9 7.19 [23.00) 2 [7) 4.11 [13.30] 1 [4] 72.39 211990 448.8 24.69 [79.90] 6 [18] 40.07 [129.69] 9 [293 60.06 13. Percentage of wastewater input.2• NLrbers in brackets represent nutrient çtake rates at zeromortaLity conditions.208209Table 4.32 Calcium removal efficiency by thesoil—plant systemYear Soil Ca Irriga— Soil Irriga— Soil Elementand at tion solu— tion colu— removaltreat— 0—60cm water tion water tion eff i—ment (content) (content) ciency[a) [b) [c=l00_b/a*lOO)(kg/ha) (mg/i) (mg/i) (kg/ha) (kg/ha) (%)Control1988 9150a 29.6 254.0 177 665 —2751989 8365a 29.6 295.0 119 172 — 441990 9720a 29.6 204.0 152 444 —190Treat .11988 8355a 43.2 91.0 258 238 81989 8785a 48.8 95.6 196 56 711990 10470a 47.1 99.0 242 215 11Treat.21988 5970a 43.2 130.6 329 554 —681989 5950a 48.8 151.0 341 535 —571990 5800a 47.2 167.0 449 1090 —1431. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.2104.12 Magnesium (Mg)4.12.1 Soluble Mg in soil solutionRegression of Mg inputs and Mg concentration in soil solutionwas not significant (p>O.05), i.e., concentration of Mg in soil—solution was not dependent on input values of this element bywastewater (Figure 4.18). Neither control plot nor wastewaterirrigated plots showed any significant change in concentration ofMg. Like Ca, native Mg in the soil was abundant and its additionthrough wastewater did not significantly affect its concentrationin the soil-solution noticeably. Probably Mg inputs were adsorbedby the soil or taken up by the plants.The decrease of Mg concentration in 1989 under control,treatment 1 and treatment 2 plots (Table 4.33) might be attributedto fixation of this element after disturbance and probably toabsorption by the plants. However wastewater did not seem tocontribute much to Mg concentration in soil—solution.4.12.2 Soil MgPlant available Mg increased with time in treatments 1 and 2in the 0—30 cm layer of soil (p<0.05) (Figure 4.19).In the 30—60 cm layer no changes in available Mg were observed.These results agree with those found by Red and Nutter (1986). Theincrease in Ca and Mg may be due to the strong adsorptive powerthat soil colloids have for these cations.211E0-0C101000100I I I I I I I I1001011988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 29901 19902 1990.3 1990.4 1990.8Outputs of soluble Mg in control1988.1 19882 1989.1 19892 1989.4 1989.5 1989.8 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of soluble Mg in treatment 1•1000b00L10OUTPUTS INPUTOUTPUTS INPUT1988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of soluble Mg in treatment 2Figure 4.18. Comparison of the inputs (wastewater) and the outputs(soil solution) of Mg at different irrigation Ireatments.212Table 4.33 Mean annual concentration of Mg in soil solutionunder each irrigation treatment with percentageof establishment year concentration’YearTreatment 1988 1989 1990Control (xng/L) 65.2[27] 48.7[21] 76.3[17](%) 100 75 117Treat.1 (mg/L) 26.7[5] 18.8[4] 18.7[7](%) 100 70 70Treat.2 (mg/L) 42.5[6] 39.5[9] 41.4[13](Poplar) (%) 100 93 97Treat.2 (xng/L) 27.0[4] 28.0[8] 26.4[8](Grass) (%) 100 104 98. Values are means of 5 determinations, with standard deviationsin brackets.3021.3SS’200SzC)100S0 I I))9@)q iBç9is’Control TreaU Treat.2.o0 - - I150SC?0A100S50CCr20- -‘Control TreaLl TreaL2Figure 4.19. Effect of irrigation on concentration of plant-available Mg in soil at 0-30 and 30-60 cm depths.2144.12.3 Foliar MgIn 1988 treatment 2 had higher foliar Mg than control(p<O.05), however the difference between treatment 1 and controlwas not significant (Table 4.34).In 1989, treatments 1 and 2 were lower than control (p<0.05).However there was no difference between treatment 1 and 2.In 1990, wastewater irrigation did not affect concentration ofMg in the foliage. However, mean values of treatments 1 and 2showed a trend towards decrease.4.12.4 Magnesium uptake and removal efficiencyIn 1990 uptake of Mg in treatment 1 and treatment 2 by woodwas 4% and 2%, respectively. Potential Mg uptake rates would be 10%and 6%, respectively (Table 4.35). Uptake rates by foliage were 6%and 4% in treatments 1 and 2 respectively. Under potentialconditions they would be 18% and 12%. Grass took up 19% and 10% ofMg input in treatments 1 and 2 respectively. Elemental removalefficiency was 62% in treatment 1 while in treatment 2 it was —40%,(i.e., content of Mg in soil solution was higher than Mg inputrates) (Table 4.36). This implies that some native Mg was releasedinto soil solution. Decrease in soil Mg content was most likely dueto leaching of the native Mg.215Table 4.34 Mean concentration of Mg in foliage and wood ofall clones under 3 irrigation treatments (mg/kg)’Foliage Wood1988 2Control 3.2[O.1] 2.5[.7]Treat.1 3.4[O.2] 1.9[.5]Treat.2 3.8[O.2) 2.O[.5)1989Control 4.2[O.5) l.l[.2)Treat.l 3.O[O.7) l.2E.3]Treat.2 3.3[O.4] l.2[.3]1990Control 3.7[0.4] 0.6[.l]Treat.,1 3.2[0.3J 0.7[.2]Treat.2 3.O[0.4] O.6t.l). Values are means of 112 observations.2 Standard deviations are indicated in brackets.21.6Table 4.35 Magnesium uptake of wood and foliage comparedwith its inputs by wastewater irrigationYear ---Input-- - Uptakeandtreat- Irrigation Wood FoLiage----Graswent water(kg/ha) (kg/ha) CX) (kg/ha) CX) (kg/ha) CX)Control1988 106.5 0.03 [0.14)2 0.03 [0.1) 0.07 [0.32) 0.1 [0.3)28.56 271989 71.4 0.84 [2.35) 1.17 [3) 2.00 [5.71) 3 (8) 5.5081990 91.6 2.12 [6.05) 2.30 [7) 4.72 [13.48) 5 [15] 3.16 3Treat .11988 110.0 0.06 [0.28] 0.1 [0.3] 0.13 [0.57) 0.1 [0.5)57.11 521989 79.6 1.48 [4.30] 2 [5] 1.80 [5.33] 2 (7)36.75 461990 108.0 3.79 [11.24) 4 [10) 6.26 (18.58) 6 [17)20.81 19Treat.2198,8 140.0 0.07 [0.32] 0.1 [0.2) 0.18 [0.81) 0.1 [0.6] 57.11 411989 138.5 1.52 [4.85) 1.1 [3.5) 1.28 [4.14] 1 [3]35.80 261990 199.9 3.98 [12.89) 2.0 [6.4) 7.10 [22.99] 4 [12] 20.23 17Percentage of wastewater input.2 W.rters in brackets represent nutrient ttake rates at zero mortality conditions.217Table 4.36 Magnesium removal efficiency by the soil-plantsystemYear Soil Mg Irriga— Soil Irriga— Soil Elementand at tion solu— tion solu— removaltreat— 0-60cm water tion water tion effiment (content) (content) ciency[a] [b) [c=l00_b/a*l00)(kg/ha) (mg/i) (mg/l) (kg/ha) (kg/ha) (%)Control1988 1300a 17.8 65.2 106 170 —601989 lO5Oab 17.8 43.5 71 25 651990 1150b 17.8 76.3 92 166 —80Treat. 11988 1272a 18.4 26.7 110 70 361989 1200a 19.8 18.8 80 11 861990 1226b 21.0 18.7 108 41 62Treat.21988 955a 18.4 42.5 140 180 —291989 999ab 19.8 37.5 138 133 41990 1047b 21.0 43.4 200 284 —401. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.2184.13 Sodium (Na)4.13.1 Soluble Na in soil solutionRegression of soluble Na in the soil—solution did not show asignificant relationship with its input rates through wastewaterirrigation (Table 4.4) although the concentration of Na inwastewater is as high as 68 — 82 mg/L. The concentration of thiselement in the soil solution under treatment 1 was not affected bywastewater irrigation (Figure 4.20). This might be attributed toheavy rainfall which diluted and leached down Na in the soilsolution. In treatment 2, concentration of soil solution Naincreased from 1988 to 1990 (Table 4.37).4.13.2 Soil NaAlthough some researchers have reported accumulation of Na inthe soil after a few years of wastewater irrigation (Richeriderferet al. 1976; Evans and Sopper 1972; Brockway et al. 1986),concentration of this element in the soil decreased with time inthe 0—30 and 30—60 cm layers in treatments 1 and 2 (Figure 4.21).One possible explanation is the presence of high levels of Cacarbonates (and possibly gypsum) in the soil that have a saturatedexchange complex (Russel 1988). High levels of Na in the soilsolution also point to leaching of this element from the soil.4.13.3 Sodium uptake and removal efficiencySodium is not an essential element for plant nutrition.However it is an important element in terms of soil salinity.21910001001988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.8Outputs of Na in control11000 I I I I1988.1 1988.2 1989.1 19892 1989.4 1969.5 1989.6 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of Na in treatment 1! 1000 I I I I I I 1 I1988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.8— Inputs and outputs of Na in treatment 2Figure 4.20. Comparison of the inputs (wastewater) and the outputs(soil solution) of Na at different irrigation treatments.I I I I I I I I 1FHbHCD OUTPUT• INPUT220Table 437 Mean annual concentration of Na in soilsolution under each irrigation treatment withpercentage of establishment year concentration1Treatment 1988 1989 1990Control (xng/L) 215.0(21] 157.0(52) 240.0(41](%) 100 73 112Treat.1 (mg/L) 187.0(40] 132.0(26] 172.0(49](%) 100 71 92Treat.2 (mg/L) 137.0(31) 195(43) 229.0(34)(Poplar) (%) 100 142 167Treat.2 (mg/L) 156.0(27) 159(20) 164.0(35](Grass) (%) 100 102 105. Values are means of 5 determinations, with standard deviationsin brackets.80223.70E2 40SI201001008040200Figure 4.21. Effect of irrigation on concentration of plantavailable Na in soil at 0-30 and 30-60 cm depths.gOControl Treat,l Treat.2____3Control TreaLl Treat2222Its buildup in soils can cause nutritional imbalances in plants.(Feigin et al. 1991). Under both wastewater treatments, uptakerates of Na by wood was 0.2% of the input, while woody biomass onthe control plots took up 0.4% (Table 4.38). At potentialconditions uptake rates would be 1% and 1% of the input bywastewater in treatments 1 and 2 respectively. Foliage took up 0.7%and 0.5%. Under potential conditions foliage uptake rate would notexceed 2% and 2%. Grass took up 2% and 1% of Na input. Thedecrease in soil Na content can be attributed to leaching of thiselement to groundwater (Table 4.39). Under treatment 1 Na removalefficiency was 12%, while under treatment 2 because some native orpreviously accumulated Na was leached downward, efficiency was—90%. Similar low renovation efficiencies of Na by soils has beenmentioned by McKim et al. (1982).4.14 Manganese (Mn)4.14.1 Soluble Mn in soil solutionThe regression analyses of the Mn input rates and theirconcentrations in soil solution were not significant (p>0.05)(Figure 4.22). It seems that the grass could absorb higher amountsof Mn than the trees (Table 4.40). In control plots, the concentration of Mn decreased with time, most likely due to uptake by theplants.223Table 4.38 Sodium uptake of wood and foliage comparedwith its inputs through wastewater irrigationYear -- -input- - - Uptakeandtreat- Irrigation Wood FoLiage Grass----ment water(kg/ha) (kg/ha CX) 1 (kg/ha) CX) (kg/ha) CX)ControL1988 89.8 0.00 [0.02]2 0.0 [0.02) 0.02 [0.08] 0.02 [0.1] 16.37 181989 60.2 0.06 [0.16) 0.1 [0.3] 0.41 [1.17) 1 [2) 3.44 61990 77.2 0.31 [0.89) 0.4 [1] 1.12 [3.20) 1.5 [5) 1.57 2Treat.11988 411.8 0.02 [0.07) 0.0 [0.01) 0.05 [0.24) 0.0 [0.1) 32.74 81989 281.0 0.15 [0.41) 0.1 [0.1) 1.11 [3.29] 0.4 [1] 22.95 81990 426.4 1.04 [3.09) 0.2 [1) 3.17 [9.41] 0.7 [2] 10.36 2Treat.21988 524.13 0.02 [0.07) 0.0 [0.02] 0.08 [0.37] 0.0 [0.1) 32.74 61989 488.95 0.20 [0.63) 0.0 [0.1) 0.80 [2.60] 0.2 [0.5) 22.35 41990 789.03 1.56 [5.05) 0.2 [1) 3.78 [12.24) 0.5 [2) 10.07 1. Percentage of wastewater input.2• Wrers in brackets represent nutrient uptake rates at zero mortaLity conditions.224Table 4.39 Sodium removal efficiency by thesoil-plant systemYear Soil Na Irriga— Soil Irriga— Soil Elementand at tion solu— tion solu— removaltreat— 0—60cm water tion water tion eff i—ment (content) (content) ciency[a) [b) [c=100_b/a*1003(kg/ha) (mg/i) (mg/i) (kg/ha) (kg/ha) (%)Control1988 402a 15.0 215 90 560 —5221989 231b 15.0 157 60 91 —521990 194b 15.0 240 77 520 —575Treat. 11988 485a 68.8 187 412 489 —921989 340b 70.0 132 281 77 721990 310b 82.9 172 426 379 12Treat. 21988 420a 68.8 137 524 580 —111989 270b 70.0 195 489 692 —411990 220b 82.9 229 789 1500 —901. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.2251988.1 19882 1969.1 19892 1989.4 1989.5 1989.8 1990.1 19902Outputs of soluble Mn in control1988.1 19882 19891 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.8Inputs and outputs of soluble Mn in treatment 11988.1 1986.2 19891 19892 1989.4 1969.5 1989.8 1990.1 19902 1990.3 1990.4 1990.6Inputs and outputs of soluble Mn in treatment 2Figure 4.22. Comparison of the inputs (wastewater) and the outputs(soil solution) of Mn at different irrigation treatments.1.990.3 1990.4 1990.61.0000•:: 0.1000S• 0.01000.00100.0001N1.000• 0.100C0.0100.001N,S 1.000• 0.100C0.010• 0.001OUTPUT• INPUTOUTPUT• INPUT226Table 4.40 Mean annual concentration of Mn in soilsolution under each irrigation treatment withpercentage of establishment year concentration’Treatment 1988 1989 1990Control (ing/L) 0.02(0.01) 0.02(0.01) 0.02(0.01](%) 100 0 0Treat.1 (mg/L) 0.04(0.01] 0.03(0.01] 0.03(0.01](%) 100 75 75Treat.2 (mg/L) 0.04(0.01) 0.03(0.01) 0.04(0.0](Poplar) (%) 100 75 75Treat.2 (mg/L) 0.15(0.01] 0.09(0.02) 0.01(0.0)(Grass) (%) 100 60 7. Values are means of 5 determinations, with standard deviationsin brackets.2274.14.2 Soil MnIn the 0—30 cm layer of soil the concentration of Mn decreasedin control and treatment 1 from 1988 to 1990 (p<0.01) (Figure4.23). In treatment 2, concentration of Mn did not changesignificantly with time. In the 30-60 cm the layer concentration ofMn did not show any significant change.4.14.3 Poliar manganeseIn 1988 and 1990, wastewater irrigation had no significanteffect on foliar Mn concentration. (Table 4.41).In 1989, the concentration of Mn in treatment 2 was lower thancontrol (p<O.O5), while the difference between treatment 1 andcontrol was not significant.4.14.4 Manganese uptake and removal efficiencyUptake of Mn by woody biomass was 38% and 28% in treatment 1and treatment 2, respectively. Foliage took up 54% and 33% andgrass took up 179% and 94% of Mn inputs in treatments 1 and 2,respectively (Table 4.42). Potential uptake rates would exceedinput, rates of Mn. Soil contents of Mn in all three irrigationtreatments did not change significantly over the three years(Table 4.43). Removal efficiency of the soil-plant system at thethird year was 58% in treatment 1 and 31% in treatment 2. Thesevalues are quite low compared with those presented by EPA (1981)(Table 2.6). A possible explanation is because the suctionlysimeters operated under 80 centibars of negative pressure, some80 I I I — 228NbC60E4O200—.— e9)9. 9O1Control Treat.1 TreaL26t1 IN 504000 —Control Treat.1 Treat2Figure 4.23. Effect of irrigation on concentration of plant-available Mn in soil at 0-30 and 30-60 cm depths.229Table 4.41 Mean concentration of Mn in foliage and woodof all clones under 3 irrigation treatments’ (mg/kg)Foliage Wood1988 2Control 82.4(11] 28.1(6.3)Treat.l 68.0(17] 16.8(3.0)Treat.2 61.3(5) 17.2(3.0)1989Control 73.6(14] 15.8(6.0]Treat.1 66.0(12] 14.6(4.6]Treat.2 49.4(18) 14.6(4.3)1990Control 68.8(16) 6.9(1.7)Treat.1 57.8(22) 7.9(2.7]Treat.2 56.0(19) 7.9(2.6). Values are means of 112 observations.2 Standard deviations are indicated in brackets.Table 4.42 Manganese uptake of wood and foliage comparedwith its inputs by wastewater irrigationYear ---Input--- Uptakeandtreat- Irrigation Wood FoLiage Grasment water(g/ha) (g!ha(%)1 (g/he) CX) g/ha CX)ControL1988 60.0 0.3 (1.5)2 1 [3] 1.86 (8.25] 3 [14] 836.74 13951989 40.1 12.3 [35) 31 [86) 32.46 [92.76) 81 [231) 444.16 11101990 51.4 38.8 [111] 76 [216] 87.19 [249.18] 170 (485) 356.94 700Treat. 11988 179.5 0.57 [2.5) 0.3 [1) 2.20 (9.76) 1 [5] 836.74 4681989 160.5 19.3 [56) 12 (35) 26.26 [77.89) 16 [48) 463.42 2891990 205.8 79.3 [253) 38 [115) 110.82 [328.76) 54 (160) 367.19 179Treat .21988 228.5 0.7 [3) 0.3 (1] 3.50 [15.54] 2 [7] 836.74 3671989 279.3 21.2 [68) 8 [24) 22.96 [74.31) 8 [27] 451.38 2691990 380.8 105.5 [342) 28 [90] 127.28 [411.96] 33 [108) 356.94 94. Percentage of wastewater input.2 Weters in brackets represent nutrient £take rates at zeromortaLity conditions.230231Table 4.43 Manganese removal efficiency by the soil—plantsystemYear Soil Mn Irriga— Soil Irriga— Soil Elementand at tion soiu- tion solu— removaltreat— 0—60cm water tion water tion effiment (content) (content) ciency[a] [b3 (c=l00_b/a*l00](kg/ha) (mg/i) (mg/i) (g/ha) (g/ha) (%)Control1988 260a 0.04 0.02 60 52 131989 290a 0.04 0.02 40 12 701990 245a 0.04 0.02 51 43 16Treat. 11988 330a 0.03 0.04 180 114 371989 280ab 0.04 0.03 161 20 871990 285b 0.04 0.04 206 87 58Treat. 21988 270a 0.03 0.04 228 150 341989 260a 0.04 0.03 279 116 591990 310a 0.04 0.04 381 262 311. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.232native Mn might have been removed together with soil solution. Thismay have resulted in some inaccuracies in calculation of Mn removalefficiency. Soil solution under freshwater (control) plotscontained 0.02 mg/L of Mn although freshwater used for irrigationof these plots contained less than 0.01 mg/L. After subtracting0.02 mg/L of Mn from concentrations of this nutrient in groundwaterunder treatment 1 and treatment 2, Mn removal efficiencies would be79% and 66% of Mn input, respectively.4.15 Zinc (Zn)4.15.1 Soluble Zn in soil solutionIn the case of Zn no clear relationship can be found betweeninputs and soil solution. However the trend is toward decrease(Figure 4.24.), and stabilization of this nutrient’s concentrationin soil solution in all treatments following the initial flushcaused by cultivation. (Table 4.44).4.15.2 Soil ZnConcentration of plant—available Zn which is a relativelymobile micronutrient did not show any change in any of thetreatments (p>0.O5) (Figure 4.25.).2330.10010000.010C0.0011968.1 1988.2 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 1990.5Outputs of soluble zinc in controlN1..000J I I I I I I I I0.100 I-o[1III[[[[Ii[[[[0.010 1-N 1 OUTPUTI • INPUT0.0011988.1 19882 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 1990.5Inputs and outputs of soluble zinc in treatment 1I-NE L000 I I I I?0.100I:: IIIi[[iiiiIiIi[[1988.1 1988.2 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 1990.5Inputs and outputs of soluble zinc in treatment 2Figure 4.24. Comparison of the inputs (wastewater) and the outputs(soil solution) of Zn at different irrigation treatments.234Table 4.44 Mean annual concentration of Zn in soil solutionunder each irrigation treatment with percentageof establishment year concentration’Treatment 1988 1989 1990Control (mg/L) 0.13(0.1] 0.05(0.01] 0.01(0.01)(%) 100 35 8Treat.1 (mg/L) 0.70(0.0) 0.05(0.01) 0.02(0.03](%) 100 7 3Treat.2 (mg/L) 0.17(0.0) 0.05(0.02) 0.03(0.01](Poplar) (%) 100 29 18Treat.2 (mg/L) 0.1(0.01] 0.03(0.01] 0.02(0.01)(Grass) (%) 100 38 25Values are means of 5 determinations, with standard deviationsin brackets.5 I I235IControl Treat_i Treat22.JN15SSQCI0ia•0/0.0 ——Control Treat.i Treat2Figure 4.25. Effect of irrigation on concentration of plant-available Zn in soil at 0-30 and 30-60 cm depths.2364.15.3 Foliar zincIn 1988, wastewater irrigation did not affect concentrationof foliar Zn significantly (Table 4.45).In 1989, foliar Zn in treatment 2 was higher than control(p<O.OS). However the difference between treatments 1 and controlwas not significant.In 1990, foliar Zn in treatment 2 was higher than thecontrol (p<O.O5). The difference between treatment 1 and controlwas not significant.4.15.4 Zinc uptake and removal efficiencyWoody biomass took up 33% and 27% of Zn in treatment 1 andtreatment 2, respectively while foliage uptake was 30% and 16%under the same treatments. Grass uptake rates were 23% and 12% ofthe input in treatments 1 and 2, respectively (Table 4.46). Underpotential conditions Zn uptake by wood, foliage and grass would besufficient to remove or immobilize most of the added Zn. Soil Zncontent did not change significantly (Table 4.47). Elementremoval efficiency was 87% and 69% in treatments 1 and 2,respectively. After correction, i.e., subtraction of Zn in soilsolution under control plots from those soil solutions intreatment 1 and treatment 2, efficiency values would reach 93% and80% respectively. These values correspond to the data given by EPA(1981) (Table 2.6).237Table 4.45 Mean concentration of Zn in foliage and wood ofall clones under 3 irrigation teatments’ (mg/kg)Foliage Wood1988 2Control 23.7(2.0) 34.8(6.0)Treat.1 23.3(2.2] 22.2(4.6)Treat.2 28.0(1.5] 34.0(2.1)1989Control 19.2(11.0] 17.7(9.0)Treat.l 28.9(6.7) 23.0(5.0)Treat.2 31.4(5.3) 27.5(7.0]1990Control 34.5(3.5] 25.0(1.0]Treat.1 35.5(3.0) 23.4(2.0)Treat.2 41.2(2.4] 19.6(6.0)Values are means of 112 observations.2 Standard deviations are indicated in brackets.Table 4.46 Zinc uptake of wood and foliage compared withits inputs by wastewater irrigationYear ---Input Uptakeandtreat- Irrigation Wood Foliage Grassment water(kg/he) (kg/ha) CX) (kg/ha) (X) (kg/he) CX)Control1988 - 0.42 [1.89)2 - 0.54 [2.42) 274.581989 - 14.64 [41.17) - 8.59 [24.54] - 189.791990 - 98.07 [280.28) - 113.98 [325.73) - 79.99Treat. 11988 299.2 1.08 [4.80) 0.4 [2) 1.08 [4.80) 0.4 [2) 274.58 921989 200.6 35.43 [103.52) 18 [52) 19.38 [57.49] 10 [29) 198.02 981990 360.1 118.35 [351.10) 33 [98) 108.65 [322.32) 30 [90] 82.28 23Treat.21988 380.9 0.90 [4.00) 0.2 [1] 1.28 [5.71) 0.3 [2] 274.58 721989 349.1 29.75 [95.22] 9 [27) 9.58 [31.00) 3 [9) 192.88 771990 666.3 178.80 [578.74] 27 [87) 104.60 [338.56) 16 [51] 79.99 12. Percentage of wastewater input.Wimters in brackets represent nutrient i.take rates at zeromortaLity conditions.238- 239Table 4.47 Zinc removal efficiency by the soil—plant systemYear Soil Zn Irriga— Soil Irriga— Soil Elementand at tion solu— tion selu— removaltreat— 0—60cm water tion water tion eff i—ment (content) (content) ciency(a] (b] [c=100_b/a*100](kg/ha) (mg/l) (mg/l) (g/ha) (g/ha) (%)Control1988 ha — 0.13 — 177 —1989 ha — 0.05 — 32 —1990 15a — 0.01 — 76 —Treat.11988 12a 0.05 0.07 299 182 391989 lOa 0.05 0.05 201 29 851990 12a 0.07 0.02 360 48 87Treat.21988 14a 0.05 0.08 381 340 101989 15a 0.05 0.05 349 177 491990 16a 0.07 0.03 666 197 701. ValueB with the same letter within each treatment are not significantlydifferent at 0.05 level.2404.16 copper (Cu)4.16.1 Soluble Cu in soil solutionFluctuations of Cu concentration in soil solution did notfollow any clear pattern (Figure 4.26). The grass plantation wasnot efficient in removing this nutrient therefore concentration ofCu in soil solution in 1990 increased (Table 4.48)4.16.2 Soil CuConcentration of Cu in 0-30 cm and 30-60 cm layers of soil didnot change from 1988 to 1990. However, treatments 1 and 2 showeda trend towards increase in available Cu concentration with time(Figure 4.27).4.16.3 Foliar CuIn 1988, wastewater irrigation did not affect concentrationsof foliar Cu significantly (Table 4.49).In 1989 and 1990 foliar Cu in treatments 1 and 2 was lowerthan control (p<0.O5)4.16.4 copper uptake and removal efficiency ratesUptake of Cu by the woody biomass was 7% and 4% of the inputrates in treatments 1 and 2 respectively. Foliage took up as littleas 4% and 3% of the input rate in treatments 1 and 2, respectively.Grass uptake was 15% and 8% (Table 4.50).241NECNE 1.000• 0.100C0.0100.0011988.1 19882 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 1990.5Inputs and outputs of soluble Cu in treatment 1OUTPUT• INPUT-z1.000- 0.100C0.010N• 0.001Figure 4.26. Comparison of the inputs (wastewater) and the outputs(soil solution) of Cu at different irrigation treatments.OUTPUTI INPUT• I I I I I I I I IHhk1988.1 19882 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 1990.5Outputs of soluble Cu in control1988.1 19882 1989.1 19892 1989.3 1989.4 1989.5 1990.1 19902 1990.3 1990.4 19905Inputs and outputs of soluble Cu in treatment 2242Table 4.48 Mean annual concentration of Cu in soil solutionunder each irrigation treatment with percentageof establishment year concentration’Treatment 1988 1989 1990Control (nigfL) O.12E0.05) 0.15f0.06) 0.10tO.05)(%) 100 125 75Treat.l (zng/L) O.15[0.1) 0.1O[0.07) O.04t0.0l](%) 100 67 27Treat.2 (mg/L) 0.09[0.04) O.07[0.03] O.08[0.01](Poplar) (%) 100 78 89Treat.2 (xngfL) 0.03E0.Ol) O.03[O.0lJ O.05[O.01)(Grass) (%) 100 0 167. Values are means of 5 determinations, with standard deviationsin brackets.2434EC)S •20C)0 IControl TreaLl TreaL2IIEC)I00iV00 IControl TreaLl Treat2Figure 4.27. Effect of irrigation on concentration of plant-available Cu in soil at 0-30 and 30-60 cm depths.244Table 4.49 Mean concentration of Cu in foliage and wood ofall clones under 3 irrigation treatments’ (mg/kg)Foliage Wood1988 2Control 4.1[O.3) 8.7[3.2)Treat.1 4.3[O.2] 5.2[1.2]Treat.2 3.6[O.l] 4.7[1.3J1989Control 7.l[1.1J 4.3[O.6]Treat.1 3.8[l.5] 4.5[1.1]Treat.2 4.7[1.l] 5.3(0.5]1990Control 8.7(1.1] 3.4(1.0]Treat.1 6.1(1.2] 3.8(1.1)Treat.2 5.5(1.3] 3.6(1.2]1. Values are means of 112 observations.2 Standard deviations are indicated in brackets.245Table 4.50 Copper uptake rates of wood and foliage comparedwith its inputs by wastewater irrigationYear - --Input--- Uptakeandtreat- Irrigation Wood FoLiage Grass.ent water(g/ha) (g/he) (g/ha) CX) g/ha CX)Contro- 0.11 [0.47)2 • 0.09 [0.41) - 112.151989 - 10.89 [8.63) - 3.02 [8.643 - 62.251990 - 17.00 [37.90) - 12.24 [34.98) - 4554Treat .11988 239.4 0.15 [0.67) 0.1 [0.3) 0.14 [0.64) 0.1 [0.3) 112.15 471989 120.4 7.67 [22.54) 6 [19] 2.77 [8.23) 2 [7] 64.95 541990 308.6 22.75 [67.48) 7 [22) 12.05 [35.76] 4 [12) 46.85 15Treat.21988 304.7 0.22 [0.96) 0.1 [0.3] 0.19 [0.84) 0.1 [0.3) 112.15 371989 209.5 8.01 [74.60] 4 [36) 1.90 [6.17] 0.9 [2.9] 63.27 301990 571.1 23.13 [25.92) 4 [5) 15.22 [49.26) 2.7 [8.6) 45.54 8l• Percentage of wastewater input.2 Wiirbers in brackets represent nutrient Ltake rates at zero mortaLity conditions.246Even under potential conditions the plantation would be. able toremove only a part of the Cu added to the site. The remaining Cumost likely would be retained by the soil organic matter (KabataPendias and Kabata 1984) (Table 4.51). Copper removal efficiency ofthe plantation in 1990 was 72% and 8% for treatments 1 and 2,respectively. After correction it was as high as 100% for each ofthe treatments.4.17 Iron (Fe)4.17.1 Soluble Fe in soil—solutionIron in soil solution was initially low but its concentrationslightly increased in 1989 and 1990 (Table 4.52) (Figure 4.28.).Concentrations of the micronutrients in soil solution duringresearch period never exceeded recommended maximum concentrationsfor irrigation water (Table 4.1). Most of the added micronutrientswere most likely immobilized at the organic horizons of soil (Reedand Crites 1984) or were absorbed by the plants.4.17.2 Soil FeThere was no difference in soil Fe from year to year intreatment 1 or 2 (Figure 4.29). In the 0-30 cm layer, soil Feshowed a trend toward decrease.247Table 4.51 Copper removal efficiency by the soil-plant systemYear Soil Cu Irriga- Soil Irriga- Soil Elementand at tion solu— tion solu— removaltreat— 0-60cm water tion water tion effment (content) (content) ciency[a) [b) [c=i00_b/a*l00)(kg/ha) (mg/i) (mg/i) (g/ha) (g/ha) (%)Control1988 16a — 0.12 — 71 —1989 19b — 0.15 — 47 —1990 19b — 0.09 — 153 —Treat. 11988 13a 0.04 0.15 239 392 —641989 16a 0.03 0.10 120 58 521990 19b 0.06 0.04 309 87 72Treat. 21988 iSa 0.04 0.09 305 383 —261989 17b 0.03 0.07 209 248 —191990 18b 0.06 0.08 571 523 81. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.248Table 4.52 Mean annual concentration of Fe in soil solutionunder each irrigation treatment’Treatment 1988 1989 1990Control (mg/L) O.OO[O.OO) 0.04[O.01) 0.Ol[O.00)Treat.l (mg/L) 0.OO[0.O0) 0.02[0.01) 0.03[O.02)Treat.2 (mg/L) O.OO[O.OO) 0.03[O.Ol) O.02f0.0l](Poplar)Treat.2 (mg/L) O.O0[0.O0] O.03[O.02] O.02[O.Ol)(Grass). Values are means of 5 determinations, with standard deviationsin brackets.2490.010)1ooI. I-., II j010.0011988.1 1988.2 1989.1 19892 1989.4 1989.5 1989.8 1990.1 19902 1990.3 1990.4 1990.8Outputs of soluble Fe in controlI I 4. L[iiiii1iiiiiI [1ii1988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.8Inputs and outputs of soluble Fe in treatment 1-‘..b0100 L0EL000.S 0.010 .N I OUTPUTbI II ]NPUT0.0011988.1 19882 1989.1 19892 1989.4 1989.5 1989.6 1990.1 19902 1990.3 1990.4 1990.8—Inputs and outputs of soluble Fe in treatment 2Figure 4.28. Comparison of the inputs (wastewater) and the outputs(soil solution) of Fe at different irrigation treatments.NS i.ooo0.10000.010. 0.001—OUTPUT.• INPUT200NSC)100C50Cd)0B)g gB-gO.Control TreaLl TreaL2150NSC)500Figure 4.29. Effect of irrigation on concentration of plant-available Fe in soil at 0-30 and 30-60cm depths.250Control Treat.1 Treat202514.17.3 Foliar ironIn 1988 and 1989, wastewater irrigation did not affectconcentrations of foliar Fe significantly (Table 4.53).In 1990, Treatments 1 and 2 were significantly lower thancontrol.4.17.4 Iron uptake and removal efficiencyWoody biomass took up 13% and 9% of Fe input in treatments 1and 2, respectively. Foliage uptake was 26% and 16% while grasstook up as much as 604% and 317% of Fe input in treatment 1 andtreatment 2, respectively. Under potential conditions Fe uptakerates by wood and foliage would exceed the input by wastewater intreatment 1 while its uptake under treatment 2 would be about 80%of the input (Table 4.54).Iron is one of the most abundant elements in soil (Kabata—Pendias and Pendias 1984), thus addition by wastewater irrigationdoes not affect its concentrations in soil significantly (Table4.55). Soil Fe content decreased from 1988 to 1990 in all threetreatments. Elemental removal efficiency for treatment 1 andtreatment 2 were 94% and 93%, respectively. After correction, itwould be almost 100% for both treatments.252Table 4.53 Mean concentration of Fe in foliage and wood ofall clones under 3 irrigation treatments’ (mg/kg)Foliage Wood1988 2Control 133.7[22] 31.4[11)Treat.l 153[32) 31.2[13JTreat.2 106[11] 22.4[9)1989Control 134[20) 24.l[8]Treat.1 77[17) 34.2[9)Treat.2 98[8) 39.1[2]1990Control 120[22] 14.2[5)Treat.1 86[11) 22.4[8JTreat.2 83[9) 20.3(7]‘. Values are means of 112 observations.2 Standard deviations are indicated in brackets.253Table 4.54 Iron uptake of wood and foliage as compared with itsinputs through wastewater irrigationYear ---Input-— Uptakeandtreat- Irrigation Wood FoLiage Grasment water(9/ha) (g/ha) (%) (g/ha) CX) 9/he CX)Cont rot1988 239.4 0.62 [2.78)2 0.2 [1) 3.01 [13.38) 1 [6) 1299.90 5431989 160.1 25.88 [72.98) 16 [46) 65.38 [186.85) 41 [117] 834.20 5211990 205.8 40.70 [116.30) 20 [56) 139.55 [398.80] 68 (194] 4229.55 2053Treat.11988 538.6 0.71 [3.14] 0.1 [0.6) 373 [16.56) 1 [3) 1299.91 2411989 280.9 67.33 [198.70) 24 [71) 61.30 (181.87) 22 [65] 870.37 3101990 720.2 91.46 [271.33) 13 [38) 187.66 [556.72) 26 [77) 4351.02 601.Treat.21988 685.5 1.19 [5.29) 0.2 [1] 7.48 [33.25) 1 [5] 1299.91 1901989 488.7 72.96 [234.72] 15 [48) 39.67 [128.38) 8 [26] 847.77 1731990 1332.7 114.12 [369.37) 9 [28) 218.72 [707.95] 16 [53] 4229.55 318- Percentage of wastewater input.2 W.rters in brackets represent nutrient ttake rates at zero mortaLity conditions.254Table 4.55 Iron removal efficiency by the soil—plant systemYear Soil Fe Irriga— Soil Irriga— Soil Elementand at tion solu— tion solu— removaltreat— 0—60cm water tion water tion effment (content) (content) ciency[a) [b) [c=100_b/a*100)(kg/ha) (mg/i) (mg/I) (g/ha) (q/ha) (%)Control1988 500a 0.04 0.01 239 13 941989 38Db 0.04 0.03 160 18 891990 475ab 0.04 0.02 206 41 80Tneat.l1988 720a 0.09 0.01 539 13 981989 660a 0.07 0.03 281 16 931990 56Db 0.14 0.02 720 43 94Tneat.21988 760a 0.09 0.01 685 21 971989 640a 0.07 0.03 489 103 791990 625a 0.14 0.03 1333 164 931. Values with the same letter within each treatment are not significantlydifferent at 0.05 level.2. Negative percentages represent losses due to leaching.2554.18 Graphical vector analysisIn order to find the effect of wastewater irrigation onnutritional status of the trees the mean of 12 clones were testedwith graphical vector analysis to determine their nutritionalstatus. For a description of the graphical analysis method see‘Literature review’ and ‘Materials and methods’ sections.Foliar N which was diluted in 1988 became sufficient in1989 and with the vigorous growth of the trees in 1990 becamedeficient (Figure 4.30.).Phosphorus was always deficient in the plants during the 3years of wastewater irrigation.Supply of K was sufficient during all three years in bothtreatments.Calcium which was sufficient during the first two years andwas diluted in 1990.Magnesium deficiency in 1988 switched to dilution and remainedat the same stage in 1990.Manganese was always in the state of dilution. Zinc which wasdeficient in treatment 2 during 1988 and 1989 was diluted in1990. In treatment 1 Zn moved from sufficiency in 1988 todeficiency and remained there in 1990.Copper moved from relative sufficiency to dilution in 1989 andremained at the same stage during 1990.Iron in treatment 1 was deficient during 1988. Later, in1989, it moved to dilution zone and remained there during 1990. Intreatment 2, Fe was diluted during all three years of wastewater256irrigation.The term ‘deficiency’ in this research should not beinterpreted as a shortage of certain nutrients since the controlplots were established on quite fertile soil where no shortage ofnutrients was observed. It should rather be interpreted as apositive response of the trees to higher inputs of nutrients andtheir capacity to take up nutrients.The conclusions that can be drawn from graphical vectoranalyses are: 1) The nutritional status of trees changed with timeand treatments. However the general trend of most nutrients wastowards dilution in 1990 which was likely caused by fast growthrates of the plants resulting from fertilization-irrigation of thesite. 2) No toxic effects were observed in any of the clones as aresult of addition of nutrients. Luxury consumption was also rare.As a result, the application of wastewater at levels as high asTreatment 2 (2 x treatment 1) is likely to be safe for the trees.Leaft. 1 2Relative Content %Figure 4.30. Relative response in nutrient concentration, nutrientcontent and dry weight of leaves in hybrid poplars (all 12 clones)irrigated with municipal wastewater at two levels (treatments 1 and 2).Status of control (freshwater irrigation) was normalized to 100 toallow comparison on common base.C 257/7/ * FE 1988• ///N/7/i I0 100 200 300 400Leaf wt.1601400J1201004)8060200150.tdlOO50130120o 1101004)90804)706019891990C12* Fe* Cu* Zno MnMgCa* Fe* Cu* Zno Mn* Mg0 CaQN50 100 150 200Relative content %Leafwt.C120 100 200 3002585. Summary and Conclusions1. Results of this study may have been influenced by the effectsof effluent loading previous to this research project.2. Almost all nutrients taken up by the foliage and groundvegetation will return to the soil eventually as a result ofdecomposition and mineralization of the litter. Only woodybiomass will remain relatively intact until it is removed atharvest time.3. It would be ideal to mow and remove ground vegetation duringthe first few years until canopy closure. As a result, lessnutrients will be accumulated in the site. Harvesting thetrees before litterfall and removal of entire trees fromthe site will also be helpful in extending the life of theliving filter. However the most reliable and certain way toprolong the life of a plantation as a living filter is tocreate a balance between inputs and outputs of the nutrients.The first step is the estimation of nutrient uptake rates bythe woody biomass (i.e., boles and branches). Based on thesedata, it is possible to calculate how much nutrients orother elements can be added to the site so that theiraccumulation in the soil and their leaching to groundwaterwould be minimal. This data will determine how much wastewatercan be added to the site. However it should be taken intoaccount that irrigation amounts based on a nutrient input—output balance should not be less than the potential ET rateof the site. Sometimes, wastewaters contain excessive levels259of certain elements or nutrients. In arid and -semiaridregions where potential ET is high this might restrict theamount of wastewater that can be applied to plantationsbecause it would cause nutrient overloading in soils. In theVernon project, wastewater is dilute and potential ET isrelatively low, thus there is no restriction on applyingwastewater at high levels if desired.4. During the three year period, nutrient uptake by woody biomassat potential conditions (i.e., no mortality) would have beenonly a fraction of nutrient inputs (Table 5.1). Most of thenutrients would have been either taken up by the foliage andground vegetation, sorbed by the soil or leached to the lowerhorizons. Elemental removal efficiencies, which arecalculated for actual conditions (i.e., taking into accounttree mortality) (Tables 4.19, 4.24, 4.28, 4.32, 4.36, 4.39,4.43, 4.47, 4.51 and 4.55), indicate that most of the addednutrients were retained by the soil—plant system. It is safeto assume that under no or very low mortality nutrientremoval efficiency would be even higher.5. Although application of high levels of wastewater (treatment2) increased growth of poplars, the proportion of nutrientuptake rates by woody biomass to input by wastewater wassmaller than in treatment 1. Thus treatment 2 is notrecommended at this stage, because it would eventually causebuildup of nutrients in soils and contamination ofgroundwater.2606. It is recommended that treatment 1 be used for the firstthree years, then irrigation levels be increased gradually,the amount being based on the inputs of a limiting element,likely to be nitrogen.Table 5.1. Potential nutrient uptake by woody biomass asa percentage of the input rate1988 1989 1990Treatment1 2 1 2 1 2N 2 2 37 23 88 52P 1 1 12 8 36 25K 1 1 18 12 62 41Ca 0.4 0.3 10 7 26 18Mg 0.3 0.2 5 4 10 6Na 0 0 0 0 1 1Mn 1 1 35 24 104 90Zn 2 1 52 27 98 87Cu 0.3 0.3 19 36 22 5Fe 1 1 71 48 38 28261.7. The concentration of cations in wastewater is relatively lowand with the moderate soil cation exchange capacity ofl5meg/l00 gm., low wastewater electroconductivity ( EC = 0.79mmhos/cm) and sodium adsorption rates (SAR = 2.27) it isunlikely that cations of any kind would be a limiting factor,especially that their inputs to the site are negligible.8. That portion of P that is not taken up by the woody biomasscan be easily immobilized by the soil, therefore it is not alimiting element.9. Nitrogen, although not abundant in wastewater, might becomea problem at higher irrigation levels. However, underpotential conditions 88% of this element can be taken up bythe woody biomass. It does not seem necessary to adjust theirrigation rates to N uptake rates by wood at the third yearbecause the 12% surplus of N can be removed from theenvironment through ways such as denitrification and uptake bythe roots10. Wastewater application increased tree height, basal diametergrowth, total leaf area and biomass of wood and foliage of thepoplars. Among the poplar clones, in general performance andalso in reaction to wastewater irrigation, Populus trichocarpax deltoides (clones 44-135 and 52-234) were superior to theother clones. Next came P. deltoides x nigra (DN—152 clone).Under potential (no mortality) conditions and disregardingedge effect, mean annual woody biomass production of all 12clones at the end of the third year would be roughly 20 and 24Mg/ha for treatments 1 and 2, respectively. Compared to 11262Mg/ha of woody biomass in control, these values are 182% and218% higher for treatments 1 and 2, respectively.11. Wastewater application quantities influenced concentrations ofsoluble N, P, K, Ca, Mg, and Na in soil solution.Concentrations of Mn, Zn, Cu, and Fe were not influenced bywastewater application rates probably because these nutrientswere sorbed or taken up in the upper 75 cm of soil.12. Irrigation with wastewater at rates as high as treatment 2did not add sufficient micro— and macro—nutrients to thesite to cause any growth disorders such as toxicity orantagonism between nutrients in trees. In many cases‘dilution’ of nutrients was observed due to fast growth oftrees.13. By the end of the third year the soil-plant system is capableof retaining most of the nutrients added through wastewaterirrigation. Ground vegetation (grass) played an important rolein retarding nutrient leaching to groundwater. At this age theforest plantation relies primarily on the organic litterlayers produced by ground vegetation plus tree foliage forwastewater renovation.14. Only at the end of the third growing season did nutrientuptake by the woody biomass reach nutrient input levels intreatment 1, thus higher wastewater irrigation rates thanthose of treatment 1 (ET + 30%ET) are not recommended for thefirst three years of plantation so that there will be nogroundwater contamination.26315. Tree spacing of 1.5 m x 1.5 m was not suitable formechanization of grass removal from the site. Thus asuitable environment was created for rodents which caused asignificant damage to the trees. It is proposed that aspacing be selected that would facilitate movement of a moweralong the rows and without decreasing the number of trees/ha.A spacing of 2.5 m x 1 m would serve this purpose.16. With proper site cultivation, right tree spacing, carefultending and frequent replanting woody biomass production willrise significantly. 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In: Poplar Council of Canada andENFOR Programme. Canada Department of Supply and Services,62p.xTpuedd01£311Table A.1 Calculation of ET in Vernon B.C. using ModifiedPenman Method (May 1 — Oct 15, 1988).May Jun. Jul. Aug. Sep. Oct.(°C) 12.90 16.50 19.65 18.80 14.15 8.55T (°C) 18.80 22.30 26.60 25.70 20.20 12.10T (°C) 7.00 10.70 12.70 11.90 8.10 5.00TD (°C) 11.80 11.60 13.90 13.80 12.10 7.10T1 (°K) 291.80 295.30 299.60 298.70 293.20 255.10Tb (°K) 280.00 283.70 285.70 284.90 281.10 278.00RA (cal/day) 15.78 17.08 16.38 14.05 10.83 7.31Rb (cal/day) 510.84 548.22 575.51 491.87 355.02 183.56S (%) 51.00 51.00 64.00 62.00 54.00 39.00R,, (cal/day) 715.32 767.66 719.39 624.68 483.13 293.93e, (mbar) 21.70 26.92 34.81 33.01 23.67 14.13e (mbar) 10.03 12.88 14.70 13.94 10.81 8.74e1 (mbar) 14.89 18.78 22.88 21.70 16.15 11.15e (mbar) 15.87 19.90 24.75 23.48 17.24 11.43efie 0.98 1.12 1.87 1.77 1.09 0.28R (cal/cm2/day) 154.57 142.92 129.99 133.80 150.92 164.28Rb (cal/cm/day) 103.76 95.94 100.10 101.09 104.90 93.34(cal/cm2/day) 289.59 326.19 343.05 277.65 168.47 48.00w1+w2u 3.26 3.33 3.03 2.93 2.80 2.78A (nibar/°C) 0.97 1.19 1.42 1.35 1.04 0.75X (cal/g) 588.81 586.83 585.09 585.56 588.12 591.20— 0.63 0.63 0.63 0.63 0.63 0.63Etp (cal/day) 195.18 233.31 264.19 214.80 122.84 31.74Etp (mm/day) 3.31 3.98 4.52 3.68 2.09 0.54Ztp (Ma/aonth) 102.76 119.27 139.97 113.72 62.66 8.05312Table A.2 Calculation of ET in Vernon B.C. using ModifiedPenman Method (May 1 — Oct 15, 1989).May Jun. Jul. Aug. Sep. Oct.T (°C) 13.25 18.00 20.25 18.50 14.90 8.35T, (°C) 19.10 24.2 27.2 24.5 21.2 12.5T, (°C) 7.40 11.8 13.3 12.5 8.6 4.2TD (°C) 11.70 12.4 13.9 12.0 12.6 8.3T1 (°K) 292.10 297.20 300.20 297.50 294.20 285.50Tb (°K) 280.40 284.80 286.30 285.50 281.60 277.20RA (cal/day) 15.78 17.08 16.38 14.05 10.83 7.31Rb (cal/day) 508.67 566.81 575.51 458.67 362.28 198.47S (%) 51.00 51.00 64.00 62.00 54.00 39.00R. (cal/day) 712.28 793.69 719.39 582.51 493.01 317.80e (nibar) 22.11 30.19 36.06 30.73 25.17 14.51e (mbar) 10.31 13.85 15.28 14.51 11.19 8.26ea (mbar) 15.23 20.64 23.74 21.30 16.95 11.00e1 (mbar) 16.21 22.02 25.67 22.62 18.18 11.38e—e1 0.98 1.38 1.93 1.32 1.23 0.38R (cal/cm2/day) 153.57 137.10 127.17 134.98 148.56 164.70Rb (cal/cm/day) 103.09 92.03 97.92 101.98 103.26 93.58R.(cal/crn2/d y) 288.59 344.41 345.23 251.20 175.70 59.24w1+w2u 3.26 3.33 3.03 2.93 2.80 2.78A (mbar/°C) 0.99 1.30 1.46 1.33 1.09 0.75A (cal/g) 588.61 586.00 584.76 585.73 587.71 591.31— 0.63 0.63 0.63 0.63 0.63 0.63Etp (cal/day) 195.70 254.74 268.18 189.57 130.76 39.71Etp (mm/day) 3.32 4.35 4.59 3.24 2.22 0.67Etp (R/onth) 103.07 130.41 142.17 100.33 66.75 10.07313Table A.3 Calculation of ET in Vernon B.C. using ModifiedPenman Method (May 1 — Oct 15, 1990).May Jun. Jul. Aug. Sep. Oct.(°C) 12.50 15.70 21.10 21.15 17.20 7.35T (°C) 17.50 21.10 27.50 27.50 24.20 11.50T (°C) 7.50 10.30 14.70 14.80 10.20 3.20TD (°C) 10.00 10.80 12.80 12.70 14.00 8.30T1 (°K) 290.50 294.10 300.50 300.50 297.20 284.50T6 (°K) 280.50 283.30 287.70 287.80 283.20 276.20RA (cal/day) 15.78 17.08 16.38 14.05 10.83 7.31R (cal/day) 470.26 528.97 552.27 471.86 381.88 198.47S (%) 51.00 51.00 64.00 62.00 54.00 39.00R 658.50 740.71 690.34 599.26 519.67 317.80e, (mbar) 20.00 25.02 36.70 36.70 30.19 13.58e (rnbar) 10.38 12.54 16.73 16.84 12.46 7.70e (mbar) 14.51 17.84 25.02 25.10 19.63 10.27e1 (mbar) 15.19 18.78 26.72 26.77 21.32 10.64e—e 0.69 0.94 1.70 1.67 1.69 0.36R, (cal/cm2/day) 155.55 145.75 122.92 122.66 140.41 166.40R. (cal/cm/day) 104.42 97.83 94.65 92.67 97.60 94.54R (cal/cm2/day) 257.69 309.48 330.61 270.66 196.45 58.28w+w2u 3.26 3.33 3.03 2.93 2.80 2.78(mbar/°C) 0.95 1.14 1.53 1.54 1.24 0.70X (cal/g) 589.03 587.27 584.30 584.27 586.44 591.86— 0.63 0.63 0.63 0.63 0.63 0.62Etp (cal/day) 168.90 216.45 257.11 213.76 154.82 38.19Etp (mm/day) 2.87 3.69 4.40 3.66 2.64 0.65Ftp (./onth) 88.89 110.57 136.41 113.42 79.20 9.68314Table A.4 Monthly precipitation rates in Vernon B.C. fromMay 1 to Oct.15 (mm)’.1988 1989 1990May 52.8 48.8 84.6Jun. 67.8 45.4 83.0Jul. 32.6 35.0 31.0Aug. 42.2 45.2 24.4Sep 53.2 26.6 3.2Oct. 12.0 2.8 8.61. Environment Canada 1993.axpueddySTE3160)Particle size (urn)0-15cm15-30 cm30—60cmFigure B. 1. Soil particle distribution curvefor 3 different depths.100908070604030200 10 20 30 40 50 60 70 80


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