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Effect of urea fertilizer on leaching in some forest soils Otchere-Boateng, Jacob 1976

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EFFECT OF UREA FERTILIZER O N LEACHING IN SOME FOREST SOILS by JACOB OTCHERE-BOATENG B . S . F . , University of British Columbia, 1970 M . S c , University of British Colunr i a , 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY CF GRADUATE STUDIES (Dept. of Soil Science) We accept this thesis as conforming to the required • tandard THE UNIVERSITY OF BRITISH COLUMBIA March, 1976 <c) Jacob Otchere-Boateng, 1976 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representative. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Forest Soils Department of Soil Science University of British Columbia Vancouver, Canada V6T I W 5 March, 1976 ABSTRACT The study examined, by means of a series of field and laboratory experiments, the impact of urea fertilizer on soil nutrient leaching from four forest soil sites including a coarse-textured soil with little organic matter, a soil with substantial nitrification ability, a soil with relatively high organic matter content, and one with a thick forest floor. Duplicate tension lysimeters, installed near the surface and below the root zone in control and fertilized plots on each site, were used to obtain soil leachate solutions. After soil sampling and analyses, a year of lysimeter installation, and about seven months of pre-fertilization solution monitoring and analyses, urea (448 kg/ha urea-N) was applied in the fa l l . Soil - water sampling was continued for 246 days following fertilization. Some additional field soil sampling and analyses and laboratory soil - column leaching studies and soil analyses were conducted to confirm the field lysimeter results, and study the physico-chemical reactions and mechanisms responsible for those results. Field lysimeter soil-solutions were analysed for pH, electrical con-ductivity, N a , K, C a , M g , N H ^ - N , N O - ^ - N , total N and P, while in the laboratory experiments, solution analyses included pH,electrical conductivity, N a , K, C a , M g , Fe, M n , A l , organic matter and urea. Soil analyses included pH, cation exchange capacity, exchangeable cations and extractable P. The results indicated that the mechanism underlying leaching following urea application is not dominated simply by cation exchange reactions and mass ion effect. There were no serious losses of N a , K, Ca , and Mg immediately following a i i i i i fall urea application. On the contrary, urea fertilizer caused a decline in Ca and Mg leaching. This was confirmed by laboratory leaching studies at 4°C. Leachate concentration of A l , Fe, Mn and organic matter, however, increased substantially (especially at 22°C) following urea treatment. Increases in CEC (caused by a rise in pH associated with (NH^^CO^ production by urea hydrolysis), the Donnan distribution, and organic colloid dispersion appear to define the behaviour of these cations. Increased leaching losses of bases (e.g. Ca and Mg), however, occurred in the field during the warmer months. The leaching was found to relate to pH decreases associated with increased nitrification (nitric acid formation). Decreased pH resulted in subsequent decreased CEC and promoted metal cation leaching because of the mobile nitrate anion and the strongly adsorbed hydrogen ion. Studies in the laboratory showed that urea fertilizer may cause increases in the effective CEC and exchangeable N a , K, Ca and M g , and decreases in "exchange-able" A l , Fe and Mn. Increases in CEC were larger at 22°C than at 4°C. At only one of the sites, dissolved N concentration increased to more than 10 mg/l in the soil solution below the root zone, after urea application. The soil at that site is characterized by very coarse texture, extremely low organic content, and limited root distribution. Subjective evaluation of such morphological features in the profile of nitrogen-deficient soil might be adequate to predict the likelihood of serious N contamination of ground water, caused by urea at conventional rates. Results from all sites and consideration of climate and geography suggest that fall urea application in southwestern British Columbia forests is unlikely to cause sufficient metal cation leaching to be detrimental to water quality. TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS Iv LIST OF FIGURES x LIST OF TABLES x i i i ACKNOWLEDGMENT xv 1.0 INTRODUCTION I 2.0 THEORY A N D REVIEW 3 2.1 LEACHING IN FOREST ECOSYSTEM 3 2.1.1 Unmanipulated Forests 4 2.1.2 Chemically-treated Forests 5 2.2 THE FATE OF APPLIED UREA FERTILIZER IN FOREST SOILS 6 2.3 UREA TRANSFORMATION AND ASSOCIATED PHENOMENA IN FOREST SOILS 7 2.3.1 Urea Hydrolysis (ureolysis or ammonification of urea) and its Effects on soil Chemistry 7 2.3.1.1 The Carbonate and NH^/NH^ Equilibria 10 2.3.1.2 pH of The Soil (Soil Reaction) . . . . II 2 .3 .2 Dispersion and Flocculation of Organic Colloids . 12 2.3 .3 Nitrogen Immobilization 15 2.3 .4 Nitrification 15 iv V Page 2 .3 .5 Gaseous Losses of Nitrogen and Nitrogen Compounds 20 2.3.5.1 Denitrification (Chemo-denitrifica-tion and Biodenitrification (dissimi-latory nitrate reduction)) 20 2 . 3 . 5 . 2 Volati lization of Ammonia . . . . 21 2.4 THEORY OF ION EXCHANGE A N D ITS IMPORTANCE TO LEACHING LOSSES 22 2.4.1 CEC and the Nature of The Exchange System . 22 2 .4 .2 Cation Exchange Phenomena 24 2 .4 .3 The Donnan Equilibrium 27 2 .4 .4 Anion Adsorption 28 2.5 INFLUENCE OF HUMIC SUBSTANCES O N ION LEACHING 29 2.5.1 Reactions of Humic Substances (especially, the Fulvic Acids) with Metal Ions 29 2 .5 .2 Reactions of Humic Substances with N - contain-ing compounds 32 2.5.2.1 Urea 32 2 . 5 . 2 . 2 Ammonia 33 2.6 THE ANIONIC THEORY FOR CATION LEACHING . . . 33 2.7 LEACHING MODELS 35 2.7.1 Forms in which Urea-N Fertilizer may be leached 35 2 .7 .2 General Mathematical Models for Chemical Leaching 36 2.8 METHODS FOR EVALUATING LEACHING 37 vi Page 3.0 MATERIALS A N D METHODS 39 3.1 FIELD EXPERIMENT # l 39 3.1.1 Study Area 39 3.1.2 Experimental Sites 42 3.1.2.1 General Characterization of the Sites 48 3.1.3 Lysimeter Installation 53 3.1.4 Throughfall Sampling 56 3.1.5 Fertilization 57 3.1.6 Sampling, Storage and Analyses of Lysimeter Soil Leachates 57 3.2 FIELD EXPERIMENT # 2 59 3.3 LABORATORY EXPERIMENT # 1 60 3.4 LABORATORY EXPERIMENT # 2 61 3.4.1 Leachate Analyses 62 3 . 4 . 2 Soil Analyses 63 3 . 4 . 3 Determination of the organically bound A l , Fe, Ca and Mg in the urea fertilized leachates 63 4.0 RESULTS AND DISCUSSION 64 4.1 LEACHATE VOLUME 64 4 .2 SOIL REACTION (PH) 65 4.3 CONDUCTIVITY OF SOIL LEACHATE 75 vii Page 4 .4 NITROGEN CONSTITUENTS IN SOIL LEACHATES . . . 79 4.4.1 Organic Nitrogen (including urea-N) 79 4 . 4 . 2 Ammonium Nitrogen (NH^-N) 81 4 . 4 . 3 Nitrate Nitrogen (NO3 - N ) 85 4 . 4 . 4 Total Nitrogen 88 4.5 PHOSPHORUS 88 4.6 ORGANIC MATTER 89 4.7 CATION EXCHANGE AND EXCHANGEABLE CATIONS . 90 4 . 7 . 2 Exchangeable cations (Na, K, C a , M g , A l , Fe, Mn and NH 4 ) 95 4.8 LEACHING AND BEHAVIOUR OF EXCHANGEABLE CATIONS 98 4.8.1 Leaching of Alkali and Alkaline-earth metals . . 98 4 . 8 . 2 Leaching of A l , Fe and Mn 102 4 .9 OBSERVED PARAMETERS INFLUENCING LEACHING . . . 103 4.9.1 The Carbonate Equilibrium and Nutrient Cation Leaching 103 4 . 9 . 2 pH and Leach ing 105 4 . 9 . 3 Nitrate Formation and Leaching of Nutrient Cations 105 4.10 CHANGES IN NUTRIENT BALANCE .; 113 4.10.1 Leaching of "Nutrient" Cation Balance . . . . . 113 4.10.1.1 Cation Balance and Nitrification Inhibitors " 8 Page 4.10.2 Exchangeable Al Balance 120 4.11 FREE A M M O N I A 120 5.0 SUMMARY A N D CONCLUSIONS 121 6.0 REFERENCES 125 APPENDICES Appendix A . UBC Forest Weather Data 139 A.I Illustration of Site I 140 A . 2 Illustration of Site II 142 A . 3 Illustration of Site III 144 A . 4 Illustration of Site IV 145 A . 5 Field Lysimeter System: Vacuum Tank and Cartesian Monostat 147 A . 6 Field Lysimeter System: Housing of Shallow Plate Carboy Collectors 148 A . 7 Field Lysimeter System: Housing of Deep Plate Carboy Collectors 149 A . 8 Field Lysimeter System: Portion of the installation as seen on a Plot (Site III) 150 Appendix B Analyses of Leachates from Lysimeter Soil Columns incubated at 22°C (Laboratory , Experiment # l ) 151 Appendix C.I Analyses of Leachates from lysimeter soil-columns incubated at 4°C (Laboratory Experiment ^2A) . . 153 Appendix C .2 Analyses of leachates from lysimeter soil columns incubated at 22°C (Laboratory Experiment^2A). . 154 Appendix D.I.I Post-fertilization leaching data,Site l(Shallow) . 155 Appendix D.I.2 Post-ferti'ization leaching data, Site l(Deep) . . 156 Appendix D.2.1 Post-fertilization leaching data,Site ll(Shallow). 157 Appendix D.2.2 Post-fertilization leaching data, Site II (Deep) . 158 Appendix D.3.1 Post-fertilization leaching data, Site III (Shallow). 159 Appendix D.3.2 Post-fertilization leaching data, Site III (Deep) . . 160 Appendix D.4.1 Post-fertilization leaching data, Site IV (Shallow). ' ° ' Appendix D.4.2 Post-fertilization leaching data, Site IV (Deep) . . IX Page Appendix D.5.1 Unfertilized plots leaching data, Site I (Shallow) '63 Appendix D.5.2 Unfertilized plots leaching data, Site I (Deep) I 6 4 -Appendix D.6.1 Unfertilized plots leaching data, Site II (Shallow) 1 6 5 Appendix D.6.2 Unfertilized plots leaching data, Site II (Deep) 1 6 6 Appendix D.7.1 Unfertilized plots leaching data, * Site III (Shallow) 1 6 7 _ Appendix D.7.2 Unfertilized plots leaching data, Site III (Deep) 1 6 8 Appendix D.8.1 Unfertilized plots leaching data, Site IV (Shallow) 1 6 9 Appendix D.8.2 Unfertilized plots leaching data, Site IV (Deep) 1 7 0 Appendix E Summary of Regression Analyses of data presented in Appendix D 1 7 1 Appendix F Throughfall data for Sites I, II, III and IV 1 7 6 LIST OF FIGURES Figure Page 1 Temperature and precipitation data for two D.O.T . stations at the UBC Research Forest, Haney 40 2 Collecting system for soil Leachates (Field) 55 3 A Soil-leachate pH changes: shallow soil solution data, Site I . . 66 3B Soi l-leachate pH changes: deep soil solution data, Site I . . . 66 4A SoiIrleachate pH changes: shallow soil solution data, Site II . . 67 4B Soil-leachate pH changes: deep soil solution data, Site II . . . 67 5A Soil-leachate pH changes: shallow soil solution data, Site III . 68 5B Soil-leachate pH changes: deep soil solution data, Site III . . . 68 6A Shallow-leachate pH changes shallow soil solution data, Site IV 69 7 Shallow lysimeter data for pH, conductivity and nitrate following fertilization, Site 1(A) 76 8 Shallow lysimeter data for pH, conductivity and nitrate following fertilization, Site 11 (B) . . 76 9 Shallow lysimeter data for pH, conductivity and nitrate following fertilization, Site 111(B) 77 10 Shallow lysimeter data for pH, conductivity and nitrate following fertilization, Site IV (A) 77 11 Shallow lysimeter data for ammonium-nitrogen and nitrate-nitrogen following urea fertilization 83 12 Relationship between pH and calcium leaching (shallow plate data) following urea fertilization 106 x xi Figure Page 13 Relationship between pH and calcium leaching (deep plate data) following urea fertilization 107 14 Relationship between calcium and magnesium leaching following urea fertilization (Fertilized plates IA, 11(B), 111(B), IV(A) data ) 108 I5A Leaching of Ca and N O ^ - N following urea fertilization: shallow soil solution data, Site 1 10° I5B Leaching of Ca and N O q - N following urea fertilization: deep soil solution data, Site I '09 I6A Leaching of Ca and N O 3 - N following urea fertilization: shallow soil solution data Site II 110 I6B Leaching of Ca and N O ^ - N following urea fertilization: deep soi I solution data, Site 11 110 I7A Leaching of Ca and N O ^ - N following urea fertilization: shal low soi I solution data, Site III . . Ill I7B Leaching of Ca and N O 3 - N following urea fertilization: deep soil solution data, Site III Ill I8A Leaching of Ca and N O g - N following urea fertilization: shallow soil solution data, Site IV 112 I8B Leaching of Ca and N O 3 - N following urea fertilization: shallow soil solution data, Site IV 112 I9A Changes in the Ca/Total Cation ratios: shallow soil solution data, Site I 114 I9B Changes in the Ca/Total Cation ratios: deep soil solution data, Site 1 114 20A Changes in the Ca/Total Cation ratios: shallow soil solution data, Site II 115 20B Changes in the Ca/Total Cation ratios: deep soil solution data, Site II . . 115 xii Figure Page 21A Changes in the Ca/Total Cation ratios: shallow soil solution data, Site III 116 2IB Changes in the Ca/Total cation ratios: deep soil solution data, Site III "6 22A Changes in the Ca/Total cation ratios: shallow soil solution data, Site IV 117 22B Changes in the Ca/Total cation ratios: deep soil solution data, Site IV 117 LIST OF TABLES Table Page 1 Pre-fertilization soil analyses, Site 1 (Gravel Pit, near Administration Building) 49 2 Pre-fertilization soil analyses, Site II (Mixed Douglas-fir-Alder Site) 5 0 3 Pre-fertilization soil analyses, Site III (Micrometeorology Station) 5 1 4 Pre-fertilization soil analyses, Site IV, (Mature Douglas-fir Site (Mare's Farm)) 5 2 5 Locations of the Tension Lysimeter Plates in the Soils of the Study Plots 5 4 6 pH changes following Urea-fertilization (surface soil solutions) ^0 7 Effects of urea and ammonium sulphate on soil pH (Field Experiment ^2) ^1 8 Soil pH of lysimeter plots, 540 days following urea application (Field Experiment ^2) 7 2 9 Effects of urea treatment on soil pH (Laboratory Experiment ^2A) 7 4 10 Comparison of some soil leachate constituents .of lysimeter soil columns (samples from sites I, II, III and IV) (Laboratory Experiment ^1) ^4 11 Effect of urea application on CEC and exchangeable cations of Site III lysimeter Plots (Field Experiment ^2) 9\ 12 Effect of urea application on the CEC of the soil , (Laboratory Experiment ^2B) ^2 x i i i Effect of urea application on exchangeable cations (Laboratory Experiment ^2B) Balance of Al on the exchange complex following urea application (Laboratory Experiment ^2B) . . . ACKNOWLEDGMENT I wish to acknowledge my sincere gratitude and appreciation to Dr. T . M . Ballard (Associate Professor of the Dept. of Soil Science and Faculty of Forestry), who supervised the whole of my PhD programme. His valuable suggestions, guidance, criticisms and encouragement are very much appreciated. My thanks also go to the other members of my thesis committee: - Dr. C A . Rowles (Chairman and Professor of Soil Science Dept.), Dr. L.E. Lowe (Professor, Dept. of Soil Science), Dr. A . A . Bomke (Assistant Professor, Dept. of Soil Science), and Dr. J . P . Kimmins (Associate Professor, Faculty of Forestry) for their valuable contributions to my programme. I extend my gratitude and appreciation to Mr. R. Wedd, to the Director and staff of the U .B .C . Research Forest, to my fellow students as well as the faculty and technical staff of the Faculty of Forestry and the Dept. of Soil Science, who contributed in diverse and countless ways during various stages of this study, and to Mrs. S. Friesen for her patience in the typing of this thesis. Finally, my thanks are due to my family and friends for their encourage-ment and friendship. The study was funded two years by the British Columbia Forest Service Forest Productivity Committee and subsequently by the U .B .C . Research Committee. xv I 1.0 INTRODUCTION Experiment's and practice have shown that fertilization may be one of the most effective means to improve forest tree growth (Stoeckeler and Arneman, I960; Swan, I960, 1969; Weetman, 1968; Hagner, 1967; Gessel et_aL, 1965, 1969, 1971; Belluschi, 1970) and could probably be a major silvicultural tool in many forest regions of the world. In the Pacific Northwest,urea fertilizer is commonly used because of its high nitrogen content and low cost. Recently, the application of these fertilizers has become^  a problem of much concern, not only to foresters but also to others, because of the possible leaching losses of added and native elements from the forest soil system. Leaching may affect tree growth and may also lead to pollution of ground and surface waters. The general objectives of this thesis are to study the effects of urea fertilization on leaching losses of nutrient substances from soils under second growth forests, and to examine the evidence that nutrient losses of urea fertilizer are small in forest soils. The evaluation was conducted mainly by a tension lysimeter technique on four forest soils with distinct properties (one being coarse textured and having little organic matter content, one with a substantial nitrification capacity, the third with relatively high organic matter content, and the last with a thick, well developed forest floor). These sites also represented somewhat different developmental stages of the forest ecosystem (from young to mature). The urea fertilizer (448 kg N/ha) was applied in the fa l l , following a year of lysimeter installation and about 7 months of prefertilization leachate (lysimeter solution) monitoring. Leachate sampling was continued for a period of 246 days following fertilization. Field soil sampling, and also laboratory lysimeter-soiI 2 column studies were conducted to confirm the main field results and to determine the physico-chemical mechanism responsible for the observed behaviour. The specific aims of the study were: (i) to review a) the theory underlying the reactions of molecular urea and nitrogencompounds resulting from urea transformation in soils, and b) soil properties and phenomena which may influence nutrient leaching in the forest soils, -(ii) to study the trends in the chemical behaviour or transformation of urea in soils. (iii) to study the effects of urea behaviour on leaching losses of the introduced N and on other nutrient cations over time. (iv) to determine the major variables and mechanisms that may influence nutrient leaching following urea application. 3 2.0 THEORY A N D REVIEW The literature on elemental leaching of chemicals from agricultural and forest soils is very extensive. A comprehensive review of all the materials , therefore, cannot be made here. This review is therefore limited in scope to the forest soils of the northern hemisphere with major emphasis on the Douglas fir region of the Pacific North-west. Also, the chemical rather than the physical or mathematical aspects of leaching will be emphasized. In the course of the study, the topics treated below (Sections 2.1 to 2.8) were found to be pertinent, or provided a theoretical base to the understanding and discussion of the results obtained. 2.1 LEACHING IN FOREST ECOSYSTEMS A number of factors can influence the leaching losses of added or native nutrients in soils. From the literature (Nye and Greenland, I960; Allison, 1965; Cooke, 1967, 1972; M c C o l l , 1969; Hornbeck and Pierce, 1973), the most important of these variables may be outlined as follows: (i) Quality and amount of water draining through the soil profile (which depends partly on the ionic concentration and composition of the water, and rainfall intensity, duration and frequency) (ii) Temperature conditions (iii) Soil texture (iv) Soil reaction (v) Cation exchange capacity (CEC) (influenced by the amount of organic matter and clay) 4 (vi) Microbial activity (vii) Amount and type of anions present in soil solution (or produced subse-quently by fertilizer addition) (vii?) Presence and type of plants as well as the nutrient-uptake efficiencies of the roots of these plants. The importance of these variables will be mentioned in the subsequent sections. 2.1.1 Unmanipulated Forests Leaching of elements from soils of undisturbed temperate forests is known to be very small (Viro, 1955; Remezov, 1958, 1961; Remezov, et a l . , 1964; Cole and Gessel, 1965, 1968; Cooper, 1969). The literature adds also that the release of elements from the littler layer far exceeds the amounts lost from the root zone (Remezov et al. ,1964; Smirnova and Sukhanova, 1964; Cole and Gessel, 1965, 1968). The ability of the soi l -plant system to retain elements in almost aclosed cycle (Ovington, I960; Nye and Greenland, I960) and the limited concentrations of mobile anions in forest soils (Nye and Greenland, I960) are believed to be responsible for this behaviour. It may be suggested (in addition to these two reasons) that the small losses of ions are due to the fact that many forest soils are relatively infertile and hence the excess of soluble nutrients, above the requirements of plants and micro-organisms, which is susceptible to leaching, is often small. Various researchers have experimented and reported on the relative elemental leaching in soils based on lysimeter and watershed studies. Some of these are reviewed below. From a lysimeter study, Remezov (1961) arranged elemental leaching in this order: Al 7 Ca > Mg 7 N 7 K > 5 Si > P. In another lysimeter study by Vazhenin et_a_L (1972), the leaching or mobility order was Ca > Al ^ Mg > Si > Na > K 7 Fe.. Average drainage water concentra-tions at Woburn or Saxmundham ('n r r i e United Kingdom) were found by Cooke (1972) to follow the series, Ca 7 SC>4-S > CI 7 Na > N O g - N > Mg > K ? N H 4 - N 7 P 0 4 - P , In an aspen-birch forest occupying a heavily glaciated area of low relief and poor drainage in northern Minnesota, the average concentrations of drainage waters of four watersheds were, Ca = 43.25 mg/1; N H 4 - N = 0.05 mg/l; N O g - N = 0.54 mg/l organi c - N = 0.48 mg/l; P = 0.041 mg/l (Cooper, 1969). Also at the University of British Columbia Research Forest at Haney (B.C. ) , Feller (1975), reported the average chemical composition of stream water collected during two summers as: Ca= 1.7 mg/l; Na = 1.2 mg/l; Mg = 0.4 mg/l; K = 0.1 mg/l; Fe = 0 mg/l; NH4 = 0 mg/l; HCO3 = 8.6 mg/l; SO4 = 3.0 mg/l; CI = 1.2 mg/l; NO3 = 0.3 mg/l; H2PC>4 = 0 mg/l. While a single series cannot be definitely assigned for elemental leaching, a few conclusions may be drawn. I) Phosphorus is one of the least mobile elements in the forest soils since it is very strongly adsorbed by various soil constituents, 2) Compared with potassium, calcium and magnesium are lost in larger amounts by leaching. 2.1.2 Chemically-treated Forests Forest ecosystems are also capable of accumulating and retaining some introduced chemicals(e.g.fertilizers).With tension lysimeters, Cole and Gessel (1965) showed that leaching losses of N were very small over a ten-month period following urea fertilization of a Douglas-fir plantation on a coarse-textured soi l . In another lysimeter 6 study (conducted in a dense black spruce stand established on a podzolic soil with a thick raw humus layer), Roberge_e_t aj.(1970) found N leaching losses to be less than I kg/ha during the growing season following application of 448 kg urea-N/ha. Sopper's (1971) report on a 7-year study in Pennsylvania concerning renovation and conservation of municipal waste water has supported the conclusion that forest ecosystems and more specifically forest soils can tie up nutrients. Similar small N leaching losses can be inferred from watershed studies of McCall (1970), Moore (1970), Malueg et_aL (1972) and Tiedemann (1973). In all these studies (conducted in forests of the Pacific Northwest), N increases in stream water following urea-N application were only slightly above the background levels. Studies in Europe and in eastern Canada (Overrein, 1968, 1969, 1970, 1971a, 1971b; Nommik and Popovic, 1971; Weetman et a l . , 1971) have demonstrated that, of the three common forms of N fertilizers (urea, ammonium-N, nitrate-N), urea is the one least subject to leaching losses. Most of the N applied as nitrate is leached into the mineral soil below the rooting depth (Weetman and H i l l , 1973). It can be suggested that the very small leaching losses observed following urea application may be the result of the absent or limited nitrate (nitric acid) formation in the forest soils studied. 2.2 THE FATE OF APPLIED UREA FERTILIZER IN FOREST SOILS The application of urea fertilizer on forest soils leads to biological and physico-chemical reactions which in turn influence the susceptibility of this fertilizer to losses and its availability to trees. Parr (1973) has outlined the main channels through which 7 nitrogen fertilizers may be lost to plants. These are: (i) Leaching of nitrite (NO2 - ) and nitrate (NO3 - ) (ii) Biological denitrification of both N 0 2 and N O g -(iii) Chemical denitrification (iv) Volatilization of ammonia (NHg) (v) Surface runoff and erosion (vi) Inter-lattice fixation of ammonium (NH 4 + ) by clay minerals (vii) Microbiological immobilization (viii) Chemical immobilization involving reactions of fertilizer N with components of organic matter Though this study is mainly concerned with leaching of elements in forest soils, the phenomena (ii - vi i i) are all important since they can influence the amount of elements susceptible to loss through leaching. 2.3 UREA TRANS FORMATION A N D ASSOCIATED PHENOMENA IN FOREST SOILS 2.3.1 Urea Hydrolysis (Ureolysis or Ammonification of Urea) and its Effects on Soi I Chemistry The initial reaction of urea in forest soils is its hydrolysis into ammonia. Ureolysis is mediated by the urease enzyme which is produced by many micro-organisms— bacteria, actinomycetes and fungi (Fisher and Parks, 1958; Alexander, 1961). Sterilization studies have demonstrated that the reaction is strictly catalytic in nature (Conrad , 1940; McLaren_et a L , 1957) and not directly mediated by micro-organisms as recognized by Pasteur in I860 (Fisher and Parks, 1958). Thus urease can function even when the organisms responsible for its production are ki l led. Ureolysis occurs at a good rate 8 even at very low temperatures such as 2°C (Conrad, 1940). The rate, however, would increase with the rise in temperature (Laidler and Hoard, 1945; Broadbent_et a l . , 1958; Alexander, 1961; Overrein and Moe, 1967; Crane, 1972). Overrein and Moe (1967) have reported a reaction at 28°C to be 5.4 times greater than 4°C, and Crane (1972) determined the rate at 25°C to be 30% faster than at I0°C and 60% faster than at 2°C. Crane (1972) disagrees with the often quoted two to three days for the completion of ureolysis. According to him, the soil samples used in these reported laboratory experiments were sieved and mixed with urea and hence do not reflect operational situations. In his work employing relatively undisturbed soil columns, complete hydrolysis at incubated temperatures of 2°C, I0°C and 25°C was achieved in 25, 13 and 6 days respectively. In comparable soils, the higher the organic matter content, the faster the rate of urea hydrolysis (Conrad, 1940) and hence we may infer that the rate typically decreases with soil depth. The pH effect on the hydrolysis of urea is not clear. Laidler and Hoard (1945) recorded the maximum hydrolysis rate at pH 6 . 2 . However, under very acid conditions such as the black spruce (Picea mariana Mi l l ) humus used by Roberge and Knowles (1966), urea (equivalent to 448 kg urea-N/ba) was rapidly hydro-lized within two or three days at 20°C and within several days at 4°C. Similar rapid catalytic hydrolysis has been reported by Overrein (1967) after three days incubation of humus material (with initial pH 4.15) at 4°C and by Gibson in 1930 (Fisher and Parks, 1958) with a highly acid peat (pH 3.1 - 3 .3 . ) incubated between 20°C - 23°C. Overrein (1967) has proposed the possibility of the high organic matter content having an overriding effect on the pH. Pinck and Allison (1961) have concluded that ureolysis occurs in solution rather than in the adsorbed state. The reactions involved in ureolysis are as follows: C O ( N H 2 ) 2 + H 2 0 N H 2 C O O N H 4 + H 2 0 ( N H 4 ) 2 C 0 3 * 2NH 3(g) Urease K b, = 58.9 H 2 0 N H 2 C O O N H 4 » ( N H 4 ) 2 C 0 3 + C 0 2 ( g ) + H 2 0 ( | ) Henry's Law Const, at I0°C = 0.08 x I0 7 mm Hg/unit mole, fraction 2NH3(aq) C0 2 (aq) + HoO K b 2 = I .73xl0" 5 H 2 0 K a i = 3.38 x I0" 2 + 2 N H 4 + 20H H 2 CO s (aq) Ka T , = 4 . 4 5 x lO - 7 H C 0 3 ~ + H 3 Q + H 2 0 CO . K II a 2 = 4.67 x I0~M + H 3 Q + (K values from Adams (1971)) The major product of urea hydrolysis in acid forest soils is usually N H ^ C O g . The conversion is associated with some important reactions of the soil system such as the carbonate equilibrium, N H 3 / N H 4 equilibrium and organic matter dispersion. 10 2.3.1.1 The Carbonate and NH^/NH^ equilibria The decomposition of (NH^^COg leads to the production of C0 2 (gas) , H 2 0 , and NHg(gas). C 0 2 and NH3 enter into equilibrium reactions as indicated above. In aqueous solutions, CC>2 and liquid H 2 0 are in equilibrium with carbonic acid (f^COg). Thus, H2CO3 is essentially dissolved C 0 2 . b^COg in turn is capable of undergoing two successive proton transfer reactions which result in the formation of bicarbonate (HC03~) and carbonate, (CO3-) ; o n s depending on the C 0 2 partial pressure and the pH of-the system. At pH > 8 . 2 , 4 . 5 - 8 . 2 , and < 4 . 5 , the components of the equi l -ibrium consist mainly of C O g - ion, HCO^ ion and H2CO3, respectively (Stumm and Morgan, 1970). The solubility equilibria for the carbonate system at various temperatures have been presented by Stumm and Morgan (1970). As given in the carbonate equilibria above, C 0 2 is soluble in water (90 ml CC^/IO ml H 2 0 at I atm and 20°C),but only a small fraction (about 1%) of it reacts to produce h^COg and the latter is weakly dissociated. Hence the maximum concentration of H C O g - ions in soil water is small. However, the removal or neutralization of the associated hydronium ions (HgO*) results in formation of more H C O ^ - . In most forest soil systems moderate to high acidity prevents the.equi librium from shifting to the C O g - state. The carbonate equilibrium is important in respect to nutrient leaching (or transport) from the soils. In soils, respiratory activities and decomposition of organic matter can contribute considerable CC>2 which may increase acidity and the concentration of dissolved carbonate species. The dissolved C 0 2 ( H ^ O ^ ) , provides H + ions through dissociation that can replace exchangeable bases from the soil colloids. The replaced cations are then transported with the mobile H C C L - ion. A general reaction is: II Exchange Complex Ca Ca H + 2 H 2 C O s H -» H Ca H Exchange Complex C a ( H C 0 3 ) 2 Crane (1972) has reviewed the NHg/NH^ equilibrium in relation to urea-N losses through volatilization. In most forest soils, due to the presence of large amounts of protons, the equilibrium is shifted to the production of N H ^ ions. Thus, in urea-fertilized soils, the pH of the soil system becomes important in determining the amount of N H ^ + ion or NH3 gas formation. With high levels of urea application, subsequent production of ( N H ^ ) 2 C 0 3 may lead to N H 3 gas volatilization (Overrein and Moe, 1967). 2.3.1.2 pH of the Soil (Soil Reaction) Most studies have indicated a temporary rise in soil or solution pH immediately following urea application (Knowles, 1964; Roberge and Knowles, 1966; Gessel, 1968; Beaton£t al_., 1969; Crane et al_. ,1971 ; Crane, 1972). Baker (1972) has also reported per cent reduction in salt extractable soil acidity ranging from 20% to 50%, and 40% to 73% for urea-N treatments equivalent to 448 kg/ha and 896 kg/ha respectively in a laboratory study using surface soil samples taken from Vancouver Island, B.C. This pH change has direct and indirect effects on the forest floor and the mineral soil (Beaton, 1973). The pH rise is a result of urea hydrolysis and the extent of the increase depends on the initial pH, cation exchange capacity, per cent base saturation, buffering capacity and reactions involving complex organic chemistry (Crane, 1972). Urea fertilizer is regarded as an acid former in agricultural soils (Pierre, 1928). The acidity produced by urea would result from nitrification of the N H ^ + ions formed on 12 hydrolysis of urea. In soils with substantial capacity to nitrify, losses of bases through leaching wil l be expected following urea application. Lysimeter studies by Overrein (1972c) have indicated a large increase in calcium leaching from soil when the pH of the percolating water dropped below 3. 2 .3 .2 Dispersion and Flocculation of Organic Colloids Urea, oxamide and urea-containing fertilizers have been found to disperse organic matter from forest humus layers (Gessel, 1968; Knowles, 1964; Beaton et a l . , 1969; Crane_etal_., 1969; Fieldler and Weetman, 1971; Crane, 1972; Ogner, 1972). Solubilization of organic matter increased with temperature in the range 5.5 to 22°C (Beaton_et al_., 1969). Mortland (1958) has stated that NH^"1" ion has a strong solvent and hydrolytic action on organic matter. Flocculation of colloidal particles is normally considered to result from approach sufficiently close for van der Waals - London attractive forces to overcome the repulsive forces associated with overlapping, similarly-charged double layers (Kirkham and Powers, 1972). The probability of such close approach is increased by double layer collapse. Where flocculation is effected by salting, the double layer collapse results from increasing ion concentration. Similarly, the double-layer may be collapsed by replacement of counter-ions with ions of higher valence("Schulze-Hardy rule") or with other more strongly adsorbed ions, e . g . ions of similar charge but of smaller hydrated radius. Double layer collapse reduces the zeta potential, (the electrical potential at the slipping or shearing plane of the particle, as measured during electrophoretic m i -gration). Thus the tendency for particles to be flocculated or dispersed has often been 13 related to their zeta potential (Baver, 1956), although it has been recognized for some time that interpretation of the zeta potential in relation to colloidal sol stability is quantitatively inexact (van Olphen, 1963). The theory outlined above is applicable to the hydrophobic colloids, but there also seems to be considerable applicability of this theory to the humus colloids which are normally considered to have hydrophilic properties. Ong and Bisque (1968) suggested that the Fuoss effect may account for this, where humus colloids are flocculated by salt addition. Viscosity observations suggest that the stretched molecular configuration is replaced by one which is tightly coiled, because there is no longer the strong mutual repulsion of negative functional groups. The coiling results in reduced hydration of the colloid and makes its behaviour more closely resemble that of the hydrophobic colloids. (Another way of looking at i t , they suggest, is to consider that reduced charge decreases the amount of hydration water that can be held by the colloid.) Organic colloids possessing negatively charged functional groups, such as carboxyls and phenolic hydroxyls, would be expected to flocculate more readily (if at all) at lower pH, because of the relationship between dissociation and potential (Scheffer and Ulrich, I960). Increasing pH and concomitant introduction of monovalent meta! cations or ammonium would be expected to promote dispersion. Moreover, high pH might increase precipitation of divalent or polyvalent metal hydroxides, enhancing double-layer thickness and possibly eliminating some cationic "bridges" between colloidal particles. 14 The above considerations, the additive nature of van der Waals -London forces, the effects of particle size and shape on the decay of such forces with distance, and the relationship between particle charge density and potentia1 are probably among major reasons for differences in the tendency of various humic substances (e.g. humic, hymato melanic, and fulvic acids) to be dispersed or flocculated under certain conditions. Though aqueous urea extractions of humic substances, presumably under near neutral conditions, have been reported, it is clear from the above that hydrolyzed urea can be expected to have a considerable dispersive effect on the soil colloids. Crane (1972) has discussed, and has also applied Edwards' microaggregate theory (Edwards, 1966; Edwards and Bremner, 1967) to describe the organic matter dispersion usually following urea application. The monovalent N H ^ + ions resulting from ureolysis are believed to dissociate some of the polyvalent cations bridging the colloidaf particle. However, the assumptions and principles upon which Edwards bases his theory are contradictory to some established theories such as those of.Gouy, Stern and Bolt. 2 .3.3 Nitrogen Immobilization Immobilization is the conversion of mineral (e.g. NH^-N) or simple organic (urea), substances into organically bound forms. The reverse of this process is mineralization. These two processes occur simultaneously in most soil systems. Apart 15 from affecting the availability of nutrients to plants, N immobilization leads to limited leaching and volatilization losses of applied N fertilizers. Urea has been demonstrated to be more immobilized in soils than C a ^ O , ^ or (NH^^SO^ (Roberge and Knowles, 1966; Overrein, 1967, 1970, 1971a, 1971b, 1972a, 1972b , Nbmmik and Popovic, 1971). Immobilization of urea is found to be extensive in the litter layer (Bjbrkman et aL , 1967; Overrein, 1967; N6mmik and Popovic, 1971; Popovic and Nommik, 1972), and in some situations in the humus layers also (Overrein, 1971a; Nommik and Popovic, 1971). Overrejn (1967) and, Nommik and Popovic (1971) attributed the high microbial immobili-zation of urea to the pH increase caused by urea hydrolysis, the higher pH favouring increased biochemical activity in the raw humus. Urea immobilization is temperature . 1 5 dependent. In Overrein's (1967) experiment using N technique, the amounts of urea-N immobilized during a 90-day period were about 25%, 40% and 65% of the added total at 4 ° , 12° and 20°C respectively. 2 .3 .4 Nitrification Nitrif ication, the biological conversion of reduced organic- and inorganic -nitrogen compounds to a more oxidized state (Alexander,et a l . , I960) is a two-stage process, namely: (i) the conversion of N H ^ + to N 0 2 ~ , and (ii) the conversion of N O j to N O ^ - . Each stage is carried out by specific-organisms. According to Quastel (1946), Schloessing and Muntz were the first to show that the process is biological; the organisms involved were described and isolated by Warington and Winogradsky, respectively. It is generally 16 accepted that autotrophic bacteria are responsible for most nitrate production (Alexander, 1965). But under severe acid conditions (such as those of some forest humus layers), where autotrophic nitrifiers are likely to be absent or ineffective, heterotrophic nitrifiers (fungi) may be more important (Keeney and Gardner, 1970; Keeney, 1972). Nitrosomonas, Nitrosococcus, Nitrosocystis, Nitrosospira and Nitrosogloea species (autotrophs) mediate the first stage of the process but the most important group in nitrifying forest soils (with mull or mor types of humus layers) seems to be the Nitro-socystis (Romell, 1932); the Nitrosomonas species are the dominant or the exclusive representatives in fertile agricultural soils (Lutz and Chandler, 1959). Winogradsky and Winograsky (1933, as referenced by Lutz and Chandler, 1959) reported the Nitro-sospiras form only in poor^uncultivated soils. The second stage of oxidation is carried on by Nitrobacter (and Nitrocystis). In forest soils, probably due to the high acidities, Nitrobacter species are few in number (Feher, 1929; see also Lutz and Chandler, 1959). This possibly explains the limited nitrification often associated with forest soils (Rode, 1955). The factors controlling nitrification rates have been reviewed by many workers (e.g. Quastel and Schofield, 1951; Alexander, 1961, 1965; Cambell and Lees, 1967). In laboratory studies, Quastel and Schofield (1951) reported that the optimum temperature and the pH range for nitrification depend on the site of isolation of nitrifying bacteria. In general, the optimum conditions for nitrification are given as follows: pH value of 6.8 - 7.3 (Waksman, 1932), temperatures of 30 - 35°C, oxygen concentrations near 20% (Keeney, 1972) and moisture content which is not less than 10 - 20% or more than 80% of the water-holding capacity of the soil (Gaardner and Hagem, 1921; referenced 17 by Lutz and Chandler, 1959). Waksman (1932) placed the limiting pH at 3.7 - 4 . 0 . It is also generally maintained that some natural organic substances often associated with mor humus inhibit nitrification. A high pH and high ammonium concentrations in soils can prevent conversion of nitrite to nitrate, because of free ammonia formation (Alexander, 1961; 1965). Other workers have reported lack of correlation between nitrate production and carbon/nitrogen (C/N) ratio or the soil pH (Weber and Gainey, 1962; Heilman, 1974). In Heilman's (1974) study, it was found that the untreated soil sample'with the lowest pH (4.3) had the next to the highest nitrification while nitrate produced by the soil with the highest pH (6.0 - 6.2) was less than the average of the 14 soil types used in the study. Reports of Quastel and associates (Lees and Quastel, 1946; Quastel and Schofield, 1951) indicate that the conversion of N H ^ + — > N O g " by soil microorganisms occurs largely at the surfaces of the soil crumbs. Quastel and Schofield (1951) reported the rate of nitrification of a given quantity of ( N H ^ S O ^ to be a function of the degree to which the N H ^ + ions are adsorbed on, or combined in the soil in the form of soil's base-exchange complex. They consequently concluded that when all the relevant sites at the soil surface have been occupied, further growth of the nitrifying organisms will not occur except to replace dead and disintegrated cells. Reduced aeration as found in water-logged soils reduces or entirely suppresses nitr if i -cation (Harmsen and Kolenbrander, 1965). Research with coniferous forest soils has shown that nitrification is very limited or absent in most very strongly and extremely acid soils (Lutz and Chandler, 1959; Harmsen and van Schreven, 1955; Rode, 1955; Strand, 1957; Weetman, 1961; Cole and Gessel, 1968; Beaton et_aL, 1969; Crane, 1972; Theobald and Smith, 1974). The review by 18 Gracanin (1961) indicared that it is the second stage of the process which is limited in coniferous podzolic soils. In the Pacific Northwest, Strand (1957) conducted incubation studies on several Douglas-fir forest soils and found limited nitrification or none • Field experiments involving urea application have given similar results (Cole and Gessel, 1968; Crane e t a l . , 1969; Crane, 1972). Beaton_et aj_. (1969) have also reported similar results in their studies with L-F horizon samples obtained near Port Alberni on Vancouver Island (British Columbia). Urea application did not promote nitrification of these samples at any of the incubation temperatures of 5.5°, 11°, or 22°C. In Eastern Canada, Roberge and Knowles (1966) detected negligible nitrification in their incubation studies with podzolic humus (of a highly productive black spruce (Picea mariana. Mi l l ) following fertilization with an equivalent of 448 kg/ha u rea -N . They concluded that nitrate leaching loss after urea application to acid forest soils is not likely to be a problem. Contrary to the above results, some investigators have reported significant nitrification in coniferous forest soils. Bollen and Lu (1967) incubating forest soils with (NH^^SO^ plus CaCOg at 28°C for 28 days found nitrification to be rapid under coastal Oregon stand of red alder (Alnus rubra Bong), conifers, and mixed stands of alders and conifers. Highest nitrate formation was measured for samples obtained from the L-F horizons of the alder stands, though these samples had low initial pH values. Likens et a l . (1969) have also reported considerable nitrification at pH 4 . 3 . In a lysimeter study at the UBC Research Forest at Haney, Bourgeois and Lavkulich (1972, see also Bourgeois, 1969) found evidence of abundant nitrification (in the soil solution) ranging from I to 43 mg/l NOg concentration. Recent investigations in the Pacific Northwest forest soils with urea have also substantiated that nitrification can occur in 19 some forest soils (De Bel l , 1973; Heilman, 1974). Heilman's (1974) investigation with soil materials of different series, sampled beneath second-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) stands in western Washington before and after urea application, has demonstrated that nitrification may be limited in some forest soils but not in others. In most of the soils studied, urea treatment considerably increased nitrification. The contradictory views on nitrate formation in forest soils have been attributed to the differences between laboratory incubation conditions and those in the field (Heilman, 1974). The productivity of the site, as well as the tree species,may seem also to explain why nitrification is active or inactive under some coniferous stands. Krajina ^ t a l . (1973) reported abundant nitrification in soils from the most productive Douglas-fir stands (site index/100 years, 54-60m). According to Heilman (1974), Bourgeois and Gessel have shown with field application, using urea, that no nitrate is produced in poor-site Douglas-fir stands whereas on the better sites, nitrate levels more than doubled after five months. The limited nitrification in unproductive sites may imply that ammonium is absent or limited in the soils of these poor sites to support nitrifiers. Nitrifiers could also be inhibited by the occurrence of mor humus in poor sites. Krajina and co-workers (Krajina, 1969; Krajina et al_. 1973) noted also that Douglas-fir plants treated with N H ^ , either died or were small and light with the least leaf area. On the other hand, western hemlock grew better in soils where nitrification does not actively occur (Krajina, 1969). 20 2.3 .5 Gaseous Losses of Nitrogen and Nitrogen Compounds 2.3.5.1 Denitrification (Chemo-denitrification and Bio-denitrification (dissimilatory nitrate reduction)) Denitrification is the reduction of NO2 ~N or N O 3 - N to gaseous N forms (molecular N 2 and oxides of N) . The biochemical reduction (bio-denitrification) of N O 2 - N or N O g - N is mediated by certain facultatively anaerobic soil heterotrophs. Where little or no oxygen is available, these use NOg or N 0 2 " " as terminal electron acceptors in their respiratory processes. Chemo-denitrification on the other hand involves chemical or nonenzymatic reactions leading to the decomposition of N 0 2 ~ " - N . Nommik and Thorin (1972) also discussed the mechanisms which have been proposed for chemo-denitrification. These are: (i) Self-decomposition of nitrous acid under acid soil conditions 3 H N 0 2 > 2NO + HNO3 + H 2 C (ii) Reaction of H N 0 2 WTth oC -amino acids or ammonium R N H 2 + H N 0 2 » ROH + N 2 + H 2 0 This is supposed to contribute little to N j formation from added nitrate, (iii) Reaction of nitrite or nitrous acid with reducing materials of soil organic matter with evolution of N O , N 2 0 and N^. The phenolic constituents are believed to be important in fixation of the nitrite and its reduction to N 2 0 and N 2 > Mechanism (i) may only be used to describe chemo-denitrification in acid forest soils, since nitrite does not decompose above pH 6 (Nbmmik and Thorin, 1972). In general, denitrification in acid forest soils is very limited (Overrein, 1968, 1969), but may increase as the pH rises to 6 or 7 (Nbmmik and Thorin, 1972). Thus 21 liming or urea fertilization should substantially increase the rate of denitrification. Nevertheless, even at 1000 kg urea-N/ha, Overrein detected only trace amounts of N 2 and no gaseous N oxides. Low temperatures slow the denitrification rate. Nommik (1956) reported that the process occurred at a slower rate at 2°C, but increased to the maximum at temperatures between 60 and 65°C. When urea is applied in the cooler months (fall) in the Pacific Northwest, denitrificafion is expected to be low even though the pH of the soil increases after application. 2 . 3 . 5 . 2 Volatilization of ammonia Another means of gaseous loss of applied urea is through the volatilization of ammonia. Though it is very limited in acid forest soils it may be substantial following urea application as a consequence of ureolysis to (NH^^COg which may raise the initial pH of the surface layers of the soil to neutral or slightly alkaline sides (Gasser, 1964). Watkins_et aj_. (1972) found greater NHg losses when urea was applied to a soil covered with plant residues than when it is applied to a bare soil . High temperatures, high urea application rate and large-grained pelleted-urea promote losses while rainfall immediately after fertilization reduces losses (Crane, 1972). In a 20-day sampling period Watkins et_al.(l972) determined a more rapid and substantial volat i l i -zation of NHg with soil samples collected from the Douglas-fir site than with those obtained from hemlock (Tsuga heterophylla) site. The experiment was performed at I9°C and the applied N was equivalent to 224 kg urea-N/ha. In a similar experiment using 1000 kg urea-N/ha, Overrein (1968) measured small losses (the accummulated amount was 3 . 5 % of the total) after 48 days. In Quebec, Bernier et a l . (1969) found 22 affer 10 days, volatilizafion losses of about 20% of a 224 kg urea-N/ha application, and much higher losses at higher application rates (e.g. about 32% losses for 448 kg urea-N/ha). But Bhure (1970) reported small loss of N by volatilization with surface soil samples (including the organic horizons) treated with 600 lb urea-N/acre (1344 kg urea/ha) in Newfoundland. Most of these losses reported occurred within 3 to 5 days following the fertilizer application (Overrein, 1968; Bernier et. a l . 1969; Crane, 1972). 2.4 THEORY OF ION EXCHANGE AND ITS IMPORTANCE TO LEACHING LOSSES 2.4.1 CEC and the Nature of the Exchanger System Cation exchange capacity of the soil is a measure of the number of reversibly adsorbed cations retained by a mass of soi l . Soil texture, the content of clay and its mineralogical make-up, as well as the amount and kind of organic matter and the pH are the most important soil factors influencing the CEC. Soils rich in clays and/or organic matter have higher adsorptive capabilities than soils which are poor in these components. The general chemistry of organic matter has been discussed by Kononova (1966), Ponomareva (1969), Stevenson (1972) and Stevenson and Ardakani (1972). The most active fractions of organic matter are the humic substances (fulvic and humic acids) due to their possession of high contents of oxygen-containing functional groups: - C O O H , phenolic - O H , aliphatic - O H , enolic - O H , and C=0 structures of various types in their molecules. Comparatively the fulvic acids have lower molecular weights and carbon contents but more oxygen-containing functional groups than the humic acids. The exchange capacity of fulvic acids is normally between 900 - 1,400 me/IOOg (contributed mainly by the - C O O H group) while that of the humic acids ranges between 23 485 - 870 me/100 g (Sfevenson, 1972; Stevenson and Ardakani, 1972). Fulvic acids are strong organic acids; their dissociation ("strength") is close to that of strong acids such as HCI and H S 0 4 . According to Ponomareva (1969), the pH values of 0.005 -0.006N solutions of HCI or H2SO4, fulvic acid and humic acid were 2.4 to 2 . 5 , 2.6 to 2.8 and 3.7 respectively. The neutralization point of fulvic acid and KOH or NaOH is not far from pH 7 . 0 . However, since fulvic acids are polybasic, their final stage of dissociation is reached only when the pH is greater than 10 (Panomareva, 1969),. The clay particles (< 2AJ) are characterized by the so-called ionic double layers. There is an inner, negatively charged layer associated with the particle itself. This is surrounded by a replaceable layer of counterions ( C a + + , M g + + , N a + , K + , N H ^ + , H + , A l + + + ) which neutralize the charges of the particle. Both layers form the "diffuse double layer" and have been modelled as a condenser (Helmholtz), as a diffuse layer ( Gouy-Chapman) and as a combination of the two (Stern) (Wiklander, 1964). The overall charge on a colloidal particle (clay or humus) is negative. The negative charges originate in the following manner (Buckman and Brady, 1969; Stumm and Morgan, 1970; Schuffelen, 1972): (i) Lattice imperfections at the solid surface and isomorphous substitution within the clay mineral lattice as the substitution of S i + + + + by A l + + + or A l 1 ' ' by M g + + . (ii) Preferential ion adsorption arising from van der Waals - London interaction and from H-bonding e .g . the adsorption of a humic acid on a silica surface, (iii) Chemical reactions at the colloidal surface through 24 a) Ionization (proton transfer) of functional groups ( -OH, - C O O H ) , e .g . Al - O H + K l • Al - OH K 2 . Al - O" 2 ' / C O O H ^ C O O " ^,COO~ R K ! , R R X N H 3 + NH 3+" X n h 2 b) Coordinate bonding of solutes to solid surfaces, e . g . R(COOH) + m C a 2 + : > R- [(COO)nCa 1 " n + 2 m n L m_ + n H + (surface) The adsorption capacity of the charges created by isomorphous.substitution, referred to as "permanent charge CEC" (Coleman and Thomas, 1967) is independent of the reacting medium, while those resulting from dissociation of H + ions are strongly pH dependent ('pH dependent CEC"). The organic matter and most oxides and hydroxides behave amphoterically. Thus at high pH they have negativecharges ; the opposite is true at low pH conditions. The negative charges resulting from the weak acid groups Si-OH and OH of clay colloids are mostly active above pH 5.5 (Wiklander, I960). The C O O H - and - O H of the non-soluble humus undergo substantial dissociation at pH values below pH 6 and above pH > respectively (Schuffelen, 1972). The above discussion implies that when a pH increase results from urea fertilization, an increase in CEC may take place in the surface horizons of the forest soi l , and thus more cations may be adsorbed by the soil colloids. 2 .4 .2 Cation Exchange Phenomena Mobility and adsorption of ions in soils, among other phenomena in soils, are based partly upon principles of cation exchange. The first to study cation exchange was Thompson who showed in 1850 that by mixing soils with ammonia and then leaching them with water, a large proportion of the ammonia was held back on the soils (Grim, 25 1952). Thompson's work was followed shortly after by Way's detailed study of the phenomenon; Way demonstrated that the clay fraction was responsible for the cation exchange (Grim, 1952). We know now that organic matter is also important in exchange reactions. Cation exchange in soils may be defined as an equilibrium reaction between an exchange (solid) and solution phases, and between solid phases if in close contact with each other (Wiklander, 1964). A cation exchange may be represented as follows: CcM| + M 2 v C c M 2 + M, where Cc is the colloidal complex and Mj and M 2 are cations. For example, an exchange reaction between N H ^ + and colloidal K, wi l l be Colloid] K + + N H 4 + , Colloid N H 4 + + K i e com-Though cation exchange has been studied since the middle of the last century there are still some uncertainties about the phenomenon. The reactions in soils are highly complex because of the participation of clay (which differs from one material to another) and organic matter; the structure and behaviour of the organic matter is not clearly understood. Attempts to represent cation exchange reactions with a methemat-ical expression which could be applied universally have failed (Grim, 1952). The plexity of the reaction has been well stated by Kelley (1948), p. 6 0 - 6 1 . " . . . it is doubtful whether any purely mechanical or kinetic explanation of cation exchange wil l ever be found adequate to explain all the facts. The literature on cation exchange is replete with theories, one or another of which seems to explain certain experimental results wel l , but when applied to results obtained by other experimental methods and techniques, they either break down or else require substantial modification The phenomena accompanying cation exchange are evidently complex and the serious student wil l be advised to maintain a critical attitude towards theories in general." Even though there are poor quantitative relationships between factors and phenomena of cation exchange some generalizations could be made from the work of Kelley (1948), Wiklander (1964) and Ermolenko (1972). (i) The reaction is rapid, reversible, and is accelerated somewhat by raising the temperature. (Kelley, 1948) (ii) Cation exchange takes place in equivalent ratios, and the reaction obeys the Law of Mass Action (Ermolenko, 1972). (iii) The relative replacement tendency of cations is determined according to Wiklander (1964) and Ermolenko (1972) by a) the nature of the exchange material (e.g. humic acids, montmoriN oni te, muscovite, vermiculite,.among others, each of which displays some selectivity for particular cations; b) cation exchange capacity and the degree of neutralization in relation to solution concentration; c) the energy of displacement, namely, valency, atomic number, the hydrated and non-hydrated size, and the polarizability and polarizing power of the ion. For ions under the same conditions, adsorption is greater for those having the larger ion charge, higher atomic number, smaller hydrated ion radius, or lower zeta potential. The adsorption of ions could be represented as below: a) Valency effect: K + < C a + + < AI Th H _ H " + b) Atomic number and hydrated ion radius effects (i) l]+c bia <K+ = NH4 < Rb+ < Cs + (monovalent) (Ii) M g ^ C a ^ < S r + + ^ Ba"^ (divalent) Increasing atomic size or decreasing size of the atom (or decreasing zeta potential). (iv) The higher the concentration of the replacing solution, the more ions wil l be replaced. This is however true for cation pairs with different replacing power. Essentially the valence effect is decreased at high solution concentrations (Ermolenko, 1972). Thus the replacement potential of monovalent ions (e.g. K) to that of divalent ions (e.g. Ca ) is greater at high solution concentrations than at low concentrations. For example, at low concentrations, the adsorption of the major cations increases in the order N a + < K + < M g + + < Co*"1". At high concentrations the order is either N a + < Mg 4 - 1 " < K + < Ca""" or N a + < M g + + < C a + + < K + (Wiklander, 1958). The valence and dilution effects should be applicable when concentrations of the soil solutions are increased by chemical addition to the soil system. However, the composition of cations in solution and on the exchange sites is also controlled by the exchange capacity. The higher the exchange capacity, the larger would be the ratio of adsorbed polyvalent ions to monovalent ions. Schachtschabel (1940), as reviewed by Wiklander (1958), reported a ratio of 92:8 adsorption of Ca against NH^ by leaching humus (high CEC) with a solution equivalent in amounts of Ca and NH^ . This would imply that chemicals which could increase the soil CEC (by creating extra negative charges on the colloidal complex) would favor more polyvalent cations (e.g. Ca and Mg) than monovalent ions (e.g. K or Na) being adsorbed. A review of the literature on exchange theories indicated that the Donnan Equilibrium appears to explain the exchange reactions (Wiklander, 1964). 2 .4.3 The Donnan Equilibrium The phenomenon whereby an increase in CEC leads to greater adsorption of 28 divalent rather than monovalent cations may be explained by considering the Donnan Equilibrium (Drake, 1964; Wiklander and Lax, 1967). Wiklander (1964) stated that: / ( C a + + ) e = y f M g + + ) e = (K±)e = (Na +)e = ( N H ^ e = _(H+)e / (Ca + + )s • (K+)s (Na+)s (NH 4 + ) S ( H + ) s ' where e = exchangeable ions, s = ions in "free" solution, and parentheses denote ion activity. According to this equation, when the total concentrafion of an ion, for example NH^"1", is increased, there would be changes in both the ammonium ions in the free solution and those in the exchange complex. This change would also lead to proportional changes in the exchange-solution ratios of the other cations (Wiklander, I960) in order to maintain the exchange equilibrium between N H 4 + and the other cations. The square root relationships of the divalent cations would favour preferential adsorption of divalent ions over the monovalent ions where the soil solution is dilute. 2 .4 .4 Anion Adsorption According to Wiklander (1958, 1964), the behaviour of anions in adsorption and exchange reactions is similar to that of cations. However, for elements like phosphorus and boron the reactions are more complicated. Soils with low pH and high content of hydrated Al and Fe oxides have a large capacity to hold anions. For example, Kinjo and Pratt (1971a, 1971b) have demonstrated N O ^ - adsorption and the competitive adsorption of CI"", SC>4~, and phosphate with NO3 in tropical soils., where the above conditions are expected. Adsorption of NOg has been shown to be similar to CI a n d considerably lower than that of SO^ in the subsoil in south-eastern U .S .A . (Thomas, 1969). It is also expected that the A horizon of a podzolic soil would have a low anion adsorption capacity while the B horizon would have a high 29 affinity for anions. In general, CI and NO3 are practically not adsorbed at pH around 7 whereas phosphate is adsorbed at both low and high pH regions. Grim (1952) has stated that CI is not adsorbed because it does not fit on the clay structure. Mobility of the major anions decreases in the order: CI — NOg > SO4 » phosphate • 2.5 INFLUENCE OF HUMIC SUBSTANCES O N ION LEACHING 2.5.1 Reactions of Humic Substances (especially, the Fulvic Acids) with Metal Ions The understanding of the behaviour of the organic constituents of the soil is pertinent to the understanding of the fate of the applied chemicals in the soi l . Mortensen (1963) has described the complexes formed between humus and metals by the reactions of ion exchange, surface adsorption, chelation, complex coagulation and peptization. Metal-organic matter interactions have shown that humic substances can form stable water-soluble and water insoluble complexes with metals and hydrous oxides (Schnitzer and Khan, 1972). Schnitzer (1968) considered that fulvic acids are the most prominent humic substances in soil solution and that.they influence all soil reactions. The fulvic acid-metal complexes : are very soluble and mobile, and are therefore easily available to plants, animals and micro-organisms (Schnitzer and Khan, 1972). It is believed that the - C O O H , phenolic - O H and possibly the - N H 2 functional groups are involved in complexing mechanisms (Schnitzer and Khan, 1972). According to Schnitzer (1968;1969), the major reaction is the one in which both the acidic - C O O H and phenolic - O H groups react simultaneously. " The complex formation frequently involves the displacement of H 4 ions from the humic subtances leading to a drop in the pH of the solution. Examples of reactions involving humic or fulvic acids and divalent metals have been 30 described by Schnitzer and Khan (1972). Fe forms the most stable metal-FA complexes. At 3+ 3+ 2+ low pH, Schnitzer and Khan (1972) stated this stability sequence: F e J > A r > G J y N i 2 + 7 C o 2 + ^ P b 2 + - C a 2 + > Zn 2 + > Mn 2 + > M g 2 + . This order is in accord with the Irving-William's (1948) series (Pb2+> C u 2 + ? N i 2 + > Co 2 +> Z n 2 + ? Ca 2V Fe 2 + > M n 2 + 2+ > Mg ). It was shown earlier that the orders of stabilities at pH values of 3 .5 and 5.0 were different from that of Irving-William's series (Schnitzer and Skinner, 1967; Schnitzer, 1968). Stable FA-meta! complex formation was found to increase with rise in pH (Schnitzer and Skinner, 1967; Schnitzer, 1968) and also with a decrease in ionic strength (Schnitzer and Khan, 1972). Alexandrova (I960) has proposed that organo-mineral colloids of alkali bases, alkaline-earth bases and Fe- or Al sesquioxides are formed as a result of exchange reactions between the H of the active group of humic acids and the exchangeable or water soluble cations of the mineral fraction of the soi l . The probable schemes are as follows: (I) Humic substances with cations of alkali and alkali-earth bases (after Alexandrova, I960) Mineral Colloid M e + + R(COOH)n — — M i n e r a l Col loid (COOH)n-H + + PT X COOMe (2) Humic substances with Fe or Al sesquioxides (denoted by X) (After Lavashk-v ich, 1966) X(OH) + / ( C O O H ) n n-2(HOOC) COO-X(OH) 1 +R > ^ R 2 2+ X ^ C~COa-X ( O H r (OH)m m-l(HO) \ XOH O Solutions of alkali hydroxides, e . g . NaOH or K O H , neutralize fulvic acid 31 to form salts: Na or K fulvate (Ponomareva, 1969). These salts are soluble in water in all proportions, and their solutions are more highly dispersed than the free fulvic acid solutions. Ponomareva (1969) discussed the importance of fulvic acid and alkaline earth hydroxides (e.g. Ba(OH)2 , CatOH^) from the pedological point of view . The reactions of the two fractions of fulvic acids - "crenic acid" (which precipitates with Al or Fe at pH 5.9) and "apocrenic acid" (which does not precipitate with Al or Fe at-pH 5.9) differ. The "crenic acids" do not form precipitates with alkaline earth hydroxides (Ponomareva, 1969). The "apocrenic acids" may precipitate with alkaline earth hydroxides, forming calcium or magnesium salts, for example. This occurs when the reaction is alkaline, so that many of the functional groups are dissociated. At neutral or acid pH, the "apocrenic acids" do not bind with dilute alkaline-earth metals (Ponomareva, 1969). As most forest soils are acid and contain low concentrations of alkaline earth metals in solution, formation of stable fulvic acid - calcium compounds would usually be limited unless the pH is raised by liming or urea fertilization. In the grassland soils the situation would be different since humic acids predominate (Stevenson, 1972), which can form stable compounds with calcium (Ponomareva, 1969). 0 _ i _ O J . Both Fe and Al hydroxides are adsorbed by humic substances, and are precipitated at certain definite metal - humus ratios. Precipitation of the soluble metallo-organic substances occurs deeper in the soil profile by further reaction with Fe^ + and/or A l ^ + and very small quantities of C a 2 + and/or M g 2 + ions (Wright and Schnitzer, 1963). According to Ponomareva (1969), Aarnio established in 1915 that at an FejOg/humus ratio of 0.2/3.0 and an A^Og/humus ratio of 1/30, organo-mineral 32 deposits occur. At lower ratios, the humic complexes of Al and Fe are soluble. Under the conditions usually occurring in forest soils, the mobility of Fe within the soil is greater than A l . However Deb (1949) and Wright and Schnitzer (1963) found that an Fe-humus complex is more liable to flocculation by Ca and Mg than an Al-humus complex and thus would result in deeper movement of the Al-humus complex than of the Fe-humus complex. Fulvic acids are more capable of causing greater mobilities of F e 3 + and A l 3 + th an are humic acids (Lavashksvich, 1966). 2 .5 .2 Reactions of Humic Substances with N - containing Compounds 2.5.2.1 Urea Chin and Kroontje (1962) found that adsorption of urea on soil is not related to the CEC of the soil but to the amount of organic matter. They postulated the phenomena of physical adsorption and chemisorption (which lead to the formation of relatively stable urea-organic matter complexes) to be operative. Mitsui and Takatoh (1962) have concluded from infra-red studies that urea adsorption on soil material results through H bondings (from - C O O H , - O H or -G=0 of humates; - O and - O H of broken edges of crystalline clays, and -S iOH of amorphous clays). The most likely mechanism, according to Broadbent and Lewis (1964) would involve the reaction of the carboxylic acids of the soil organic matter with the weakly basic urea (dissociation constant = 1.5 x 10 '^). These investigators found also that the salt of the urea-carboxylic groupings is unstable and liable to leaching with water, although at a lesser rate than nitrate. Deeper leaching of urea is expected if it rains immediately after urea fertilization when the fertilizer is mostly in the unhydrolysed state. Crane (1972) found rainfall to be an important variable in N leaching when urea is applied. 33 2 . 5 . 2 . 2 Ammonia Reaction of NH^ with organic substances is also important because urea hydrolysis leads to the formation of NHg/NH^* in the soi l . The reaction of NHg with humic acids results in N being firmly adsorbed and fixed in the macromolecule of humic acid (Mortland, 1958; Stepanov, 1967). Hudig and van Reesema (1940) observed this only under oxidizing conditions. Stepanov (1967) found urea-humic acid fixation to be similar to that of NHg. Ponomareva (1969) mentioned that during the separation of fulvic acids by the ammonium carbonate method, both exchange binding of NHg by fulvic acids and fixation of NHg into the molecules of fulvic acids occur. The capacity for fulvic acids of podzolic soils to adsorb NH^"1" is about 300 me/ lOOg substance (Tyurin, 1940; cited by Kononova, 1966 and Ponomareva, 1969). 2.6 THE ANIONIC THEORY FOR CATION LEACHING Nye and Greenland (I960) stated that the total concentration of cations in soil solution and therefore the amount liable to leaching depends on the total concentration of mobile anions. It has been proposed that for cations to be lost in percolating water, they must be accompanied by mobile anions (HCO , SO CI", N O o " , HPO . o 4 o 4 or H2PO4 ) to maintain electrical neutrality (Cook, 1967, 1972). The small amounts of nutrients lost from many forest soils are attributed to the lack of mobile anions in the solutions of these soils (Nye and Greenland, I960). The kind of anion is also critical in leaching of cations. Munson and Nelson (1963) have established a leachability scale for K fertilizer. The sequence, in decreasing order, is: K G = K N O ^ > ^ S O ^ > K H2PO^ = KgPO^ > K2CaP2Cy. Likewise Crane (1972) has compared nitrogen 34 forms in respect ro leaching susceptibility as: nitrate forms > unhydrolysed urea > NH 4 CI > ( N H 4 ) 2 S 0 4 > N H 4 N 0 3 ( N H 4 - N only) > ( N H ^ P C ^ > ( N H ^ C C ^ > N H 4 H C 0 3 based mainly on the work of Benson and Barnette with Norfolk sand in 1939. Also, experiments involving applications with u rea -N , (Nr i^^SC^ and N H 4 N O have shown that N H 4 + leaching is influenced by the ease of diffusibility of the associated anions. NH + leaching foil ows the decreasing order of (NH ) 0 S 0 . 4 A'*- 4 > N H 4 N 0 3 > urea-N (Roberge and Knowles, 1966; Overrein, 1967, 1970; Popovic - 2 -and Nbmmik, 1972). Though the N O ion is more mobile than the SO ion, ammonium nitrogen leaches more readily in association with S 0 4 than with N O j " . The reason for this observation is not clear. The HCOg" ion has been considered by McCol l and Cole (McColl and Cole, 1968; McCo l l , 1969, 1972) as the major mobile anion influencing cation transport in forest soils at the Thompson Research Center near Seattle, Washington. They presented experimental evidence to support their theory. Also in support of this theory, Fredriksen (1972) reported from an Oregon watershed study that calcium outflow and content of carbonate and bicarbonate (the predominent anions of the stream) were closely correlated. Ponomareva (1969) stated that the carbonate equilibrium controls the behaviour of the alkali and alkaline earth cations but it is far from controlling the entire transport of bases in the soi l . According to Ponomareva (1969) most natural soils are dominated by organic acids which are stronger than the carbonic acid. These organic acids (e.g. fulvic acids) due to their high dissociation constants are capable of providing large quantities of protons (H + ions) for exchange and in forming soluble compounds with bases which can then move with gravitational water. It is actually these strong acids 35 which can solubilize sparingly soluble elements like Al or Fe (Ponomareva, 1969). In the study by Johnson et a l . (1974) in an Abies amabilis stand at Findley Lake, near the Thompson Research Center, it was found that the carbonic acid mechanism does not play any major role in cation leaching because of the large acidity produced by fulvic acids. The organic acids were found to dominate the pH and consequently, the bicarbonate activity, in most of the soil profile. Cole et aj_. (1973) have reported that forest management practices (e.g. fertilization, clearcutting, and burning) influence cation leaching through the carbonic acid mechanism. McColl and others (McCol l , 1969; Crane et a L , 1969; Crane, 1972) hypothesized that since the mobile HCOg" anion is the product of urea hydrolysis, urea fertilization will lead to accelerated cation transport (losses) as has been proposed by McCol l and Cole (1968) and McColl (1969, 1972). The importance of the HCO^ Ion originating from urea fertilization wil l be treated in the discussion (Section 3.9.1) in relation to the above hypothesis. 2.7 LEACHING MODELS 2.7.1 Forms in which Urea-N Fertilizer may be Leached Following urea application, N leaching may occur as (i) molecular urea or aqueous ammonia, (ii) cationic N H ^ + and (iii) anionic N O ^ or NOg . Unhydrolysed urea-N is fairly mobile in soil but slower than NO^ (Chin and Kroontje, 1962). However due to rapid ureolysis, movement of urea usually does not occur unless it rains heavily immediately after application (Crane, 1972). Ammonium - N ions are almost completely adsorbed by the soil colloids and are freely mobile only in soils with very 36 low CEC, low base saturation or cation content greatly exceeding the CEC (Thomas, 1969). Movement of NH^ is therefore greater in sandy soils than in clay or organic soils. The nitrate is the form which is most mobile and is usually found in leaching and drainage waters. In soils with high water content, medium to low CEC, low Fe and Al oxides and near neutral pH, NO^ leaches very freely (Thomas, 1969). 2 .7 .2 General Mathematical Models for Chemical Leaching The changes in soils water contents (due to evaporation, infiltration, drainage, or plant uptake) lead to simultaneous movement of water and solutes (Nielsen et a l . , 1972). However, due to chemical, biological, and other interactions between the chemicals and the soi l , it is difficult to predict quantitatively the exact relationship between soluble nutrients and the movement of water. A very brief mention w i l l , however, be made here. In general, the classical equation of continuity (Gardner, 1965; Boast, 1973; Bresler, 1973) is used to describe chemical transport in soil water. For simplicity, "salt sieving" and interactions (which make this classical quantitative model more complicated to be applied practically), are sometimes ignored. The simplified model ( i .e . the convective flow model) may be applicable for predicting the movement of some soluble and less interactive ions like NOg and CI" . Recently, Cho (1971), has also applied dispersion equations with first-order reaction rates for N transformation to describe the convective transport of continuously applied N H 4 + . He considered ion exchange reactions, ionic diffusion and simultaneously occurring nitrification and denitrification. Cho's work has been extended by Misra et a l . (1974) and Nielsen et a l . (1974). 37 2.8 METHODS FOR EVALUATING LEACHING Leaching may be estimated indir3ctly from precipitation and evapotranspiration data (Allison, 1965). This approach provides us with no information on the quality of the leachate hence it is not very useful in the study of impacts of agricultural and forestry practices on the environment. Two direct methods, namely, the small watershed approach (Bormann and Likens, 1967) and lysimeters (e.g. Cole, 1958; Cole and Gessel, 1968) are used in forest soil studies. Hornbeck and Pierce (1973) have reviewed these directmethods in terms of stream water quality. In the present study, Cole's fixed-tension microlysimeter system (Section 3.1.1.3) was used in both laboratory and field experiments. This approach has been criticized on the grounds that it cannot monitor quantitatively the volume of leachate in the field (Cochran et al„ 1970). This limitation has also been recognized by many investi-gators who have developed and used this kind of lysimeter. However, if the soil water tension does not fall below the failure tension of the lysimeter, the applied tension may be adjusted from time to time to match the tension in adjacent soi l . Unless the hydraulic conductivity of the plate is excessively low, this approach yields excellent quantitative estimates of vertical flow. Some lysimetry errors are less important than others. For example, lysimeter failure at high tensions may be unimportant in some soils, because of the hydraulic conductivity-tension characteristic. Also, in freely-drained coarse-textured soils, the conductivity-tension charcrerlstic yields relatively little flow divergence with a f ixed-tension lysimeter plate oriented to evaluate vertical flow. (Even a qualitative interpre-tation of lateral flow is problematic with a tension lysimeter.) Where the quantitative 38 errors appear excessive, the tension lysimeter may be used merely to sample water quality, though its failure to sample at high tensions may be a drawback in some studies. Stream water sampling is of interest in studies which are oriented to water pollution and certain other problems. However, it usually yields unreliable information about processes in the soil or in specific soil layers or horizons, because it indicates only a net result of reactions in the total column of soil plus geologic material down to and through the aquifer zone. Also, the watershed approach is very much more expensive and in most cases replication is limited by cost or location (lack of similar watershed). 3.0 MATERIALS AND METHODS 3.1 FIELD EXPERIMENT #\ The main objective of this field experiment was to evaluate by means of a tension-lysimeter technique, the effects of fall-applied urea fertilizer on soil solution chemistry, nitrogen transformations and leaching of nutrient elements from four different forest soil sites. 3.1.1. Study Area The study was conducted at the University of British Columbia (UBC) Research Forest, located approximately 60 kilometers east of Vancouver, B .C. The area lies in the drier Coastal Western Hemlock (CWHa) Biogeoclimatic 2one (Krajina, 1969). Historically, the area was subjected to four glaciations (Seymour, Semiamu, Vashon and Sumas). The Sumas was a minor one which probably affected only the valleys (Armstrong, 1954; 1957). Glacial ti l l is the most widespread earth material in the area (Eis, 1962). The bedrock consists predominantly of acid igneous rocks -quartz diorite (the most common), granodiorite, and some granite syenite and monzonite. There are also isolated masses of volcanic and sedimentary rocks (Roddick, 1965). The climate is Cfb (after Koppen) which is described as mesothermal equable (marine) humid to rainy (Krajina, 1969). The coldest month is January ( l . l°C) , while July and August are the hottest months (I6.6°C). The total annual precipitation of the southern part of the forest is about 2280 mm and most of this occurs in November, December and January. Snow may accummulate to depths of 30cm during winter but melts within one to two weeks. The driest months are June, July and August. Appendix 40 I;:;M.'.'I."JK'IITIO.'I s u i t I O N i w x i m w C . . . V r.'. II l M'JM c . . . e Figure I: Temperature and Precipitation Data for two D.O.T . Stations. (Administration Station is close to Sites I and III) Figure I (continued): Temperature and Precipitation Data for two D.O.T . Station (Marc's Farm Station is close to Site IV) 42 A shows the weather data taken during the whole study period, and the mean tempera-ture and precipitation for the sampling periods (following fertilization) are presented in Figure I. 3 .1 .2 . Experimental Sites Four contrasting sites, designated as Site I (Gravel Pit), Site II (Mixed Douglas fir - alder stand), Site III (Micrometeorological Station), and Site IV (Marc's Farm) were selected in the southern portion of the UBC Research Forest for the study. (Equi-valent drabic numerals are assigned to the sites in the figures)- Two plots (a control and treated plot) were established on each of the sites. A pit was excavated on each plot. One profile from each site is described below. . The sites are also illustrated in Appendix A . I - A . 4 . Site I: Gravel Pit Site The surface of the soil of this area was disturbed by bulldozing for qn adjacent gravel pit. The A and upper B soil horizons were removed. The land form is an outwash terrace with nearly level relief. The parent material consists of glacial outwash sand and gravels. The area was planted with Douglas fir (Pseudotsuga menziesii Franco) in March 1967. Shrubby red alder (Alnus rubra Bong.) trees are occasionally found in the area. The forest floor and the tree canopy are not developed. Horizon Depth Description cm Bg 0-13 brown - dark brown (7.5YR4/4, moist) loamy sand; moderate fine granular; friable, non sticky non plastic Horizon Depth Description cnv r _43_ 10-15% coarse fragments (gravels); very few cemetations, very fine and plentiful medium roots, abrupt and smooth boundary; 9 -26.5 cm thick; pH 6.01 (1/2 soil/H 20) B 13-30 strong brown (7.5YR 5/6, moist) and olive grey (5Y 5/2 moist) sand; lenses and lamina of oxidized mottles; single grain; firm, non sticky and non-plastic; less than 5 % gravels; abundant medium roots; abrupt and smooth boundary; 10-23 cm thick; pH 5.86 (1/2 soil/H 20) C2 30-42 variegated, oxidized mottles; coarse sand; structureless single grain; very friable, non sticky and non plastic; 15-20% gravels and cobbles; no roots; abrupt and smooth boundary; 9-16.5 cm thick; pH 5.60 (1/2 soil/H 20) C3 42-47 olive grey (5Y 5/2, moist) sand; lenses and lamina of oxidized mottles; single grain, firm, non sticky and non plastic; 0-5 cm thick; pH 5.78 (1/2 soil/H 20) C4 47-57 variegated, approximately greyish brown to dark greyish brown (2.5Y 4.5/2, moist) sand; somewhat oxidized, mottles; single grain; very friable, non sticky and non plastic; 5-10% of coarse fragments (up to 5.1 cm); no roots; abrupt and smooth boundary; 5-9 cm thick; pH 5.58 (1/2 soi l/H20) C5 57-62 olive grey (5Y 5/2, moist) sand; lenses and lamina of ox i -dized mottles; single grain, firm, non sticky and non plastic; less than 5% coarse fragments; no roots, abrupt and broken boundary; 7 .5 -9 cm thick; pH 5.54 (1/2 soil H20) C6 62-65 variegated, oxidized mottles, gravelly coarse sand; single grain; very friable, non sticky and non plastic; 20% coarse fragments (up 7.6 cm); no roots; abrupt boundary; 0-15 cm thick; pH 5.53 (1/2 soil H20) C7 65-104 light grey to grey (5Y 6/1 moist) gravel sand to gravelly coarse sand; single grain; very friable, non sticky and non plastic; 15-20% coarse fragments (5.1 cm); no roots, pH 5.46 (1/2 soil/H 20) Site II: Mixed Douglas Fir - Alder Stand The soil profile was truncated during logging. As a result, the B horizons are exposed. 44 The parent material is t i l l over glacio-marine drift. The surface soil is poorly drained; the water table comes close to the surface during winter. The tree vegetation consists of Douglas fir (planted in 1965 with 2-0 and 2-1 seedlings) and red alder. Understory vegetation consists of sword fern (Polystichum munitum, Kaulf. Presl.) and mosses. Horizon Depth Description cm LF 1-0 fresh and partially decomposed Douglas fir needles and red alder leaves. pH 4.9(1/4 soil/H 20) Bfh 0-10.5 dark brown (7.5YR 3.5/4,moist) loam; fine moderate crumb; friable, slightly sticky, slightly plastic, 5% or less coarse fragments; abundant medium, plentiful coarse and very few to few fine roots, abrupt and wavy boundary. 3.5-19.5 cm thick. P H 5.0 (1/2 soil/H 20) Bf 10.5-65 dark yellowish brown (10 YR 3.5/4, moist) gravelly loam, single grain to fine moderate crumb, charcoal present, friable, slightly sticky and slightly plastic, 15% coarse fragments, plentiful coarse and medium, very few fine and very fine roots, abrupt and irregular boundary. 10-55 cm thick, pH 5.1 (1/2 S0M/H2O) BC 65-84 light olive brown (2.5Y 5/4, moist); sand; single grain to coarse, moderate subangular blocky; firm, non sticky, non plastic,<5% coarse fragments, few to plentiful medium roots; clear and wavy boundary, 19-58 cm thick, pH 5.2 (1/2 soil/H 20) C 84-104 light olive brown (2.5Y 5/4, moist); sand, single grain to coarse moderate subangular blocky; firm, non sticky, non plastic, <5% coarse fragments, no roots, pH 5.1 (1/2 soil/H 20). Classification: Humo-Ferric Podzol. Site III: Micrometeorological Station The land form is an outwash terrace with a nearly level relief. The soil is 45 fairly permeable and is moderately well to well drained. Like the first site, the parent material consists of outwash sands and gravels. The forest floor Is moder underlain by an Ap horizon, developed by scarification before planting. The vegetation is an immature Douglas-fir stand, planted in 1957. The forest floor is devoid of vegeta-tion except occasional salal (Gaultheria shallon Pursh)and Hylocomium splendens. Horizon Depth Description cm L 1-0 fresh Douglas-fir needles. pH 4.7 (1:4 soil/HjO) Ap 0-7 black (5YR 2.5/1, moist) sandy loam; fine moderate crumb. friable, slightly sticky and slightly plastic, 5-10% coarse fragments, rootsiabundant coarse, abundant medium, few five; abrupt wavy boundary, 5-10 cm thick, pH 4.4 (1/2 soil/H 20) H 7-8 very dark dusty red (2.5YR 2.5/1, moist) 1-4 cm thick. pH 4.7 (1/2 soil/H 20) Ae 8-10 dark reddish grey (I0YR 3/1, moist) sandy loam; single grain to medium moderate subangular blocky; friable, non sticky and non plastic; 10-15% coarse fragments; roots; few fine; abrupt wavy boundary 2-4 cm thick, pH 4.8 (1/2 sol l/H20) Bh f 10-14 dark dusty brown - dark reddish brown (2.5YR 2.5/3 moist) gravelly sandy loam; concretions; fine moderate crumb; friable, non sticky and non plastic, v 25% coarse fragments. Roots - abundant coarse, abundant medium, few fine, abrupt wavy boundary, 2-4 cm thick, pH 5.3 (1/2 soil/H 20) Bfhcc 14-32 reddish brown (5YR 3.5/4Amoist)with strong brown (5YR 3.5/4,moist) sand pocket and dark reddish brown (5YR 3/3,moist) orstein, gravelly loamy sand; concretions, fine moderate crumb, friable, non sticky and non plastic; about 30% coarse fragments, plentiful coarse and medium roots; clear wavy boundary; 28-42 cm thick, pH 5.3 (1/2 soil/H 20) 46 Horizon Depth Description cm Bf 32-60 dark reddish brown (5YR 3/3 moist) gravelly loamy sand; single grain to fine moderate crumb; weakly cemented;, firm, non sticky and non plastic (wet); ~40% coarse fragments, absence of roots, clear wavy boundary, 15-20 cm thick, pH 5.2 (1/2 soil/H 20) Bcgj 60-74 strong brown (7.5YR 5/6, moist) gravelly sand; single grain to fine moderate crumb; weakly cemented; firm, non sticky and non plastic; about 25% coarse fragments; no roots, clear wavy band; 10-15 cm thick; pH 5.3 (1/2 soil/H 20) C 74-82 pale brown (I0YR6/3, moist) gravelly sand; fine moderate crumb; friable, non sticky and non plastic; about 20% coarse fragments; no roots; 10-15 cm thick, pH 5.4 (1/2 il/H2Q) soi I Classification: Humo-Ferric Podzol. Site IV: Marc's Farm The parent material consists of a poorly sorted outwash. The soil is well drained and the slope is very slight (0-5%). The ground vegetation is well developed (several ferns,salal, Hylocomium splendens, Plagiothecium undulatum). The forest tree vegeta-tion consists of mature Douglas-fir of about 95 years of age. Horizon Depth Description cm 19-18.5 fresh needles, cones, etc. of Douglas-fir (Pseudotsuga menziesii); 1-2 cm thick; pH 4 .2 (1/4 soil/H20) 18.5-17.5 partially decomposed forest litter; plentiful medium and few very fine roots; abrupt and wavy boundary; 1-3.5 cm thick; pH 3.7 (1/4 soil/H 20) H 1 7 . 5 - 1 2 reddish black (I0YR 2/1, moist) thin granular mor; very 47 Horizon Depth Description cm friable; abundant coarse and medium plus few to plentiful very fine roots; abrupt and wavy boundary; 1-6 cm thick; pH 3 .5 (1/4 so?I/H20) F 12-0 rotten logs; abundant coarse and medium plus few micro and very fine roots; abrupt and wavy boundary; 9-22 cm thick, 0 .5 cm thick charcoal layer on top of Ae; pH 3.6 (1/4 soil/H 20) Ae 0-8 dark grey (5YR 4/1, moist) sandy loam; single grain; fine moderate subangular blocky (with pieces of charcoal); friable, slightly sticky and slightly plastic; few fine and few very fine roots; abrupt and wavy boundary; trace to 16 cm thick; pH 3.7 (1/2 soil/H 20) Bh f 8-11 dark reddish brown (2.5YR 2/4, moist) loamy sand; single grain; fine moderate to strong granular; friable to firm, non sticky, non plastic; few micro and very fine roots; clean and wavy boundary; 1-3 cm thick; pH 5.4 (1/2 soi l/H20) Bfh 11-36 reddish brown (5YR 4/4, moist) to yellowish red (5YR 4/6, moist) loamy sand; fine moderate crumb (massive in places); friable and firm, non sticky and non plastic (but weakly cemented); roots: - plentiful coarse and medium, micro and very f ine; clear and wavy boundary; 20-25 cm thick; pH 5.3 (1/2 soil/H 20) Bf 36-54 yellowish red (5YR4/6, moist gravelly sandy loam; fine moderate granular; friable to firm; non sticky and non plastic; roots: - plentiful medium, very fine roots; clear and wavy boundary; 15-20 cm thick; pH 4 .5 (1/2 soil/H 20) BC 54-77 yellowish brown (I0YR 5/5, moist) gravelly coarse sand;. structureless, single grain; friable, non sticky and non plastic; absence of roots; pH 5.5 (1/2, soil/H 20) Classification: Orthic Humo-Ferric Podzol Analyses were also done on soil samples taken from each horizon of the pits on each site. Coarse fraction (>2 mm) and percent water content were determined by the methods described in Black (1965). Soil pH was measured using a glass electrode pH meter in a 1:4 and 1:2 soil: water suspension for samples from the organic and mineral soil horizons, respectively. Carbon was determined instrumentally using a Leco induction furnace and carbon analyser (Black, 1965). The semi-microkjeldahl procedure was used for total nitrogen. Phosphorus was determined in dilute acid-fluoride extracts and also in the extracts of dilute hydrochloric acid and sulfuric acid (Black, 1965). Cation exchange capacity and total exchangeable bases were determined using the neutral IN ammonium acetate extraction procedure (Jackson, 1958; Black, 1965). The exchangeable cations - sodium, potassium, calcium and magnesium - were determined by atomic absorption spectrophotometry from the ammonium acetate leachate. After displacement by acidified NaCI , adsorbed ammonium was analyzed by Kjeldahl dis-tillation and titration for determination of CEC. The results obtained from these analyses are presented in Tables I, 2, 3 and 4. 3.1.2.1 General Characterization of the Sites The soils on the study sites were briefly characterized as follows: -Site I: A coarse textured soil containing little organic matter . Site II: A soil with substantial nitrification ability (verified by incubation studies). Site III: Mineral soil with relatively high organic matter content in the A horizon. Site IV: A soil with a thick forest floor. / Table I: Pre-fertilization Soil Analyses, Site I (Gravel Pit , near Administration Building) % (wt) or coarse Extractable P (ppm) . material i moisture a b c content ^Anm Exchangeable Cations me/IOOg Depth cm Hori: N a K Ca Mg CEC* % Base Leco Sat. %C K je l -dahl % N C/N P H Control 6.01 Plot 0-13 Bf 0.013 0.020 0.20 0.014 16.0 2.28 1.50 0.050 30.0 2.5 2.0 0 .0 2.7 46.0 13-30 CI 0.020 0.022 0.20 0.011 8 .8 2.88 0.53 0.020 26.5 2.7 2.0 0 .0 1.5 34.5 5.86 30-42 C2 0.017 0.020 0.26 0.008 5 .9 5.17 0.39 0.015 26.0 20.4 8 .4 1.0 I.I 33.6 5.60 42-47 C3 0.022 0.022 0.30 0.009 5.3 6.66 0.27 0.010 27.0 21.5 10.0 1.0 0 .7 8 . 5 5.78 47-57 C4 0.024 0.022 0.32 0.009 5 .2 7.21 0.27 0.011 24.5 22.3 7.8 0 .0 0 .7 7 .3 5.58 57-62 C5 0.023 0.023 0.30 0.008 4 . 3 8.07 0.22 0.006 36.7 27.1 11.8 1.0 0 . 5 10.0 5.54 62-65 C6 0.028 0.019 0.21 0.006 3 .3 7.97 0.25 0.003 83.3 55.2 11.4 1.0 0 . 5 62.3 5.53 65-104 C7 0.028 0.015 0.18 0.005 2.0 11.40 0.10 . 0.003 33.3 27.1 8 . 4 0 .0 0.4 34.1 5.46 Treated Plot 0 -9 Bf 0.011 0.048 0.21 0.013 10.0 2.82 1.07 0.040 26.8 .4 .6 3 .4 1.0 1.8 27.1 5.57 9-35 CI 0.019 0.017 0.20 0.006 4 . 3 5.63 0.32 0.006 53.3 21.5 6 .6 0 .0 0 .7 40.0 5.49 35-42 C2 0.032 0.019 0.25 0.010 5.9 5.27 0.65 0.015 43 .3 8 .4 3 .4 0 .0 I.I 80 .9 5.51 42-64 C3 0.020 0.014 0.23 0.007 3 . 5 7.74 0.17 0.007 24.3 18.7 3 .4 0 .0 0.6 38.0 5.39 64-76 C4 0.021 0.019 0.26 0.007 3 .4 9.03 0.15 0.005 30.0 21.5 10.0 0.0 0.6 0 .5 5.29 76-85 C5 0.026 0.016 0.19 0.005 2 .2 10.77 0.15 0.001 150.0 27.1 4.8 0 .0 0 .5 29.5 5.08 a: Dilute-acid-Fluoride Extractable P (0.03N N H 4 F in 0.025N HCI) b: Dilute-acid-soluble P c: Bicarbonate extractable P (0.5N N a H C 0 3 ) *CEC by I.ON neutral N H 4 O A C / Tcble 2: Pre-fertilization Soi! Analyses, Site II (Mixed Douglas-fir-Alder Site) Exchangeable Cations % Kjel Extractable % of coarse Depth me/100 g Base Leco dahl P (ppm) moisture material cm Horizon N a K Ca Mg CEC* Sat. %C % N C/N a b e content >-2mm pH Control' 1.5-0 L-F 0.096 1.280 11.720 2.650 94.7 0-20 Bfh 0.026 0.154 0. 116 0.044 35.3 20-54 Bf 0.022 0.083 0.040 0.017 28.2 54-98 BC 0.021 0.041 0.150 0.009 10.2 98+ C 0.027 0.032 0.200 0.008 5.5 Treated 1-0 L-F 0.068 1.160 . 14.400 2.800 85.1 0-16 Bfh 0.016 0.108 0.386 0.088 38.3 16-49 Bfl 0.016 0.046 0.090 0.014 15.7 49-97 Bf2 0.018 0.046 0.110 0.009 12.1 97+ HCg 0.029 0.063 0.140 0.018 15.2 16.62 31.80 0.940 33.8 155.5 N A 47.0 8.6 — 4.58 1.93 ' 4.40 0.200 22.0 2 .5 N A 2.0 4.6 19.7 5.14 0. 57 1.80 0.110 16.4 I.I N A 3 .0 4 .3 36 .5 5.30 2. 17 . 0 .62 0.020 20.7 12.2 N A 3 .0 1.5 13.9 5.36 4.85 0.37 0.011 33.6 36.7 N A 2.0 1.0 4 .8 5.23 21.65 33.30 0.790 42 .2 195.0 N A 46.0 8 . 2 4.88 1.56 4 .84 0.200 24.2 10.4 N A II.0 4 . 5 19.5 5.00 1.06 1.60 0.060 26.7 8 .3 N A 2.0 2.1 19.8 5.09 1.51 0.98 0.040 22.3 13.3 N A 2.0 1.9 8 . 0 5.24 3.29 0.89 0.030 29.7 10.8 N A 2.0 2.0 78 .0 5.09 N A - not available a: Dilute-ccid-Fluoride Extractable P (0.03N NH^F in 0.025NHCI) b: Dilute-acid-soluble P c: Bicarbonate extractable P (0.5N N a H C O J *CEC by I.ON neutral N H 4 O A c (j c / Table 3 : Pre-fertilization Soil Analyses, Site III (Micromefeorology Station) Exchangeab le Cations % K j e l - Extractable % % of coarse Depth me/100 9 Base Leco dahl P(ppm) ' moisture material cm Horizon N a K Ca Mg CEC* Sat. %C % N C/N a b C content y2mm PH Control Plot N A Hi 0.108 0.260 7.52 0.476 63.9 13.09 19.0 0.570 33.3 29.8 N A II.0 6 .3 18.6 4.74 N A Ap 0.096 0.200 4.44 0.356 55.7 9.14 14.80 0.520 28.5 6 . 5 10.0 10.0 5 .9 30 .0 4.89 N A Bf 0.043 0.032 0.21 0.024 21.1 1.47 1.50 0.060 25.0 2 .5 5.8 2.0 3.1 4 9 . 5 5.50 N A Bfh 0.034 0.044 1.04 0.054 38.3 3.06 3.40 0. NO 30.9 10.2 7 . 2 5 .0 4 . 5 34.3 5.43 N A BfhccI 0.034 0.038 0.80 0.046 22.5 4.08 2.80 0.090 31.1 5.8 4 . 0 2.0 3 .6 27.3 5.46 N A Bfhcc2 0.036 0.048 0.48 0.032 22.4 2.66 2.60 0.070 37.1 3 .7 3 . 4 2.0 2.0 41.6 5.48 N A BC 0.031 0.144 0.13 0.011 13.6 2.32 0.61 0.020 30 .5 7 .9 4 . 0 1.0 2.3 35.9 5.60 Treated Plot 1-0 L 0.116 1.832 17.16 1.948 63.6 33.11 35.4 0.930 38.1 162.1 N A 36.0 7 .7 — 4.66 0 -7 A P 0.054 0.224 4.36 0.347 54.5 9.15 12.3 0.420 29.3 . 7.9 9 .2 8 . 0 5 .2 21.0 4.44 7-8 H 0.064 0.196 7.20 0.760 55.9 14.70 12.5 0.470 26.6 52.2 N A — 5 .2 — 4.67 8-10 Ae 0.058 0.148 1.70 0.166 23.5 8 .82 4 . 4 0.130 33.8 19.8 10.0 9 .0 2 .2 4 3 . 5 4 .77 10-14 Bhf -0.140 0.050 0.18 0.060 49.4 0.87 5 .9 0.200 29.5 8 .4 5.8 5 .0 6 . 5 55.1 5.25 14-32 Bfhcc 0.040 0.026 0.12 0.026 32.0 0.66 2 .5 0.080 31.3 6 .5 3 .4 1.0 4.1 46 .3 5.26 32-60 Bf 0.035 0.108 0.17 0.021 19.6 1.70 1.9 0.070 27.1 6 .3 2.0 1.0 2.9 51.0 5.23 60-74 BCgJ 0.056 0.020 0.17 0.018 16.7 1.58 2.6 0.060 43.3 6 . 5 2.6 0 .0 2.6 4 7 . 5 5.25 74-82+ C 0.042 0.022 0.18 0.007 7.4 3.39 0.59 0.013 45.4 13.1 6 .6 0 .0 1.6 58.5 5.35 N A - not available a: Dilute-acid-Fluoride Extractable P (0.03N in 0.025N HCI) b: Dilute-acid-soluble P c: Bicarbonate extractable P (0.5N N a H C 0 3 ) *CEC by I.ON neutral N H . O A c Table 4: Pre-ferfilization Soil Analyses, Site IV (Mature Douglas-fir Site - Marc's Farm) %(wt) Depth cm Horizon Exchangeable Cations me/100 g CEC* % base Sat. Leco %C K j e l -dahl % N C/N Extractable P(ppm) % moisture content of coarse material ?2mm pH Na K Ca Mg a b c N A LFH/Hi 0.076 0.592 6.76 1.288 62.4 13.97 24.6 0.560 43.9 51.6 N A 27.0 6 . 3 4 .69 N A Bfl 0.043 0.039 1.38 0.048 21.9 6.89 2.6 0.070 37.1 0 . 2 0.8 0 .0 3 .9 16.1 5.49 N A Bf2 0.105 0.031 0.08 0.060 26.9 1.03 2.1 0.070 30.0 0.8 0.8 1.0 5 .2 17.0 5.73 N A Bfh 0.008 0.074 0.52 0.070 26.0 2.58 2.9 0.130 22.3 7 .4 5.8 3 .0 4 . 2 18.0, , 5.33 N A C 0.086 0.029 0.25 0.015 7 .9 4.81 0.25 0.006 41.7 4 . 2 6 .8 1.0 1.3 14.5 3 5.83 19-18.5 L 0.172 1.992 17.56 .3.148 98.17 23.17 46.10 1.070 43.1 171.5 N A 83.0 9 .7 4.20 18.5-17.5 F 0.152 1.672 16.76 2.268 116.6 17.88 39.00 1.090 39.0 115.8 N A 6 9 . 0 9.6 — 3.73 17.5-12 H 3.040 1.112 15.16 2.308 141.6 15.27 48.90 0.940 52.0 65.8 N A 34.0 10.2 — 3.52 12-0 F 0.840 0.328 8.48 0.908 113.7 9.28 49 .7 0.330 150.0 23.2 N A 15.0 8 .8 — 3.63 0-8 Ae 0.036 0.068 0.46 0.064 9.1 6 .90 1.5 0.100 37 .5 8 .8 3 .4 3 . 0 0 .7 39.8 3.67 8-11 Bhf 0.034 I.05C 0.08 0.034 38.6 0.51 4 . 3 0.040 43.0 1.4 26.8 26.0 5 .3 32.5 5.37 11-36 Bfh 0.040 0.030 0.38 0.040 27.6 3 .55 1.9 0.070 27.1 1.7 2.6 2.6 4 .8 41.0 5.28 36-54 Bf 0.032 0.021 0.16 0.020 18.9 1.23 1.2 0.040 30.0 31.0 2.6 1.0 3 . 4 46.4 4.51 54-77 BC 0.046 0.036 0.36 0.016 8 .9 5.15 0.44 0.010 44.0 5.6 3 .0 1.0 1.6 39.6 5.48 Control Plot Treated Plot N A - not available a : Dilute-acid-Fluoride Extractable (0.03N in 0.025N HCI) b: Dilute-acid-soluble P c: Bicarbonate extractable P (0.5N N a H C O J *CEC by I.ON neutral N H ^ O A C 3.1 .3 . Lysimeter Installation A tension-lysimeter plate technique was used to obtain soil leachates. Each plate was constructed from a fused alundum disc having a diameter of 15.24 cm. A detailed description of the design and construction of the plates have been reported by Cole and his co-workers (Cole, 1958, 1968; Cole and Gessel, 1968; Cole et a l , 1961). In the present study, the lysimeter plates were installed in the surface soil horizon and below the rooting zone in the lower soil horizon in November 1972. The locations of the plates are presented in Table 5. The pit excavated on each plot was used for the installation of the deep plates and the housing of two glass carboys used for collecting deep plate leachates. Two lysimeters were first installed at the lower end of walls of each pit. The side walls of the pits were then plywood-lined to maintain them intact and limit evaporation losses. The tops were protected by a plywood lid whose inner side was lined with a styrofoam sheet (2.54 cm thick). Two plates were similarly installed at shallow levels but the trenches were covered after their installation. A plywood box (with its inner sides and lid lined with styrofoam sheets) was constructed to contain the two collecting carboys for the shallow plates. A total of four shallow (surface) and four deep plates was installed at each study site. The eight plates were connected to a single vacuum source at a constant tension, approximately equal to that of the soil at field capacity (0.1 atmospheres), to extract the leachates through the plates into the carboy bottles. The collecting system includes the following components: I. Vacuum cylinder: A 100-lb propane cylinder (91-litre capacity) was used as a Table 5: Locations of the Tension Lysimeter Plates in the Soils of the Study Plots. / Site I Site II Site III Site IV Depth (cm) Horizon Depth (cm) Horizon Depth (cm) Horizon Depth (cm) Horizon Control Plots Shal low A 15 CI 7 Bfh 5 Ap 6 .5 above Ae Shal low B 15 CI 7 Bfh 5 Ap 10 above Ae Deep A 93 C7 102 C 75 BC 75 C Deep B 93 C7 102 C 75 BC 75 C Fertilized Plots Shal low A 15 CI 10 Bfh 5 Ap 6 .5 above Ae Shal low B 15 CI 10 Bfh 5 Ap 10 above Ae Deep A 93 C5 90 llCg 85 C 80 C Deep B 93 C5 90 HCg 85 C 80 c Depths were taken from the surface of the soi l . Figure 2: Collecting System for Soi! Leachates (Field) / 1 Vacuum Cylinder IA Vacuum Pump 2 Cartesian Manostat 3 Guage 4 Hand Pump 5 Manifold 6 Glass Carboy 7 Lysimeter Plate 56 vacuum tank. The cylinder was evacuated with a vacuum pump and used as a vacuum supply. 2. Cartesian manostat: for regulating and maintaining the required tension (about 90 mm Hg) to the system. The manostat was checked and adjusted, if necessary, twice weekly. 3 . Gauge: for checking the tension in the system. 4. Hand pump: for re-establishing the tension within the system after sampling (instead of consuming the vacuum in the vacuum cylinder). 5. Manifold: for distributing tension to the plates and the collectors. 6. Glass carboy: for collecting leachates passing through the plates. 7. Lysimeter plates: for col lecting water -The set up is illustrated in Figure 2. (See also Appendices A . 5 to A .9 ) . 3 .1.4. Throughfall Sampling Input of throughfall (crownwash) was sampled on each plot with two collectors. A collector consisted of 9 .5 cm diameter screened plastic funnel whose wider end is a 9.5 cm (diameter) x 6.5 cm (height) acrylic cylinder. The acrylic cylinder gave the collector a conventional rainguage configuration and minimized splash loss. Each collector was mounted in the neck of a one-gallon plastic bottle. Entry of small particles into the plastic bottle was prevented by loosely plugging the funnel with nylon wool. In this study, throughfall data will not be discussed. However, the results will be presented at the Appendix F. 57 3 .1 .5 . Fertilization A plot on each site was fertilized with fertilizer-grade urea ( (NH^CO) pellets (45-0-0) at the rate of 448 kg/ha on November 12, 1973. Hand broadcasting method was used for the urea application except in the areas above the shallow plates, where application was done by pipetting a solution made from the pellets, to ensure uniform application. 3 .1 .6 . Sampling, Storage and Analyses of Lysimeter Soil Leachates Lysimeter leachates were sampled at weekly intervals from March 1973 (about 8 months prior to the urea fertilization) to July 1974(246 days after fertilization). The volumes of solutions leached were measured with graduated cylinders and portions were taken into 250 ml plastic bottles for analyses. -The samples were cooled with ice during transit. In the laboratory, the solutions were analysed immediately upon arrival for pH (with a glass electrode pH meter), and electrical conductivity by the method described in the Instruction and Operating Manual for Type CDM2e conductivity Meter (1st ed.) (Radiometer, Copenhagen). The remaining portions of the samples were stored in cold rooms at 2°C ti l l the following day. Each sample was then divided into three lots. One portion was used for N a , K, Ca , and Mg determinations. The second fraction was stored without any preservative at 0°C for nitrate-nitrogen analysis, and the last was preserved with concentrated H2SO4 (I ml H2SO4 per 100 ml solution) and stored at 2°C for ammonium-nitrogen, Kjeldahl total nitrogen and phosphorus determinations. Four subsequent weekly samples from each plate (except those taken 9 weeks following fertilization) were proportionally bulked according to the original volumes of the leachate collected before analysing for Kjeldahl total N , N H ^ - N and N O 3 - N . 58 Sodium, potassium, calcium and magnesium were determined on the lysimeter leachates with a Perkin-Elmer 306 Atomic Absorption Spectrophotometer using air -acetylene flame. Kjeldahl nitrogen, N H ^ - N , N O g - N and total P were determined using the Technicon Autoanalyser II. N H 4 - N was determined as described by Technicon Industrial Method AAII ^98-70W which employs the Berthelot reaction whereby a blue colored compound related to indophenol is formed with phenol and sodium hypochlorite in alkaline solution. Nitrate - N was preserved, pretreated and determined by the .procedure described by Johnson (1972). Nitrate is reduced by hydrazine and a copper catalyst in alkaline solution to nitrite. The nitrite, in turn, reacts with sulphanilamide and N - (l-Naphthyl)-ethylene diamine dihydrochloride in acid solution to form an azo dye having an absorbance maximum of 520 mu . (This method also recovers nitrite, but normally, soil nitrite concentrations are very low.) Kjeldahl N and total P were analyzed simultaneously by a modified Technicon method of Johnson et a l . (1973). Organic N and organic P were converted to ammonia and orthophosphate respectively by automatic digestion (Technicon Continuous Digester) of the sample with concentrated H2SO4 containing perchloric acid and a selenium catalyst. The digested sample is automatically diluted and divided into two streams and analyzed simultaneously for ammonia and orthophosphate. The ammonia was determined as stated above. For the ortho-phosphate, ammonium molybdate and antimony potassium tartrate react with orthophosphate to form a phosphomolybdate-antimony complex which is reduced by hydrazine to form an intensely blue colored compound with an absorbing maximum at 660 m L^. The detection limits for N H ^ - N , N O 3 - N , Kjeldahl total N and total P were 0.1, 0 .02, 0.05 and 0.05 mg/l respectively, except for the samples taken between the period before fertilization and one month after fertilization which were determined at 0.5 mg/l for Kjeldahl total N and total P. Organic N was calculated from Kjeldahl total nitrogen and N H ^ - N for each sample. The sum of N H ^ - N , N O g - N and organic-N was taken as total nitrogen. 3.2 FIELD EXPERIMENT # 2 The aim of this experiment was to study the changes of soil pH, CEC and exchangeable cations following fertilization with (NH^^SO^ or urea. a) Twelve 2m x 2m plots, each buffered on all sites by similarly-treated 2-m-wide strips, were established on Site III in the later part of May 1974. The plots were randomly treated as follows: 4 controls, 4 fertilized with fertilizer grade urea pellets and 4 fertilized with reagent grade ( N H ^ S O ^ , . The fertilizers were hand broadcast at the rate of 448 kg N/ha.Soil core samples, 6 in.(15.24cm) high, from the top mineral soil were taken from each plot prior to fertilization and at 10, 15 and 345 days following fertilization. Exchangeable cations, CEC, and pH were determined as described in Section 3 .1 .2 . Similar analyses were made for control and experiment samples from the lysimeter installation plots of Site III. Samples were taken in November, February, April and June following urea application. b) Soil core samples were taken from the lysimeter plots on all the 4 study sites in early May 1975 (ie. 540 days following urea fertilization of the field experimental plots). Soil reaction was measured in 1:2 suspensions of moist soil: f ^ O and 1:2 moist soil: O.OIM C a C ^ solution. 3.3 LABORATORY EXPERIMENT # l Laboratory Experiment ^1 , was set up with similar purpose as Field Experiment ^1. The aim here was to repeat the experiment under controlled laboratory conditions. Four soil samples were taken almost intact (to a depth of about 12 cm) from each of the four field experimental sites described in Section 3.1.1 in August 1973. Each sample was put into a plastic bag with a minimum of disturbance and stored at 4°C in a cold room. Each sample was then trimmed to fit well into a tension lysimeter column constructed by fixing a cast acrylic tube (15.24 cm outside diameter x 10.40 cm length) on a 15.24 cm diameter alundum lysimeter plate. The 16 soil columns (8 controls and 8 experiments) were set up on a rack in a laboratory at a temperature of 22°C. The soils in the columns were leached with distilled water and brought to moisture equilibrium by applying a tension of 90 mm Hg on the plates. The columns were each loosely covered with a styrofoam sheet to reduce water loss by evaporation. Each column was leached with 500 ml distilled water (in 5 lots at 30 minutes interval) twice a week. A tension of 90 mm Hg was applied during sampling to extract soil solutions. After sampling for 2 weeks, the samples were fertilized by pipetting a solution of analytical grade urea (equivalent to 448 kg/ha urea-N). The experiment was then continued for six more weeks. Immediately after collection, a water sample aliquot was treated with toluene for NOg~N and N H ^ - N analyses. The leachate volumes, electrical conductivity, pH, sodium, potassium, calcium, magnesium, ammonium-N, ni trate-N, were determined on the leachates as described in Section 3 .1 .6 . 3.4 LABORATORY EXPERIMENT # 2 The principal purposes of this study were to test (with a uniform soil material), the hypothesis that urea fertilizer could increase the CEC of soils, to confirm the leaching results obtained for the basic and nitrogenous ions following field urea application in the fall (Field Experiment ^1), and to examine both organically-bound and free ion forms of some nutrients leached through the profile. Soil samples were taken from the Ap horizon of field experimental Site III in mid-October 1974. The roots in the samples were removed and the samples were passed through a 4.76 mm sieve (mesh # 4 ) . The sieved samples were then mixed thoroughly together, placed into plastic bags and stored in a 4°C - cold room. Analyses of the mixed soil indicated 10.85% Leco carbon (9.57% C by Walkley - Black method), a water content of 14.2%, and 84% of <2 mm material. Throughfall samples were also collected, mixed and stored at the same temperature as the soil samples. The contents of the throughfall water samples as determined by the methods described below were 0.43 mg/l Na^O.40 mg/l K, 0.37 mg/l Ca , 0.09 mg/l C a , 0.0 mg/l Fe, 0.0 mg/l A l , 0.11 mg/l M n , 3 mg/l HCOg - , and 0.163% organic matter. The pH and conductivity were 5.6 and 8.0jjmho/cm (25%C) respectively. 200 g soil samples were packed into a (9.5 cm inner diameter x 7.6 cm length) cast acrylic tube fixed on a 10.1 cm diameter alundum tension lysimeter plate to a depth of 4 cm and an average bulk density of 0.605 gm/crn . 16 soil columns were prepared. The soil columns were leached with 200 ml throughfall water per column and a tension of about 0.1 atmospheres was applied to bring them approximately to field capacity. Each was covered with a styrofoam sheet. Eight of the columns were 62 incubated in a 4°C cold storage room and the other half in the laboratory at 22°C. Prior to fertilization, designated as day 0, each column was leached again with 200 ml throughfall water (50 ml at a time) and a suction of 0.1 atm was applied for leachate extraction. Four columns incubated at each of the two temperatures were fertilized with a solution of reagent grade urea (equivalent to 448 kg/ha urea-N) and the other 8 samples were treated as controls. The same sampling method as above was used after fertilization. After 55 days of sampling, all the lysimeter soil-columns were incubated at 22°C. This experiment was repeated with fertilizer grade pelleted-urea. Sampling was done for 20 days. Results confirmed those obtained with analytical grade urea, hence they are not reported in this thesis.. 3.4.1 Leachate Analyses Immediately after leachate collection, bicarbonate ("total alkalinity") concen-tration was determined by acid titration using a pH meter to detect the endpoint pH of 4.5 (Brown et a l . 1970). The pH of the solution was taken at the beginning of the alkalinity determination. Specific conductivity was then taken as described in Section 3 .1 .6 . Sodium, potassium, calcium, magnesium, iron, manganese, and aluminium were analysed with atomic absorption spectrophotometer. With the exception of A l , which was determined with a nitrous oxide-acetylene flame, the rest were assayed with an air acetylene flame. The other constituents of the leachates measured were: urea by the method described in Black (1965), organic matter by the Walkley Black method (Black, 1965), N O 3 - N by chromorropic method (Kowalenko and Lowe, 1973), and N H 4 - N by the phenol hypochlorite method (Hinds, 1974), which uses the Berthelot reaction. 3 . 4 . 2 Soi I Analyses A soil column from the control and analytical-grade urea treatments (at both 4° and 22°C) was destructively sampled on the 3rd, 10th, 20th and 70th day following urea treatment for the determination of pH, exchangeable cations and CEC. "Exchange-able" N a , C a , M g , Fe, A l , Mn and where applicable NH4 or K, were extracted with (i) IN KCI solution, (ii) IN N H 4 O A c at pH 3 .0 and (iii) IN Nb^OAc at pH 7 (Jackson, 1958; Black, 1965). Cation exchange capacity (CEC) was by 1.0 N KCI method. The pH was taken immediately after sampling on the moist samples (1:2 soihb^O and 1:2 soil: O.IM CaCI ). 3 .4 .3 Determination of the organically bound A l , Fe, Ca and Mg in the urea fertilized leachates Leachates from the urea-fertilized soil columns maintained at the laboratory temperature of 22°C were used for this study. 30 ml of each of the leachate samples were treated with 2.0 g Rexyn 101 (H) to remove free cations. Each treatment was filtered with Whatman # 4 2 filter paper after 4-hour equilibration. The solutions were further analysed for A l , Fe, Ca and Mg by atomic absorption spectrophotometry to provide the amounts of elements present as "organo-mineral complexes". From the solution concentrations determined before and after resin treatment, the percentages of the organically bound ions were calculated. As some organic anions with d i - or poly-valent cations may have been adsorbed on the column, the estimated percent-ages of organically bound cations might be low. 4.0 RESULTS A N D DISCUSSION 4.1 LEACHATE VOLUME Results of both the urea-treated and the control plots (Appendices D.I.I, to D.8.2.)* indicated that the ionic concentrations of the leachate were not related to the volume of soil leachates collected. Remezov (1958) and also Raney (I960) similarly observed no direct relationship between the drainage volume and the total amount of Ca or bases lost in leaching. In the present study, the leachate ion concentrations seemed .rather to correlate with the temperature conditions. Higher concentrations were measured in both surface and deep plate leachates in the warmer than in the colder months no matter what the volume of the leachate was. This is expected since biological activities and other reactions in the soil are slowed down in winter months. The ionic concentrations in the fertilized plots were mostly related to urea reactions. Poor drainage conditions occurred in Site II. For most of the winter and early spring, the water table came very close to the surface. Occasionally, the pits were partly filled with drainage water. This situation could create reducing conditions in the deeper soil horizons. The closeness of the water table to the position of the deep plates was also observed in Site I. However, because of the extremely coarse-textured nature of the soil of this site, drainage was fast and no water was observed in the pits. Because of the water table problem, volume measurements were not taken for the deep solutions of Sites I and II. Within the limitations of the equipment (Cole's fixed-tension lysimeter) used to obtain soil solutions in this study, analyses and discussions are based on the concentra-tions of the leachates. * These Appendices are regarded together as Appendix D. 4.2 SOIL REACTION (pH) The pH of the soil leachates collected through the shallow plates of all the urea-applied field plots followed similar trends during the study period. The immediate observed reaction was an increase in the solution pH over the control or the prefertiliza-tion level . This was followed by a decrease such that pH declined below the initial level. The pH seemed to be rising back to the original value when the study was . terminated ( Figures 3A, 4A, 5A, 6A, 7, 8 , 9, 10). The maximum pH increases were observed for the leachates sampled during the first 14 days following application. The lowest pH values were measured approximately 6 months after fertilization even though the drop below the initial values occurred earlier. Site II was the first to indicate a pH drop below the prefertilization level (February 6) and the last was Site IV (April 10). Table 6 shows the maximum pH changes over and below the prefertilization levels. The pH of the deep-plate solutions did not show significant changes after urea application from the prefertilization levels until later in the following March (Figures 3B, 4B, 5B, 6B). In the deep plates, there appeared to be no differences in the pH trends between the control and the fertilized plot leachates except those of Site I, where the fertilized plot indicated some minor decreases below the control during the warmer season. In general, the pH of all the leachates (shallow and deep) of the fertilized and unfertilized plots was higher during the winter than in the warmer periods. Similarly, the pH of the soil was increased immediately after fertilization and then dropped with time. (See Table 7 which compares the effects of urea and (NH^^SO^ applications on soil pH). The long term effect of pH on the soils of the four sites is presented in Table 8. 66 S I T E 1 SURFACE P L R T E - B ' CON FR3L . . . . © F E R T I L I Z E D . . . A 243.0 Shallow soil solution data Site I S I T E 1 D E E P P L R T E ' f i -CONTROL . . . .© FERTILIZED. —I 1 1 1 1 63.0 93.0 121.0 155.0 106.0 DAYS FOLLOWING UREA FERTILIZATION. Figure 3 B : Soil leachate pH Changes: Deep soil solution data Site I SITE 2 SURFACE PLflTE 'A ' ' CONTROL . . O FERTILIZED. . .A 6? 0 93.0 l?4.0 155.0 IB5.0 DATS FOLLOWING UREA FERTILIZATION. Figure 4A: Soil Leachate pH Changes: Shallow soil solution data Site SITE ; Z D E E P P L R T E ' A • CONTROL F E R T I L I Z E D . . . & 6? 0 93.0 124.0 155.0 IBS.O DATS FOLLOWING UREA FERTILIZATION. 217.0 Figure 4B: Soil Leachate pH Changes: Deep soil solution data Site II Figure 5A: Soil Leachate pH Changes: Shallow soil solution data Site III S H E 3 DEEP PLATE *fl' CONTROL . . . J © FERTILIZED...j& 62.0 93,0 124.0 DAYS FOLLOWING L'RER FE 155,0 1E6.0 .RT1LIZRTION . Figure 5B: Soil Leachate pH Changes: Deep soil solution data Site III 69 S I T E A S U R F A C E P L A T E 'A ' CONTROL . . . e F E R T I L I Z E D ^ .0 0.0 31.0 62.0 93.0 IJ4.0 155.0 106.0 DAYS FOLLOWING UREA FERTILIZATION. Figure 6A: Soil Leachate pH Changes: Shallow soil solution data Site IV I T E 4 O E E P P L A T E ' A • CONTROL . . . .9 F E R T I L I Z E D . . , 02 0 93.0 IP4.0 155.0 185.0 DATS FOLLOWING UREA FERTILIZATION. Figure 6B: Soil Leachate pH Changes: Deep soil solution data Site IV 70 Table 6: pH Changes Following Urea-Fertilization (Surface Soil Solutions) pH Valu es * Ferti lized Plots Prefertiliza-tion Maximum Increase Minimum Decrease IA 6.00 7.00 1.00 4.10 1.90 IB 5.60 6.40 0.80 4.05 1.55 IIA 5.40 6.50 1 -10 3.65 1.75 IIB 5.20 6.40 1.20 3.30 1.90 IIIA 5.20 7.00 1.80 4.00 1.20 NIB 5.20 7.40 2.20 4.10 1 -10 IV 4.90 7.30 2.40 3.85 1.05 IV 4.10 5.20 1 -10 3.60 0.50 * Measurements to nearest 0.05 pH unit 71 Table 7: Effects of Urea and Ammonium Sulphate on Soil pH (Field Experiment ^2) Depth Days after Control Urea Ammonium sulphate (cm) fertilization *pH (|/2 soil / H 2 0 ) 0-7.62 0 4.83 4.94 4.83 10 4.75 7.00 4.83 15 4.63 6.11 4.80 345 4.40 4.50 4.09 7.62-15.24 0 4.85 5.09 5.03 10 4.83 5.70 4.68 15 4.63 5.11 4.48 345 4.43 4.54 4.13 * Average of 4 replicate plots Table 8: Soil pH*of lysimeter plots, 540 days following urea application (Field experiment ^2) Site Control Fertilized pH, 1/2 soil / H 2 Q (1/2 soil/ 0.01 M CaCI2)** 1 5.15 (4.48) 5.15 (4.38) II 4.90 (4.15) 4.68 (3.85) III 4.60 (3.78) 4.80 (3.90) IV 4.28 (3.45) 4.10 (3.25) * Averages of data from four replicate samples for each plot * Values in brackets ( ) are values for 1/2 soil/ 0.0IM C a C L readings. 73 The hydrogen Ion concentration of both leachate and soil samples was also found In the laboratory to decrease on urea application (Table 9 and Appendix B) and then increased with time. Temperature treatments indicated that the increase in soil solution pH was higher at a low temperature (4°C) than at a high temperature (22°C) (Table 9). The effect of urea application on the increases of the pH of the soil is in accord with the observations of Knowles (1964), Roberge and Knowles (1966), Beaton et al.(1969), Crane et a l . (1971) and Crane (1972). The pH rise occurred as a result of hydrolysis of urea to ammonium carbonate in the soi l . The (NH^^COg in turn hydrolyses Into NH4OH and H2C0 3 (aq) . However since NH4OH is more ionized in water (Kb= 1.73 xlO"^) than H 2 C 0 3 or solution of C0 2(Ka-= 4.45 x I0~7), m 0 r e O H " Ions than H + ( H 3 0 + ) ions are produced making the soil solution less acid. In soils where fewer organic acids are present to neutralize the action of O H - ions, or where fewer buffering substances occur, high pH increases would be expected. The above may actually be a secondary reaction imparted by urea on soil solutions. It seems that the actual initial reaction is not an immediate increase in solution pH but rather a decrease (Table 9) until more OH ions are produced to neutralize the effect of H + Ions. It Is believed that some of the NH4+ ions initially displace the H + and A l + + + ions from the exchange complex into solution. The A l 1 ' ' ions in turn undergo hydrolysis to produce more H + ions (Wiklander, 1964). As a result, solution pH may decrease. This is clearly seen at high temperature where, due to rapid exchange reactions, greater quantities of A l + + + a n c j H + ions are expected to be displaced into solution by the N H 4 + ions. The pH drop which occurred later on in the study was due to the formation of Table 9: Effecf of Urea Treatment on Soil pH (Laboratory Experiment ^2A) Treatment Days after pH values (4°C incubated samples) pH values (22°C inct ibated samples) fertilization 1/2 soil/ 1/2 soi 1/ Lysimeter 1/2 soil/ 1/2 so! 1/ Lysimeter H 2 0 0.IM soi 1 H 2 0 0.IM soi 1 CaCI 2 leachate CaCI 2 leachate C ontrol 3 4.9 3.9 5.6 5.0 4.0 5.4 10 5.0 4.0 5.0 5.0 4.1 5.5 20 5.0 4.0 5.4 4.8 4.0 5.1 *70 4.6 4.0 5.9 4.8 4.1 5.9 Urea ferti lized 3 6.6 5.6 5.2 7.2 5.3 5.4 10 7.2 5.6 6 .5 6.9 5.6 5.0 20 - 6.8 5.4 6.6 6.8 5.6 5.7 *70 6.1 4.8 6 .2 5.9 4.9 6.0 * A l l the Lysimeter soil co lumns were incubated at 22 °C after 55 days following urea fertilization. 75 nitric acid during nitrification. Statistical analyses of the shallow-plate leachate pH and N O 3 - N indicated a close correlation between these two parameters (Appendix E). Though soil pH changes are influenced by other reactions such as the buffering capacity of the soil (Buckman and Brady, 1969) and leaching, the extent of the pH increases and decreases reported in Table 6 may partly be explained by the differences in the rates of ureolysis and nitrification of the soils of these sites. Thus Site I with low organic matter is expected to have low rate of ureolysis and hence small increases in pH. ^Conversely, Site II, which apparently has higher buffering capacity may be said to have a much higher nitrification rate because of the larger decreases in solution pH. The long term effect of urea application on soil pH was not as drastic as that of ( N H 4 ) 2 S 0 4 which indicates that urea is not a good acid former, except where the nitrification ability of the soil is high. Analysis of variance showed significant differences among the means of the pH measured for samples taken 345 days following application on the control, ( N H 4 ) 2 S 0 4 - applied, and (NH 2 ) 2 CO - applied plots. Pierre (1928) has similarly reported larger soil pH decreases with ( N H 4 ) 2 S 0 4 than with ( N H 2 ) 2 ^ 0 . 4 . 3 CONDUCTIVITY OF SOIL LEACHATE Urea application increased the specific conductivities of the surface (shallow) leachates (Figures 7, 8 , 9, 10). A l l the shallow'plate leachates (except those of a plate on Site I) maintained conductivity levels higher than the pretreatment levels during the study period., The conductivity trend showed at least two peaks. The first occurred immediately following fertilization (mid-November) and the second after February. The second peak for Site IV was delayed until July. Conductivities were DAYS RFTER UREfl FERTILIZATION Figure 7: Shallow lysimeter data for pH, conductivity and nitrate, following fertil ization. Site 1(A) Figure 8: Shallow lysimeter data for pH, conductivity and nitrate, fol lowing ferti l ization. Site 11(B) 77 highest at Site II, followed by Site III, Site IV and Site I. The deep plate solutions of Site I showed significant steady increases from the end of February to the end of the study (mid-July). An increasing trend was also shown by one of the plates of Site III. There were minor increases at Site IV and practically none at Site II. The specific conductivities for the control leachates were lower during the cold season than in the warm months. Higher conductivities were also measured for the urea-treated soil columns in the Laboratory (Appendices B, C.I and C.2) . In the 56-day study (Laboratory Experiment ^1, Appendix B), the average leachate conductivities (in/u.mho/cm at 25°C) for the fertilized soil columns followed the order: Site II (400), Site I (298), Site III (217) and Site IV (100). The specific conductance (which is a measure of total ions) was related to nitrogen transformations (see data summary in Appendix D and correlation coefficients for N O g - N and conductivity in Appendix E) . The initial conductivity peaks following fertilization were contributed mainly by the NH4+ ions resulting from ureolysis and partly by the ions replaced into solution. The second main peaks were related to the nitric acid formation (H + and NO3 ions) (Figures 7, 8 , 9, 10) and the subsequent movement of cations, especially Ca and Mg. In the deep-plate solutions, specific conductivities correlated well with the NOg~N and Ca or Mg leaching in all the sites except at Site II where practically no increase in nutrient losses occurred. Based on the laboratory results, (Laboratory Experiment ^1), one might have predicted different results for the deep plates in Field Experiment ^1. With the large nitric acid formation in the shallow soil solutions at Site II, greater quantities 79 of ions would be expected in the deep leachates at Site II than Sites III and IV. One can speculate about possible reasons for the difference between these expectations and observations. The absence of considerable deep leaching of ions at Site II may have been due to the water table fluctuations. The small ionic-concentration increases for the shallow plate in Site I were possibly caused by initial deep leaching of the unhydro-lysed urea or by dilution (since large volumes of leaching water were measured through this plate). The results for Site IV (laboratory and field) may be due to the higher immo-bilization and lower nitrification, and the greater ability of the surface soil of this site to adsorb ions (high CEC and thick organic layer). 4 .4 NITROGEN CONSTITUENTS IN SOIL LEACHATES 4 . 4 . 1 . Organic Nitrogen (including Urea-nitrogen) Significant amounts of organic - N were found in all the shallow plate leachates of the fertilized plots just after urea fertilization. Throughout the study the organic nitrogen concentrations of the treated plots were higher than the control plots (Appendix D). However, only the fertilized Site I contained large quantities of organic-nitrogen in deep plate solutions. During the first three weeks following fertilization, up to 30.10 mg/l were detected in the deep soil solutions in spite of the large amount of leachate volumes collected. In a laboratory soil column study (Laboratory Experiment ^2), urea-N (of an amount greater than 50 mg/l) was found, 20 days after urea treatment, in the leachates of the soil column incubated at 4°C. No detectable quantities of urea-N were found for the columns stored at 22°C (Laboratory Experiment *2, Appendices C.I and C.2).The laboratory results indicate that urea hydrolysis is slowed down and may possibly take more 80 than three weeks to complete at low temperature. Crane (1972) reported urea hydrolysis to be completed in about 20 days. At higher temperatures (e.g. 22°C), ureolysis may be completed within 3 days. It is very likely that the significant quantities of organic-N which were detected in all the shallow plate solutions for at least the first 3 weeks following field urea application were mostly in urea-N form if it is accepted that ureolysis would take more than 3 weeks to complete at the time when the urea was applied. This does not imply that all the organic-N was in the form of u rea -N . It is expected that some of the organic - N was liberated through the dispersion caused by the urea hydrolysis or the "priming action" of the urea. It may also be said that the organic-N detected in the deep soi I-solution from Site I was mostly urea. One cannot attribute all this organic-N to organic matter dispersion, since the amounts measured in these solutions were too large to be released from such a nitrogen-deficient soil . The characteristics of this site (low CEC, coarse textured nature, lack of organic layer), coupled with the ample rain which fell soon after the urea application, were factors which could affect deep leaching of the molecular urea. Not only would urea absorption be limited in this soi l , but urease would probably not be present in large amounts. Also, rainfall occurring immediately after urea fert i l i -zation was found by Crane (1972) to be an important factor influencing nitrogen leaching losses. The absence of organic -N, or more specifically urea-N in the deeper zones of the soils of the other three sites may indicate fast ureolytic rates or a possible urea absorption in the soils of these sites. These results may support the proposition that organic 81 matter favours urea hydrolysis (and/or absorption). The implication of the results of deep leaching of urea-N in these soils is that urea fertilization in the fall on coarse-textured soils (low in organic matter) may lead to nitrogen leaching into the deeper soil horizons. 4 . 4 . 2 . Ammonium Nitrogen (NH4 -N) Ammonium-nitrogen concentrations of the shallow-plate solutions of the experiment plots of Sites I, II and III peaked following urea application, but decreased to very small quantities or dropped below the detection limit (0 .05 mg/l) before termina-tion of the study (Appendix D, and Figure II). Site IV solutions however contained measurable amounts of N H ^ - N throughout the study period. With the exception of the deep-plate leachates of Site I in which 0.75 mg/l and 1.60 mg/l were measured in the first and second week respectively, following fertilization, no detectable amounts (or extremely small quantities) of N H 4 - N were determined in the deep plates. On ihe control plots, no measurable amount of N H ^ - N was defected in either the shallow or deep plate leachates. The laboratory incubation study indicated loss of N H 4 - N by leaching at both low and high temperatures. It seems however that leaching of N H ^ - N is larger at a low than at a high temperature (Appendices C.I and C .2) . Table 10 shows re-sults that N H 4 - N leaching was largest at Site I followed by Sites II, III and IV. In several studies of acid forest soils, N H 4 - N apparently was the predominant form of inorganic nitrogen in the soil solution following urea application (Cole and Gessel, 1965; Roberge and Knowles, 1966; Beatonj^t a l . , 1969; Overrein, 1968). 82 The laboratory and field experiments of this study show that where nitrification is slow N H 4 - N is dominant, but where nitrification is abundant, N O 3 - N becomes the dominant nitrogen component in solution. The absence of N H 4 - N in the deep plates of Site II, III and IV agrees with the generalization that N H ^ - N is relatively immobile unless the soil has a low CEC, is coarse textured, or has "overloaded" exchange sites (Thomas, 1969). The detection of some N H 4 - N in deep leachates of the fertilized Site I is due to the coarse-textured nature of the soil of this site. The differences in amounts of N H ^ - N measured.in the Laboratory Study 1^ for the samples from the four sites may similarly be explained by soil properties (e.g. CEC, texture, amount of organic matter, and organic layer thickness). Results also suggest that higher temperatures decrease the amount of N leached as N H ^ , The reason underlying this may be the influence of temperature on urea hydrolysis and cation exchange. Beaton_et al_. (1969) reported a higher N H ^ - N leachate concentration at ll°C than at 5.5°C. However, the leachate N H 4 - N content at 22°C was slightly lower than that at 5.5°C. This may be rationalized as follows: At very low temperatures (e.g. 5.5°C) hydrolysis of urea into NH4 ; o n s w ; || be expected to be slower than at l l°C. However, since exchange reactions are accelerated with high temperature (Kelley, 1948), the efficiency of an exchange column wil l be higher at higher temperatures. The observed results in this study would be expected if the effect of temperature on exchange reactions, overrides that on ureolysis. Doubtless the former effect does override in some temperature ranges, as the enzyme's activity must decline above its optimum temperature. 83 Figure Ii.: Shallow Lysimeter Data for Ammonium-nitrogen and Nitrate-nitrogen following Urea Fertilization. 84 Table 10: Comparison of some soil Constituents of Lysimeter Soil-columns (samples from Sites I, II, III and IV) (Laboratory Experiment # l ) Treatment Determinations Site 1 samples Site II samples Site III samples Site IV samples Control pH 4.82 4.94 4.73 3.80 K(mg/I) 0.87 3.88 1.18 3.96 Ca " 0.89 1.90 1.53 0.99 N H 4 - N " 0.16 0.15 0.14 0.44 N O j - N " 1.24 3.91 0.92 * 0 . 0 5 Urea- pH 5.71 4.51 5.03 3.93 Treatment K(mg/I) 2.18 9.31 2.53 4.24 Ca " 2.71 14.66 4.08 1.95 N H 4 - N " 26.56 19.54 11.49 6.37 N O 3 - N " 17.23 36.91 6.27 . <0.05 Values are averages of data sampled after urea treatment (See Appendix B) 85 4 . 4 . 3 Nitrate-Nitrogen (NOg-N) At least small quantities of N O g - N were detected in the shallow lysimeter solutions from the fertilized plots immediately following fertilization. Leachates from Site II con-tained the highest concentrations of N O g - N . Nitrate formations intensified on this site and then dropped. A similar trend was found at Sites I and III, though the concentrations were lower than at Site II. Nitrification was somewhat delayed at Site IV. The plate (IV B) which was installed 10 cm below the organic horizon showed very little nitrification until about the end of the study. The other plate (IVA) however, behaved like those of Sites I and III. A maximum of 16.57 mg/l was measured in the solutions from plate IV A , 177 days following fertilization, and even at the termination of the study, the solution contained 11.20 mg/l. For the deep-plate solutions, the concentrations of N O g - N were highest in Site I. Concentrations at this site increased steadily following fertilization until the end of the study; 11.00 mg/l and 7.5 mg/l were determined on the last sampling for the two replicates at this site. Deep leaching of N O g - N occurred also on the other sites. In Site III, peak concentrations of 2.80 and 5.60 mg/l were measured in the two plates. The highest value determined in Site II and IV were 2.22 and 2.12 mg/l respectively. The N O g - N concentrations of the field solutions from the control plots (shallow and deep) remained below the detection limits. The laboratory lysimeter soil column studies with the almost-intact samples (Laboratory Experiment ^1) showed a behaviour generally similar to that found in the field (Appendices D.I.I to D.8.2). It was found that nitrification was very rapid at Site II (even in the control samples). Nitrification occurred also in Sites I and III samples even though that in Site III was delayed. But practically no nitrate was present in both control and fertilized soil leachates of Site IV. The nitrification capacities of sites followed 86 this order: Site II > S i t e I > Site III > Site IV (Appendix B). No appreciable amounts of N O g - N were determined in the leachates of laboratory study ^2 (with the Ap soil samples from Site III) at either 4°C or 22°C (Appendices C.I and C.2) . Contrary to some observations from other studies conducted with coniferous forest soils (Roberge &. Knowles, 1966; Cole and 065361,1968; Beaton_et al_. 1969; Crane, 1972), some nitrate was produced following urea application in all the forest soils studied (except the disturbed Ap samples). The results of this study agree with observations of Heilman (1974), t^hat nitrification occurs in some coniferous forest soils in this region. The results also agree that nitrification occurs in the presence of alder trees, as reported by Bollen and Lu (1968). The high nitrification observed in the mixed Douglas fir - alder site is due to the fact that nitrifying organisms are often associated with the root zone of alder trees, which provide ammonium used as an energy source by Nitrosomonas spp and similar nitrifiers. From the results also, it could be said that nitrification is slow at low tempera-tures. With the exception of Site II, nitrate formation was slow in the field until the end of February. The limited amounts of nitrate detected in the leachates immediately after urea treatment may partly have resulted from the urea pellets themselves. Analysis of I gm of urea pellets dissolved in I litre (8 samples) gave average values of 444.10 mg/l organic -N, 14.13 mg/l N H ^ - N and 0.03 mg/l N O 3 - N . Small quantities of N O 3 - N have been measured in streams immediately following urea application (Malueg et a l . , 1972; Tiedemann, 1973). Malueg_et al_. (1972), concluded that the peak content of N O g - N was caused by direct application of urea which contained 19.33 mg/kg N O 3 - N . Calculations made by Tiedemann (1973) showed however that N O ^ - N in urea cannot account for all the N O ~ - N measured in the streams and suggested a need for further 87 study to elaborate the pathways and mechanisms responsible for the rapid N O g - N increase. Tiedemann (1973) also proposed that the immediate N O g - N increase may have resulted from exchange of HCOg and CO3 ions for NO^ ion at anion exchange sites. Consider-ation should also be given to the fact that AEC could be greatly reduced by increasing pH. The fact that different N O g - N concentrations were measured, at low fall temper-atures in the surface soil leachates in the present study at the four sites (Site I: 0.14 and 0.22 mg/l; Site II: 0.27 and 1.45 mg/l; Site III: 0.09 and 0.10 mg/l; Site IV: 0.08 and 0.07 mg/l) with in eight days following urea application supports Tiedemann (1973) that N O 3 - N content of the fertilizer may not be solely responsible for the initial N O 3 - N determined in streams (or soil leachates). These different N O ^ - N concentrations presumably represent the differences in the nitrifying capacity of the soils, but it is not clear to what extent they reflect nitrification of native soil N versus fertilizer. The same uncertainty applies to the studies reported Malueg et a l . (1972) and Tiedemann (1973), where urea application resulted in immediate nitrate losses. The results of the study support the hypothesis that humus materials inhibit nitr i f i -cation (Alexander, 1965). In the f ield, nitrification was delayed on the site (Site IV) which had a thicker (mor) layer of organic material. The first laboratory study confirmed the results in the f ie ld . Also studies of the Ap horizon from Site III did not show any appreciable nitrification at either 4°C or 22°C. The results suggest also that urea fertilization can lead to substantial deep leach-ing of N O 3 - N in some coniferous forest soils but less so in soils of mature coniferous stands, possibly because of both limited nitrification and higher immobi lization . The 88 large quantifies of N O ^ - N (11.00 mg/l) measured in the deep solutions of Site I at the end of the study indicate that urea fertilization on a coarse-textured soil lacking much organic matter may lead to heavy nitrogen losses. This may be a potential hazard to water quality since 10 mg/l N O ^ - N is the usual "safe" limit for drinking water. The large quantities of N O g - N in Site 1 deep solutions may have been accentuated by initial flushing of both N H ^ + and unhydrolysed urea into the deep soil layers (see also: Crane, 1972). Significant amounts of N O ^ - N were expected in the bottom layers of Site II on account^of the high nitrate in the shallow soil solutions. The limited amount of nitrate in the deep solutions was possibly caused by the poor drainage conditions of the soil of this site (Section 3.1). This situation might have led to denitrification in the deep layers of the soil or caused dilution of the leachate constituents. 4.4.4. Total Nitrogen In fertilized plots, the total N in shallow plate leachates consisted of organic -N, N H 4 - N and N O g - N . On the other hand, the total N measured in deep-plate samples was practically all in the N O g - N form, except at Site I, where both organic-N and NH^_K| were also detected. The dominance of N O g - N in the deep soil solutions is consistent with the view that N O g - N is the most mobile nitrogen form in the soil (Appendi D.I .1 to D.8.2). However, in a coarse-textured soi l , abundant N H ^ + may also be leached, since the exchange capacity of such a soil is very low unless much organic matter is present. 4 .5 PHOSPHORUS Very small increases (or no increases) in P leaching were inferred to take place after urea fertilization, judging from comparison of fertilized and control plots at all the study sites. Both the control and urea-applied plots have supported conclusively that P is not very mobile in soils. Immobility of P in soils has been reported by many workers (e.g. Remezov, 1958, 1961; Cooper, 1967). 4.6 ORGANIC MATTER Though the organic matter in field solutions was not determined, visual colour observations of the shallow soil leachates indicated that urea hydrolysis resulted in the dispersion of organic matter Into solution. In terms of colour, apparent dispersion of organic matter of the sites followed this order: Site IV > Site III >Site II >Site I. The same order was observed in Laboratory Experiment ^1 for samples obtained from these sites. Unlike the shallow soil solutions, leachates of the deeper plates were very clear, suggesting that the organic matter was filtered in the top soils. Dispersion of organic matter was further confirmed in the Laboratory Experiment ^2 (Appendices C.I and C.2) . Colour observations suggested more organic matter solubilization at a high temperature than at a low temperature. However, chemical analysis indicated a generally higher organic matter content for the leachates at 4°C than those at 22°C. This discrepancy may be due to a) Incomplete oxidation in the analysis of the organic materials dispersed into solution at high temperatures; b) Interferences of the analysis by the freshly pre-cipitated Mn oxides (Black, 1965) (higher polyvalent cations were released in the high-temperature treated samples , c) unhydrolyzed urea in low-temperature leachates, and d) dissolved colourless or weakly coloured organic materials. The solubilization of more organic matter following urea application is in agree-90 menf with the results of other workers (Beaton_et aj_., 1969; Crane e_j_aL, 1971; Crane, 1972; Ogner; 1972). The action is partly due to the increase in pH and possibly to N H ^ + exchange with adsorbed polyvalent cations, leading to a partial collapse of the physical structure of the humus layer (Ogner, 1972). 4 .7 CATION EXCHANGE CAPACITY A N D EXCHANGEABLE CATIONS The exchangeable cations and CEC determinations for field Experiment ^2 samples are presented in Table II and the results of the Laboratory Experiment ^2 conducted with uniform Ap samples from Site III and in Tables 12 and !3 . Though the results of the control and experiment samples taken from the lysimeter plot III indicated more exchangeable bases (Ca, M g , N a , K) and higher CEC for the urea-fertilized plot, it cannot be firmly concluded that the increase resulted from urea application because of the possible inherent variability between the two field plots. The results obtained from the randomized designed field plots (Field Experiment ^2) to compare the effects of urea and ( N H 4 ) 2 S 0 4 applications on the exchangeable ions and CEC of the soil supported the point that variability within this site was large. These results would indicate that destructive soil sampling from different spots may not accurately reveal the actual phenomena occurring in soils because of the differences in field plots. This drawback puts the tension lysimeter ahead of destructive field soil-sampling method, despite the disadvantages of the tension lysimeter (see Section 2.8). The lysimeter can be used to evaluate conditions at the same location in the soil over time and thus eliminates the problem of sample differences. On account of this variability, only the results (Tables 12 and 13) obtained from the laboratory study conducted under controlled conditions wil l be discussed. Table II: Effect of Urea Application on CEC ;and Exchangeable Cations of Site III Lysimeter Plots (I.ON NH^OAc solution extraction; Field Experiment ^2) Treatment Sampling Control Plot Fertilized Plot Depth Date pH** Na K Ca Mg CEC pH Na K Ca Mg CEC (cm) 1/2 soil/ 1/2 soil/ H 2 Q me/100 g H 2 Q me/100 g 0 - 7.62 7.62 - 15. 26:11:73 4.50 0.029 0.081 0.195 0.078 33.00 5.45 0.068 0.230 3.078 0.473 52.50 21:2:74 4.65 0.039 0.076 0.183 0.080 35.50 4.90 0.039 0.132 3.480 0.576 51.00 4:4:74 4.80 0.031 0.080 0.124 0.083 39.57 4.80 0.045 0.131 2.944 0.346 50.06 19:6:74 4.65 0.051 0.133 0.960 0.197 41.94 4.70 0.032 0.132 2.630 0.384 47.92 \ 26:11:73 5.45 0.023 0.045 0.025 0.040 32.00 4.75 0.060 0.082 1.570 0.177 39.00 21:2:74 4.90 0.048 0.067 0.188 0.065 33.50 4.80 0.037 0.083 1.540 0.134 41.50 4: 4:74 4.60 0.016 0.056 0.023 0.036 30.55 4.70 0.054 0.111 2.660 0.194 45.81 19:6:74 4.60 0.091 0.153 1.44 0.222 46.16 4.75 0.032 0.125 2.290 0.260 48.36 ** pH of the samples were determined in June 27, 1974; some change might have occurred in the samples * Determinations were done on duplicate samples. Table 12: Effect of Urea Application on the CEC of the Soil ("Effective CEC" by 1.0 N KCI solution method; Laboratory Experiment #2B) Days after Untreated soil Untreated soi I Treated soi I Treated Soil Incubation samples (4°C) samples (22°C) samples (4°C) samples (22°C) me/100 g 3 15.86 17.65 19.43 20.46 10 14.87 14.07 17.65 19.95 20 13.08 17.18 17.90 22.51 70* 16.11 16.41 18.93 24.04 Average 14.98 16.33 18.48 21.74** A l l lysimeter soil columns incubated at 22°C after 55 days following fertilizer treatment. '* Significant at 1% level. Table 13: Effects of Urea Application on Exchangeable Cations (Laboratory Expe riment #2B) Extraction Solution Exchangeable cations Untreated (4°C) soi Untreated soil (22°C) me /I00 g Treated (4°C) soi Treated soi l (22°C) ,0N KCI I.ON N H 4 O A c (pH 3.0) Na 0.118 0.108 0.112 0.113 N H 4 0.113 0.120 8.085 11.778 Ca 1.120 1.260 1.910 1.910 Mg 0.180 0.193 0.214 0.222 Fe 0.125 0.125 0.072 0.072 Mn 0.060 0.062 0.037 0.035 A l 3.278 3.222 0.333 0.278 Na+Ca+Mg 1.390 1.564 2.236 2.242 Total Cations 4.991 5.093 10.730 14.404 Na 0.068 0.068 0.053 0.055 K 0.197 0.199 0.190 0.191 Ca 0.433 0.373 0.501 0.558 Mg 0.192 0.184 0.207 0.219 Fe 0.548 0.543 0.459 0.435 Mn 0.192 0.184 0.170 0.170 Al 27.928 29.211 21.689 22.367 Na+K+Ca+Mg 0.928 0.824 0.951 1.022 Total cations 29.551 30.719 23.268 23.994 continued Table 13 (continued): Effects of Urea Application on Exchangeable Cations (Laboratory Experiment ^2B) / Extraction Exchangeable Untreated Untreated Treated Treated Solution cations soil (4°C) soil (22°C) soil (4°C) soil (22°C) -me/100 g I.ON N H 4 C A c (PH 7.0) Na 0.052 0.050 0.051 0.073 K 0.194 0.210 0.203 0.192 Ca 1.391 1.478 1.479 1.476 Mg 0.215 0.230 0.237 0.245 Fe 0.029 0.029 0.000 0.000 Mn 0.059 0.071 0.045 0.049 Al 0.695 0.711 0.311 0.233 Na+K+Ca+Mg 1.852 1.922 1.970 1.985 Total cations 2.574 2.757 2.326 2.267 Each figure is an average of 4 sample determinations. 4 . 7 . 1 CEC ( or more accurately "Effective CEC") The CEC determined by I.ON KCI solution saturation and followed by 1.0 N NaCI displacement (Table 12) or CEC_calculated by summation of N a , Ca , M g , A l , Fe, Mn and NH4 (extracted with 1.0 N KCI solution) have shown that urea fertilization may in fact increase the effective CEC of acid soils. The effective CEC increases have been similarly reported by Coleman and Thomas (1967) and Kamprath and Foy (1971) in limed acid soils. In the present study, the increases of the CEC in the urea-treated samples is attributed to the dissociation of the functional groups (namely, the coordinately bound hydroxyl and hydronium groups on the hydrous oxides and clay minerals and the organic hydroxyl and carboxyl groups (Wiklander, 1964) ) as a result of the pH increase (Section 2.4.1). Larger CEC was measured for the soil columns incubated at a high temperature than at a low temperature for either the control or untreated samples. Analysis of variance indicated the effect of the two temperatures to be significant at 1% level. Differences between the fertilized and the control samples were also highly significant at 1% level. Thus, the treated and untreated soils acted independently from 4°C and 22°C. This could be due to more oxidation at high temperature producing more C ^ _ groups. 4 - 7 . 2 . Exchangeable cations ( N g , K, C a , M g , A l , Fe and NH4) The nature of the exchangeable Ca, M g , N a , K and NH4 in soils poses no problem. However, the species of A l , Fe and Mn in certain pH ranges could be controversial. According to Thomas (1961; Black, 1965) all Al extracted with neutral 96 sali" solufion is trivalent whether the pH is 4.36 or 5.22. Baker (1972) reported that salt-extracts (KG) of mineral soils of Port Renfrew and Woss Camp on Vancouver Island, 3+ B.C. consisted mostly of the trivalent hydrated AKH^O)^ and comparatively negligible 2+ divalent hydroxy-aluminium ion (A l (h^O^OH) . Extraction with acidified IN NH^OAc (pH 4.8) is reported to include exchangeable Al plus soluble AKOH)^ and probably somehydroxy-AI monomers or polymers (Thomas, 1961; Black, 1965). Exchange-able Fe occurs in soils as Fe"^ and (Fe(OH)n/3 (Jackson, 1958). The ordinary IN neutral NH^OAc method does not completely extract exchangeable Fe-1"4" because of the oxidation of F e + + to F e + + + (which are largely precipitated and incompletely extracted)(Jackson, 1958; Black, 1965). In the acid pH range (e.g. with IN NH^OAc at pH 3) all the exchangeable F e + + + and some nonexchangeable Fe are kept in solufion (Jackson, 1958). Mn probably occurs at the cation exchange sites and in the soil solution as divalent cations (Black, 1965). Also investigations of signal strength (Electron Spin Resonance) with M n + + concentration as a function of pH and 0 2 , N 2 2+ and C 0 2 suggested that M n ( H 2 0 ) 0 is the major species present between the pH of 2 and 6.3 (Angino et a l . , 1971). These researchers obtained a mixed precipitate of Mn(lll) compound at pH's above 8 . 0 . In the present study, exchangeable A l , Fe and M n , for simplicity, were assumed trivalent, divalent and divalent respectively. Each value of the data for the determinations of the exchangeable cations presented in. Table 13 is the average of the samples taken 3 , 10, 20, and 70 days following treatment. Al l the three extraction solutions showed decreases in exchange-able A l , Fe and Mn for the urea-treated samples. Aluminium was the element which showed the largest decrease on urea application. On the other hand there were 97 increases in the sums of the exchangeable N a , K, Ca and Mg (or N a , Ca and Mg in the case of IN KCI solution extraction). The extraction with solutions of IN KCI and IN_ NH^OAc at pH 3 indicated fairly large increases in exchangeable Ca and M g . The totals of the exchangeable cations (excluding NH^) were found to be less in the treated than in the control samples (because of the displacement of large quantities of A l ) . It was found by I.ON KCI extraction method that large amounts of N H ^ + ions were adsorbed ~ by the soil particles.This adsorption was greater at 22°C than at 4°C, which agrees with some workers (Kelley, 1948) that exchange reactions are increased by raising the temperature. The l .0N_ KCI showed also that Al occupies most of the active sites of the exchange complex. According to Coleman and Thomas (1967), exchangeable H + ions are negligible in soils though appreciable amounts are present in soil solution as a result of Al hydrolysis. The increase in the exchangeable Ca and Mg of the urea-applied soil samples confirms the pH rises (see Section 2.4). The decreases of the exchangeable A l , Fe and Mn may be the results of the displacement or dissociation of some of these ions by NH^* ions produced through ureolysis. The effect of the pH increase may also render these polyvalent cations insoluble and hence could have contributed to their smaller amounts determined for the urea-fertilized soils. Conclusions from the effective CEC and exchangeable cation determinations are (I) that the effective CEC is increased on urea application, (2) that a large proportion of the very strongly adsorbed or difficultly displaced Al is.* desorbed and possibly precipitated. These phenomena affect retention of fertilizer and native nutrient cations. 98 4 . 8 LEACHING A N D BEHAVIOUR OF EXCHANGEABLE CATIONS 4.8 .1 Leaching of Alkali and Alkaline earth Metals The impacts of urea fertilization on the alkali and alkaline earth cations in the surface soil solution were similar for all the sites (AppendicesD. I.I to D.4.2) . For the first weeks following urea application in the f ie ld, K concentrations of the leachates generally increased over, or maintained the pre-fertilization levels until about the sixth week when concentrations began to drop at Sites I, III and IV. There was practically no decrease in K concentrations of solutions from Site II. Sodium concentra-tions did not increase after fertilization, but dropped gradually. Unlike Na and K, Ca and Mg concentrations decreased drastically to almost zero in some cases (e.g. Sites I and II). These decreases in the concentrations of bases were reversed with the onset of nitrification. The K and Na concentrations were little affected but those of Mg and especially Ca increased greatly. The site which showed the highest Ca in the surface soil solution was II, where a concentration of 17.40 mg/l was determined about mid-February even though only 0.08 mg/l was measured in the leachate of the same plate, three weeks following fertilization. Leaching of these bases (Na, K, C a , Mg) into deep soil layers did not change immediately after fertilization. However, when nitrate leaching started some increases In the amounts of cations were found in the deep plate leachates except in Site II. Sites I and III experienced the most deep-leaching of cations, especially of Ca and M g . Large amounts of K and Na were also leached at Site I. At the termination of the study, deep leaching of bases was still increasing from this site. Leaching of bases from the control plots (surface and deep plates) was 99 generally smaller during the winter months than in the warmer periods. Similarly, solution decreases of cations (especially of Ca) were found in the laboratory study ^2 for samples treated at 4°C. The laboratory experiments at both 4°C and 22°C revealed initial increases of cations, especially K and M g , before the decreases began (Appendices C.I and C.2) . At high temperature (22°C), leaching of cations other than Ca and Na was not much reduced (Appendices C.I and C .2) , and the decrease of solution concentration of these elements was delayed for some days. In Laboratory Experiment ^1, decreases of Ca and Mg were evident (prior to the formation of large quantities of nitrate) only in the leachates of samples obtained from Site I (Appendix B). Solutions of Site IV soils released the largest-quantities of C a , M g , K, and Na immediately after urea application and before decreases occurred (Appendix B). There was practically no nitrification in the soils from Site IV at the experimental temperature of 22°C. A similar release (exceeding the control or preferti I ization level) of K into solution following urea treatment has been reported by Cole and Gessel (1965), Beaton et_aL (1961) and Crane ej_al_. (1971). The results may be explained by means of ionic exchange. With production of large quantities of NH^"1" ions in soil solution following ureolysis, the N H ^ + ions displace K + ions and other ions from the exchange complex. However, since NH^"1" and K + ions have the same valency and similar size (and hence similar ionic potential and hydration status), the exchange between these two ions may occur more easily than the case of NH^"1" ions with other ions (e.g. N a , Ca and Mg). Results in this study indicate rapid exchange between NH^"1" and K + j o n s e v e n a t | o w temperatures (see Appendices C and D). As observed for the fertilized samples(Appendices C.I 100 & C.2) larger quantities of native cations were released at 22°C than at 4°C. Beaton et aL (1969) have also found Ca concentrations to decrease following urea application at low temperature (5.5°C). Increase at high temperature was small. Their work was short-term however, and did not follow the trend of the present experimental behaviour. No explanation was provided for the decrease. Cole and Gessel (1965) also reported that the total release of Ca (by urea action) from the forest floor during the first 10 months following treatment was less than half (41%) of that released by ( N H ^ j S O These researchers attributed the differences in leaching to result from the differences in the anion equivalents of urea and (NH^^SO^. This has been partly criticized by Crane (1972) as not completely responsible for this action. Crane considered the mobilities of the anions produced by (Nh^^CO and (NH^^SO^ to be cr i t ical . The decrease of the solufion concentrations of C a , M g , Na and K following urea , application (especially at low temperatures) observed in this study is similar to the effect of lime on acid soils reported by Wiklander (I960), and Wiklander and Lax (1967 ). In these studies M g , K, and Na concentrations in solution decreased as the pH was increased by liming (CaCOg addition). The explanations offered for the action of lime (Wiklander, I960; Wiklander and Lax, 1967) are applicable to the effect of urea on soils in this study. With the hydrolysis of urea and the consequent increase in the soil pH, the "t ~f" j j | produced NH^ ions replace the H and Al ions from the exchange complex of the soil and as a result the competition for the reactive sites is reduced. However by increasing the NH^"1" saturation of the soi l , the base saturation of the soil as a whole increases. Consequently, the bonding strenth of NH^ + would be decreased because 101 the pH increase leads to an increase in the change in molar free energy of hf1 ( i .e . increasing |_|) and a decrease in that of NH/ 1" ( i .e . decreasing ^ F|\|H4), where negative signs are omitted. Analogous conclusions are reached by Wiklander (I960), where lime is added and /\^C a is considered. Wiklander's further argument is developed in two ways: consideration of molar free energies and the Donnan equilibrium. The latter is more straightforward for examination of net changes in nutrient cation retention associated with urea addition. Wiklander (1964) notes that: (NH 4 + ) s /(Mg + +)s • J C o % (K+)s • (Na+)s (NH 4 + )e /(Mg+^e v/fca+^e (K+)e (Na +)e where parentheses denote activity, s denotes ions in the "free" solution, and e denotes exchangeable ions. Thus, when the total NH^ concentration of the soil [_NH4 J j. increases , the increase is reflected in changes in both (NH 4 + )s and ( N H 4 + ) e . Although ( N H 4 + ) S increases, the change in pH may reduce (NH 4 + )s/(NH 4 + )e if the j ^ N H ^ J j . is not too large, partly because of loss of competition from H and Al ,and partly because of increased CEC. The results would be reduction in solution concentrations of the alkali and alkaline-earth metals, especially the latter, and a complementary increase in the adsorbed concentrations of these ions. If the increase in £ N H 4 + J t were very large, saturating the capacity of the exchange sites despite the effects of pH change, a reverse effect would be expected, as the consequence would be an increase in ( N H 4 +) s/(NH 4 + ) e . This may be part of the temperature effect. Other reactions in the soi l , such as organic matter dispersion resulting from ureol-ysis may more or less overshadow this behaviour and lead to higher concentrations of these cations in solution, especially at high temperatures. Thus at high temperatures, soils with high organic matter content may show high Ca and Mg solution concentrations following urea fertilization (compare Sites I and IV, Appendix B). Release of cations through dispersion ma/ explain the observations made at high and low temperatures (Appendices C.I and C.2) . It ma/ be concluded that the observed Ca and Mg con-centration decrease in solution is temperature dependent. At high temperatures, more Ca and Mg in the form of metal-organic complexes may be measured in solution. (Also high temperatures would speed up the rate of nitrification and hence lead to greater nutrient cation losses as discussed below). The increase of solution Ca , M g , Na and K concentrations later on in the study , ma/ be explained in the following way. As the conversion of N H 4 + to nitric acid started, the pH of the soil decreased and the CEC was expected to be decreased in turn. In comparison with Ca , M g , K or N a , the H + ions, produced as a result of nitrification, have greater potential to displace large quantities of bases into solution. The displaced bases are transported in solution with the N O g " i ° n s -4 . 8 . 2 Leaching of A l , Fe and Mn The effect of urea on the release of A l , Fe and Mn info solution is presented in Appendices C.I and C .2 . Leaching from control samples was minor and was not affected by temperature. Cn the other hand, urea-fertilized samples released much larger amounts of Al and Fe. At high temperature, the leaching of these elements (especially of Al) was substantially more than at low temperature. There was no major difference in Mn leaching between the control and urea-treated samples at low temperatures, though there was a difference at high temperatures. The increase of solution Fe and Mn was similarly reported by Crane et al.(l97l) following urea treatment of forest soil samples in the laboratory. It is likely that both exchange reactions (between N H 4 + ions and these ions) and organic reactions were involved in the release of A l , Fe, and Mn info solution. Determinations made of the leachates of the fertilized soil columns incubated at 22°C indicated the organic-bound portions to be Fe= 6 9 . 8 % , Al = 5 4 . 6 % , Ca = 18.4%, Mg - 16.9%. Since greater fractions of Al and^e were complexed organically, their • toxicities to plants and microorganisms may likely be limited. In this study, A l , Fe and Mn concentration data are not available for the period when the pH was decreased following nitrification. However it is expected that concentrations of these elements wil l be high, and might even approach toxic levels, since these elements become more soluble at low pH values. 4 .9 OBSERVED MECHANISMS INFLUENCING LEACHING 4 .9.1 The Carbonate Equilibrium and Nutrient Cation Leaching Though the bicarbonate anion (HCOg ) was measured in large quantifies in the urea-fertilized soil leachates of the Laboratory Experiment ^2 (and was likely to be equally present in the field leachates collected immediately after urea fertilization), cation leaching (e.g. Ca and Mg) was decreased, contrary to the proposition of McColl and Cole (1968) and McColl (1969,1972). The decreasing effect was more pronounced at a low temperature. McCol l and Cole (1968) proposed that bicarbonate formation increased leaching of bases, bicarbonate being a mobile anion which can accompany the cation leaching 104 When is dissolved in the soil solution, bicarbonate production is associated with production of H + ions which, by cation exchange, can release adsorbed bases and make them susceptible to leaching. Of course this mechanism is effective only within the pH range where bicarbonate is formed in large amounts. In this study, urea hydrolysis might result in formation of ammonium and bicarbonate ions. However, whereas C 0 2 + H 2 0 * H + + HCO3-resultsJn lower pH, 2 H 2 G + (NH 2 ) 2 CO + H+ + HCO3- 2 N I V + 2HCO3-results in higher pH. In ion exchange, NH^"1" is not as effective a replacing cation as H + . Moreover, the effects of pH - dependent CEC and Donnan distribution tend to compensate for the mechanism proposed by McCol l and Cole. Since some polyvalent cations (Al , Fe and Mn) were mostly in complex form, it may be said that the HCOg movement was associated mostly with the "free" N H 4 + ions. Analysis of variance indicated a significant relationship between N H ^ + and the H C O 3 -ions in the leachates of the fertilized soils at 5% level. It is concluded here that whenever there are mobile anions and free high potential cations ( A l + + + , H+) to displace bases into solution, leaching of these bases is expected to occur. The activity of H + ions seems to be reduced immediately following urea hydrolysis by the production of NH3. 4 . 9 . 2 pH and Leaching At least for the elements Ca and M g , leaching was influenced by the pfi of the medium. With pH increase, less leaching of these elements occurred. Increased leaching of these bases occurred as the pH decreased below the original levels. Figure 12 indicates a very high curvilinear relationship between the pH and calcium leaching in all the surface solutions of the fertilized plots. The regression equations were more or less the same for all the sites.The curvilinear relationship between pH and Ca-o«vas significant at 1% for the surface and deep plates except the deep plate of Site II. The leaching of calcium in the field was strongly correlated with that of Mg (Figure 14 and Appendix E). This suggests that a common mechanism is responsible to their displacement or adsorption in the soi l . Beaton et a l . (1969) reported a similar displacement for both cations. The mechanisms underlying the pH influence are discussed in Section 2 .4 . Thus the impact of urea on leaching of cations is mediated by the reaction urea imparts on the soi l . Measurements of the soil pH may be a good indicator of leaching of bases (notably Ca and Mg) in the soil following urea fertil ization. 4 . 9 . 3 Nitrate Formation and Leaching of Nutrient Cations The nitrate in solufion should closely relate to the changes in the soil pH since H + ion is a product of nitrification. Figures I5A to I8B show that Ca leaching followed a trend similar to nitrate ion formation. Whenever there was nitrate, leaching of bases (especially Ca and Mg) occurred. The H + ions from nitric and formation displace the cations from the exchange sites and these cations are leached with the N C ^ - anions in the percolating water. This agrees with the anion concept of cation leaching (Section 2.6). 106 SITE !: SHALLOW PLATE A PH:5.3SI4J-1 .2<Wa9rt(LO(S C A ) RKX2=0.S0 - 1 . 2 -0.4 0 4 LOG(CALCIUM) SITE 2: SHALLOW PLATE A -0.4 0 .4 LDGICPLCIUI) Figure 12: Relationship between pM and Calcium Leaching (Shallow plare data) following Urea Fertilization. 107 S H E 1 : D E E P P L A T E A P H = S . 7 1 9 1 3 - 0 . 6 4 2 3 0 5 . K ( L O G oM -0.4 0.4 LCG(CfilCIUM) S I T E 2 : D E E P P L A T E A -o.< o.« L C G ( C R L C J U M ) S I T E 3 : D E E P P L A T E A P H = 6 . G K 5 5 - 1 . 6 4 ! 3 0 K ( L O G C A ) R X X 2 = 0 . 6 7 -0.< 0.4 L C G ( C A L C I U M I S I T E -1: D E E P P L A T E A P H = 5 . S 3 E S 0 - 2 . 1 5 2 6 0 K ( L O G C A ) R K X 2 - 0 . 7 6 • -n.< D.4 i&r.icmciij:ii Figure 13: Relationship between pH and Calc ium U o c h i r vdeep plate data) fol lowing Urea Fert i l i zat ion SITE 4 RXX2 : 0.96479 2.0 1.15 hgure 14: Relationship between Calcium: and Magnesium Leaching from the four Sites following Urea Fertilization. (Fertilized plates 1(A), 11(B), 111(B), IV(A) data) 109 S I T E 1 S U R F A C E P L A T E ' A - [ F E R T I L I Z E D ) C A L C I U M . N 0 3 - N . 93.0 124.0 IS5.0 IBS 0 DAYS FOLLOWING UREA FERTILIZATION. Figure I 5 A : Leaching of Ca and N O g - N following urea fertilization Shallow soil solufion data Site I S I T E 1 D E E P P L A T E ( F E R T I L I Z E D ! 62.0 93.0 124.0 155.0 IDS 0 DAYS FOLLOWING UREA FERTILIZATION. ' Figure I 5 B : Leaching of Ca and N C L - N following urea fertilization: Deep soil solution data Site I no S I T E 2 D E E P P L A T E ' H ' ( F E R T I L I Z E D ) C A L C I U M . N 0 3 - N . 4 62.0 03.0 124.0 155.0 106.0 DAYS FOLLOWING UREA FERTILIZATION. Figure I6B: Leaching of Ca and N O - N following urea fertilization: Deep soil solution data oite II SITE 3 S U R F A C E PLATE -R " (FERTILIZED! CALCIUM » N03-N i 62.0 DAYS FOLLOWING UREA FERTILIZATION. Figure I7A : Leaching of Ca and N O g - N following urea fertilization Shallow soil solution data Site III Figure I7B: Leaching of Ca and N O g - N following urea fertilization: Deep soil solution data Site III S I T E A S U R F A C E P L A T E 'fl ' ( F E R T I L I Z E D ) 62.0 93.0 124.0 155.0 1B6.0 DAYS FOLLOWING UREA FERTILIZATION. Figure 18A: Leaching of Ca and N O 3 - N following urea fertilization Shallow soil solution data Site IV S I T E 4 D E E P P L A T E 'fl * ( F E R T I L I Z E D ) C A L C I U M . N 0 3 - N . 4 0.0 62 0 93.0 124.0 155.0 1B6.0 DAYS FOLLOWING UREA FERTILIZATION. Figure I8B: Leaching of Ca and N O g - N following urea fertilization Deep soil solution data Site IV 113 4.10 CHANGES IN NUTRIENT BALANCE 4 .10.1 Leaching and "Nutrient" Cation Balance Figures I9A and 22B demonstrate that urea fertilization affects the nutrient cation balance of the soil solution. As the illustrations show, the ratios of Ca to the total cations (Ca, M g , N a , K) released into the shallow soil solution of the fertilized plots decreased to a very low level during fall months (or prior to nitrification) and rose above the prefertilization ratio later on in the study. Ca/total cation ratios for the deep solutions of the treated plots also showed relative increases over the control during the warmer months. The figures also indicate that among the four exchangeable bases, Ca is comparatively the most affected cation following fertilization of these soils. It may also be confirmed from these results that Ca was leached in greater quantities in Sites I and III than in Sites II and IV in this study. The change in the balance of C a , M g , Na and K may have important nutrient implications for forest trees (though no information is available for coniferous frees to support this claim) since this change may affect the availability of several nutrients. Howard (1964) and Adams (1965) as referenced by Pearson (1971) showed conclusively that the rate of plant (Gossypium hirsutum L) root growth was related to Ca/total cation balance in displaced soil solutions but not to Ca concentration. Root extension was decreased when the Ca/fotal cation ratio was less than 0 . 2 . If seems that the loss of Ca per se may not have direct effect on plant growth but could indirectly affect soil properties such as pH, percent base saturation, biological activity and nutrient avai l -ability which in turn would affect plant growth. SITE I SURFACE PLATE ' R ' CONTROL . . . . © FERTILIZED 4 Figure I9A: Changes in the Ca/Total Cation Ratios Shallow Soil Solution data Site I Figure I9B: Changes in the Ca/Total Cation Ratios Deep Soil Solution data Site I SITE 2 SURFACE PLATE ' f l ' CONTROL . . . . » F E R T I L I Z E D & ~i r 0.0 31.0 62.0 93.0 124.0 155.0 IBS.O 217.0 ORYS FOLLOWING URER FERT1L1ZRT1CN. Figure 20A: Changes in the Ca/Total Cation Ratios: Shallow soil solution data Site II SITE 2 DEEP PLATE 62.0 93.0 124.0 155.0 166.0 DRYS FOLLOWING URER FERTILIZATION. Figure 20B: Changes in the Ca/Total Cation Ratios: Deep soil solution data Site II SITE 3 SURFACE PLATE - f l -CONTROL FERTILIZED A o I I I 1 1 I I I I 0.0 31.0 62.0 93.0 124.0 155.0 165.0 217.0 243 DAYS FOLLOWING URER FERTILIZRTION. Figure 2IA: Changes in the Ca/Total Cation Ratios: Shallow soil solution data Site III Figure 21B: Changes in the Ca/Total Cation RaHos: Deep soil solution data Site til 3 - | I I 1 ; 1 1 1 1 0 . 0 3 1 . 0 6 3 . 0 9 3 . 0 124.0 155.0 186.0 2 )7 0 DAYS FOLLOWING UREA FERTILIZATION. Figure 22A: Changes in the Ca/Total Cation Ratios: Shallow soil solutions Site IV SITE 4 DEEP PLRTE 'R CONTROL 0 F E R T I L I Z E D . . . ^ Figure 22B: Changes in the Ca/Total Cation Ratios: Deep soil solution data Site IV 118 4 .10.1.1 Cation Balance and Nitrification Inhibitors The decreases in nutrient cations in solution and the changes in nutrient balance (Figures I9A, 20A, 2IA and 22A) following urea application and prior to nitrification raise a question in the use of nitrification inhibitors* in the formulation of ammoniacal fertilizers in practical forestry. As has been reviewed by Parr (1973),plants which are fed with N H 4 - N rather than N O ^ - N often contain lower concentrations of certain inorganic cations such as C a , M g , and K; higher concentrations of S, P and CI adsorbed as anions; and, higher and lower concentrations of amino acids and organic acids, respectively. Also plants receiving their whole N diet as N H ^ - N grow less vigorously than those receiving N O 3 - N . The decrease or lack of soil-solution nutrient cations following urea hydrolysis or NH^ formation (and prior to nitric acid production) substantiates and may explain why plants supplied with N H ^ - N contain lower amounts of Ca , Mg and K. In addition Kirby and Hughes (1970, as reported by Parr, 1973) stated the possible N O g - N effect on plant nutrition to include (?) effect on electron transfer systems (ii) inter-relationship with carbohydrate metabolism (iii) NHg toxicity (iv) ion uptake and competi-tive interactions and (v) effects of pH. * Examples are (I) Dow Chemical Company's N-serve £2- chloro-b- (trichloromefhyl) pyridine] a specific inhibitor of the genus: Nitrosomonas which oxidizes N H 4 + - + N O " (2) AM (2- amino - 4 - chloro - 6 - methyl pyrimidine) manufactured by Toyo Koafsu Industries, Tokyo (3) Thiourea, (4) methionine (5) dicyandiamide. 119 Table 14: Balance of Al on the Exchange Complex following Urea Application (Laboratory Experiment ^2) A l / l Exchangeable cations(%) A l / n Bases + Al(%) 4oc 22°C 4°C 22°C I.ON , KCI solution Control 65.68 63.26 70.22 67.32 Fertilized 3.10 1.93 12.96 11.03 I.ON N H 4 O A c (pH 3.0) Extraction Control 94.51 95.09 96.92 97.26 Fertilized 93.21 93.22 95.80 95.63 I.ON N H 4 O A c ( P H7.0) Extraction Control 27.00 27.00 27.29 25.79 Fertilized 13.37 10.28 13.63 10.50 £ Exchangeable cations = N a + + (K +) + C a + + + M g 4 ^ + AI + 4 + + F e + + + M n + + Z Bases = N a + + (K+) + C a + + + M g + + 4 .10.2 Exchangeable Al Balance The relative decrease in the exchangeable Al ions on the soil exchange complex, as a result of urea application, is seen from the data of Table 14. The extraction with the unbuffered neutral salt (KCI) indicated that most of the exchangeable Al at the active exchange sites was replaced. This may be beneficial to plant growth. How-ever in soils where large amounts of nitric acid are produced (decreasing the soil pH) , this beneflcialaffect would turn out to be an unfavourable one since large quantities of soluble Al wil l be found in the soil solution (see I.ON NH^OAc (pH 3.0) extraction). 4.11 FREE A M M O N I A Although no data on free ammonia were collected in this study, this topic deserves some mention. It is possible, because of high pH and the N H ^ + concentration, that concentration of free NHg may reach toxic levels following urea application. Bennett and Adams (1970, as reported by Pearson, 1971) found cotton root-growth depressed when NHg concentration reached about 0 .2 mM. Because reactions are slow and the physiological activity of plants is reduced in the fa l l , the detrimental effect of NHg might be less where urea is applied in the fall rather than in the warm season. 121 5 . 0 SUMMARY A N D CONCLUSIONS 1. Contrary to reports of some other workers elsewhere in this region some nitrification was observed after urea application, in the soils of all the sites used in this study. Rapid nitrification was found on the site with a mixture of Douglas-fir and red alder trees. The presence of nitrifiers associated with alder trees is the possible cause of this observation. Nitrification was delayed at the site with a well developed, thick forest floor, and no nitrate was produced with samples from this mature forest site in the laboratory studies at 22°C. 2. The effect of urea fertilizer on leaching losses is very complex and cannot be explained simply by cation exchange processes and mass ion effect since other processes such as dispersion of organic matter, microbial activity, immobilization and fixation of certain nutrients in non-exchangeable forms, and the reactions of urea-transformed products occur or intensify in the soil following urea application. 3 . Laboratory study demonstrated increases in the soil CEC (effective) and exchangeable nutrient cations, and decreases in exchangeable A l , Fe, and Mn following urea treatment, due to the soil pH increase. Increases in CEC were larger at 22°C than at 4°C. 4 . There was no evidence of serious losses of N a , K, Ca and Mg immediately following a fall urea fertilization (in the field). On the contrary, Ca and Mg leaching declined somewhat after the fertilizer application. Laboratory leaching studies at 4°C confirmed the decline of Ca and Mg concentrations in leachate solutions (after initial increases). 122 The rise in pH caused by (NH^^COg production by urea hydrolysis, leading to (a) the dispersion of organic colloids, and (b) increases in CEC, as well as the Donnan distribu-tion^ is responsible for the behaviour of the bases. 5. Laboratory studies showed greater concentration increases of A l , Fe and Mn in the leachates of the urea-treated soil columns. The release of these elements was greater at 22°C than at 4°C. Organic matter dispersion was responsible for this action. The released elements appeared organically bound. 6. Increased nutrient cation leaching in the field occurred in the warmer periods and was found to relate to pH decreases associated with increased nitrification (nitric acid production). The decreased pH tesulted in decreased CEC and promoted ion exchange through mass ion effect because of the mobile anion and the strongly adsorbed hydrogen ion. At 22°C in the laboratory, C a , M g , K, and Na losses often increased soon after fertilization, apparently because of increased dispersion init ial ly, and because of subsequent nitric acid production. 7 . Calcium and magnesium leaching seemed to be highly influenced by urea application. Losses of Ca and Mg follow similar trends, though more Ca is leached (partly because the soil contains greater quantities of exchangeable Ca). 8. Water quality is not likely to be adversely affected by fall urea-fertilizer application in so far as the metal nutrient cations are concerned. However, nitrogen leaching itself may be an important consideration. Heavy rains immediately after fertilization may result in flushing of unhydrolysed urea through the soil profile. Over a 246-day sampling period in the f ie ld, the maximum total N concentration measured in soil solution collected at the bottom of the root zone was 11.2 mg/l of which 11.0 mg/l was nitrate-N (which Is excessive in terms of the usual 10-ppm limit for drinking water). This high value was obtained at the site having very limited roof distribution in a soil lacking much organic matter or clay, so that retention of nutrients by trees or soil was limited. For other sites, the highest N concentration in solution was 5.85 mg/l of which 5.6 mg/l was ni t rate-N. The results suggest that ordinary rates of urea fertilizer application are Inappropriate for young plantations established on coarse textured soils which lack either Incorporated organic matter or forest floor development. 9. Some industrial sources have reported fertilizer responses being better in the case of fall rather than spring application. The absence of documentation limits the evaluation of this possibility. However, some considerations might support it: a) Since large quantities of urea fertilizer are often applied In forestry, it may be possible for the free ammonia to reach toxic levels. The slower hydrolysis at low temperature and the physiological condition of trees in the fall might reduce this detrimental effect. b) Massive application of ammoniacal fertilizers might seriously upset the nutrient balance, where excessive amounts of C a , M g , and K.are first displaced by ammonium and then lost by leaching. The laboratory evidence suggests that displacement by ammonium (following urea hydrolysis) would be less at low (fall) temperatures than at high temperatures which might prevail earlier in the growing season. Field results support the evidence that little displacement of major nutrient cations occurs in the fall season. Large quantifies may, however, be released into solution with the formation of nitric acid in the warmer months. 10. 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Wiklander, L. 1964. Cation and anion exchange phenomena. Chemistry of the Soil, In Bear (ed.) Chemistry of the soil ACS Monogr. No . 160. Reinhold Publ. Corpor., N . Y . 163-205. Wiklander, L. and A . Lax. 1967. Adsorption of calcium, magnesium, potassium and sodium as influenced by liming. Anales. de Edafologia y Agrobiologia 26: 371-379. Winogradsky, S . , and H. Winogradsky. 1933. Etudes sur la microbiologie du sol. Nouvelles recherches sur les organismes de la nitrification. Annales de I'institut Pasteur, 50 : 350-432. Wright, J .R. and M . Schnitzer. 1963. Metallo-organic interactions associated with podzolization. Soil Sc i . Soc. Proc. Amer. 27: 171 — 176. Appendix A: (jBC F o r e s t W e a t h e r Da t o M o n t h l y M e a n T e m p e r a t u r e s a n d P r e c i p i t a t i o n M a r c ' s F a r m S t a " ( A l t i t u d e = 183 N o n x rn) Adrni n i f i t r a t i o n S t a t i o n * ( A l t i t u d e = I 4 3 rn) M a x . M i n . M a x . M i n . temf ) . t e r n p . P r e c i p i t a t i o n t e m p . t e m p . P r e c i p i t a t i on ° C ° C (mm) ° C . ° G (mm) I 9 7 3 M a r c h 7 . 69 3 . 2 8 1 0 2 . 87 8 . 15 1 . 9 7 1 6 5 . 86 A p r i I 1 2 . . 5 2 4 . 8 3 4 4 . 9 6 1 2 . 85 6 7 4 3 . 9 4 May ' 16 . 8 9 8 . 76 7 7 . 9 8 1 6 . 1 1 4 . 4 4 - 8 0 . 77 J une I 7 . , 6 7 1 1 . 39 1 0 5 . ,41 1 7 . 37 8 . . 4 4 1 3 8 . 89 J u l y 2 2 . . 3 1 1 3 . 24 4 1 . i 5 21 . , 7 6 1 0 . . 8 2 4 7 . , 2 4 A u g u s t - 19 . . 8 9 1 2 . 50 2 3 . , 3 7 ' 20. 2 2 10. , 2 8 4 2 . . 4 2 S e p t e m b e r I 8 . , 6 7 1 2 . 2 8 6 2 , . 9 9 -- -- --O c t o b e r 9 . 5 6 7 . , 3 3 171 , . 7 0 12 . , 8 3 5 , . 7 2 2 6 3 , . 7 3 M o v e m b e r 3 , . 4 4 2 . 0 0 2 1 1 . . 3 3 4 . . 2 8 0 . 0 0 3 1 7 , . 2 5 D e c e m b e r 4 , . 3 3 3 . 2 8 2 8 4 , . 2 3 5 . . 6 7 2 . 3 3 29 1 . 8 5 1974 J a n u a r y 7 J . 56 1 . , 1 7 . 3 4 5 . 9 5 3 . 0 6 - 2 . 61 4 0 5 . 89 Feb r ua r y 6 . 39 5 . , 1 1 3 3 7 . 8 2 5 . 67 1 . , 2 2 3 0 4 . 80 M a r c h 8 . 6 7 2 . , 9 4 2 9 9 . 7 2 8 . 22 1 , . 7 2 2 5 8 . , 3 2 A p r i 1 1 1 . , 5 2 4 . . 2 4 1 7 7 . 8 0 10. , 4 3 2 . , 6 9 181 . 10 May 14. . 3 3 . 3 8 1 8 8 . 7 8 1 2 . , 5 8 ' 4 , . 4 4 1 9 4 . , 5 6 J u n e 16. , 76 6 . 4 6 7 3 . 1 5 18. . 39 8 . 6 8 8 0 . . 0 1 J u l y 2 0 , . 9 7 1 1 , . 5 6 •1 3 6 . 6 5 18. . 10 9 , . 3 6 . 1 3 3 . . 6 0 * C l o s e t o S i t e s I I a n d IV * * C l o s e t o S i t e s I a n d I I I Appendix A . I General View of Site I Appendix A . 2 General View of Site II 143 Appendix A.2 (continued) A Soil Profile of Site II Appendix A . 3 General View of Site III 144B A p p e n d i x A A . 3 ( c o n t i n u e d ) S o i l P r o f i l e o f S i t e I I I A ppendix A . 4 General View of Site IV Appendix A . 4 (continued) A Soil Profile of Site IV Appendix A . 5 Field Lysimeter System: Vacuum Tank and Cartesian Manostat A p p e n d i x A . 6 F i e l d Lys imeter System: Housing of Shal low P l a t e Carboy C o l l e c t o r s Appendix A . 7 Field Lysimeter System: Housing of Deep Plate Carboy Collectors / Appendix B Analyses of Leachafes from Lysimeter Soil Columns Incubated at 22°C (Laboratory Experiment *l) Site I Samples Site II Samples Days pH Conductivity Control Soil Samples P H Conductivity Urea-treated Soil Samples -um ho/ cm N a K Ca Mg NH^N N O 3 - N >umho/ cm N a K Ca Mg N H 4 - N N O 3 . mg/l mg/l 7 6 .05 24 1.32 0.79 0.58 0.29 <0.05 0.47 6 .05 23 1.57 0.52 0.66 0.32 <0.05 0.29 14 4.43 18 1.16 0.80 0.63 0.32 0.05 1.24 4 .65 20 1.42 0.63 0.41 0.25 0.05 0.57 19 4.90 20 1.14 0.95 0.77 0.29 0.05 0.76 4 .65 33 1.74 0.73 0.72 0.31 0.38 \ 0.33 21 4.40 19 0.99 0.91 0.78 0.27 0.05 0.78 6.50 531 3.02 3.20 0.42 0.20 21.65 0.87 28 4.78 21 0.87 1.01 1.02 0.31 0.33 1.60 6 .55 509 2.22 2.64 0.38 0.21 42.85 2.12 35 4 .55 - 0.66 0.87 0.92 0.26 0.22 1.35 6 .20 - 1.32 1.65 0.22 0.12 28.25 5.10 42 5.25 18 0.55 0.82 0.88 0.25 0.15 1.33 6.10 416 1.53 2.43 1.51 0.35 41.75 33.20 49 5.10 19 0.44 0.77 1.00 0.26 0.14 1.39 5 .45 376 1.26 2.52 4.91 0.76 32.80 43.63 56 4 .75 22 0.38 0.77 0.88 0.27 0.20 1.47 4 .55 479 0.97 2.12 10.82 2.08 18.24 35.35 7 5.85 61 1.51 4.45 1.62 0.87 1.01 3.10 5 .75 41 0.96 2.81 1.29 0.71 0.13 1.40 14 4.63 52 1.15 4.40 1.68 0.93 0.40 6.25 4.48 39 0.90 2.79 1.45 0.71 0.05 . 2.74 19 4.70 • 52 1.11 4.97 1.96 1.04 0.14 6.88 5.20 55 1.10 3.88 2.19 0.95 3.10 3.10 21 4.50 47 0.83 4.45 1.80 0.92 0.18 2.41 4.80 85 1.06 4.67 2.96 1.16 5.35 5.89 28 4.78 34 0.75 4.30 1.94 0.92 0.15 3.93 5.25 130 1.16 5.89 5.76 1.98 5.41 17.83 35 4.63 - 0.58 3.98 2.00 0.90 0.12 2.00 4.43 - 1.02 12.18 14.20 4.28 18.35 17.68 42 5.05 41 0.42 3.16 1.79 0.81 0.20 2.40 4.15 633 0.60 14.75 23.55 5.75 35.75 65.15 49 5.00 44 0.35 3.10 2.05 0.88 0.16 3.06 3 .95 749 0.92 14.45 34.60 7.05 40.35 82.63 56 5.95 42 0.28 3.17 1.73 0.77 0.13 3.11 3 .80 745 0.46 ' 9.36 19.35 5.36 28.50 66.10 continued / Site II! Samples Appendix B (continued): Analyses of Leachates from Lysimeter Soil Columns Incubated at 22°C (Laboratory Experiment ^1) Days pH Conductivity Control Soil Samples P H Conductivi Urea-treated Soil Samples .umho/cm Na K Ca Mg NH^ -N N C L - N .urn ho/ cm Na K Ca Mg NH - N N O -mg/l o m g/l 4 3 7 5.05 31 1.72 1.33 0.86 0.35 0.17 0.05 4.50 26 1.46 0.76 0.73 0.35 0.19 <0.05 14 ' 4 .40 27 1.43 1.21 0.94 0.34 0.14 0.05 4.43 21 1.27 0.80 0.67 0.31 0.05 <0 .05 19 4.60 25 1.32 1.24 1.05 0.36 0.08 0 . 0 5 ' 5.60 87 1.42 1.48 1 -10 0.45 7.75 < 0 .05 21 4 .45 24 1.11 1.17 1.04 0.32 0.09 0.05 5.25 105 1.36 1.83 0.85 0.53 12.25 < 0 . 0 5 28 4.73 25 1.01 1.19 1.22 0.34 0.31 0.05 5.20 81 1.31 2.19 0.82 0.64 8.25 < 0.05 35 4.70 - 0.86 1.25 1.44 0.36 0.10 0.40 5.10 - 0.91 2.37 1.02 0.62 8.86 0.10 42 5.10 30 0.54 1.07 1.43 0.34 0.13 1.22 5 .25 150 0.61 2.59 2.55 0.80 12.28 3.60 49 5.10 31 0.51 1.13 2.00 0.39 0.07 2.03 4.'70 358 0.54 3.65 12.33 1.88 16.11 9.45 56 4.40 43 0.48 1.24 2.53 0.43 0.18 2.65 4.10 520 0.40 3.61 9.91 2.11 14.91 30.60 7 4 .70 61 1.00 4.73 0.49 0.36 2.72 0.05 4 .50 48 1.18 3.13 0.57 0.42 1.82 ^ 0 . 0 5 14 3.65 54 0.89 4.73 0.65 0.35 1.90 0.05 3 .45 49 1.18 3.46 0.66 0.39 1.12 < 0.05 19 3 .70 53 0.94 5.28 0.99 0.43 1.88 0.05 3 .70 73 1.62 5.69 1.56 0.73 5.40 i. 0 .05 21 3.60 44 0.73 4.30 0.89 0.35 1.52 0.05 3 .70 119 1.86 7.15 2.76 1.20 9.00 < 0.05 28 4 .25 44 0.72 4.41 1.00 0.36 0.80 0.05 3 .60 148 1.55 6 .95 4.70 1.47 17.20 < 0.05 35 3 .55 - 0.62 4.01 1.06 0.35 0.57 0.05 3 .60 - 0.90 4.27 2.02 0.81 3.44 < 0.05 42 3.90 46 0.52 3.31 0.92 0.31 0.53 0.05 4 .30 86 0.50 2.31 0.99 0.51 3.11 < 0.05 49 3.90 44 0.44 3.12 0.93 0.31 0.64 0.05 4 .20 91 0.39 1.95 0.81 0.46 3.96 < 0.05 56 3.70 58 0.39 3.22 1.14 0.22 0.64 0.05 4 .40 82 0.25 1.39 0.80 0.27 2.46 < 0.15 * Urea application was done on the 16th day of the experiment Each value is an average of 2 soil columns and weekly data are averages of two sampling periods. / Appendix C. I : Analyses of Leachates from Lysimeter Soil-Columns Incubated (Laboratory Experiment #2A) at 4°C Dcys after P H Conductivity Organic Concentration mg/litre ferti i l izction .umho/crn matter Urea H C O , N H . - N N a K Ca Mg Fe Mn A l C ontrol 25°C o Columns 0 (4) 5.79 47 1115 6 < 0.05 3.94 1.34 1.12 0.80 0.1 0 .02 0.4 3 (4) 5.23 33 1428 - 7 < 0.05 2.84 1.01 0.70 0.80 0.1 0.02 0.6 10 (3) 5.03 24 1429 - 4 <0.05 1.61 0.86 0.62 0.70 0 .3 0.02 0 . 5 20 (2) 5.40 28 1180 - 4 < 0.05 1.40 0.90 0.72 0.81 0 .2 0.01 0 .3 28 (1) 5.50 22 1166 - 3 0.15 1.24 0.86 0.62 0.65 0 . 2 0.04 0 .6 41 0) 5.50 24 1263 - 3 0.46 1.09 1.00 0.50 0.69 0.1 0.03 0 .6 55 (1) 5.50 24 1317 - 2 0.05 0.92 0.80 0.66 0.53 0.1 0 . 0 ! 0.1 *63 (1) 5.90 28 1191 - 4 0.06 1.-28 0.90 0.65 0.75 0 .2 0.01 0 . 2 *70 0) 5.80 26 1019 - 8 1.35 1.36 C.88 0.75 0.75 0 . 2 0.03 0 .3 Ferti l ized Columns 0 (4) 5.81 39 1129 - 4 < 0.05 2.64 1.24 1.20 0.66 0.1 0 .02 0 .4 3 (4) 5.29 124 3225 288 II 8.86 2.81 2.74 1.55 1.12 0.6 0.07 3 . 2 . 10 (3) 6.50 333 6978 138 80 41.50 0.76 1.54 0.26 1.58 2.9 0.01 7 .0 20 (2) 6.53 239 5560 56 54 24.00 0.54 1.15 0.17 1.51 2.6 0.01 5.8 28 (1) 6.50 171 3761 15 52 36.00 0.37 0.83 0.13 0.31 1.4 0.02 4 . 0 41 (1) 6.50 14! 4002 - 40 20.35 0.44 0.75 0.10 0.36 1.5 0.01 4 .4 55 (!) 6.50 130 4328 - 50 19.80 0.33 0.40 0.14 0.44 I.I 0.01 2.9 *63 (!) 6.35 161 4871 - 36 24.60 0.34 0.40 0.22 0.96 3 . 0 0.01 6 .3 *70 0) 6.15 149 4328 - 28 14.70 0.70 0.57 0.17 0.65 2 .5 0 . 0 ! 6 . 2 Figures in 0 represent number of soil columns. *Samples were incubated at 22 C after 55 days following ferti l ization. cn C O / Appendix C . 2 : Analyses of Leachates from Lysimeter Soil-Columns Incubated at 22 C (Laboratory Experiment ^2A) Control Columns Coiumns Days after pH Conductivity Organic Concentration m g/litre fertilization wmKo/cm 25°C matter Urea HCO3 N H . -4 N Na K Ca Mg Fe Mn A l 0 (4) 5.84 38 1113 6 0.05 2.54 1.30 1.15 0.61 0.1 0.02 0.3 3 (4) 5.31 38 1127 9 0.05 2.62 1.35 0.91 0.98 .0.1 0.04 0 .7 10 (3) 5.25 36 1076 6 0.05 2.36 1.35 0.78 0.97 0 .3 0.03 0 .7 20 (2) 5.05 31 1065 3 0.05 1.55 1.00 0.84 0.49 0 . 2 0.02 0.4 28 (0 5.25 25 1051 2 0.10. 1.33 0.95 0.62 0.37 0 . 2 0.06 0 .7 41 (1) 5.20 26 974 2 1.33 1.18 0.90 0.50 0.40 0.1 0.04 0 .7 55 0) 5.20 26 992 4 2.08 1.20 0.80 0 .65 0.43 0.1 0.01 0 .2 63 (1) 5.80 22 1137 4 0.19 1.05 1.05 0.64 0.42 0.1 0.01 0.1 70 d (1) 5.90 26 956 8 0.05 1.14 1.23 0.82 0.45 0.1 0.01 0 .3 0 (4) 5.95 42 1154 7 0.05 3.01 1.31 1-10 0.81 0.1 0.02 0.4 3 (4) 5.33 205 1935 28 15.27 4.10 3.84 2.15 3.16 3 .8 0.17 16.3 10 (3) 5.25 205 4118 33 27.00 1.42 2.51 1.33 3.95 5.1 0.14 16.9 20 (2) 5.63 203 3900 34 23.75 0.69 1.38 0.55 3.13 5.4 0.19 12.4 28 (!) 5.80 144 2605 28 26.00 0.54 1.05 0.47 1.00 4 .6 0.20 9.1 41 (1) 6.10 185 2747 32 36.60 0.93 1.52 0.58 1.57 12.5 0.14 15.2 55 0) 5.90 178 4328 28 22.65 0.97 1.50 0.42 1.23 5 .7 0.15 12.0 63 0) 6.05 162 3967 47 31.85 0.71 1.50 0.23 0.68 6 . 7 0.16 14.8 70 (0 6.00 168 3696 27 16.70 0.76 0.90 0.16 0.60 5.6 0.13 12.8 Figures in ( ) represent number of soil columns. Appendix D.I.I Posr-ferfilization Leaching Dafa, Site I (Shallow) S I T E I : URSA F E R T I L I Z E D (SHALLOW P L A T E A) OAYS'ftFTER VOLUME C O L L E C T I ON PH C O N D U C T I V I T Y M I L L I G R A M S PER L I T R E F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) ^.MHO/CM(25°C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT 0 3.46 21 6.0 3 3 2. 10 0.51 1. 70 0.48 ^ 0. 02 0. 15 4 0.35 < 0.5 0 40-<Sf: 3 2.40 8 6.8 2 2 0 1.80 1.31 0.73 0.25 3 0 . 7 5 0.14 1 8 1 . 1 4 1 5 0 . 2 5 14 0.30 6 7.0 2 7 5 1.27 1.23 0.30 0.08 2 9 . 0 0 0.49 4 4 . 6 9 1 5 . 2 0 21 0. 5 0 7 6.8 176 0.95 0.82 0.13 0 . 0 5 6. 15 0. 68 1 7 . 93 1 1 . 1 5' 2 S • 0 o 0 0 42 i ° 95 14 6. 7 95 0 . 5 3 0. 54 0. 07 0. 02 8. 3 0 0.63 < 3.98 4 0.05 0. 11 65 i . i 2 23 6.7 6 3 0.54 0.45 0.06 0 . 0 2 6.46 0.57 7.41 0 . 3 S 0.06 9- 3 o 3 0 28 6.5 4 4 0.28 0 . 2 7 ' 0.13 0.02 3.85 0.40 4 . 6 5 C.40 < 0 . 0 5 121 7. 35 28 6.0 4 0 0.36 0.31 0 . 5 3 0.09 2. 95 2. 0 3 5. 13 0. 15 -'0.05 149 1 1 . 4 6 2 8 5.1 48 0.39 0.25 2.63 0 . 4 5 0.76 5.08 5.90 0.06 i 0 . 0 5 177 1 2 . 6 4 28 4.2 5 6 0.45 0.13 4 . 4 5 0 . 6 0 0.21 6.20 6.53 0.12 ^ 0 . 0 5 2 0 5 1 3 . 1 0 2 8 4 . 9 4 3 0.41 0 . 1 2 3.05 0 . 3 9 0 . 0 5 3 . 9 3 4 . 0 8 0.05 - 0 . 0 5 2 4 6 1.32 4 2 5.1 3 ? n. ^  A m •> >•' ~ " -5 0 < 0 . 5 0 i 0. 50 4 0 . 5 0 <0.5'0 2.46 0 . 2 7 0„05 2.85 < 2.95 < 0.05 0.24 S I T E I : UREA F E R T I L I Z E D (SHALLOW P L A T E 3) DAYS AFTER F E R T I L I Z A T I O N 0 8 14 21 28 42 65 93 121 149 1 7 7 20 5 2 4 6 VOLUME ( L I T R E S ) 1. 77 2. 25 1.85 3.43 0. 35 1 6 . 1 5 1 0 . 6 2 3 0 . 70 4 2 . 90 4 5 . 60 4 6 . 29 4 1 . 1 7 5.90 C O L L E C T I O N P E R I O D ( D A Y S ) PH C O N D U C T I V I T Y 28 5.2 22 3 6. 4 120 6 6.0 53 7 6. 1 36 14 6. 0 5. 9 3 3 21 23 5. 9 16 2 3 60 0 9 28 5.5 9 23 5. 1 9 23 4.2 18 23 4.8 13 42 5. 1 13 M I L L I G R A M S PE N A K CA MG NH4-N 0. 55 1. 13 0. 86 0. 4 5 ^ 0. 2 0 1.04 0.65 0.23 0.03 1 0 . 6 5 0.51 0. 32 Oo 14 0. 02 6. 05 0.38 0.23 0. 10 0.02 3. 20 0.79 0. 19 0. 10 0.02 2.40 0.24 0. 17 0. 19 0. 02 1. 15 0.25 0. 12 0.24 0 . 0 5 1. 00 0.16 Oo 05 0. 26 Oo 04 0. 30 0. 21 0. 07 0. 26 0. 06 0. 24 0.20 0. 07 0.29 0.06 o . i o 0. 34 0. 07 0. 75 0. 13 0. 10 0.35 0. 09 0.41 0.08 0. 13 0.32 0.05 0.39 0 . 0 7 4 0.05 R L I TR: NQ3-.N 0. 2 0.22 O.Zi 0. 3 0 0.47 0.2 3 0. 26 0.12 0. 11 0.46 1.56 0. 82 0.63 N-TOT. 0. 2 1 9 . 2 2 7.53 4 3 . 5 3 4 2.77 4 1 . 4 3 1 .31 0.60 0.61 0.61 1.81 4 1.00 4 0.78 ORG N ^ 0 . 4 0 3. 3 5 1.15 4 0. 50 < 0.50 4 0. 05 C . 05 0. 18 0. 26 0. 05 0.15 4 0 . 05 0.10 P-TOT. 4 0.40 4 0. 50 '•0,50 0.50 4 0. 50 0.09 0., 0 5 4 0. 05 ^ 0.05 4 0. 05 4 0.05 4 0 . 0 5 0. 25 Appendix D.1.2 Posf-ferfilization Leaching Data, Site I (Deep) S I T E I : UREA F E R T I L I Z E D ( D E E P P L A T E A) DAYS A F T E R COLLECT ION PH C C M D U C T I V I T Y F E R T I L I Z A T I O N PERIOD ( D A Y S ) A u M H 0 7 C M(25' : ,C) NA 0 2 3 6. 0 17 2>22 8 8 6.1 19 1.40 14 6 5. 9 21 1 .68 21 7 5o9 23 l a 34 26 2 5.8 21 1.35 42 14 6. 0 22 1.29 65 23 6o 0 22 1» 15 93 23 5.9 21 0.91 121 28 5. 5 29 l o 2 1 1 4 9 28 5.3 34 1.34 177 23 4. 7 62 1.65 2 0 5 28 5.3 30 2„ 15 2 4 6 42 5.3 109 2.51 M I L L I G R A M S P EP. L I T R 3 K CA MG \IH4-N N03-M N-TOT. ORG N P - T O T . 0.1 7 0.73 0. 1.1 < Oo 20 0.02 < 0.72 i. . 0.50 ±0. 50 0.16 0. 95 0. 11 0. 75 0. 03 1 7 . 0 3 1 6 . 2 5 ^ 0 . 5 0 0*18 1.19 0. 14 l o 6 0 0. 12 3 1 . 3 2 30o 10 4 Co 50 0. 15 1. 05 0. 1 0 0.40 OoOS 4.23 3.30 < Oo 50 0. 18 0. 95 C. 09 0. 22 0. 1 0 < 0. 32 i. 0.50- < 0. 50 0.21 0.93 0 . 0 9 Oo 15 0. 28 0.5 5 0. 12 C.20 0. 21 0. 93 0. 0 3 0. 25 0.51 0.31 0.05 0.05 0.15 0. 90 0.07 0. 29 Oo 48 0. 97 0. 2 0 0.05 0.21 1.46 0 . 1 5 0.26 1.76 2.13 O o l l i 0 o 0 5 0. 25 2. 31 0..21 0. 05 3.45 ^ 3.55 0.05 i 0 . 0 5 0.32 5. 04 0. 34 0. 21 4. 57 5.25 0. 47 <0. 05 0»42 7. 05 0. 4 7 Oo 06 7.60 <- 7.71 4. 0.05 - 0 . 0 5 0.46 9.3 3 0. 5 8 < 0.05 1 1 . 00 .4 1 1 . 2 0 0. 1 5 0. 15 S I T E I : UREA F E R T I L I Z E D ( D E E P P L A T E B) DAYS AFTER C O L L E C T ION PH C O N D U C T I V I T Y MI L L I GRAMS PER L I T R c F E R T I L I Z A T I O N PERIOD ( D A Y S ) -uMHO/CMI25°C) NA K CA MG NH4-.M N0 3-N N-TOT. ORG N P-TOT. 0 23 6. 1 21 1.49 Oo 18 1.12 0 . 3.9 < 0 o 2 0 0.04 £• 0.64 <: 0. 4 0 * 0 . 4 0 8 8 5.9 18 1. 10 Oo 17 1.16 0. 13 < 0. 10 0.05 •c 3.65 3.50 < 0 . 50 14 6 5.9 2 5 1.13 0.15 1.2 1 0.14 Oo 50 0. 12 10 . 22 9.60 0. 5 0 21 7 5. 9 19 0« 93 0.14 1.16 0. 12 Oo 15 0.07 2.17 1.95 <t Oo 50 28 2 6. 1 21 1.09 0. 13 1. Co 0. 1 i < 0. 10 0. i 4 i. 0.74 .10.50 0.50 42 14 6. 0 20 1.17 0.16 0.95 0.09 < 0. 10 0.21 0.53 Oo 26 0. 10 65 23 6. 0 19 1. 07 Oo 16 0. 94 0. 0 3 ^ 0. 10 0.43 4. 0.72 0.19 ^ 0 . 0 5 93 23 6.0 19 0. 95 0. 14 0. 97 0. OS < 0. 10 0. 39 < 0.65 0. 1 6 < 0. 05 121 28 5. 7 24 1.16 0.19 1.16 Oo 13 0. 10 1.12 1.33 0. 11 0. 05 1 4 9 28 5. 5 32 1.41 Oo 23 1. 71 0. 1 9 0. 05 2.37 2.47 0.05 ^ 0 . 0 5 1 7 7 23 5.0 50 1 .96 0.32 3.51 0.34 0„ 2'2 3. 6 0 4.30 0.43 0.G5 2 0 5 28 5. 5 53 2.01 0. 35 4.07 Oo 39 0.13 4.70 <: 4.83 < 0 o 0 5 < 0.05 2 4 6 4 2 5.2 80 2.22 0.39 5. 82 0. 51 * 0 . 05 7.40 4 7.50 0.05 0. 20 Appendix D.2.1 Post-fertilization Leaching Data, Site II (Shallow) / S I T S I I : U R E A F E R T I L I Z E D ( S H A L L O W P L A T E A) D A Y S A F T E R V O L U M E C O L L E C T I O N P H C O N D U C T I V I T Y M I L L I G R A M S P E R L I T R P E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( C A Y S ) X L M H O / C M ( 2 5 ° C ) NA K C A M G N H 4 - N N 0 3 - N N - T O T . O R G N P - T O T . 0 4.93 28 5.6 13 0. 76 0. 13 0. 63 0. 0 9 < 0.20 0.02 4 0.72 0.40 4 0.40 8 1. 60 8 6. 5 148 0.50 2 . 1 3 Oo 65 0. 30 1 4. 50 0.27 3 3.27 18c 50 4 0. 50 14 0.87 6 6. 5 1 3 0 0.40 l o 89 0. 16 0. 08 2 7 . 15 0.78 3 3 . 1 8 5.25 4 0.50 21 2 . 3 0 7 6.3 33 0. 27 i . 34 0. 07 0. 05 7. 63 0. 6 5 9. 15 0. 62 < 0.50 23 0. 70 7 6.3 77 0.32 1.38 0. 07 0.07 4. 60 1.33 8.68 2. 50 4 0. 50 42 3. 95 14 6„ 3 70 0.25 1.45 0. 17 Oo 0 9 5. 37 2.00 9.34 1.47 0.0 7 65 0. 7 0 23 6.2 6 9 0.26 1.50 0.30 0. 11 5. 85 3. 70 1 1 . 3 1 1. 76 0.09 9 3 7c 85 28 5. 9 42 0.45 I . 93 2 o 46 0.60 3.40 3.23 7.06 0.43 0. 10 121 8.59 23 4.6 1 2 2 0. 56 1. 34 4. 75 0. 98 3. 20 9. 70 1 3 . 0 9 0. 19 4 0 . 0 5 1 4 9 7. 95 28 4.2 97 0.55 1.30 4.62 0. 7 6 0. 44 9.64 1 0 . 13 0.05 0. 05 1 7 7 4„60 28 3. 8 1 0 6 0. 53 1. 14 4.41 0.95 0.26 9.93 1 0 . 6 8 0.44 4 0 . 0 5 2 0 5 4. 10 28 4.6 57 0.64 0. 7 6 1. 74 0. 6 7 < 0. 05 5.02 5.12 0.05 c 0 . 05 2 4 6 0. 16 21 5.6 23 0.90 0.44 1.02 0 . 4 0 0 . 2 5 1.75 < 2 . 0 5 < 0. 0 5 •=0.05 S I T E I I : U R c A F E R T I L I Z E D ( S H A L L O W P L A T E B) D A Y S A F T E R VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S P E R L I T R E F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) - H M H D / C M ( ?<5° r I w « r ,\ vr. N H 4 - N N O E - N N - T O T . ORG M P - T O T 4 0 . 2 0 4 0 . 0 2 ^ 0 . 7 2 4 0 . 5 0 4 0 . 5 0 1 2 . 0 5 1 . 4 5 2 3 . 4 5 1 4 . 9 5 < 0 . 5 0 1 4 0 . 8 3 6 6 . 4 2 9 0 0 . 2 1 1 . 7 2 0 . 1 7 0 . 3 3 2 5 . 2 0 1 . 1 5 3 3 . 2 5 1 1 . 9 0 4 0 . 5 0 " 1 c "* ' " " " 3 . 4 0 1 . 9 5 2 0 . 2 5 9 . 9 0 4 0 . 5 0 . . 4 . 6 5 3 . 1 0 2 1 . 6 0 ' 1 3 . 8 5 4 0 . 5 0 4 0 7 . 9 5 1 4 6 . 0 3 3 0 0 . 21 1 . 9 9 0 o 4 2 0 . 6 2 1 7 . 5 0 6 . 15 2 4 . 6 5 1 „ 0 C 0 5 . 0 4 8 4 . 0 0 6 5 1 . 4 0 9 3 1 0 . 7 0 1 7 7 5 . 7 6 ACTI I L L ) ( Y S ) u O t 2 5 C) NA K CA MG 2 8 5 . 2 2 6 0 . 7 1 1 . 9 0 0 . 5 9 0 . 7 6 8 6 . 2 1 4 8 0 . 6 5 1 . 8 5 0 . 6 8 0 . 8 6 6 6 . 4 2 9 0 0 . 2 1 . 7 2 0 . 1 7 . 2  7 6 . 2 1 3 3 0 . 1 9 1 . 3 2 0 . 0 3 0 . 1 7 7 6 . 2 2 5 6 0 . 3 4 1 . 7 4 Oo 1 1 0 . 2 9 1 4 6 . 0 3 3 0 Oo 2 1 I .  0 » 4 2 .  2 3 5 . 9 2 6 6 0 . 3 0 2 . 5 0 1 . 0 5 1 . 2 9 2 3 5 . 2 1 7 4 0 . 3 2 1 . 8 5 8 . 1 9 2 . 3 4 2 8 4 . 2 3 3 4 0 . 5 3 2 . 3 6 7 . 3 6 2 . 6 3 2 8 3 . 8 2 1 6 0 . 6 6 1 . 4 5 4 . 3 9 1 . 8 6 2 8 3 . 5 1 5 0 0 . 7 3 0 . 7 3 3 . 9 9 1 . 6 3 2 3 4 . 7 1 8 0 . 3 2 0 . 1 0 0 . 3 3 0 . 2 6 4 2 4 . 9 1 8 0 . 4 1 0 . 0 5 0 . 4 0 0 . 2 6 2 1 . 2 0 6 . 0 0 2 7 . 5 0 0 . 3 0 0 . 1 3 , ; f V ' " H b ' z 1 7 4 °*32 1. 5 8.19 2.34 1 3 . 0 0 1 5 . 3 0 2 1 . 5 0 3.20 0 . i 0 *°tl H 334 0.53 o 6 3.30 3 1 . 2 0 4 6 . 2 0 6.70 4 Q . 0 5 0 . 8 2 1 4 . 2 2 4 1 5 . 0 9 4 0 . 0 5 4 0 . 0 5 0 . 1 3 1 4 . 2 5 1 4 . 9 2 0 . 4 9 0 . 0 3 \ll I'll f ? 1 8 0 - 3 2 0 . 1 0 . 3 . 6 0 . 0 6 0 . 1 3 0 . 3 a 0 . 1 7 4 Q . 0 5 2 4 6 0 . 9 2  l f i n . A i n . r > - n A n n O o l Q 0 o 0 4 Q o 5 g Q<>^5 g ^ -Appendix D.2.2 Posf-Ferfi I ization Leaching Data, Site II (Deep) S I T E I I : UREA F E R T I L I Z E D (DEEP P L A T E A) DAYS AFTER C O L L E C T ION PH C O N D U C T I V I T Y M I L L I G R A M iS P SR L I T R F E R T I L I Z AT I ON P E R I O D (DAYS ) -U.MHO/CM ( 25° C ) MA K CA MG NM4 -,N NOB - N Ni-•TC IT. ORG N P-T OTo 0 .28 5.4 2 3 1.72 0„36 0. 76 0. 24 <0. 20 02 4 Oo 62 4 0. 4C 4 Oo 40 S 8 5.3 23 5.60 0. 4 0 0. 6 0 0. 22 0. 25 4 0. 02 4 1. 82 1. 55 4" 0. 5 0 14 6 5.5 2 5 1.36 0.27 1. 09 0. 2 9 < 0. 10 0. 09 4 0. 6 9 0. 50 4" 0. 50 21 7 5. 3 18 0.99 0.25 1. 26 0.32 0. 13 Oo 06 4 Oo 56 4 0. 37 4 0. 5 0 2 3 7 5. 6 25 1.32 0. 16 1. 16 0. 3 2 0. 15 0. 09 4 0. 63 0. 35- 4 0. 50 42 14 5.3 2 6 1.01 0.23 1. 29 0 . 3 9 < 0. 10 0. 32 4 0. 4 0 0. 0 3 4 Oo 0 5 65 23 5. 5 25 0. 94 0.16 1. 15 0.36 0. 2.2 Oo 4 3 1. 20 0. 6 0 Oo I I 93 28 5.6 24 0.94 0. 23 X • 26 0. 33 10 0. 43 4 0. 53 0. 02 4 0. 0 2 121 2 3 5.5 26 0.93 0.21 ' l . 18 0 . 3 3 10 Oo 4 5 4 Oo 35 0. 2 0 4 0. 0 5 149 28 5.3 29 0.95 0.24 l . 32 0.42 < 0. 05 0. 95 4 1. 0 5 Oo OS 4 0. 05 1 7 7 2 3 5.0 28 0.95 0. 21 l . 51 0. 33 < c. 05 0. 44 4 ! • 70 0. 4 0 t f l . 0 5 2 0 5 23 5.4 27 1.08 0.22 l . 54 0.26 < 0. 05 0. 27 4 Oo 3 ? 4.0. 0 5 < 0. 05 246 4 2 5.3 21 0.93 0.22 i . 1 5 0 .23 * 0. 05 0. 10 c 0. 5 0 0. 3 5 < 0 . 05 S I T E I I : UREA F E R T I L I Z E D ( D E E P P L A T E 6J DAYS AFTER C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G.R V I S P ER L I T R F E R T I L I Z A T I O N PERIOD ( D A Y S ) AM HO/CM(25°C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 0 28 5.4 26 2.06 0.50 0.60 0. 26 4 0 . 20 4 0 . 02 4 0 . 72 4 0 . 50 4 0. 50 8 3 5. 3 2 0 2 o l l 0.25 0.69 0. 2 0 4 0.10 4 0 o 0 2 4 0.62 4 0. 5 0 4 0.50 14 6 5.7 33 3-70 0.59 C. 70 0. 23 <0. 10 0. 04 4 0. 64 4 0.50 4 0 . 5 0 21 7 5. 5 33 3 . 70 0.52 0.65 0.21 4 0 , 10 Oo 57 4 0.57 4 0. 50 4 0. 5 0 23 7 5. 9 32 3.46 0.47 Oo 64 0.23 0. 16 0.13 < 0.73 4 0.50 4 0.50 42 14 5.7 33 3.55 0.49 0.77 0. 27 <0. 10 0. 32 0.49 0. 07 0. 18 65 23 5. 7 2 9 2,69 0.46 0.77 0.2 6 4 0 . 1 0 0.35 ^ 0.64 Q. 19 Oo 1 2 93 28 5.9 27 2,79 0. 41 0. 84 0. 2 6 4 Oo 10 0.52 i. 0.63 0.06 4 0.05 121 23 5.8 23 2.60 0.44 0.84 . 0.30 4. Oo 10 0. 57 < 0. 37 0. 2 0 < Oo 05 1 4 9 2S 5. 6 28 2.33 0 o 4 7 0. 94 Oo 26 <:0o05 1.00 < 1.10 • 0.0 5 ^ 0 . 0 5 1 7 7 28 5.1 3 1 2.61 0. 48 1. i 4 0. 3 6 4 . 0 . 05 1.25 4 1.67 0.37 0.06 2 0 5 2 8 5.6 33 3.07 0.48 1.08 0.34 4 0 o 0 5 l o 2 6 C 1.36 4 0. 05 4 Oo 0 5 2 4 6 42 5.4 4 0 3.33 0.48 1.19 0. 36 4 0 . 05 2.22 4 . 2.42 0.15 4:0. 15 Appendix D.3.1 Posf-ferrilizarion Leaching Data, Site III (Shallow) / S I T E I I I UREA F E R T I L I Z E D (SHALLOW P L A T E A) DAYS AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PE :R L I T R F E R T I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) * A M H O / C M ( 2 5 ° C ) NA K CA MG NH4-N N0 3-N N - T 0 T . ORG N P-TOTo 0 1 3 . 5 6 21 5.2 2 0 Oo 40 Oo 65 1.25 Oo 52 ^ 0 o 2 0 4 0.02 4 0 .62 4 0.40 4 0. 40 8 6.50 8 7.0 135 0.24 0. 64 0.47 0. 13 2 4 . 75 0. 0 9 5 7. 09 3 2 . 2 5 4 0. 50 14 2. 50 6 6. 9 1 0 0 0.:. 8 Oo52 0.20 0 , 0 5 8o 55 0.24 1 3 . 4 2 4.65 4 Oo 50 21 2.40 7 6. 8 84 0.12 0.41 C. 07 0. 0 3 4. 30 0. 31 1 3 . 4 1 8.30 4 0 . 5 0 23 0.40 2 6.5 99 0.12 0.47 0.07 0 . 0 1 3. 95 0. 55 1 0 . 25 So 75 4 Oo 5 0 42 3. 95 14 6. 3 88 0.13 0 o 4 5 Oo 09 0.02 9.77 1.35 1 1 . 3 3 0 . 2 1 0.12 65 2. SO 23 7.0 96 0. 13 0.47 0. 08 0. 03 9. 78 2.55 1 2 . 4 5 0.12 G. 20 93 9. 90 28 6.6 72 0.26 Oo 72 0.60 0 . 1 3 5.70 1.96 9„ 66 2. 0 0 0. 05 1 ~y i. 1. 4» 32 28 5.0 1 3 7 Oo 30 1„ 52 4o 12 0. 73 1 2 . 4 0 1 3 . 0 0 2 9 . 5 0 4.10 4 0.05 149 4. 65 28 4.3 1 0 3 0. 31 1.17 6. 12 2. 02 1. 63 9. 8 4 1 1 . 7 7 0 . 3 0 0.15 177 4. 24 2& 4.3 51 0.46 0.46 3.56 0.71 0. 12 3 . 3 6 3.71 0 . 2 2 4 0. 05 2 0 5 5.10 28 4. 9 24 0.44 0.26 1.37 0. 34 0. 09 0.60 1.00 0.31 0.05 2 4 6 3. 50 28 4.8 17 0.40 0.17 0.94 0.26 4 0 . 0 5 0 . 0 5 4 0 . 2 4 0.23 0. 10 S I T E I I I UREA F E R T I L I Z E D (SHALLOW P L A T E B) DAYS AFTER VOLUME COLLECT ION PH C O N D U C T I V I T Y M I L L I G R A M S P ER L I T R E F E R T I L I Z A T I O N ( L I T R E S ) PERJ.OD ( D A Y S ) '".MHO/ CM ( 25° C) r.'A K CA MG NH4-N NG3-N N-TOT. ORG N P-TOT. 0 1 5 . 4 5 21 5.2 25 0.83 0„ 62 l o 10 0. 3 6 4 0 . 2 0 4 0 o 0 2 0.72 < 0.50 4 0 . 50 3 4.40 8 7.2 307 0. 61 0. 63 0. 67 0. 13 3 1 . 50 0. 10 2 1 9 . 1 0 1 8 7 . 5 0 4 0.50 14 1. 50 6 7.4 2 2 9 C.23 Oo 60 0.22 0.16 3 0 . 50 0„27 3 5 . 2 7 4. 4 0 4 0. 50 21 1.60 7 7.0 1 4 5 0. 16 Oo 4 9 0„ 09 Oo 03 4. 80 0„40 1 9 . 0 0 1 3 . 8 0 4 0.50 28 0.45 • 2 7.0 146 0.19 0. 54 0. 05 0. 04 3. 50 0. 75 1 5 . 1 9 1 0 . 94 4 0.50 42 4. 55 14 7. 0 162 0.14 0„ 58 0 o 0 3 0 o 0 2 1 5 . 3 0 ? 2 . 0 0 20„ 50 3.20 0. 13 65 1.45 23 6. 9 160 0.16 0. 69 0. 08 0. 04 1 5 . 6 0 2.90 2 2 . 9 0 4 . 4 0 0. 20 93 4. 50 28 6.5 116 0,26 Oo 86 0.30 0.07 6. 89 3. 2 5 1 1 . 65 2. 51 4 0. 05 121 2. 96 2S 5.2 2 9 4 0. 30 l o 91 1.45 0 o 3 3 2 3 . 70 2 6 . 2 0 5 3 . 6 0 3„ 70 4 0 . 0 5 1 4 9 3.31 28 4. 5 137 1.00 1. 56 4. 62 0.93 3. 81 1 1 . 4 0 1 5 . 6 2 0.41 0.08 177 4. 26 28 4.2 70 0.60 0. 75 4. 86 1.05 0.19 5.28 5 . 6 2 0. 15 4 0. 05 2 0 5 5o 3 5 28 4.9 35 0. 51 0 o 4 4 1.93 0.47 0. 08 1.76 2 . 0 3 0. 19 4 0 . 0 5 2 4 6 3o 03 42 5. 1 23 0.42 0.43 1.05 0.28 4 0 . 0 5 0. 2 1 0. 44 0. 18 0.11 Cn Appendix D.3.2 Post-fertilization Leaching Data, Site III (Deep) / S I T E I I I U R E A F E R T I L I Z E D ( D E E P P L A T E A ) D A Y S A F T E R V O L U M E C O L L E C T I O N P H C O N D U C T I V I T Y M I L L I G R A M S P E P L T T R = F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) A ^ M H O / C M [ 2 5" C ) N A K 0 0. 55 3 0. 75 14 0 o 6 0 21 0.75 23 - 0„25 42 2 . 3 5 6 5 1.50 93 3 . 9 0 121 4.42 149 3.66 1 7 7 . 1.93 2 0 5 2 . 6 7 2 4 6 0.64 2 1 6 . 0 6 9 1 0 . 4 0 8 6 . 1 5 3 7 . 6 0 6 6 . 1 5 0 5 . 9 0 7 6 . 0 4 5 4 . 9 0 -1 i - 6 . 0 3 9 3 . 8 3 1 4 6 . 0 3 2 1 . 9 2 2 3 6 . 1 3 2 2 , 3 8 2 8 5 . 9 2 9 1 . 6 0 2 8 5 . 3 2 8 1 . 3 5 2 3 5 . 5 3 4 1 . 4 2 2 3 5 . 2 3 7 1 . 5 1 2 8 5 . 6 4 2 1 . 7 0 2 8 5 . 4 4 1 1 . 6 7 0 . 4 2 0 . 3 5 0 . 3 2 0 . 3 0 0 . 3 0 0 . 2 5 0 . 2 8 Oo 2 5 0 . 2 6 0 C 2 9 0 . 2 8 0 . 2 7 0 . 2 3 C A MG NH4-N N03-N N-TOT. ORG N P - T O - . 0.64 0. 2 0 <0. 2 0 0. 4 0 4 1. 00 .-=0.40 4 0 . 4 0 0.71 0.14 < 0 . 10 0.11 ^ 0 . 61 <• 0. 40 4 0. 50 0 . 90 0. 15 < 0. 10 0. 11 4 0 . 6 1 4 0.40 4 0 . 5 0 0.86 0. 15 < 0. 10 0.09 - 0 . 5 9 4 0. 4 0 4 0.50 Oo 99 Oo 16 < 0. 10 0.06 4 0 . 5 6 4 0.50 4 0 . 50 1 . 25 0. 18 0. 10 0.2 9 4 0. 44 4 0 . 0 5 0. 13 1.10 0 . 1 3 < 0. 10 0.22 4 0 . 4 6 0. 14 0, 05 1.40 0 . 1 7 4 0. 10 0.15 4 0.52 0.27 4 0 . 0 5 1.31 0. 17 0. 13 0. 4 3 0. 93 0. 37 4 0 . 05 1.74 Oo 22 4 0 . 0 5 1.51 4 1 . 6 1 0. 05 4 0. 05 2. 13 0. 26 0. 13 1.81 2 . 1 i 0 . 17 4 0.05 2.31 0 . 2 7 4 0 . 0 5 2. 30 4 2 . 9 6 0. 11 ^-0. 05 2. 59 0. 27 4 0.05 1.56 4 1 . 6 6 0 . 0 5 0.10 S I T E I I I U R E A F E R T I L I Z E D ( D E E P P L A T E 3 ) D A Y S A F T E R F E R T I L I Z A T I O N 0 8 1 4 2 1 2 3 4 2 6 5 9 3 1 2 1 1 4 9 1 7 7 2 0 5 2 4 6 V O L U M E ( L I T R E S : 3 . 0 5 2 . 3 0 1. 7 6 2 . 2 0 0 . 3 5 2 . 9 5 4. 0 0 8 . 0 0 7 . 0 6 6 . 2 5 3 . 9 9 4. 6 3 1 . 4 7 C O L L E C T I O N P E R I O D ( D A Y S ) P H C O N D U C T I V I T Y ^ M H O / C M ( 2 5 ° C ) NA 2 1 6 . 0 4 1 5 . 0 0 8 5 . 9 4 2 5 . 4 0 6 5 . 3 4 2 4 . 6 7 7 5 . 3 3 1 3 . 0 9 2 5 . 8 3 2 2 . 3 5 1 4 6 . 0 3 3 2 . 6 6 2 3 5 . 8 3 1 1 . 9 2 2 8 5 . 8 4 2 1 . 4 8 2 3 5 . 7 4 4 i a 4 6 2 8 5 . 3 6 2 1 . 6 6 2 8 4 . 9 6 8 1 . 5 3 2 8 5 . 2 7 1 1 . 4 5 4 2 5 . 7 4 5 1 o 2 7 K 0 . 2 3 0 . 2 2 0 . 2 3 0 . 1 9 0 „ 1 4 0 . 2 1 0 . 1 7 Oo 1 5 0 . 1 3 0 . 2 0 Oo 1 9 0 . 1 8 0 . 2 2 C A 0 . 8 3 0 . 9 6 0 . 9 8 1 . 2 0 1 . 2 7 1 . 1 6 1 „ 2 7 2 . 4 3 2 . 4 2 4 . 5 1 5 . 6 0 5 . 6 6 3 . 0 4 M I L L I G R A M S P M G 0 . 1 8 0 . 1 2 0 . 1 2 0 . 1 4 0 . 1 5 0 . 1 7 0 . 1 6 0 . 2 0 0 . 1 9 0 . 2 9 0 . 3 2 0 . 3 1 0 . 2 1 N H 4 - N < 0 . 2 0 4 0 . 1 0 4 0 . 1 0 < 0 . 1 0 < 0 . 1 0 4 0 . 1 0 0 . 1 3 4 Oo 1 0 0 . 3 5 0 . 2 5 0 . 1 8 0 . 0 5 4 0 . 0 5 H R L I T R N 0 3 - N 4 0 . 0 2 < 0 . 0 2 0 . 0 4 0 . 1 2 0 . 1 7 0 . 2 9 0 . 4 9 0 . 7 3 2 . 4 0 5 . 1 9 5 . 6 0 4 . 7 0 2 . 9 3 N - T O T . 4 0 . 7 2 4 0 . 6 2 4 0 . 6 4 4 0 . 7 2 4 0 . 7 7 4 0 . 4 4 0 . 6 9 4 2 . 3 7 2 . 9 7 4 5 . 4 9 5 . 3 5 5 . 6 5 4 3 . 0 8 O R G N 4 0 . 5 0 £. C o 4 3 4 0 . 4 0 4 0 . 4 0 4 0 . 5 0 4 0 . 0 5 0 . 0 7 1 . 5 1 0 . 22 4 0 . 0 5 0 . 0 7 0 . 0 9 4 0 . 0 5 P - T O T , 4 0 . 5 0 4 0 . 5 0 4 0 . 5 0 < 0 . 5 0 4 0 . 5 0 0 . 0 9 4 0 . 0 5 4 0 . 0 5 4 0 . 0 5 4 0 . 0 5 4 0 . 0 5 4 0 . 0 5 0 . 1 5 o-o Appendix D.4.1 Post-fertilization Leaching Data, Site IV (Shallow) FER1 S I T E I V : U R E A F E R T I L I Z E D ( S H A L L O W P L A T E A ) A F T E R V O L U M E C O L L E C T I O N P H C O N D U C T I V I T Y M I L L I G R A M S P E R L I T R : L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) M M H 0 / C M { 2 5 ° C ) M A K C A M G N H 4 - N N 0 3 - N N - T O T . 0 8. 88 28 4. 9 33 0. 74 1.41 2.76 0. 5 7 4 Oo 20 0.02 4 0.72 3 0 c 9 5 3 7.3 2 2 7 0.57 1. 54 1.65 0. 4 0 2 5 . 75 0. 08 1 0 5 . 0 8 14 0. 30 6 6. 6 107 0.21 0.65 0.36 0. 09 5. 16 0. 16 1 6.46 21 0. 75 7 6. 6 1 0 0 0. 25 0. 65 0.25 0. 08 l o 3 5 0. 14 1 4 . 3 6 28 0.80 7 6. 5 85 0.20 0. 53 0. 13 0. 06 8. 02 0.21 4 8 . 3 1 42 1. 65 14 6. 5 68 0.17 0.45 0. 17 0 „ 0 4 7. 73 0.17 9. 59 65 1.30 23 6.6 6 0 0. 16 0. 3 8 0. 15 0. 05 6. 76 0.40 7. 64 93 2. 88 23 6. 3 58 0.17 0.27 .0. 19 0.04 6.20 0. 51 l O . O i 1 2 1 3.25 28 5. 9 33 0. 20 0. 51 0.17 0. 06 8.13 4.45 1 7 . 0 5 1 4 9 3. 12 28 5.3 116 0.37 0. 9 7 1.47 0.29 3. 30 1 0 . 09 2 0 . 39 1 7 7 1. 74 28 4.3 153 0.35 1.73 4.77 0.92 8. 10 1 6 . 5 7 2 5 . 2 7 2 0 5 1.28 28 4. 5 1 6 4 1. 38 2. 04 5. 78 1.15 5.60 1 4 . 4 0 2 4 . 4 0 2 4 6 1.70 4 2 4.2 147 1.63 2.01 6.76 1.21 0. 75 1 1 . 2 0 1 2 . 4 7 ORG N P-TOT. 4 0 . 5 0 4 0 . 0 5 7 9 . 2 5 4 0 . 5 0 1 1 . 14 4 0 . 50 1 2 . 8 5 4 0.50 4 0 . 5 0 '<0.50 0.17 0.10 0.48 0.12 2.20 0. 07 4.47 0.20 2 . 0 0 4 0.05 0.60 0.30 4 . 4 0 4 0 . 0 5 0.52 0.05 S I T E I V : UREA F E R T I L I Z E D (SHALLOW P L A T E B) , AFTER VOLUME COLLECT ION PH C O N D U C T I V I T Y MI L L I GRAMS PER L I T R E I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) M M H O / C M ( 2 5 ° C ) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 0 6. 95 28 4. 1 76 1 . 4 0 3 . 6 6 2.54 0. 76 4 0 . 20 4 0 . 0 2 4 0 o 6 2 4 0.40 4 0.40 8 0. 95 8 5.2 76 0.36 2. CO 1. 48 0. 52 5. 60 0. 07 7.57 1.90 4 0.50 14 0. 95 6 5. 0 76 0.30 1. 15 0.37 . 0 . 1 3 8. 50 0. 15 9. 95 4. 64 4 Oo 5 0 21 0. 00 7 4. 3 4 6 0. 17 Oo 62 0. 12 0. 06 4. 05 0„0£ 4.38 0 . 2 5 4 0.50 28 1. 05 7 4. 7 73 0. 27 0. 99 0.23 0. 11 6. 94 0. 13 4 7. 57 4 0 . 50 4 0.50 42 1. 65 14 5. 0 43 0. 15 0. 57 0.17 0.07 5.34 0.12 5. 37 0. 4 1 C. 63 65 2.35 23 5. 4 31 0. 09 Oo 34 0. 06 0. 04 3. 20 0 . 1 1 3.64 0.33 0.50 93 4. 51 23 5.0 34 0.11 0.26 0. 15 0.04 3. 12 0. 11 3. 72 0.49 0.28 1 2 1 4. 22 28 5. 0 62 Oo 16 0.49 0.19 0 o 0 8 5. 87 0.12 1 0 . 1 2 4. 13 0. 50 1 4 9 2.55 28 4.7 3 9 0. 24 0.37 0. 17 0. 05 3. 86 0. 18 4.86 0.82 0.23 177 1. 76 28 4.0 6 2 0.26 0.50 0.40 0 . 1 3 5.69 0.39 7.99 1. 91 0. 2 0 2 0 5 1.24 28 4.3 76 0.43 0. 53 0.45 0. 19 6.00 0.61 1 0 . O i 3 . 4 0 4 0.05 2 4 6 1.66 42 4.2 1 7 0 0.S5 0.62 2.20 0.67 1 2 . 00 1 1 . 3 0 2 4 . 4 0 1.10 4 0.05 Appendix D.4.2 Posf-ferfilization Leaching Dafa, Site IV (Deep) S I T E I V : UREA F E R T I L I Z E D ( D E E P P L A T E A) DAYS AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) >uMHO/CM ( 2 5° C) 0 2 4 . 4 0 28 6.0 21 8 7. 75 8 6. 0 19 14 6. 10 6 5.9 21 21 7.00 7 5.8 21 28 4.00 7 5. 9 25 42 8.50 14 6.0 22 65 1 6 . 8 0 23 5.9 22 93 3 7 . 4 1 28 5. 8 22 121 1 6 . 6 5 23 5.8 2 3 149 14. 81 2 8 5. 5 23 1 7 7 9. 54 28 5.0 4 0 205 6.40 28 5.6 3 2 2 4 6 8. 80 42 5.3 34 M I L L I G R A M S PER L I T R E NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 1 .66 0. 23 1. 0 0 0. 2 5 <0. 2 0 0.03 <0.73 4 0 . 5 0 4 0 . 50 1.40 0. 21 1.03 0.21 <0. 10 4 0 . 0 2 4 0 . 6 2 4 0. 5 0 4 0. 50 1.40 0. 20 1. 11 Oo 22 <0. 1 0 4 0 . 0 2 4 0 . 6 2 < 0. 50 4.0. 50 1.35 0.21 1. 05 0. 2 2 <0. 10 4 0. 0 2 4 0. 62 4 0. 5 0 4 0 . 50 1.40 0. 14 1 . 0 9 0 . 2 3 4 0 . 1 0 4 0.02 4 0 . 62 4 0.50 4 0. 5 0 1.40 0.20 1. 04 0. 24 4 0. 10 4 0.02 • 4 0 . 1 7 ^ 0 . 0 5 < 0. 05 1 .48 , 0.17 0.96 0 . 2 3 < 0. 10 0. 0 8 ^ 0 . 3 0 0. 12 4 0 . 0 5 1. 54 Oo 18. 1.07 0. 23 < 0 . 10 0.30 ' 0 . 6 4 Oo 24 4 0 . 05 1.56 0. 19 0. 95 0. 2 5 4 0. 1 0 0.23 4 0 . 5 9 0. 26 4- 0. 05 1.70 0.23 1.26 0 . 3 3 4 0 . 05 1.26 4 1. 50 0. 09 4 Oo 05 l o 96 0. 2 7 2.21 0.46 0. 11 2.12 2 . 6 9 0. 4 6 4 0. 05 1.82 0.25 1.56 0.39 0. 09 1. 56 1. 70 < 0. 05 4 0. 05 1.62 0.25 1.71 0.46 0. 10 1.90 2 . 0 5 4 0. 05 *-0. 05 S I T E I V : UREA F E R T I L I Z E D ( D E E P P L A T E B) DAYS A F T E R VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) -UjMHO/CM (25° C) 0 2 8 . 3 2 28 5.9 2 4 8 1 1 . 6 0 6 5. 8 21 14 1 1 . 0 0 7 5. 9 24 21 3.40 7 5.7 23 28 6. 80 7 5. 9 2 4 42 1 2 . 3 0 14 6. 0 23 65 1 9 . 2 0 23 5. 3 22 93 5 3 . 85 28 5. 9 22 121 3 3 . 15 28 5. S 23 1 4 9 3 3 . 75 28 5. 6 25 1 7 7 1 8 . 4 3 28 5. 1 27 2 0 5 1 3 . 5 5 28 5.7 26 2 4 6 17. 31 42 5.4 32 M I L L I G R A M S PER L I T R E NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT 1.22 0.17 1. 22 0. 23 4 0 . 2 0 4 0.02 4 0 . 6 2 4 0.4 0 4 0.40 1.16 0. 15 1.41 0. 24 4 0. 10 < 0. 02 4 0.62 4 0. 5 0 4 0. 50 1 o 2 6 Oo 16 1.48 0.25 <0. 10 4 0.02 ^ 0.62 4 0.5 0 4 0.50 1.15 0. 15 1.35 0. 2 4 4 0. 10 4 0. 02 <• 0.62 0. 5 0 4 0 . 5 0 1.23 0„ 14 1.31 0.24 4 Oo 10 4 0 . 0 2 4 0.-62 4 0. 5 0 4.0. 50 1. 26 0. 15 l o 2 6 0.25 4 Oo 10 0.05 4 0.17 4 0.05 4 0.05 1.20 0. 12 1.12 0.24 < 0. 10 0. 05 4 0.35 0.20 4 0.05 1.25 Oo 13 1.24 0 . 2 2 4 0 . 1 0 0.12 4 0 . 9 2 Oo 70 4 0.05 1.41 0. 15 1. 03 0.24 4 0. 10 0. 05 4 0.2 9 0. 14 4-0.0 5 1.63 0. 16 2.24 0 . 2 6 4 0 . 0 5 0. 5 7 ^ 0. 67 4 0. 05 4 0. 05 1.83 Oo 17 1.31 0.28 < 0.0 5 0.72 4 0.32 0.05 4 0.05 1.65 0. 16 1. 21 0.32 4 0. 05 0. 51 4 0.61 4 0. 05 4 0 . 0 5 1.77 0. 16 1.76 0 . 4 6 4 0.05 1.53 4. 1.63 4 0. 05 4 0. 05 CN NO Appendix D.5.1 Unfertilized Plots Leaching Data, Site I (Shallow) S I T E I : CONTROL (SHALLOW P L A T E A) DAYS AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PER L I T R E F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) 4/-MH0/CM ( 25° C) NA K CA MG NH4-N N03-N N-TOT. ORG N- P-TOT. 0 4. 92 28 5. 6 11 0.38 0. 19 0.63 0 . 0 9 4 0 . 1 0 0.06 ^ 0 . 6 6 4 0.50 4-0.50 8 2. 70 8 5.4 11 0.36 0. 17 0. 80 0. 07 4 0 . 1 0 0 . 0 3 4 0 . 6 3 < 0 . 5 0 4 0 . 5 0 14 0. 15 6 5.6 10 0.51 0. 18 0.84 0.07 <0. 10 0. 03 4 0 . 6 3 < 0 . 5 0 < 0 , 5 0 28 0.00 21 0.00 42 1. 30 14 5.6 11 65 2.25 23 5. 6 9 93 - 2 . 0 0 28 5. 7 8 121 1. 71 28 5. 5 9 1 4 9 7.67 28 5.4 7 1 7 7 5.95 23 4.7 9 2 0 5 0. 94 2 8 5. 8 9 2 4 6 0.18 42 5.8 12 0.39 0.12 0.56 0.06 <0. 10 4 0 . 02 4 0. 17 4 0. 05 4 0 . 05 0.24 0. 09 0. 50 Go 05 <0. 10 4 0. 02 4 0.17 4 0.05 4 G. 05 0.25 0. 1 0 0. 5 0 0. 05 4 0. 10 0. 06 4 0 . 3 0 0.14 0. 03 0.28 0.09 0.42 0. 0 5 <0. 10 4 0 . 0 2 < 0.27 0. 15 <• 0. 05 0. 26 Oo 11 Oo 34 0. 0 4 0.05 4 0 o 0 2 < 0 . 1 2 4 0 . 0 5 4 Oo 0 5 0.34 0. 1 3 0.24 0. 05 0. 10 4 0. 02 4.0.36 0.24 0. 07 0.33 0.10 0.43 0 o 0 7 < 0 . 0 5 4 0.02 4 0 . 1 2 4 0 . 05 4 0. 05 0. 90 0. 1 0 0. 5 3 0. 07 <0. 05 4" 0.02 4 0 . 1 2 4 0 . 05 0. 15 S I T E I : CONTROL (SHALLOW P L A T E B) AFTER VOLUME COLLECT ION PH C O N D U C T I V I T Y M I L L I G R A M S 1 PER L I T R = L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) -u.MHO/CM< 25°C) MA K CA MG NH4-N N03-N N-TOT. ORG N. P- TOT, 0 1.44 28 ' 6.0 17 0.91 0. 18 1. 03 0. 1 8 4 0 . 20 4 0 . 0 2 4 0 . 6 2 4 0 . 4 0 4 0 . 4 0 8 0. 65 8 5.6 15 0.55 0. 15 1.03 0. 16 4 0 . 10 4 0 . 02 4 0. 62 4 0. 50 4 0. 5 0 14 0. 10 6 5. 6 15 C.55 0 o l 6 1. 05 0. 14 4 0 . 10 4 0 . 0 2 4 0.62 4 Oo 50 4 0. 50 21 0.00 23 0. 00 42 1.05 14 5»6 14 0. 34 Oo 10 0.68 0. 1 0 4 0 . 10 4 O o02 4 0 o l 7 4 0 o 0 5 4 0.05 65 0. 26 23 5.6 I t 0.36 0. 12 1.03 0.09 4 0. 10 4 0. 02 4 0.17 4 0. 05 4 0. 05-9 3 2. 75 28 5. 7 10 C.28 0.10 0.63 0.07 4 0 . 1 0 0.03 4 0. 24 0. i l 4 0. 05 1 2 1 i . 4 9 28 5. 6 9 Oo 26 Oo 1 0 0.48 0. 05 4 0. 10 4 0.02 4 0.24 0.12 4 0.05 1 4 9 3. 17 28 5.3 10 0.38 0 . 1 2 0.32 0.07 4 0 . 0 5 4 0. 0 2 4 0. 12 4 0. 05 4 0 . 0 5 177 1.69 28 4. 7 26 0. 99 0 o 3 3 0.34 0. 11 0 . 1 5 4 0 o 0 2 4 0.49 0.32 0 . 0 5 2 0 5 0. 5S 23 5. 8 20 1.11 0.25 0. 78 0. 19 0. 07 4 0. 02 4 0.20 0.11 4 0 . 0 5 2 4 6 0. 10 21 0.0 16 1.42 0 . 2 5 1.15 0. 13 < 0. 05 4 0.02 4-0.12 4 0. 05 0. 1 4 O N C O Appendix D.5.2 Unfertilized Plots Leaching Data, Site I (Deep) S I T E I : C O N T R O L . (DEEP P L A T E A ) D A Y S A F T E R C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N P E R I O D ( D A Y S ) A M H D / C M ( 2 5 ° C ) 0 28 5. 9 17 8 8 6o 0 13 14 6 5.9 17 21 7 5. 9 16 28 2 5. 8 16 42 14 5.9 15 65 23 5. 8 14 93 28 5. 9 12 121 28 6. 0 10 1 4 9 28 5.6 11 1 7 7 23 5.0 12 2 0 5 23 5.6 14 2 4 6 42 5.6 15 M I L L I G R A M S PER L I T R E NA K CA MG N H 4 - N N 0 3 - N N - T O T . ORG N P - T O T . 0 . 3 4 0 . 2 3 0 . 3 5 0 . 15 4 0 . 1 0 4 0 . 0 2 ' 0 . 6 2 4 0 . 5 0 4 . 0 . 5 0 0 . 7 1 0 . 1 7 1 . 3 4 0 . 1 5 - 0 . 10 4 0 . 0 2 * 0 . 6 2 4 0 . 5 0 < 0 . 5 0 0 . 9 8 0 . 1 4 1 . 2 3 0 . 1 4 4 0 . 10 4 0 . 0 2 4 0 . 6 2 4 - 0 . 5 0 4 0 . 5 0 0 . 6 1 0 . 1 6 1 . 0 4 0 . 1 2 4. 0 . 10 4 0 . 0 2 4 0 . 6 2 4 0 . 5C 4 . 0 . 5 3 0 . 6 1 0 . 1 4 0 . 9 3 0 . 1 1 4 : 0 . 1 0 4. 0 . 0 2 4 0 . 6 2 4 . 0 . 5 C 4 0 . 5 0 0 . 5 7 0 . 1 3 0 . 3 7 0 . 10 4 . 0 . 10 4. 0 . 0 2 4. 0 . 1 7 4. 0 . 0 5 < 0 . 0 5 0 . 6 0 0 . 1 3 0 . 7 2 0 . 0 3 4 O 0 10 4. G . 0 2 4 0 . 1 7 4 0 - 0 5 4 0 . 0 5 0 . 4 8 0 . 1 2 0 . 77 0 . 0 7 4: 0 . 1 0 4 0 . 0 2 4 0 . 2 7 0 . 1 5 ' 4 . 0 . 0'5 0 . 4 9 0 . 1 2 0 . 5 3 0 . 0 7 4. 0 . 10 4- 0 . 0 2 4. 0 . 1 3 0 . 0 9 < 0 . 0 5 0 . 5 3 0 . 1 3 0 . 5 3 0 . 0 6 4. 0 . 0 5 4. 0 . 0 2 4 0 . 1 2 4 0 . 0 5 4 0 . 0 5 0 . 6 4 0 . 1 5 . 0 . 6 5 0 . OS 0 . OS 4. 0 . 0 2 4 0 . 1 8 0 . 0 8 4 0 . 0 5 0 . 7 7 0 . 1 9 0 . 7 3 0 . 0 9 4 . 0 . 0 5 ^ 0 . 0 2 4 0 . 1 2 4 0 . 0 5 4 0 . 0 5 0 . 8 1 , 0 . 1 9 0 . 85 0 . 10 4 :0.05 0 . 0 3 4: 0 . 3 5 0 . 2 7 0 . 10 S I T E I: CONTROL ( D E E P P L A T E B ) D A Y S A F T E R C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N P E R I O D ( D A Y S ) . - u M H O / C M l 2 5 ° C ) 0 2 8 5 . 9 18 8 8 6 . 0 1 9 1 4 6 5 . 9 18 21 7 5 . 8 15 28 2 5 . 3 17 4 2 1 4 5 . 3 16 6 5 2 3 5 . 3 . 1 5 9 3 2 8 5 . 8 1 2 1 2 1 2 8 6 . 0 11 1 4 9 2 3 5 . 6 12 1 7 7 2 3 5 . 0 12 2 0 5 2 3 5 . 6 1 4 2 4 6 4 2 5 . 6 1 6 M I L L I G R A M S PER L I T R E NA K CA MG N H 4 - N N 0 3 - N N - T O T . ORG N P - T O T 0. 7 3 0 . 1 7 1 . 06 0 . 1 7 4 0 . 20 0 . 0 3 4 0 . 6 3 4 0 . 4 0 4 0 . 4 0 0 . 6 7 0 . 1 8 1 . 3 7 0 . 15 4 0 . 10 4 0 . 0 2 4 0 . 6 2 4 0 . 5 0 4 0 . 5 0 0 . 6 2 0 . 1 6 1 . 3 2 0. 1 5 4 0 . 10 4 0 . 0 2 4 0 . 6 2 4 0 . 5 0 •'. 0 . 5 0 0 . 5 . 3 0 . 12 1 . 1 3 0 . 1 2 4 0 . 10 4 0 . 0 2 4 0 . 6 2 4 0 . 5 0 ^ 0 . 5 0 0 . 5 4 0 . 0 9 1 . 0 6 0 . 12 4 0 . 10 < 0 . 0 2 4 0 . 6 2 4 0 . 5 0 4 0 . 50 0 . 5 0 0 . 1 1 0 . 9 9 0 . 12 4 J . 10 4 0 . 0 2 4 0 . 1 7 4 0 . 0 5 0 . 1 5 0 . 5 4 0 . 1 2 0 . 3 3 0 . 0 9 4 0 . 10 4 0 . 0 2 4 0 . 17 < 0 . 0 5 0 . 1 5 0 . 4 3 0 . 0 9 0 . 7 7 0 . 0 3 4 : 0 . 1 0 4 0 . 0 2 4 - 0 . 2 7 0 . 1 5 4 0 . 0 5 0 . 4 9 0 . 1 1 0 . 6 3 0 . 0 7 4 0 . 1 0 < 0 . 0 2 4 0 . 2 4 0 . 1 1 ^ 0 . 0 5 0 . 5 2 0 . 1 2 0 . 6 1 0 . 0 7 4 . 0 . 0 5 4 0 . 0 2 4: 0 . 12 0 . 0 5 £ 0 . 0 5 0 . 5 8 0 . 1 1 0 . 7 2 0. 0 8 0 . 0 8 4 0 . 0 2 4 0 . 4 9 0 . 3 9 4 0 . 0 5 0 . 7 0 0 . 1 5 0 . 8 1 0 . 1 0 4 0 . - 0 5 ^ . 0 . 0 2 4 0 . 1 4 0 . 0 7 4 0 . 0 5 0 . 7 6 0 . 1 7 0 . 9 1 0. 1 1 < 0 . 0 5 . 0 . 0 2 ' 0 . 1 2 4 0 . 0 5 0 . 1 4 Appendix D.6.1 Unfertilized Plots Leaching Data, Site II (Shallow) S I T E I I : CONTROL ( S H A L L O W P L A T E A) DAYS A F - £ * VOLUME COLLECT ION PH C O N D U C T I V I T Y F E R T I L I Z A T I O N ( L I T R E S ) P ERIOD ( D A Y S ) -u.MH0/CM(25° C) NA 0 Oc 20 14 6. 9 75 7.55 9 0. 75 8 5.4 4 7 1.31 14 0. 00 2 i , 1.00 13 5. 3 4 5 0.92 23 0. 15 7 5.5 27 0.94 42 3. 40 14 5. 4 41 0.61 65 1.00 23 5.6 35 0.51 93 7. 20 20 5. 6 27 0 .40 121 2 . 0 9 28 5„ 7 23 0. 42 149 1. 22 28 5.4 25 0.50 177 1. 12 23 4. 9 29 0.67 2 0 5 0.10 28 5. 9 31 1.14 2 4 6 0. 00 M I L L I G R A M S PER L I T R E K CA MG NH4-N N03-N N-TOT. ORG K P-TOT. 2.31 2. 52 0.61 <0.20 <0.02 4 0 . 6 2 4 0 . 4 0 4 0 . 4 0 2 . 2 5 2.72 0 . 6 9 0. 12 4 0 . 0 2 4 0.64 -4 0. 5 0 4.0.50 2. 14 2. 54 0. 6 3 0. 12 < 0 . 0 2 4 0 . 6 4 ^ 0 . 5 0 4 0 . 5 0 2 . 0 3 2.22 0 . 6 0 0.12 4 0 . 0 2 4 0 . 6 4 4 0 . 5 0 4 0.50 2 . i 4 2.04 0.58 4 0 . 10 4 0.02 4 0.28 0 . 2 2 0.'06 1.82 2.23 0.53 4 0 . 1 0 0.02 4 0.28 0.22 0.06 1.51 1.45 0 . 3 6 4 0 . 10 4 0 . 0 2 4 0.32 0. 0 6 4 o„ 05 1.41 1.16 0 . 3 0 4 0 . 10 0.02 4 0 . 3 0 0 . 2 3 4 0 . 0 3 1.50 1. 13 0 . 3 3 4 0 . 05 4 0. 02 < 0. 13 0.06 4 0.05 i . 5 8 1.38 0 . 3 3 0.08 4 0 . 0 2 4 0.32 0. 22 4 0. 05 1.57 1.42 0 . 4 1 4 Q . 0 5 0.02 4 0 . 5 3 0.46 4 0 . 0 5 S U E I I : CONTROL (SHALLOW P L A T E 3) ^ ; ! T , A ^ = R VOLUM- C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PER L TT R F Fz*. i I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) ^MHO/CM (? ^  r) M A * r , Lr « , , , , , 0 1.36 3 23 0.35 42 3. 55 65 1.10 S3. 6.25 3. 01 .ECTI  CD ( D A Y S ) .".MHO/CM (25° C) NA K CA 23 5o 7 29 1.39 1.05 1.16 3 5. 1 25 0.59 1. i 4 1. 4 0 13 5.2 27 0. 43 1. 12 I . 32 7 5.4 29 0.74 1.10 1.31 14 5.4 25 0.34 1.07 1.22 23 5.6 24 0.31 Oo 91 1.40 23 5.6 19 0 .23 0.76 1. 08 23 5.4 20 0.32 0. 77 Oo 96 23 5.2 18 0.42 0. 81 0. 90 23 4. 9 22 0.54 , 0.89 0.93 28 5.0 34 0. 76 ' 0. 93 Oo 97 42 5.5 23 0.90 0.87 1. 15 MG NH4-N N0 3-N N-TOT. ORG N P- "01 i o . u 3o / 2 9 39 05 16 0„43 4 0 o 10 4 0 o 0 2 < 0 „ 6 2 -' 0. 5 0 4 0.50 1. 75 3 5. 1 25 59 0. 52 4 0 . 10 <0.02 ^ 0 . 6 2 4 0 . 5 0 4 0.50 14 0 . 0 0 21 ' 1. 75 13 5„2 ? 7 n L-i I i o i i-> 0. 53 4 0. 10 4 0.02 ' 0.62 4 0 . 5 0 < 0 . 5 0 0. 53 4 0. 10 ^ 0.02 4 0.62 4 0. 5 0 4 0. 50 0.50 4 0. 10 4 0.02 4 0. 28 0. 16 0. 0 7 0. 4 6 4 0. 10 4 0.02 4 0.28 0. 16 0.07 0. 31 4 0. 10 4 0. 02 4 0. 32 0. 2 0 4 Oo 05 1*9 2 21 ?~ = , f - ° ° 7 7 ° ° 9 6 0 o 2 3 < J ° 1 0 4 ° ° 0 2 ^ ° ° 3 0 0.18 4 0.05 20 5 0 6 5 11 t n 2 2 °'89 ° - 9 3 ° ° 3 1 ° - 0 5 < 0 ° 0 2 3.30 0. 23 4 0 . 0 5 Id °0'°2t H 5°° 3 4 ° ° 7 6 0.93 0. 97 0.34 4 0.05 0.02 0.16 0.09 <0mQ5 °* 2 4 4 2 5 " 3 " n c " " 1 , c 0. 3 3 4 0.05 4 0.02 < 0. 12 4 0 . 0 5 4 0.05 C N Appendix 0.6.2 Unferri lized Plofs Leaching Dafa, Site II (Deep) / S I T E I I : CONTROL (DEEP P L A T E A) DAYS AFTER COLLECT I ON PH CONDUCT I V I T Y M I L L I G R A M S PER L I T R F E R T I L I Z A T I O N PERIOD ( D A Y S ) AtMHO/CM(25°C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 0 28 5o 8 24 2.28 0. 4 3 0. 83 0. 2 6 4 0 . 2 0 4 0 . 0 2 0.62 4 0 . 4 0 4 0 . 4 0 8 3 5.8 36 2.09 0.35 0. 69 0. 20 4 0 . 10 4 0 . 02 4 0.62 4 0 . 50 4 0. 50 14 6 5, 7 31 4.14 0.37 0.57 0.14 4 0. 10 4 0 . 0 2 4 0.62 4 0.50 4 0. 50 21 7 5. 6 29 3.78 0.36 C. 52 0. 14 4 0. 10 4 0. 02 4 0.62 4 0.50 4 0.50 23 7 5.8 32 4.24 0 . 3 5 0.47 0.14 4 0. 10 4 0.02 4. 0. 62 4 0. 5C 4 0. 50 42 14 5. 7 23 3.17 0.33 0.66 0 . 2 1 4 0. 10 4 0.02 4 0.27 0. 15 4 0. 0.5 65 23 5.7 25 2.72 0. 27 0.49 0. 16 4 0. 10 4 0. 02 4" 0.27 0.15 4 0. 05 93 23 5. 8 21 2.07 0 . 2 5 0.71 0 . 1 9 4 0. 10 4 0.02 4 0,31 0. 19 4 0, 05 1 2 1 28 5.9 21 2.03 0. 2 6 0.63 0.23 * 0. 10 4 0.02 ^ 0 . 1 6 4 0.04 C 0.05 1 4 9 28 5.6 22 1.56 0.27 0.69 0.27 4 0 . 05 4 0. 02 4 0. 12 4 0 . 0 5 4 0.05 1 7 7 23 5. 2 23 1.68 0.28 0.91 0 . 3 3 0.07 41 0.02 4 0.24 0.15 < 0.0 5 2 0 5 28 5.5 2 5 1.69 0.28 1. 09 0. 3 9 4 0 . 05 0.02 < 0 . 1 2 4 0 . 0 5 4 0.05 2 4 6 42 5.6 23 2.12 0.30 0.83 0 . 2 9 4 0 . 05 4 0. 02 4 0 . 12 4 0,05 4. 0.05 S I T E I I : CONTROL ( D E E P P L A T E B) DAYS AFTER C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PER L I T R E F E R T I L I Z A T I O N PERIOD ( D A Y S ) /UMHO/CM(25° C) NA K CA MG NH4-N NG3-N N-TOT. ORG N P-TC'T. 0 23 5. 6 20 1.55 0. 33 0. 73 0. 24 <0. 10 0.03 4 0 . 6 3 4 0 . 5 0 4 0 , 50 8 8 5.8 36 5.50 0.40 0. 64 0 . 2 0 4 0,10 4 0.02 4 0 . 6 2 4 0.50 4 0.50 14 6 5. 5 18 0.95 0.26 0.83 0 . 2 0 <0„ 10 C 0.02 4 0.62 4 0. 5 0 4 0, 5 0 21 7 5. 6 29 0. 89 0. 23 0. 76 0.20 <0. 10 4 0.02 4 0.62 4 0 . 5 0 4 0 . 5 0 28 7 5. 5 17 0.90 0.18 0.63 0. 19 £0. 10 0. 02 4 0.62 4 0. 5C 4 0.50 42 14 5. 4 17 0.94 0.20 0.63 0 . 2 2 <0. 10 4 0.02 4 0 . 1 7 4 0 . 0 5 0. 10 65 23 5.0 21 1.12 0.16 0.59 0. 18 4 0 . 10 4 0.02 < 0.17 4 0.05 0.10 93 28 5.7 L4 1.15 0.18 0.70 0.19 4.0. 10 4 0 . 02 4 0. 32 0. 22 4 0. 05 1 2 1 23 5. 7 15 1.04 0. 16 0. 56 0. 20 4 0 . 1 0 4.0.02 4 0.36 0.24 4 0. 05 1 4 9 23 5.4 16 1.17 0.13 0. 57 0. 22 4.0. 05 4^0.02 4 0.12 4 0 . 0 5 4 0.05 177 26 5. 0 19 1.57 0. 19 0. 68 0.24 0 . 0 6 ^•0.02 4 1.35 1. 27 £0.05 2 0 5 28 5.4 21 1.96 '0.23 0. 72 0. 27 4 0 . 05 4 0.02 4 0.12 4 0 . 0 5 4 0.0.5 2 4 6 42 5.5 20 1.96 0.23 0.66 0.24 *-0. 05 £-0. 02 £ 0.12 1.45 0.30 Appendix D.7.1 Unfertilized Plots Leaching Data, Site III (Shallow) S I T E I I I : CONTROL (SHALLOW P L A T E A) DAYS AFTER VOLUME COLLECT ION PH C O N D U C T I V I T Y M I L L I G R A M S PEP. L I T R •z F E R T I L I Z AT I ON ( L I T R E S ) P E R I O D ( D A Y S ) -u-MHO/CMl 25° C) NA K CA MG NH4-N N0 3-N N-TOT. ORG N P-TOT 0 1 1 . 2 1 21 5.4 35 1.00 1.36 1.44 0 . 4 0 4 0 . 20 4 0 . 0 2 4 0 . 62 <0„4C ' 4 0 . 4 0 3 3.30 8 5. 5 2 3 0. 70 0. 75 1. 31 0. 3 0 4 0 . 10 0.04 4 0.64 4 0 . 5 0 ~ 0.50 14 5.35 6 5.4 2 0 0.57 0.65 1. 16 0 . 2 6 4 0 . 10 0. 04 4 0 . 64 4 0. 5 0 4 0. 50 21 5. 80 7 5. 5 17 0.46 0.56 1.07 0.21 4 0 . 10 Oo 04 4 0 . 64 4 0 . 5 0 4 0 . 50 23 1.30 2 5.4 20 0.50 0.60 1. 13 0. 27 40. 1 0 0. 04 4 0 . 6 4 4 0. 50 4 0 . 5 0 42 9. 55 14 5.6 17 0 .36 0.56 1.02 0. 22 4 0 . 10 4 0 . 02 4 0 . 1 7 4 0. 0 5 0. 10 65 - 5.35 23 5.4 21 0.37 Oo 5 9 1. 33 . C. 2 6 4 0 . 10 4 0 . 0 2 4 0 . 1 7 4 Oo 05 Oo 10 93 1 9 . 6 5 28 5.5 14 0.25 0.39 1. 01 0. 18 •;o. i o 0. 06 4 0 . 4 1 0.3 5 0.07 1 2 1 1 3 . 40 2 8 5. 6 15 0.31 0.39 1.00 0 . 2 1 4 0 . 1 0 4 0 . 0 2 4 0 . 4 6 0. 3 4 4 0. 05 1 4 9 1 7 . 9 0 28 5.3 16 0.32 0„32 0. 93 0. 23 4 0 . 05 4 0 . 0 2 4 0 . 2 0 0 . 1 3 <O.05 177 5.36 28 5.0 25 0.54 0.67 1.50 0.36 0. 10 0. 33 0. 68 0 . 2 5 <0,05 2 0 5 4. 42 23 5.3 31 0.53 0.81 1.37 0 . 4 1 4 0 . 0 5 0.93 4 1 . 2 8 0. 30 ^ o . o s 2 4 6 2 . 6 0 28 5.3 25 0.54 0. 67 1.47 0. 31 4 0 . 05 0. 08 4.0.43 0.30 0.15 SI TE I I I : CONTROL (SHALLOW P L A T E B) AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S i PER L I T R ' I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) -u.MH0/CM(25°C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 0 11. 30 28 5.4 25 0.43 0.95 1.11 0 . 5 7 40. 10 4 0 . 0 2 ^ 0 . 6 2 4 0 . 50 40. 50 8 4. 75 8 5o4 14 Oo 46 Oo 48 0, 75 0. 2 8 4 0 . 10 4 0 . 0 2 4 0.62 4 0.50 40. 50 l t 2 . 4 5 6 5.4 15 0. 36 0.47 0 . 82 0 . 3 0 4 0 . 10 4 0.02 4 0. 62 .40. 50 40. 50 21 3. 3 0 7 - i . 5 14 0.31 0.36 0.71 0.23 . 4 0 , 1 0 4 0.02 4 0.62 40. 5 0 4 0 . 50 28 0.00 42 7. 30 14 5.7 14 0.28 0.36 0.71 0.23 4 0. 10 4 0. 02 4 0. 17 4 0.05 4 0.05 65 3. 50 23 5.2 1 4 0.27 0.37 0.69 0. 2 6 4 0.10 4 0 . 0 2 4 0.17 4 0 . 0 5 4 0. 0 5 93 1 5 . 00 23 5. 7 11 0.29 0.27 1. 08 0. 26 4 0 . 10 4 0 . 02 4 0.43 0.36 4 0 . 0 5 1 2 1 1 2 . 4 8 2 8 5. 7 14 0.31 0.27 0.74 0 . 3 0 4 0 . 10 4 0 . 0 2 4 0 . 3 5 0. 23 4 0 . 05 1 4 9 1 0 . 70 28 5.3 15 0.33 Oo 30 Oo 6 0 Oo 3 6 4 0 . 05 0.02 4 0„15 0.C8 4 0.05 1 7 7 7.38 28 4.9 23 U.60 0.47 0. 87 0 . 5 0 0. 05 4 0. 02 4 0 . 51 0.41 4 0.05 2 0 5 7. 46 28 5.6 24 Oo 74 0.92 0.67 0 . 6 5 4.0.05 0.02 4 0 . 6 2 0. 55 4 0 . 05 2 4 6 3. 15 28 5.5 32 0. 74 1. 08 1. 14 0.66 4 0 . 0 5 4 0 . 0 2 4 0 . 5 2 0.45 4 0 . 15 Cs Appendix D.7.2 Unfertilized Plots Leaching Data, Site III (Deep) S I T E I I I : CONTROL ( D E E P P L A T E A) DAYS AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y F E R i I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) M.HHO/ CM (25° C) 0 2o 53 21 5. S 28 8 2« 20 3 5.7 26 14 l o 65 6 5 . 6 27 21 2. 35 7 5 . 6 28 28 0.70 2 5.5 29 42 3. 70 14 5. 7 2 6 65 3„55 23 5.7 24 93 1 1 . 65 28 5 . 6 19 121 7.25 26 5. 6 18 1 4 9 6 0 6 8 23 5.3 17 1 7 7 3. 96 ,23 4. 9 19 2 0 5 4. 80 23 5.3 24 2 4 6 2.52 42 5.4 20 M I L L I G R A M S PER L I T R E NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 3.24 0.23 Oo 77 0.37 < 0 o 2 0 4 0 . 0 2 4 0 . 6 2 4 0 . 4 0 4 0 . 4 0 2.70 0.20 0. 74 0. 25 < 0. 10 <0.02 4 0.62 4 0.50 4 0.50 2.67 0.22 0.69 0 . 2 5 4 0. 10 < 0.02 4 0. 62 < 0. 5 0 4 0. 50 2. 58 0„ 19 Oo 67 0. 25 c 0. 1 0 < 0.02 4 0,62 4 0.50 4 0.50 2.56 0. 17 0. 65 0. 2 5 4 0. 1 0 4 0. 02 4 0.62 4 0. 50 . 4 0.50 2.16 0.17 0„59 0 . 2 5 4 Oo 10 4 0„02 4 0 . 1 7 4 0. 0 5 • 0. 05 1.92 0. 15 0„ 56 0.22 4.0. 1 0 4 0 . 0 2 4 0.17 £ 0.05 0.05 1.37 0. 13 0.62 0.2 1 4. 0. 10 4 0. 02 C 0. 42 0. 30 4 0. 05 1.25 0.13 • 0.52 0. 22 0.17 4 . 0 . 0 2 4 0.34 0. 17 4 Oo 05 1.16 0. 14 0. 52 0. 2 3 4 0. 05 4 0.02 4^0.12 4 0.05 4 0. 05 1.24 0.14 0.64 0.27 0. 13 0 o 0 3 0 . 2 7 0. 11 4 0. 05 1. 39 0. 17 Oo 70 0.3 0 4 0.05 ' 0.02 4 - 0 . 1 5 0.03 4. 0.05 1.32 0 . 1 5 0 . 71 0. 2 9 4 0 . 05 4 0. 02 4 0 . 1 2 < 0 . 0 5 0.10 S I T E I I I : CONTROL ( D E E P P L A T E B) D A Y S A F T E R VOLUMh C O L L E C T I O N P H C O N D U C T I V I T Y M I L L I G R A M S P E R L I T R •z F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) M M H G / C M ( 2 5 ° C ) N A K C A MG N H 4 - N N03-N N - T O T . O R G N P - T O T 0 C.40 - 21 6. 3 36 3.57 0.29 0.95 0 . 6 9 < Oo 10 4 0 . 0 2 < 0 . 62 4 0 o 5 0 4 0 . 50 8 0.25 8 6. 1 2 9 1.46 0. 19 1.55 0. 51 4 0. 10 4 0 . 0 2 4 0.62 4 0 . 5 C 4 0 . 5 0 14 0. 00 21 0„4C 13 6. 1 3 0 1.68 Oo 20 1.25 0 . 4 0 £ 0. 10 4 0 . 0 2 < 0.62 4 0.50 £ 0 . 5 0 28 OoOO ' 42 0. 55 14 6.1 32 3 . i l 0 . 22 0,32 0 . 2 6 4 0. 1 0 4 0.02 4 0.17 4 Oo 05 4 0 . 0 5 65 0. 75 23 6. 2 34 3.23 ,0. 22 Oo 72 0.21 4 0. 10 4 Oo02 4 0 „ 17 4 0 . 0 5 4 0 . 0 5 93 2. 15 28 5.9 30 3.10 0.17 0. 63 0. 19 < 0. 10 4 0 . 02 4 0 . 33 0 . 2 6 4 0 . 0 5 121 1. 27 2 3 5. 3 24 2.50 0.19 0. 54 0.21 4 0.10 4^  0 o 0 2 4. Oo 23 0. 1 1 4 0 . 05 1 4 9 1. 32 2 8 5. 8 22 2. 31 0. 19 0.47 0. 21 4 0. 05 4 0 . 0 2 4 0 . 1 2 0.05 4 0 . 0 5 1 7 7 0. 72 23 5.0 32 2.61 0.27 0.22 0 . 2 3 4 0 . 11 4 0 . 02 < 0 . 44 0.31 0 . 06 2 0 5 0. 34 23 5. 1 32 2.67 0.29 0.33 0, 26 4 0 . 0 5 4 0 . 0 2 4 0 . 2 5 0. I S 4 0 . 0 5 2 4 6 0.40 4 2 5. i 25 2.45 0. 18 0. 63 0. 3 0 ^•0.05 4. 0. 02 £ 0.12 4 0 . 0 5 0 . 1 0 co Appendix D.8.1 Unfertilized Plots Leaching Data, Site IV (Shallow) S I T E I V : C O N T R O L ( S H A L L O W P L A T E A ) O A Y S A F T E R V O L U M E C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PER L I T R p F c R T I L I Z A l ION ( L I T R E S ) P E R I O D ( D A Y S ) ^ M H O / C M ! 25° C ) NA K CA MG N H 4 - N , N 0 3 - N ~ N - T 0 T . ,,,,-r n- ••_>:. ORG N P - T O T . 0 3 . 3 6 2 8 5 . 1 3 3 0 . 7 2 1 . 4 7 2 . 10 0 . 5 6 4 0 . 1 0 4 0 . 0 2 • " - O o 6 2 4 0 , 5 0 4 0 . 5 0 3 0 . 5 5 3 5 . 0 3 1 0 . . 6 4 0 . 9 7 1 . 5 6 0 . 5 2 < 0 . 1 0 4 0 . 0 2 ^ o „ 6 2 4 0 . 5 0 < 0 . 5 0 1 4 0 . 2 7 6 5 . 2 3 8 0 „ 7 4 0 . 6 7 2 . 3 6 0 . 5 6 4 0 . 1 0 4 0 . 0 2 4 0 . 6 2 4 0 . 5 0 4 Q . 5 0 2 1 0 . 6 0 7 5 . 1 2 1 0 . 3 9 0 . 6 0 1 . 0 4 0 . 2 9 4 0 . 1 0 4 0 . 0 2 4 0 . 6 2 4 0 , 5 0 . <0. 5 3 2 3 0 . 9 5 7 5 . 1 2 3 0 „ 4 0 0 . 5 4 1 . 1 3 0 . 3 0 4 0 . 1 0 4 0 . 0 2 4 0 . 6 2 4 0 . 5 0 4 0 . 5 0 4 2 1 . 6 0 1 4 5 . 3 2 0 0 „ 3 5 0 . 5 3 0 . 9 8 0 . 2 6 4 0 . 1 0 4 0 . 0 2 4 0 . 1 7 4 0 . 0 5 0 . 0 9 6 5 1 . 5 7 2 3 4 . 4 3 1 0 . 3 7 0 . 5 2 1 . 1 3 0 . 2 5 4 0 . 1 0 4 0 . 0 2 4 0 . 1 7 4 0 . 0 5 0 . 0 9 9 3 1 0 . 1 3 2 3 5 . 5 1 7 0 , 3 2 0 . 3 2 • 1 . 0 3 0 . 2 1 0 . 1 0 4 0 . 0 2 < 0 . 2 2 0 . 1 1 4 0 . 0 5 1 2 1 5 . 7 3 2 8 5 . 2 18 0 . 4 7 0 . 4 9 1 . 4 4 0 . 3 1 0 . 16 4 0 . 0 2 - ' 0 . 5 7 0 . 3 9 0 . 0 5 1 4 9 6 . 3 5 2 8 5 . 0 1 8 0 . 3 6 0 . 3 3 1 . 0 0 0 . 2 4 4 0 . 0 5 4 0 . 0 2 < 0 . 2 0 0 . 1 3 0 . 0 6 1 7 7 5 . 3 3 2 8 4 . 5 2 3 0 , 5 0 0 . 2 6 0 . 9 7 0 . 3 1 0 . 1 2 4 0 . 0 2 - 0 . 5 4 0 . 4 0 0 . 0 3 2 0 5 3 . 2 0 2 8 5 . 0 2 6 0 . 6 5 0 . 2 4 1 . 19 0 . 3 9 0 . 0 3 4 0 . 0 2 ' - 0 . 5 2 0 . 4 2 4 0 . 0 5 2 4 6 4 . 9 1 4 2 5 . 1 3 0 0., 7 2 0 . 4 4 1 . 4 0 0 . 4 4 0 . 1 0 4 0 . 0 2 4 0 . 4 2 0 . 3 0 0 . 0 5 S I T E I V : CONTROL ( S H A L L O W P L A T E B) D A Y S A F T E R V O L U M E C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S P E R L I T R ! F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) 0 2 . 6 5 2 8 8 0 . 0 0 1 4 1 . 0 0 1 4 21 0 . 0 0 2 3 0 . 4 5 1 4 4 2 1 . 0 5 1 4 6 5 1 . 3 0 2 3 9 3 5 . 3 5 2 3 1 2 1 5 . 4 2 2 8 1 4 9 2 . 7 1 2 8 1 7 7 5 . 0 9 28 2 0 5 1 . 2 4 2 8 2 4 6 1 . 9 7 4 2 M M H O / C M ( 2 5 ° C ) f\A K CA MG N H 4 - N N 0 3 - N N - T O T . O R G N P - T O T 4 . 4 3 9 0 . 7 1 1 . 4 4 2 . 3 1 0 . 5 6 4 0 . 2 0 4 0 . 0 2 4 0 . 6 2 4 0 . 4 0 4 0 . 4 0 4 . 5 2 4 0 . 4 8 1 . 1 4 1 . 3 2 0 . 3 6 0 . 13 4 0 . 0 2 4 2 . 5 2 2 . 3 7 4 0 . 5 0 4 . 5 3 0 0 . 7 7 1 . 1 5 1 . 2 4 0 . 3 4 0 . 1 3 4 0 . 0 2 4 2 . 5 2 2 . 3 7 4 0 . 5 0 4 . 5 29 0 . 4 9 0 . 9 4 1 . 4 3 0 . 3 7 4 0 . 1 0 4 0 . 0 2 4 0 . 1 9 4 0 . 0 5 0 . 1 3 4 . 4 2 7 0 . 3 8 0 . 6 6 0 . 9 6 0 . 2 4 4 0 . 1 0 4 0 . 0 2 4 0 . 1 9 4 0 . 0 5 0 . 1 3 4 . 7 2 5 0 . 3 3 0 . 4 8 1 . 2 0 0 , 2 6 0 . 11 4 0 . 0 2 4 0 . 3 0 0 . 1 9 4 0 . 0 5 4 . 5 3 2 0 . 4 4 0 . 4 7 1 . 5 3 0 , 3 4 0 . 1 5 4 0 . 0 2 4 0 . 5 4 . 0 . 3 7 4 0 . 0 5 4 . 2 2 9 0 . 3 3 0 . 5 5 1 . 7 4 0 . 3 3 0 . 1 0 4 0 . 0 2 4 0 . 2 S 0 . 1 6 4 0 . 0 5 3 . 8 3 8 0 . 4 3 0 . 4 3. 2 . 7 6 0 . 5 3 0 . 3 1 4 0 . 0 2 4 0 . 7 0 0 . 3 7 0 . 0 7 4 . 4 4 3 0 . 6 3 0 . 4 6 3 . 0 9 0 . 7 4 0 . 2 8 < 0 . 0 2 <0. 82 0 . 52 ' 0 . 0 5 4 . 2 4 6 0 . 8 3 0 . 2 8 3 . 3 3 0 . 7 4 0 . 2 0 < 0 . 0 2 < 0 . 7 7 0 . 5 5 4 0 . 0 5 C N Appendix D.8.2 Unfertilized Plots Leaching Data, Site IV (Deep) S I T E I V : CONTROL ( D E E P P L A T E A) DAYS AFTER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N ( L I T R E S ) P E R I O D ( D A Y S ) M M H 0 / C M ( 2 5 ° C) 0 3. 92 23 6. 1 27 3 1. 55 8 5. 9 22 14 1. 60 6 5.8 21 21 l c 40 7 5. 7 20 28 1.98 7 5. 8 20 42 2. 22 14 6. 0 19 65 8. 70 2 3 5. 8 15 93 1 2 . 4 0 23 5.6 14 121 6. 82 28 5. 8 14 1 4 9 7, 60 28 5.5 14 1 7 7 4.60 28 5.0 14 2 0 5 2. 28 28 5.4 18 2 4 6 4. 13 42 5.4 18 S I T E I V : CONTROL (DE EP PLATE B) DAYS A F~ ER VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y F E R T I L I Z A T I O N ( L I T R E S ) PERIOD ( D A Y S ) ^MHO/CM ( 25° C) 0 1 7 . 56 28 6. 1 24 8 6. 12 8 5. 8 20 14 5. 95 6 5.9 23 21 4. 55 7 5. 8 19 23 6. 93 7 5. 8 20 4 2 1 0 . 3 5 14 6.0 20 65 1 1 . 30 23 6. 0 21 93 4 4 . 00 23 5. 9 16 1 2 1 2 4 . 96 23 5. 9 14 1 4 9 2 5 . 50 28 5. 6 14 1 7 7 1 2 . 3 3 28 5.0 15 2 0 5 6. 59 28 5.7 14 2 4 6 1 4 . 7 5 42 5.4 16 M I L L I G R A M S PER L I T R E NA K CA MG NH4-N N02-N N-TOT. ORG N P-TOT, 3.20 0.57 0.65 0.23 4 0 . 1 0 0.37 4 0.97 4 0„ 50 4 0. 50 1. 99 Oo 41 0. 77 0.2 6 4 0. 10 0.03 4 0.63 4 0.50 4 0 . 5 0 1.62 0.34 0. 73 0. 25 4 0. 10 0. 03 4 0. 63 4 0. 5 0 4 0.50 1 . 3 9 0.32 0. 70 0.26 4 0. 10 0.03 4 0. 63 4 0. 5 0 4 0. 50 1.31 0.27 0.65 0. 2 7 4 0. 10 0.0 3 4 0.63 4 0 . 5 0 4 0.50 1.21 0.26 0. 63 0.28 4 0. 10 4 0. 02 4 0. 17 4 0. 05 0. 07 0 . 8 9 0.22 0.55 Oo 2 6 4 0 . 1 0 4 Oo02 4 0.17 4 0.05 0. 07 0 . 7 3 0. 19 0. 64 0. 24 4 0 . 1 0 4 0. 02 4 0.25 0.13 4 0 . 0 5 0.77 0.21' 0.51 0 . 2 3 4 0 . 10 4 0. 0 2 4 0. 34 0. 22 0. 10 0. 80 Oo 22 0.49 0.21 4 0. 05 4 0.02 4 0.12 4 0.05 4 0 . 0 5 0 . 9 4 0.26 0.58 0.2 2 4 0. 12 4 0. 0 2 4 0.39 0.25 4 0.05 I . 1 1 0.26 0.62 0 . 2 5 4 0 . 0 5 4 0.02 4 0.12 4 0. 0 5 < Oc 05 1. 26 0.2 7 0. 5 9 0.2 3 4.0. 05 4 0.02 < 0.12 4 0 . 0 5 4 0.05 M I L L I GRAMS PER L I T R NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 2.10 0.20 0.50 0.21 4 0. 20 0. 13 4 0 . 7 3 4 0.4 0 4 0 . 4 0 2.04 0. 16 0.59 0 o 2 3 4 0 . 1 0 4 0 . 0 2 < 0.62 4 0.50 4 0 . 50 2. 2 0 0. 17 0. 61 0. 21 4 0. 10 4 0 . 0 2 4 0.62 4 0.50 4 0.50 i . 7 3 Oo 15 0. 44 0.20 4 0. 10 4 0 o 0 2 4 0.62 4 Oo 50 4 . 0 . 50 1.98 Oo 13 0.42 0.2 0 4 Oo 10 4 0 . 0 2 4 Oo 62 4 0.50 4 0. 50 2.10 0. 15 0.41 0.2 1 4 0. 10 4 Oo 02 4 0. 21 0. 0 9 4 0.05 2.13 0.12 0.40 0.20 4 0. 10 4 0 o 0 2 4 Oo 21 Oo 09 0, 05 ?.. 53 0. 11 0.33 0. 1 9 4 0. i O 4 0.02 4 0.23 0.16 0.03 1.35 0.11 0.31 0.20 4 0. 10 4 0. 02 4 0.28 0. 16 * 0. 05 1.32 0.13 0.30 0.19 4 0 . 0 5 4 0 . 0 2 4 0.12 < 0.05 4 0. 05 1 . 5 0 0. 13 0. 39 0. 21 4 0.'05 4 0.02 4 0.45 0.38 4 0 . 0 5 1.30 0.12 0.40 0. 26 4 0.05 <-0„02 4 0.24 0.17 4 0. 05 1. 38 0. 13 0.41 0.26 4.0.05 4 0 . 0 2 4 0 . 1 2 4 0.05 4 0 . 0 5 \1 o 171 Appendix E: Summary of Regression Analyses of Data Presented in Appendix D. SIGNIFICANCE OF THE VARIANCE RATIOS (F VALUES): N.S = NON-SIGNIF ICANT *= SIGNIFICANT AT 5% LEVEL; ** = SIGNIFICANT AT 2 . 5 % LEVEL; *** = SIGNI -FICANT AT 1% LEVEL; **** = SIGNIFICANT AT 0 . 5 % LEVEL DEPENDENT VARIABLE = P H ; INDEPENDENT VARIABLE = MA ( U R E A - F E R T I L I Z E D PLOTS) SURFACE PLATES DEEP PLATES H S I T E 1 S ITF 2 S I T F 3 S I T E 4 S ITE 1 S ITF 2 SITE 3 SITE 4 NO.OF OBSFRV .A 12 13 13 13 1 3 13 13 13 B 13 13 13 13 13 13 13 13 13 R SQUARED A 1 5 . 9 2 2 4 . 80 6 9 . 5 6 6 2 . 9 4 1 1 . 3 9 I. 14 3 0 . 58 6 0 . 63 B 1 5 . 5 2 A L I O 5 5 . 16 2 3 . 70 6 7 . 4 2 7 . 76 2 0 . 79 . ' i 9 . L ' 0 F VALUE A 1 . 8 9 3 . 6 3 2 5 . 14 1 0 . 6 8 1 . 4 1 0 . 13 4 . 05 1 6 . 94 B 2 . 0 2 7 . 6 3 1 3 . 5? 3 . 4 2 2 2 . 7 7 0 . 9 3 4 . 4 5 2 4 . 2 5 S I G N I F I C A N C E 4 N.S N.S **** N. S N. S it A A* B N.S ** **** N.S N.S N.S DEPENDENT VARIABLE = P H ; INDEPENDENT V A R I A B L E = NA (CONTROL PLOTS) SURFACE PLATES DEEP PLATES # SITE 1 S I T E 2 SITE 3 S ITE 4 S ITE 1 S I T E 2 S I T E 3 S I T E 4 NO.OF OBSFRV.A 11 11 13 13 13 13 13 13 B 11 12 12 11 13 13 11 13 P SQUARED A 7 . 9 2 3 . 42 4 . 5 6 0 . 0 0 0 . 24 8 . 16 4 1 . 1 6 2 9 . 06 B 1 . 1 4 7 3 . 2 2 3 . 4 2 1. 64 0 . 0 9 1 1 . 4 6 1 . 6 1 3 1 . 68 F VALUE A 0 . 7 7 0 . 3 5 0 . 5 3 0 . 0 0 0 . 0 3 1 . 0 0 7 . 7 0 4 . 68 B 0 . 1 0 2 4 . 60 0 . 3 5 0 . 15 0 . 01 1 . 4 2 0 . 1 5 5 , 10 S I G N I F I C A N C E A N.S N.S No S N . S N . S N . S ** N . S B N.S N. S N.S N.S N.S N.S DEPENDENT VARIABLE = P H ; INDEPENDENT V A R I A B L E = K ( U R E A - F E R T I L I Z E . D PLOTS) SURFACE PLATES DEEP PLATES # S I T E 1 S I T E 2 S I T E 3 S I T E 4 S I T E 1 S I T F . 2 S I T E 3 S I T E 4 N O . O F O B S E R V . A 12 13 13 13 13 13 13 13 B 13 13 13 13 13 13 13 13 R S Q U A R E D A 5 6 . 17 9 . 52 6 . 3 0 5 1 . 53 5 1 . 6 2 4 . 1 9 1 7 . 5 5 4 0 . 9 9 B 3 6 . 34 1 3 . 31 1 4 . 03 2 . 00 7 7. , 1 2 . 60 6 . OB 2 0 . 5 9 F V A L U E A 1 2 . 02 1 . 1 6 0 . 7 4 1 1 . 7 0 1 1 . 7 4 0 . 4 0 2 . 3 4 1 0 . 56 B 6 . 2 8 1 . 69 1 . 92 0 . 32 3 8 . 3 5 0 . 3 0 0 . 7 1 2 . 0 5 S I G N I F I C A N C E 4 N . S N . S ** *t *** N . S N . S t: * * B * N . S N . S N . S **** N . S N . S N . S D E P C N O E M T V A R I A B L E = P H ; I N D E P E N D E N T V A R I A B L E = K ( C O N T R O L P L O T S ) S U R F A C E 1 PL AT E S D F E P P L A T E S H S I T E 1 S I T E 2 S I T E 3 S I T E 4 S I T E 1 S I T E 2 S I T E 3 S I T E 4 N O . O F O P S E R V . A 11 11 13 13 13 13 13 13 B 11 12 12 11 13 13 11 13 R S Q U A R E D A 2 . 07 fl. 10 3 . 2 1 1 . 2 1 4 . 06 5 . 4 4 2 2 . 3 7 2 3 . 5 2 B 2 6 . 1 0 1 . 5 2 0 . 00 9 . 9 5 0 . 7 2 2 2 . 9 5 4 . 77 9 . 8 2 F V A L U E A 0 . 2 7 0 . 0 0 0 . 3 6 0 . 1 4 0 . 4 7 0 . 63 3 . 1 7 3 . 38 B 3 . 1 8 0 . 15 0 . 00 1 . 0 0 0 . 00 3 . 2 7 0 . 4 5 • 1 . 2 0 S I G N I F I C A N C E A N . S N . S N . S N . S N . S N . S N . S N . S B N . S N . S N . S N . S N . S N . S N . S N . S Appendix E (continued) 172 DEPENDENT V A R I A B L E = PH; INDEPENDENT V A R I A B L E = N 0 3 - N ( U R E A - F E R T I L IZ ED P L O T S ) S U R F A C E P L A T E S 1 S I T E 2 S I T E 3 If SI TE NO.OF CBSERV.A 12 . 13 B 13 13 R SQUARED A 8 5 . 9 4 7 9 . 4 3 B 6 5 . 3 8 3 4 . 9 1 F VALUE A 6 1 . 1 0 4 2 . 4 7 B 2 1. 24 5. 90 S I G N I F I C A N C E A * * * * * * * * B * * * * * 13 13 2 2.40 17. 09 3.10 2. 27 N. S N. S S I T E 4 13 . 13 7 0 . 51 14. 28 2 6 . 3 0 1. 63 N. S S I T E 1 13 13 5 1 . 0 0 7 2 . 01 1 1 . 4 9 2 0 . 2 9 * ** **** D E E P S I T E 2 13 13 1.23 0. 14 1 1 . 7 2 1.46 **# N . S P L A T E S S I T E 3 13 13 6 8 . 1 0 8 6 . 2 2 2 3 . 4 9 6 3.8). **** S I T E 4 13 13 8 9 . 1 3 5 5 . 7 4 9 0 . 17 1 3 . 3 6 * * * * **** DEPENDENT V A R I A B L E = P H ; INDEPENDENT V A R I A B L E = N 0 3 - N !CONTROL PLOTS I (CCNTROL NC3-N VALUES BELCW D E T E C T I O N L I M I T S ) DEPENDENT V A R I A B L E = CA; INDEPENDENT V A R I A B L E = MG ( U R E A - F E R T I L I Z E D P L O T S ) S U R F A C E P L A T E S 1 S I T E 2 S I T E 3 * S I T E NO.OF OBSERV.A 12 13 B 13 13 R SQUAREO A 8 3 . 73 9 0 . 0 6 8 9 1 . 6 7 8 9 . 8 0 F V A L U E A 5 1 . 4 7 9 9 . 7 2 8 1 2 1 . 0 0 9 6 . 7 9 S I G N I F I C A N C E A * * * * * * * * B * * * * * * * * 13 9 0 . 83 9 3 . 5 0 S I T E 4 13 13 9 9 . 4 0 9 9 . 21 1 0 9 . 0 2 1 8 2 1 . 4 2 7 2 1 . 8 0 1 3 7 2 . 73 * * * * ttiAif.it S I T E 1 13 12 9 8 . 72 9 6 . 74 8 5 0 . 7 4 3 2 6 . 6 6 * * * * **** S I T E 2 13 13 5 7 . 7 0 8 0 . 4 7 1 5 . 01 4 5 . 3 2 **** **** P L A T E S S I T E 3 13 13 8 0 . 8 4 9 3 . 1 1 4 6 . 4 2 1 4 8 . 7 7 **** **** DEPENDENT V A R I A B L E = CA; I N D E P E N D E N T V A R I A B L E = MG (CONTROL P L O T S ) » S I T E NO.OF CBSFRV.A 11 B 11 R SOUARED A 4 4 . 1 2 B 4 0 . 7 7 F VALUE A 7.11 B 6.20 S I G N I F I C A N C E A * B * S U R F A C E P L A T E S 1 S I T E 2 S I T E 3 11 13 12 12 9 5 . 3 4 8 1 . 75 7 6 . 8 4 . 1 7 . 33 1 0 4 . 1 0 4 9 . 2 6 3 3. 18 2. 10 *+** N.S S I T E 4 13 11 7 7 . 14 9 3 . 97 3 7 . 13 14 0. 2 5 *** * S I T E l 13 13 7 0 . 00 7 3 . 39 3 9 . 1 7 3 C . 3 3 * * * * D E E P S I T E 2 13 13 8 9 . 20 2. 73 9 0 . 82 0.31 **** N.S P L A T E S S I T E . 3 13 11 5 4 . no 4 2 . 76 1 3 . 0 3 6.72 S I T E 4 13 13 8 5 . 1 5 1 1 . 6 3 6 3 . 0 3 1.45 N . S S I T E 4 13 13 3 3 . 0 2 5.31 5.42 0.62 * N.S 173 Appendix E (continued) DEPENDENT V A R I A B L E = PH ; I NOE P P N D F N T V A R I A B L E = CA (URE A-FERT IL IZ EO P L O T S ) SU R F A C E 1 P L A T E S D E E P P L A T E S # S I T E 1 S I T E 2 S I T E 3 S I T C 4 S I T E 1 S I T E 2 S I T E 3 S I T E 4 NOoOF OBSFRV.A 12 13 13 13 13 13 13 13 B 13 13 13 13 13 13 13 13 R SQUARED A 92.1/1 7 8 . 06 6 3 . 2 4 7 3 . 55 5 0 . 3 5 4 . 3 2 7 8 . 2 5 8 6 . 5 0 B 50.4 6 3 4 . 3 9 7 0 . 3 3 2 4 . 5 3 6 0 . 3 2 1 2 . 33 09. 32 1 0 . 93 F VALUE A 1 1 7 . 1 7 3 9 . 13 1 3. 93 3 0 . 5 9 1 1 . 1 6 0.50 3 9 . 5 7 7 0 . 4 8 B 1 5 . 4 8 5. 09 2 6 . 13 3. 58 2 3. 72 1. 55 9 2 . 03 1.35 S I G N I F I C A N C E A **** **** * * * A **** *** N.S **** B * **** N. S • *** k N. S **** N.S DEPENDENT V A R I A B L E = P H ; I N D E P E N D E N T V A R I A B L E = CA (CONTROL P L O T S ) S U R F A C E P L A T E S DEEP P L A T E S a S I T E 1 S I T E 2' SI TE 3 SI TE 4 S I T E 1 S I T E 2 S I T E 3 S I T E 4 NO. OF OBSFRV.A 11 11 13 13 13 13 13 13 B 11 12 12 11 1 3 13 11 13 R SQUARED A 2 2 . 7 8 5. 38 3 0 . 8 5 . 3. 0 0 2 1 . 6 3 2 7 . 2 9 1.81 1 2 . 8 2 B 3 9 . 9 3 1 0 . 7 0 0.47 3 6 . 2 0 2 0 . 0 4 2. 04 4 5. 07 6. 12 F VALUE A 2.66 0. 51 4. 91 0.35 3.04 4. 13 0.20 1.62 B 5.98 1.12 0. 05 5. 11 2. 76 0.23 7.39 0.72 S I G N I F I C A N C E A N.S N.S * N.S N.S N.S N. S N.S B M. S N.S • * No S N.S ** N.S DEPENDENT V A R I A B L E = P H ; INDEPENDENT V A R I A B L E = MG ( U R E A - F E R T I L I Z E D P L O T S ) SURFACE i P L A T E S DEEP PLA T E S n S I T E 1 S I T E 2 S I T E 3 S I T E 4 S I T E 1 S I T E 2 S I T E 3 S I T S 4 NO.CF OBSERV.A 12 13 13 13 13 13 13 13 B 13 13 13 13 13 13 13 13 R SQUARED A 6 6 . 6 2 7 7 . 3 9 5 2 . 34 7 0 . 8 9 5 3 . 0 9 1.14 7 7 . 11 8 4 . 84 B 7 6 . 6 9 3 4 . 6 6 ' 7 4 . 0 1 2 1.94 6 7 . 4 1 7.66 7 9 . 4 5 2 6 . 74 F VALUE A 1 9 . 9 5 3 7 . 6 6 1 2 . 0 8 2 6. 7 8 12. 4 5 0. 13 3 7 . 06 6 1 . 5 8 B 3 6 . 1 9 5 . 8 3 3 1 . 3 2 3.09 2 2 . 7 5 0. 9 1 4 2 . 54 4. 02 S I G N I F I C A N C E A **** **** **** N. S B * N. S **** N. S **** N.S DEPENDENT V A R I A B L E = P H ; INDEPENDENT V A R I A B L E = MG (CONTROL P L O T S ) SUR FACE P L A T E S DEEP P L A T E S « S I T E 1 S I T E 2 S I T E 3 S I T E 4 S I T E 1 S I T E 2 S I T E 3 S I T E 4 NO.OF ODSERV.A 11 11 13 13 13 13 13 13 0 11 12 12 11 13 13 11 13 R SQUARED A 1 2 . 7 7 1.77 3 5 . 7 7 0.54 1 0 . 9 5 2.94 0.00 5 8 . 1 2 B 0.04 2. 54 2.02 20. 05 1 5 . 10 3 3 . 11 1 7.67 8.97 F VALUE A 1.32 0.16 6 . 1 3 0.06 2.57 0. 33 0. 00 1 5 . 26 B 0.00 0. 2 6 0. 21 2. 37 1. 97 5.44 1.93 1.00 S I G N I F I C A N C E A N.S N.S * N. S N.S N. S N. S **** B N.S N.S N.S N.S N.S * N.S N.S 174 Appendix E (continued) DEPENDENT V A R I A B L E = CA; INDEPENDENT V A R I A B L E = N 0 3 - N ( U R E A - F E R T I L I Z E D P L O T S ) S U R F A C E P L A T E S 1 S I T E 2 S I T E 3 H S I T E NO.OF OBSERV.A 12 13 B 13 13 R SQUARED A 7 5 . 1 7 0 7 . 0 2 B 3 4 . 2 3 0 1 . 4 6 F VALUE A 3 0 . C I 7 9 . 3 0 Q 5.73 4 8 . 3 3 S I G N I F I C A N C E A **** * * * * ^ B * **#ft 13 13 6 9 . 3 7 1 2 . 9 9 2 4 . 9 2 1. 64 **** N.S S I T E 4. 13 13 6 4 . 7 1 2 8 . 90 2 0 . 17 4. 47 **** N.S S I T E 1 13 13 9 7 . 1 8 9 6 . 03 3 7 9 . 4 6 2 6 6 . 2 7 **** **** D E E P S I T E 2 13 13 2 5 . 9 1 8 5 . 0 7 3 . 0 5 6 2 . 6 9 N. S **** P L A T E S S I T E 3 13 13 7 4 . 8 0 9 3 . 64 2 2 . 6 5 1 6 1 . 0 3 **** * * * * S I T E 4 13 13 8 5 . 1 5 2 6 . 8 0 6 3 . 0 8 4.03 N.S DEPENDENT V A R I A B L E = CA; I N D E P E N D E N T V A R I A B L E = N 0 3 - N (CONTROL PLOTS ) (CCNTROL NC3-N V A L U E S BELOW D E T E C T I O N L I M I T S ) DEPENDENT V A R I A B L E = C O N C ; INDEPENDENT V A R I A B L E = K ( U R E A - F E R T I L I Z E D P L O T S ) NO.OF OBSERV.A 8 R SQUARED A F VALUE A B S I G N I F I C A N C E A B S I T E 1? 13 8 7 . 3 8 9 7 . 6 1 6 9 . 22 4 4 9 . 9 9 **** S U R F A C E P L A T E S 1 S I T E 2 S I T C 13 13 5 6 . 2 3 5 1 . 16 14. 1 3 1 1 . 52 * * * * * * * 13 13 4 2 . 02 1 8 . 0 6 8.24 2. 56 ** N.S S I T E 4 1 ? 13 4 4 . 65 3.85 8.07 0. 44 ** N.S S I T E 1 13 13 9 4 . 89 9 3 . 2 7 2 0 4 . 2 3 1 5 2 . 4 1 *** + * * * * D E E P S I T E 2 13 13 3.29 4 7 . 87 0.99 1 0 . 10 N. S * * * P L A T E S S I TE Z> 13 13 7 6 . 7 4 0.08 3 6 . 3 0 0.01 **** N.S DEPENDENT V A R I A B L E = C C N D ; INDEPENDENT V A R I A B L E = K (CONTROL P L O T S ) S U R F A C E P L A T E S 1 S I T E 2 S I T E # S I T E NO.OF C B S E P V . A 11 11 B 11 12 R SQUARED A 1 8 . 7 0 6 3 . 5 5 B 8 9 . 7 5 4 1 . 2 1 F VALUE A 2.07 1 5 . 6 9 B 7 8 . 8 3 7.01 S I G N I F I C A N C E A N.S * * * * B **+* * 13 12 0 2 . 7 4 8 3 . 31 5 2 . 7 2 5 1 . 76 **** **** S I T E 4 13 11 2 9 . 6 6 8. 13 4.64 0. 80 N.S N. S , 14 S I T ! 13 13 3 9 . 28. 6 3 7.07 4.41 * * No S D E E P S I T E 2 13 13 3 4 . 3 8 5 3 . 62 5. 76 1 2 . 7 2 * **** P L A T E S S I T E 3 13 11 6 7 . 2 0 4 6 . 44 2 2 . 5 4 7.80 31 TE 4 13 13 4 5 . 4 9 2 3 . 00 9. 18 4.28 N.S S I T E 4 13 13 8 4 . 4 3 6 0 . 6 7 5 5 . 64 1 6 . 9 7 **** Appendix E (continued) 175 DEPENDENT V A R I A B L G = C O N D ; INDEPENDENT V A R I A B L E = CA ( U R E A - F E R T I L I Z E D P L O T S ) NO.CF OBSERV.A B 9. SCUARED A B F VALUE A B S I G N I F I C A N C E A B SURFACE F L A T E S S I T E 1 S I T E 2 S I T E 3 12 13 13 13 13 13 I B . 9 7 5.57 3.01 1 0 . 09 6.22 7.09 2.34 0.65 0. 3 4 1.23 0.73 0.84 N.S N.S N.S N.S N.S N.S SI TE 4 13 13 2 4 . 4 5 4 9 . 12 3. 76 1 0 . 6 2 N.S ** * S I T E 1 13 13 9 9 . 59 9 0 . 9 5 2 6 0 4 . 0 6 1 0 3 9 . 9 5 * * * * DEEP S I T E 2 13 13 1 7 . 6 9 2 1 . 7 3 2 . 3 6 3.05 N.S N. S P L A T E S S I T E 3 13 13 1 6 . 00 8 6 . 7 0 2.10 7 1 . 72 N.S **** DEPENDENT V A R I ABLE = COND; INDEPENDENT V A R I A B L E = CA (CONTROL PLOTS) NO.CF OBSERV.A B R SCUARED A B A B A B F V A L U E S I G N I F I C A N C E S URFACE P L A T E S S I T E 1 S I T E 2 S I T E 3 11 11 13 11 12 12 3 7 . 0 6 5 2 . 1 5 7 4 . 1 9 0.01 9.74 2 6 . 1 4 5.30 9.31 2 1 . 6 2 0 . 0 0 1.08 3.54 N.S N.S N.S S I T E 4 13 11 6 2 . 7 9 9 0 . 3 0 1 8 . 59 8 3 . 7 6 S I T E 1 13 13 8 3 . 5 4 7 6 . 3 5 5 5 . 02 3 5 . 5 2 ***** **** OEEP S I T E 2 13 13 1 4 . 81 1.42 1.91 0. 16 N.S N. S P L A T E S S I T E 3 13 11 3 2 . 6 0 1.93 5.32 0. 18 * N.S S I T E 4 13 13 9 1 . 13 1 3 . 13 1 1 3 . 0 6 2. 44 **** N.S S I T E 4 13 13 4 7 . 3 5 5 5 . 7 7 1 0 . 0 9 1 3 . 07 *** **** DEPENDENT V A R I ABLE-COND; INDEPENDENT V A R I A B L E - N-TOTAL ( U R E A - F E R T I L I Z E D P L O T S , NO.CF OBSERV.A R SCUARED F VALUE B B B S I G N I F I C A N C E A S I T E 12 13 4 4 . 10 9 8 . 5 0 7.89 7 2 1 . 5 4 * * * * SURFACE P L A T E S 1 S I T E 2 S I T E 3 13 1-3 7 1 . 9 4 7 1 . 0 9 2 8 . 21 2 8 . 1 3 **** * * * * 13 13 7 8 . 25 5 2 . 82 3 5 . 58 1 2 . 3 2 *** * **** S I T E 4 13 13 6 6 . 5 0 7 5 . 7 0 2 1 . 8 4 3 4 . 2 7 **>!<* **** S I T E 1 13 1 3 C.99 3 1.03 0.11 5.08 N. S DEEP S I T E 2 13 13 7. 4 9 3 1 . 6 0 0. 8 9 5.08 N. S * P L A T E S S I T E 3 13 13 0. 01 8 7 . 3 4 0.00 S I T E 4 13 13 9 0 . 06 5 9 . 64 9 9 . 6 7 7 5 . 8 7 1 6 . 2 5 N.S **** **** * + DEPENDENT VAR I ABLE = CONC; INDEPENDENT V A R I A R . P - M rn'-r\, V A R I A B L E = N-TOTAL (CONTROL P L O T S , (CONTROL N-TOTAL VALUES BELCW D E T E C T I O N L I M I T S , Appendix F: Throughfall Dafa for Sifes I, II, III and IV S I T E I : THROUGHFALL OATA( AV. OF 4 C O L L E C T O R S ) DATE I N VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PEP. L I T R E 1 9 7 3 £. 1 9 7 4 ( L I T R E S ) P ERIOD ( D A Y S ) x.MH0/CM(25"C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT 19 : 06 1. 16 32 0.67 0.17 0.40 0 . 1 5 4 0 . 5 0 4 0.10 1 5 U C 2. 20 11 3 0.44 0.11 0.29 0.18 <0. 20 0. 70 4 1.40 4 0. 50 4 0, 50 1 5 : 11 l o 78 31 4. 5 13 0.39 0. 02 0.16 0 . 1 1 <0. 20 0.04 4 0.64 ^ 0.40 4 0.40 1 0 : 1 2 1.83 25 4. 6 11 0.2 8 0.01 0. 07 0. 11 ,<0. 10 0. 04 4 0.64 4 0 . 5 0 0.50 1 6 : 0 1 2. 01 37 4. 8 9 0.2 5 0.01 0.07 0 . 0 6 <0. 10 0„ 02 4 0.16 4 0. 04 C, 06 12 :02 1.78 28 4o 3 10 0. 27 0. 04 0. 23 0. 10 4 0 , 10 0.07 < 0.32 Oo i 5 < 0.05 1 3 : 0 3 .. 2.11 28 4. 7 10 0.24 0. 05 0. 19 0.11 <0. 10 4 0. 02 4 0.17 4 0.05 < 0.0b 10: 0 4 2. 03 28 4. 2 10 0.18 0.04 0.24 0 . 1 3 0. 05 0.07 0.17 0 . 0 5 4 0. 05 6 ;05 1. 50 23 3. 8 22 Oo 31 0. 05 0.34 0. 13 0. 07 0.14 0.51 0.30 4 0.05 5 : C6 1. 59 28 4.6 14 0.29 0.01 0.45 0 . 2 0 0. 06 0. 03 0. 14 4 0 . 0 5 4 0. 05 17-.07 1. 53 42 4. 8 10 0.13 0.05 0.41 0 . 1 5 0,05 4 0.02 0.24 0. 17 0. 23 S I T E I I : THROUGHFALL DA T A ( A V. OF 4 C O L L E C T O R S ) DATE IM VOLUME COLLECT ION PH C O N D U C T I V I T Y M I L L I GRAMS P ER L I T R c 1 9 7 3 Z. 1 5 7 4 ( L I T R E S ) P ERIOD ( D A Y S ) ^ M H 0 / C M ( 2 5 ° C) NA K CA MG NH4-N N03-N N-TOT. ORG N P-TOT. 1 9 : 0 6 1.39 32 0„ 84 3.13 0. 76 0. 26 0. 0 0 4 0.50 4 0 . 10 1 5 U 0 2.22 11 8 0.51 4. 71 1. 06 0. 47 4 0 . 2 0 0.26 4 0 . 96 4 0 . 5 0 4 0, 50 15 111 1. 64 31 - 5.5 24 0.51 3.03 1.01 0 . 3 6 4 0. 2 0 4 0.02 4 0.62 4 O . 4C 4 0. 4 0 10 11 2 1. 86 25 5. 5 12 Oo 30 0, 62 0.54 0. 17 4 0. 10 0.02 4 0.62 4 0 . 5 0 4 0 . ^  0 165 01 1.93 37 5.5 11 0.23 0.65 0.51 0.16 4 0. 10 4 0. 02 4 0. 19 0. 07 0.16 1 3 J 0 2 2. 13 2 3 5.2 11 0.31 Oo 3 6 0 o 5 9 0.14 4 0. 10 4 0.02 4 0.36 0. 24 4 0 , 05 3 5 03 . 1.78 28 5.3 11 0.30 0.66 0. 53 0. 14 4 0. 10 0. 02 ^-0.17 <0.05 4 0 . 0 5 1 0 ; 04 1. 73 28 4. 3 11 0.23 1.05 0.47 0. 1 1 4 0.05 4 0. 02 4 0. 12 4 0 . 0 5 <0.05 8:05 1.33 28 4. 7 20 0.40 2. 02 0. 74 0.16 4; 0.05 4 0 . 0 2 4 1.30 1.73 •iO. 0 5 5-806 1.51 28 5.6 : 23 0.41 3 . 2 6 0. 78 0. 23 0. 07 4 0.02 4 0.18 0.09 0.14 1 7 . 0 7 1.29 42 5.3 25 0.32 6.08 0 . 7 3 0.32 4 0. 05 < 0 . 0 2 <• 0.31 0 . 2 5 0.2 0 Appendix F (continued) S I T E I I I : THROUGHFALL D A T A ( A V . OF 4 C O L L E C T O R S ) DATE I N VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y 1 9 7 3 C 1 9 7 4 ( L I T R E S ) PERIOD ( D A Y S ) M M H O / C M ( 2 5 ° C) NA K CA 1 9 * 0 6 Oo 64 32 1.27 1.65 0. 94 15S 10 1. 36 113 0.62 2.1 7 1.07 1 5 : i l 1.21 3 1 5. 1 13 0.61 0.80 0.56 10 J 12 1.73 25 5.0 12 0.34 0. 3 9 0. 34 1 6 . 0 1 • 1. 85 37 5.2 U 0 . 3 3 0.48 0.31 1 3 : 0 2 2.17 28 < M 7 14 0.32 0.41 0. 36 1 3 ! 0 3 1.42 23 4.8 16 0.36 0.45 0. 38 10.'04 1. 33 28 4.3 12 0.26 0.39 0.48 8 s05 0. 94 23 4.5 21 Oo 44 0. 81 • 0.89 5 5 06 0. 99 28 5.2 17 0.39 0.78 0.84 1 7 : 0 7 0.83 42 5.2 22 0.34 1.36 0.94 M I L L I G R A M S PER L I T R E MG 0.37 0. 80 0.37 0. 13 0 . 1 2 0. 11 0. 14 0. 1 3 0.25 0.26 0 . 5 4 NH4-N N03-N N-TOT. ORG N P-TOT. 0. 00 4 0.50 <0. 50 4 0 . 20 0. 04 <0. 74 < C. 50 4 0. 50 < 0. 20 0.05 4 0 . 6 5 4 0.40 4 0. 40 4 0. 10 0. 03 < 0.63 4 0.50 4 0. 5C 4 0. 10 4 0 . 0 2 <0.17 0. 05 0. 17 <-o. 10 0.03 4 0 . 3 6 0. 13 4 0.05 < 0. 10 4 0 . 0 2 <0. 17 < 0. 05 4 0.05 0.07 0.09 < 0.24 0. 05 0. C5 < 0. 05 0.14 4 0 . 4 6 0. 27 < 0, 05 0.07 0. 05 4 0. 17 0.05 0.03 0.05 0.13 4 0.28 0.05 4 0. 05 i S I T E I V : THROUGHFALL D A T A ( A V . OF 4 C O L L E C T O R S ) DATE IN VOLUME C O L L E C T I O N PH C O N D U C T I V I T Y M I L L I G R A M S PER L I T R E 1 9 7 3 £ 1 9 7 4 ( L I T R E S ) PERIOD (DA.'S) •uMHO/CMl 25° C) NA K CA MG NH4-N NOB- .'J ! "J-TOT . ORG N P-TOT. 19 = 06 0. 74 32 1.35 1.78 1. 73 0. 3 9 0. 54 2. 43 4 0.10 1 5 : 1 0 1. 94 113 0.74 1.80 1.68 0. 5 3 4 0 . 2 0 0.66 <1.36 4 0. 50 4 0. 50 15 11 1.29 31 4. 8 . 24 0. 63 1.22 0. 85 0. 34 4 0 . 2 0 0.02 4 0.62 4 0.40 4 0.40 10 :12 1. 64 25 4.6 13 0.36 0.28 0.41 0. 12 4 0 . 10 4 0 . 02 4 0. 62 4 0.5G 4 0.50 16 :01 I . 38 37 4. 7 13 0.34 0.30 0.41 Oo 11 4 0 . 10 4 0 . 0 2 i 0 . 1 3 0.06 0. 13 13 =02 2.08 23 4.6 18 0.37 0.15 0. 54 0. 11 4 0 . 10 0. 09 4 0.41 0. 22 4 C 05 13 :03 1.60 23 4.4 23 0.41 0.22 0.49 0 . 1 1 4 0. 10 4 0 . 02 4 0. 17 4 0. 05 4 0. 05 10 :04 1.23 23 4. 1 13 0. 34 0.38 0 o 5 9 Oo l i O0O6 0 . 0 6 4 0.15 4 0.05 4 0. 05 8 :05 1.13 28 3.8 23 0.49 0. 65 0. 34 0. 17 0. 03 0. 0 2 2.76 2 . 6 0 4 C . G ~ 5 :06 1.05 28 4.6 21 0.46 0.73 0.35 0 . 2 1 4 0 . 0 5 0.02 4 0 . 1 6 0. 0 9 4 0. 05 17 :07 0.81 42 4. 8 2 7 0.43 1.54 1.28 0.35 0. 05 0.41 0.67 0.20 4" 0.05 V] VI 

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