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Pruning management of Leucaena leucocephala alleycropped with maize and cassava Welke, Sylvia Eliesabeth 1993

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PRUNING MANAGEMENT OF LEUCAENA LEUCOCEPHALA ALLEYCROPPED WITHMAIZE AND CASSAVAbySYLVIA ELIESABETH WELKEB.Sc., The University of Waterloo, 1988A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTIlE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE STUDIES(Department of Soil Science)We accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIADecember 1993© Sylvia Eliesabeth Welke, 1993In presenting this thesis in partial fulfilment of the requirements for an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature)__________________________Department of 8o/ SczeiiceThe University of British ColumbiaVancouver, CanadaDate________________DE-6 (2/88)AbstractAn experiment was carried out to determine suitable pruning intervals for Leucaena leucocephala inan alley cropping system with maize and cassava in Southwestern Nigeria. I considered light andsoil moisture limitations to crops in the system, in addition to nutrient contributions by Leucaenaprunings to both crops and the soil. Pruning labour was also taken into account to provide aneconomic perspective. Marked reductions in maize yield were recorded when hedgerow pruning wasdelayed beyond 10 weeks after crop planting while cassava economic yield was not affected. Iobserved a general trend of taller plants with thinner stems when Leucaena hedgerows were notpruned or pruned at intervals of 8 weeks or less. Plants adjacent to the hedgerows were usuallyshorter than those in the middle of the alleys. I attributed the yield declines and growth effects tolight limitations rather than soil moisture depletion by the hedgerows, although the potential for thelatter could exist in drought. While productivity was affected by light reductions, there was no clearindication that Leucaena prunings contributed to crop growth. Differences in leaf nutrient contentwere obvious between treatments where hedgerows were pruned at least once a season and wherethey were not. Maize nutrition was likely satisfied by inorganic fertilizer and initial application ofLeucaena pruning, but the same could not be established for cassava where nutrient concentrationswere low. I suggest that prunings applied at or just after planting could contribute to crop nutrition,while subsequent prunings are instrumental in maintaining soil fertility. When costs of differentpruning intervals were calculated, it was clear that pruning at least once during the maize growingseason was advantageous. I briefly discuss some possible economic advantages and disadvantages ofpruning every 4 and 8 weeks, or mid-season and at harvest. Upon integrating the biophysical andeconomic data gathered in the study, it is clear that hedgerow pruning can be delayed up to 10 weeksafter planting for maize. For cassava, further studies are necessary in order to recommend pruningintervals for a maize/cassava intercrop in an alley cropping system.11.9• 1010• 11• 12• 12• 12• 12• 16• 22222733374.0. Nutrient contribution ofLeucaena leucocephala to maize and cassava under dVferentpruning intervals4.1. Introduction4.2. Materials and Methods4.2.1. Leucaena foliage and crop samples4.2.2. Soil analysis4.2.3. Data analyses4.3. Results4.3.1. Crop nutrient concentrations and contents4.3.2. Leucaena nutrient yield4.3.3. Relationships between Leucaena prunings and4.3.4. Soil Fertility Status4.4. Discussion4.5. ReferencesTable of ContentsAbstract iiTable of Contents iiiList of Figures VList of Tables viiAcknowledgements ix1.0. General Introduction 12.0. Experimental Layout 53.0. Effect of Leucaena leucocephala (Lam de Wit) pruning frequency on alley croppedmaize/cassava 93.1 Introduction3.2. Materials and Methods3.2.1. Crop Growth Characteristics and Yield3.2.2. Leucaena growth and pruning biomass3.2.4. Soil Moisture3.2.5. Data analyses3.3 Results3.3.1. Crop growth characteristics3.3.2. Crop yields3.3.3. Leucaena growth and pruning biomass3.3.4. Incident light3.3.5. Soil Moisture3.4. Discussion3.5. References40crop productivity404141424243434652545660111cropping system5.1. Introduction5.2. Materials and Methods5.3. Results5.3.1. Comparing costs5.3.2. Weed biomass5.4. Discussion5.5. ReferencesConclusions 77ANOVA tables for cassava pre-harvest measurementsANOVA tables for cassava yieldANOVA tables for 1992 soil moisture samplesANOVA tables for crop nutrient concentration and contentANOVA tables for Leucaena pruning nutrient concentration and yieldANOVA tables for soil analysisANOVA tables for pruning labour requirementAppendix B5.0. Labour costs of different pruning intervals of Leucaena leucocephala in an alley62of treatments62636669697476AppendicesAppendix AANOVA tables for maize height measurementsANOVA tables for maize stem diameterANOVA tables for maize LAIANOVA tables for maize reproductive stage measurementsANOVA tables for maize grain yieldANOVA tables for cassava height measurementsANOVA tables for cassava stem diameterANOVA tables for cassava node numberANOVA tables for cassava LAI7979798184868689929495979899101105108111113ivList of Figures2. 1: Cross-sectional view of an alley cropping plot with maize in 4 m alleys betweenLeucaena hedgerows 72.2: Plot layout indicating planting pattern of maize and cassava, as well as distancebetween crops and Leucaena hedgerows 73. la: Maize plant height as affected by distance from Leucaena hedgerows in the 8week pruning interval and unpruned piots during the 1992 maize cropping season 153. ib: Maize basal stem diameter as affected by distance from Leucaena hedgerows in the8 week pruning interval and unpruned piots during the 1992 maize cropping season 153.2a: Cassava internode lengths for the 2- and 8- week pruning intervals and unprunedplots during the first 18 weeks of cassava growth in 1991 183.2b: Cassava plant height the 2-, 6- and 10- week pruning intervals and unprunedplots during the 1991 rainy season 183.3: Cassava lateral shoot dry matter yield (kg/plant) harvested 13 months after planting 213.4a: Maize, cassava and Leucaena heights under the 6-week pruning interval forthe 1991 maize growing season 243.4b: Maize, cassava and Leucaena heights in unpruned plots for the 1991maize cropping season 243.5: Mean Leucaena foliage pruning biomass (tlha) over the 1991/1992maize cropping seasons 253 .6a: Light transmission (%) to maize ear level in the middle of the alleys andadjacent to Leucaena hedgerow during the 1991 cropping season 263.6b: Light transmission (%) to maize ear level adjacent to Leucaena hedgerow duringthe 1992 cropping season under a 4-week pruning interval and unpruned plots 263.7: Relationship between % light transmission to maize ear level and the differencein height (cm) between maize and Leucaena during the 1991 maize cropping season 293.8: Relationship between Leucaena hedgerow canopy LAI (leaf area index) and% light transmission to maize cob during the 1992 cropping season 293 .9a: Light transmission (%) to cassava canopy in the middle of the alleys and adjacentto Leucaena hedgerow during the 1991 cropping season under a 10-week pruninginterval and unpruned plots 30v3.9b: Light transmission (%) to cassava canopy adjacent to Leucaena hedgerow during the1992 cropping season under a 4-week pruning interval and unpruned plots 303.10: Relationship between % light transmission to the cassava canopy and the differencein height (cm) between cassava and Leucaena during the first 4 months of cassavagrowth 313.11: Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % lighttransmission to cassava canopy during the 1992 cropping season 313.12: Differences in gravimetric soil moisture content adjacent to Leucaena hedgerowsand middle of the alleys in the 4-week pruning and unpruned plots during themonth of October 1991 324.1: Nitrogen, phosphorus and potassium yield of Leucaena prunings under 2-, 4- and8- week pruning intervals at 8, 16 and 24 weeks after planting during the 1991growing season 484.2. Nitrogen, phosphorus and potassium yield of Leucaena prunings under 4- and 8- weekpruning intervals at 8 weeks after planting during the 1992 growing season 494.3a: Nitrogen, phosphorus and potassium yield of Leucaena prunings prior to maize earleaf sampling in the 1992 growing season 504.3b: Nitrogen, phosphorus and potassium yield of Leucaena prunings during the 1992maize growing season 504.4: Total nitrogen, phosphorus and potassium yield of Leucaena during the 1991 growingseason 515.1: Relationship of pruning labour (days/ha) to time elapsed between prunings (days)before and after maize harvest 685.2: Weed dry matter under 4- and 6- week pruning intervals and in unpruned plotsduring the 1992 maize growing season 73viList of Tables2.1. Soil physical and chemical characteristics before the 1991 and 1992 cropping seasonfor the 0-15 cm surface soil layer 83.1 Maize reproductive stage measurements taken July 13,1993 143.2a. Maize grain and stover yield (tlha) as affected by Leucaena pruning interval 193.2b. Maize grain yields as affected by distance from Leucaena hedgerow 193.3. Maize yield components as affected by pruning intervals for 1992 204. la. Maize ear leaf nutrient content at silking under 4- and 6- pruning intervals andunpruned plots 444. lb. Maize ear leaf nutrient content at silking adjacent to the hedgerow and in themiddle of the alleys 444.2. Cassava leaf nutrient concentrations under 4- and 6- week pruning intervals, andunpruned plots 454.3. Cassava leaf nutrient content under 4- and 6- week pruning intervals andunpruned plots 454.4. Leucaena nitrogen, phosphorus and potassium concentrations under 4-, 6- and8- week pruning intervals 474.5. Association of maize grain yield and ear leaf nitrogen to nitrogen and potassiumfrom Leucaena prunings 534.6. Association of cassava leaf nutrient contents with nitrogen, potassium andphosphorus from Leucaena prunings 534.7. Soil surface (0-15 cm) chemical properties in the middle of alleys and adjacent toLeucaena hedgerows after 18 months of Leucaena fallow 555.1. Pruning schedule by treatment for the 1992 maize growing season 655.2. Estimation results determining the effect of time elapsed between prunings (days),operator and standing maize crop in alleys on labour for pruning hedgerows 705.3. Relationship of pruning labour (days/ha) and maize yield (t/ha) to pruning biomassand time elapsed between prunings (days) for Leucaena prunings 70vii5.4. Pruning labour (days/ha) for different pruning intervals 715.5. Total weed biomass (tiha) and estimated labour and cost requirements under 4-and 6-week pruning intervals and unpruned plots 72viiiAcknowledgementsA large number of people were involved in this project, directly and indirectly, and I amgrateful to all of them. First, I could never have realized my dream of doing agroforestry researchin the tropics if I didn’t have the financial support awarded by C.B.I.E. (CIDA award for youngcanadians). My advisor, Art Bomke, gave me belief in myself to do my best. I have no end ofthanks for him. I also am indebted to my committee members who provided valuable advice andinsights. Dr. B.T. Kang conceived the project and always available for consultation during the fieldresearch. Thanks to Karen Dvorak who was patient with all my late-night and early-morningeconomics questions.I could never have coped with all those measurements, crises and malaria attacks withoutEnoch Tanyi who was always there to help out. The same is true for Stefan Hauser and his workersin the first year of the project. I also am grateful to my four assistants who helped me despite theheat and rain. Special thanks go to Charity Nnaji who despite her overflowing work always had thetime to print something for me. I am grateful to all the other special people at IITA whocontributed to the project through their friendship and discussions.At UBC I couldn’t have completed much of the manuscript without the infinite computerknowledge of Rick Kettler or without the “light discussions” with Andy Black. And how could Ihave survived all those panic sessions without the relentless laughter of Sandy Tricycle and Maja,the Balkan wonderwoman.Finally, a big thanks to the friends that were there throughout the epic term of my thesis.Dick Repasky, Martin Carver, Ike Ezenwa, Tino Grosjean and Louise Cargill were all there in oneway or another. And there are not enough thanks for my mother who is always there.ix1.0. General IntroductionFood production in sub-Saharan African countries has been declining over the past decade, in sharpcontrast to other developing nations (Vergara, 1987). Rapid population growth, urbanization andglobal economic policies have, in large part, led to this decline. Consequently, pressure on botharable and marginal lands has increased leading to extensive degradation of the land resource base inthe sub-Saharan region (Sanchez, 1987). Yet, these lands have been fanned for centuries under thetraditional shifting cultivation or bush fallow system which allows for natural soil fertility restorationduring the fallow phase and supplies subsistence farmer needs (Vergara, 1987). The sustainability ofthe system depends on relatively short (1 to 5 years) cropping periods compared to longer fallowphases (5 to >20 years) (Nair, 1985).However, with increased pressure on land for food production, traditional crop productionsystems have broken down as fallow period length decreases or is replaced by continuous cultivationin some areas (Okigbo, 1984). While intense cultivation is feasible on some of the more fertile soilsof the subtropics, much of the area is dominated by highly weathered, low-activity clay soils such asOxisols and Ultisols (ferralsols) (Nair, 1984; Kang et al., 1990). Many studies have shown thatthese soils degrade quickly after forest or bush fallow clearing (Kang et al., 1985; Sanchez, 1976).Chemical inputs can slow the decline in soil fertility and in crop productivity, but are often not anaffordable option for many farmers. Even with external inputs, continuous cropping is notsustainable unless management of organic matter is considered (Nair, 1985; Young, 1989).Much research has been devoted to the role of organic matter in soil fertility and itsmaintenance in agricultural production in the humid and sub-humid tropics (Kang, 1991). Oneapproach to the latter is through the application of organic materials from leafy shrubs or trees inagroforestry systems. Agroforestry is a land-use system in which woody perennials are plantedtogether in space or time with crops and/or livestock (Vergara, 1987). The contribution ofagroforestry tree/shrub species to soil fertility is multifold. Litter fall as well as deliberate manuring1with prunings has been shown to increase soil organic matter and, in some cases, base saturation ofthe soil (Nair, 1984). Including nitrogen-fixing trees in agroforestry systems can contribute to cropnutrition or provide protein-rich fodder (Brewbaker, 1987). Soil physical properties are alsoenhanced by the presence of trees; for instance, water infiltrability, pore size distribution and watertransmissivity are favourably affected (Hulugalle and Kang, 1981; Lal, 1981). Agroforestry alsoseeks to provide economic security to the farmer by providing income from herbaceous and treecrops, and/or animals.Alley cropping is one example of an agroforestry practice in which arable crops are grown inrows between planted woody shrubs or trees. During the cropping season, the hedgerows are prunedperiodically to prevent shading of the crops. The prunings can be used as mulch, livestock fodder oras fuelwood. Outside the cropping season, the hedgerow species acts as a bush fallow with soilrestorative properties through litter fall and by tapping soil moisture and nutrients in lower soilhorizons (Young, 1989; Nair, 1984). Thus, alley cropping permits an extension of the croppingperiod before returning land to long-term fallow.Research on process-oriented aspects of alley cropping has been conducted at theInternational Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, since 1975 (Kang and Wilson,1987). More recently, management and economic considerations of alley cropping are beingaddressed in order to encourage adoption of the technology. One important management aspect isthe pruning of hedgerows, which must take into account both biophysical and economicconsiderations. “Optimal” hedgerow pruning intervals of 4 to 6 weeks have been established fromon-station experiments for crop production (Kang et al., 1985). But are these intervals practical oreven economical for the farmer who may adopt alley cropping?Observations from on-farms trials indicate that farmers will often delay pruning beyond therecommended intervals for various reasons. Small-scale farmers are usually faced with high labourcosts and at times, labour shortages (Dvorak, unpublished). Furthermore, conflicts with other farm2activities could hinder pruning of hedgerows. How long can pruning be delayed before crop yieldsare significantly affected? In an effort to identify appropriate pruning management for Leucaenaleucocephala in an alley cropping system that incorporates biophysical and economic aspects, a studywas conducted:(1) to determine the effect of pruning intervals of Leucaena on the growth and yield of amaize/cassava intercrop,(2) to determine the nutrient yield of hedgerows under pruning intervals and effect of prunings oncrop nutrient content and yield; and(3) to determine labour requirements of different Leucaena pruning intervals.31.1. ReferencesBrewbaker JL (1987) Significant nitrogen fixing trees in agroforestry systems. In: Gholz HL, ed,Agroforestry: Realities, Possibilities and Potentials. pp 31-35. Martinus Nijhoff Publishers,The NetherlandsHulugalle and Kang (1981) Effect of hedgerow species in alley cropping systems on surface soilphysical properties of an Oxic Paleustalf in southwestern Nigeria. Journal of AgriculturalScience (Cambridge) 14(3): 301-307.Kang, BT and GF Wilson (1987) The development of alley cropping as a promising agroforstrytechnology. In: Steppler HA and Nair PKR, eds, Agroforestry: A decade of development.pp 24-45. ICRAF, Nairobi, KenyaKang BT, GT Wilson and TL Lawson (1985) Alley cropping as a stable alternative to shifigncultivation. IITA, Thadan, NigeriaKang BT (1989) Nutrient management for sustained crop production in the humid and subhumidtropics. In: van der Heide, J, ed, Nutrient management for food crop production in tropicalfarming systems. pp 1-28. Institute for Soil Fertility and 11TA, Haren, The NetherlandsLal R (1981) Clearing a tropical forest. II Effects on crop performance, deforestation, landpreparation, growth and yield of maize, Nigeria. Field Crops Research 4(4): 345-354Nair PKR (1985) Classification of agroforestry systems. Agroforestry Systems. 3: 97-128Nair PKR (1984) Soil productivity aspects of agroforestry. ICRAF, Nairobi, Kenya.Okigbo B (1984) Cropping systems and rotations development for improving shifting cultivation andrelated intermittent production systems in tropical Africa. Soils Bulletin, FAO. 35: 121-140Sanchez PA (1987) Soil productivity and sustainability in agroforestry systems. In: Steppler HA andNair PKR, eds, Agroforestry: A decade of development. ICRAF, Nairobi, KenyaSanchez PA (1976) Properties and management of soils in the tropics. John wiley and sons, NewYorkVergara, NT (1987) Agroforestry: A sustainable land use for fragile ecosystems in the humidtropics. In: Steppler HA and Nair PKR, eds, Agroforestry: A decade of development.ICRAF, Nairobi, KenyaYoung A (1989) Agroforestry for soil conservation. Science and Practice of Agorforestry Series No.4, ICRAF/CAB International, Nairobi, Kenya.42.0. Experimental LayoutI carried out the study at the International Institute of Tropical Agriculture (IITA) in Ibadan,southwestern Nigeria (7°30’N and 3°54’E) during the 1991 and 1992 growing seasons. The meanannual rainfall at the research station is 1280 mm, which is bimodally distributed with a main rainyseason from March to the beginning of August and a minor season from September to October.Mean annual temperature is 26.2°C and average global radiation (M31m2)was 13.44 and 12.25 forthe 1991 and 1992 growing seasons, respectively.Different experimental sites were used for 1991 and 1992. Plot size in 1991 was 8 m x 4 mwhile I chose larger plots (30 m x 4 m) the following year to accomodate pruning labourmeasurements and to allow for cassava dry matter accumulation studies. Experimental plots werearranged in a randomized complete block design with three and four replications in 1991 and 1992,respectively.The soil at both sites was an Alfisol, classified as an Oxic Paleustalf (USDA) of the Egbedaand Ibadan series, in 1991 and 1992, respectively. The physical and chemical characteristics of thesesoils are summarized in Table 2.1. Leucaena leucocephala (Lam. de Wit)(K38) hedgerows wereinitially established in 1985, at both sites, at an interrow spacing of 4 m and intrarow spacing of 0.25m. The 1991 site was under yam cultivation from 1986 to 1989 and left fallow thereafter. The 1992site had been mechanically cultivated maize for 5 years and then left fallow for 2 years.Prior to planting in both years, all plots were sprayed with 3.7 kg/ha of paraquat to controlweeds. The plots were subsequently planted to maize (TZSR-W) on May 31, 1991 and May 6, 1992at a spacing of 0.4 m x 0.8 m (31, 250 plants/ha). Cassava (TMS 30572) was planted one weeklater in each year at a spacing of 0.8 m x 1.6 m (7,812 plants/ha) (Figure 2.2). Compound fertilizer(15-15-15) was applied to supply 30 kg N/ha, 13 kg P/ha and 25 kg K/ha. One month later, themaize was sidedressed with 15 kg N as CAN (Calcium ammonium nitrate). Maize was harvestedAugust 31, 1991 and August 16, 1992. Cassava was harvested June 15, 1992.5The hedgerows were pruned initially on May 14-18, 1991 and April 14-15, 1992. In 1991,the hedgerows were pruned to a height of 0.30 m every 2, 4, 6, 8 and 10 weeks after crop planting.Four, 6, 8 and 12 weekly pruning intervals (cut to 0.50 m) were implemented after crop planting in1992. Six- and 12- weekly pruning intervals simulated the situations where the farmer prunes onceduring the maize season or only at maize harvest, respectively. An unpruned treatment was includedin both years.6Figure 2.1: Cross-sectional view of an alley cropping plot with maize in 4 m alleys betweenLeucaena hedgerows.B.• Zea mays ManihotesculentaLeucaenaleucocephalaFigure 2.2: Plot layout indicating planting pattern of maize and cassava, as wellcrops and Leucaena hedgerows.as distance between4.0 m• . . •:* EEl. . •4.OmB.m7Table2.1.Soilphysicalandchemicalcharacteristicsbeforethe1991andsurfacesoillayer ofanOxicPaleustaif,IITA, Ibadan,Nigeria.001992croppingseasonforthe0-15cmpHOrg. CTotal NBray-iPNH4OAcBulkDensityTexture.(H20)(Leco)extractablecationsg/kgg/kgmg/kgKCaMg(gfcm3)%sand%clay%silt(cmol/kg)6.110.01.230.00.394.031.101.1178.011.011.0sandyloami2225.69.00.924.20.301.980.381.1676.012.012.0sandyloam3.0. Effect of Leucaena leucocephala (Lam de Wit) pruning frequency on alleycropped maizelcassava.3.1 IntroductionAgroforestry systems are inherently complex. By definition, herbaceous crops are in closeassociation with trees or shrubs in these systems. Consequently, resource pools are shared by bothcomponents and there exists the potential for competition between them. This is an important issuesince the system aims to produce large amounts of tree biomass for mulch, fodder or fuelwoodwhile simultaneously sustaining crop production (Huxley, 1983; Kang et aL, 1985). Since the goalof agroforestry practices is to minimize negative interactions and to optimize crop and treeproductivity (Young, 1989), tree management becomes an important tool with which to allocate andcontrol competition for resources between crop and tree species (Buck, 1986; Pinney, 1986;Rosecrance et al., 1992).The negative effects of excessive hedgerow biomass production on crop productivity havebeen amply demonstrated. In alley cropping systems for instance, Kang et al.(1981) and Ong et al.(1992) found lower overall crop yields in alley cropped plots and particularly depressed yields in therows of plants adjacent to infrequently pruned Leucaena compared to control plots. In otherstudies, yield reductions were also associated with increased hedgerow biomass (Rosecrance et a!.,1992; Jama et a!., 1991; Buck, 1986). Field and OeMatan (1988) found a significant decline ingrain yield in maize alley cropped with Leucaena that was pruned less than once a season.Clearly, one or more resources are limiting to cause such crop yield reductions. Alleycropping studies in the sub-humid regions of the tropics suggest that light interference by thehedgerow can severely limit crop productivity while research in semi-arid climates indicatescompetition for water between crop and tree (Singh et al., 1988). Competition for nutrients can alsobe a concern in alley cropping systems on inherently infertile soils (Gichuru and Kang, 1990) and/orwhen hedgerow prunings are exported rather than used as mulch in the field (Nair, 1984). Pruning9management can affect one or more aspects of tree/crop competition.In this chapter I will describe the effect of various pruning intervals of Leucaena on thegrowth and yield of maize and cassava. How long can hedgerow pruning be delayed before lightand/or soil moisture resources become limiting to the crop? Are crops adjacent to the hedgerowsmore affected than those in the middle of the alleys? I will address these questions in order todetermine suitable pruning intervals for production of maize and cassava.3.2. Materials and Methods3.2.1. Crop Growth Characteristics and YieldI measured growth characteristics for maize and cassava in both years for 4 plants adjacent to thehedgerow (80 cm from the trees) and in the middle of the alleys (160 cm from the trees). Maizeheight and leaf area were recorded three times during the 1991 cropping season and biweekly in1992. Biweekly maize stem diameter and leaf number measurements were also included in 1992.The percentage of maize that shed pollen, tasseled and silked was recorded at 6 weeks after plantingin 1992 to determine effects of pruning interval on maize reproductive stages. Cassava height, stemdiameter, internode length and leaf area were measured on a biweekly to monthly basis during the1991 cropping season. I repeated these measurements in 1992 but recorded them from May toAugust only, at which time the experiment was terminated.Whole plots (32 m2 or 80 plants) were harvested in 1991 to determine maize and cassavayields while 20.5 m2 (or 64 plants) were harvested for maize in 1992. Unfortunately, many cassavaplants in unpruned plots were lost at maize harvest following the accidental application of adefoliating pesticide. Consequently, this treatment was not included in the analysis for cassavayield. At maize harvest, I determined stover and grain yields in both years. Cassava plants wereseparated into roots, main and lateral shoots at harvest. All plant material was dried at 65°C forthree days for dry matter determination.103.2.2. Leucaena growth and pruning biomassLeucaena height and width were measured at weekly intervals in 1991 and only prior to prunings in1992. I determined pruned biomass at every pruning. Whole rows (8 m long) in 1991 and 5 msections in 1992 were harvested for dry matter determination. Whenstems exceeded 2 cm diameter, I recorded foliage and stems weights separately. Approximately500 g of foliage and stems were taken as subsamples for dry matter determination. These weresubsequently weighed, oven-dried at 65°C for 3 days and reweighed.3.2.3. Solar radiationLight transmission to maize and cassava was measured in both years of the experiment during themaize growing season (approximately 3 months). In 1991, I used a Li-Cor 1000 solarimeter tube torecord light transmission. In 1992, due to equipment breakdown, a Li-Cor plant canopy analyzerwas used instead, to measure LAI (leaf area index - the ratio of leaf area to land area occupied by agiven number of plants), as an indicator of direct light transmission. I converted LAI values fromthe plant canopy analyzer to light transmission values in order to be comparable to 1991 data (Blacket al., 1992). In 1991, light transmission was measured for all treatments but only for the 4-weeklypruning and no-pruning interval in 1992. I recorded light readings or LAI between 11:00 a.m. and1:00 p.m. at maize ear height, above the cassava canopy (until cassava was higher than Leucaenaand harvested maize) and under the open sky.Light transmission was recorded adjacent to the hedge and the middle of the plot in 1991, butonly adjacent to the hedge in 1992. I measured light at weekly and bi-weekly intervals during thefirst and second seasons, respectively. Transmission in 1992 refers to direct radiation (ie. only onecomponent of radiation) versus global (or total) radiation in 1991 and was calculated for 8:00 a.m.and solar noon (LiCor manual) in order to determine the effect of time of day on the degree ofhedgerow shading.113.2.4. Soil MoistureSoil moisture was determined gravimetrically for the 0-15 cm soil layer. I collected compositesamples of 5 cores adjacent to the hedgerow and in the middle of the alleys in both years. Sampleswere taken before and after pruning for all treatments in 1991 and in 4, 6 and 12 weekly prunedplots in 1992. To obtain a soil moisture profile over time, samples were collected daily towards theend of the rainy season for 1991. In 1991, I sampled plots on a total of 21 dates from July to theend of October. In 1992, soil moisture samples were collected from the 4- and 6- week pruningintervals, and the unpruned plots for 13 dates during the maize growing season.3.2.5. Data analysesData were analyzed either as a completely randomized block one-way or split-plot design usingPROC GLM in the SAS package (SAS, 1985). I analyzed medians rather means to overcomeinconsistencies among observers recording growth measurements and slower growth in transplantedmaize and cassava, in 1991 and 1992, respectively. When log or square root transformations didnot correct non-normally distributed data or those with heterogeneous variances, ranktransformations were used (Conover and Iman, 1981). Where differences between treatments weresignificant, I separated means using Duncan’s multiple range test.3.3 Results3.3.1. Crop growth characteristicsMaizeDistance from Leucaena hedgerows had a greater effect on maize growth than pruning interval,although when hedgerows were not pruned at all during the growing season, there was a significanteffect. Differences in growth were not consistent across years of the experiment. Poor germinationof maize seeds in 1991 and subsequent transplanting may have contributed to the high variationobserved (CV=30% compared to CV= 15% in 1992). In the second year of the study, maize plants12were significantly taller and had thinner stems in unpruned plots compared to pruned plots, butwere of similar height to plants in the 4-week pruning interval. Yet, both height and stem diameterdifferences did not occur until 12 weeks after planting and shortly before harvest, respectively.Leaf number and LAI did not differ significantly in 1992.In contrast to the latent effect of pruning interval on maize growth, proximity to the hedgeaffected stem diameter and height by 5 and 6 weeks after planting, respectively. Maize wasconsistently taller with greater basal diameter in the middle of the alleys than those plants adjacentto the hedge in all treatments (Figure 3.la and 3.lb). Plants adjacent to the hedge also had fewerleaves. Leaf area index did not differ significantly with pruning interval or distance from hedge.I summarized treatment differences for reproductive stage measurements in Table 3.1.Significantly fewer plants tasseled and silked in the unpruned plots versus the 4- and 8- weekpruning intervals. Furthermore, a smaller percentage of maize plants adjacent to the hedge hadsilked compared to plants in mid-alley in the unpruned plots and the 8-week pruning interval.13Table 3.1 Maize reproductive stage measurements taken July 13,1993 (standard errorin brackets).Pruning % plants tasseling %plants silkinginterval(weeks) mid-alley hedge whole plot mid-alley hedge whole plot4 85.0(0.6) 80.7(3.9) 82.2(2.0)a*l 94.5(O.8)a 91.6(4.2)a 93.l(2.1)a8 76.1(4.4) 78.7(10.0) 74.9(5. 1)a 96.8(1 .9)a 76.5(10.5)b 86.7(4.6)aunpruned 70.5(4.7) 60.8(3.5) 65.6(3.3)b 79.1(2.9)a 63.0(8.9)b 58.7(6.1)b*lwhole plot values with different letters within columns vary significantly at the 0.05level using Duncan’s multiple range test.9edge/mid-aIley values with different letters within rows vary significantly at the 0.05level using Duncan’s multiple range test.143.02.5-2.0 -1.51.00.50/1/..-7:..I....I..1/•—- 8-week, mid-alley8-week, hedge—unpruned, mid-alley• unpruned, hedge2 4 6 8 10 12 14Weeks after plantingFigure 3. la: Maize plant height as affected by distance from Leucaena hedgerows in 8- weekpruning intervals and unpruned plots during the 1992 maize cropping season (May 6to August 16). Vertical lines indicate standard error of the mean.2.01.8I‘L61.41.2Weeks after plantingFigure 3. lb: Maize basal stem diameter as affected by distance from Leucaena hedgerows in 8-week pruning intervals and unpruned plots during the 1992 maize cropping season(May 6 to August 16). Vertical lines indicate standard error of the mean.2 4 6 8 10 12 1415CassavaCassava growth characteristics were also affected by pruning interval, but the effect of distance fromhedgerow was unclear. Furthermore, growth differences were more consistent in 1991 than in1992. At least 30% of cassava were replaced at 2 weeks after planting due to poor sprouting in1992, contributing to the high variability (average CV = 30%) I observed in cassava growthcharacteristics in 1992. In 1991, cassava node lengths were most dramatically affected by pruninginterval with longer nodes under longer pruning intervals and unpruned plots compared to shorterintervals (Figure 3.2a). Cassava plants in plots that were not pruned or pruned only every 10 weekswere also significantly taller compared to a 2- week pruning interval (Figure 3.2b). Plants weretaller at the hedge compared to those in the middle of alleys, but only early in the season, whilenode length and stem diameter were generally not affected. Data collected one week prior toharvest yielded no significant differences among treatments or distance from the hedgerows innumber of branches, total number of forks and total node number.3.3.2. Crop yieldsMaize grain and stover yields differed between years but were significantly affected by pruningintervals in both years. (Table 3.2a). In plots where hedgerows were not pruned before maizeharvest, maize grain yields were reduced by almost 50% compared to pruned hedgerows. Generallygrain yields were lower adjacent to the hedge compared to the middle of the alleys in the longerpruning intervals and unpruned plots (Table 3.2b).Stover yields were unaffected by pruning interval in 1991, yet in 1992 stover production wassignificantly lower in unpruned plots compared to yields from pruned plots. All yield componentsdiffered significantly between pruned and unpruned treatments with fewer, lighter kernels andsmaller cobs in the latter (Table 3.3). This effect was also apparent adjacent to the hedge in the 8-week pruning interval and the unpruned plots. The harvest index (ratio of economic plant parts to16total biomass) was significantly lower in unpruned plots compared to pruned plots in both years.Cassava root yield was not affected by different pruning intervals; neither was total dry matterproduction. Only lateral shoot yield was significantly different among treatments. Cassava grownin plots that were pruned less frequently had higher lateral shoot yield than those grown under themore frequently pruned intervals (Figure 3.3). The position of cassava relative to the hedgerow wasnot a significant factor in determining cassava dry matter yields.17I60 -50 -40 -30 -208-” 10 12 14 -46Weeks after planting18 20Figure 3.2a: Cassava internode lengths for the 2- and 8- week pruning intervals and unprunedplots during the first 18 weeks of cassava growth in 1991 (May 31 to October 1).Vertical lines indicate standard errors of mean. Arrows indicate dates of pruning forthe 8-week pruning interval.Figure 3.2b: Cassava plant height for the 2-, 6- and 10- week pruning intervals and unprunedplots during the 1991 rainy season (May 31 to October 17). Vertical lines indicatestandard errors of the mean. Arrows indicate dates of pruning for the 10-weekpruning interval.2-week—- 8-weekunpruned— 2-week—- 10-week• .. unpruned2.52.0C) 1.1.00.500 5 —‘i0 15Weeks after planting>20 2518Table 3.2a. Maize grain and stover yield (t/ha) as affected by Leucaena pruning interval(standard error of the mean in brackets).Pruning interval Grain yield (t/ha)(weeks) 1.22! 1992grain stover grain stover2 3.12(0.18)a* 3.29(O.12)a - -4 3.11(0.24)a 3.34(O.34)a 4.33(O.13)a 7.33(0.50)a6 3.12(0.14)a 3.56(O.25)a 4.63(O.27)a 6.35(0.29)a8 3.23(0.09)a 4.16(O.24)a 4.70(O.21)a 7.76(0.36)a10 2.71(0.23)a 3.89(0.19)a - -12 - - 2.04(0.17)b 4.65(0.51)bunpruned 1.50(0.28)b 3.20(0.17)a 2.19(0.16)b 4.57(0.46)b*values with different letters differ within columns at the 0.05 significance level usingDuncan’s multiple range test.Table 3 .2b. Maize grain yields as affected by distance from Leucaena hedgerow(standard error of the mean in brackets).Pruning interval Grain yield (t/ha)(weeks) 1221 122Zhedge mid-alley hedge mid-alley4 2.96(0.45)a* 3.26(O.22)a 4.35(O.13)a 4.31(O.24)a6 3.26(0.22)a 2.97(O.27)a 4.70(O.47)a 4.57(O.36)a8 3.14(0.12)a 3.31(O.14)a 4.57(O.30)a 4.83(O.32)a10 2.08(0.28)a 3.14(O.20)b - -12 - - 1.72(0.16)a 2.36(0.22)bunpruned 1.53(0.44)a 2.43(0.06)b 1.95(0.27)a 1.48(0.38)b*values with different letters differ within rows at the 0.05 significance level usingDuncan’s multiple range test.19Table 3.3. Maize yield components as affected by pruning intervals for 1992(standard error in brackets).Pruning interval Kernel # wt./100 Cob width Cob length Harvest(weeks) kernel(g) (cm) (cm) index4 473(9.8)a* 77.9(1.6)a 4.3(O.O)a 15.6(O.2)a O.38ab6 468(1O.4)a 77.5(2.3)a 4.4(O.1)a 15.3(O.2)a O.41a8 495(11.8)a 77.8(2.2)a 4.3(O.1)a 16.2(O.2)a O.38ab12 319(21.7)b 53.8(2.6)b 3.7(O.1)b 11.7(O.6)b O.31cunpruned 319(21.1)b 58.1 (2 .6)b 3.8(O.1)b 11.8(O.4)b O.33bc*al with different letters differ within columns at the 0.05 significance levelusing Duncan’s multiple range test.200.40Pd0.30_ _00.20CC2 4 6— 10-zrJ20.100.-.____ ____ ___ ____ ___Pruning interval (weeks)Figure 3.3: Cassava lateral shoot dry matter yield (kg/plant) harvested 13 months after planting(May 31, 1991 to June 30, 1992). Vertical lines indicate standard errors of the mean.213.3.3. Leucaena growth and pruning biomassFigures 3.4a and 3.4b show the growth of Leucaena in relation to maize and cassava growth for theunpruned plot and 6-week pruning interval, respectively. When Leucaena was pruned every sixweeks, maize outgrew the hedgerow at 6 weeks after planting while cassava only had a brief shade-free period between 6 and 8 weeks after planting. However, when Leucaena was not prunedthroughout the season, both maize and cassava remain below the hedgerow canopy (Figure 3.4b).Another measure of differences in Leucaena growth among treatments and hence, canopy coverage ismean pruned biomass. A general increase in biomass is apparent with longer pruning intervals overthe first 3 month period in both years (Figure 3.5).3.3.4. Incident lightMaize and cassava were shaded by Leucaena hedgerows in both years and most markedly in plotswhere hedgerows were cut infrequently or not at all. Crops that were grown in plots whereLeucaena was cut between 2 and 6 weeks received, on average, 60% and 30% more light,respectively, than those under longer pruning intervals or no pruning at all. This was particularlynoticeable in the first 2-3 months of growth of both crops when they were relatively shorter thanLeucaena. It was also apparent that cassava received almost 50% less light than maize during thisperiod, due to a combination of hedgerow and maize light interception. As expected there wasalways greater light transmission at noon when light passed through a thin canopy directly overheadcompared to early morning (Figure 3.6b).Light transmission to maize in plots with unpruned Leucaena decreased gradually over theseason by more than 50% (Figures 3.6a and b). However, a different pattern is evident whenLeucaena is pruned every 10 weeks a different pattern is evident. Prior to pruning, lighttransmission decreased, then immediately after pruning an increase in available light was evident(Figure 3.6a). Pruning every 4 weeks did not affect light transmission to maize as dramatically, with22relatively little change until the end of the growing season (Figure 3.6b). Distance from thehedgerows also influenced light transmission to maize. In unpruned plots, crops adjacent tohedgerow received consistently less light compared to those in the middle of the alleys (Figure 3.6a).Similarly, light transmission to maize under the 10-week pruning interval was higher in the middle ofalleys compared to light transmission at the hedge. After pruning, however, more light wastransmitted adjacent to the hedge than in the middle of the alleys where shading by other maizeplants contributed to a reduction in light transmission.233.02.5, 2.01.5-IL00.5Figure 3.4a: Maize, cassava and Leucaena heights under the 6-week pruning interval for the 1991maize cropping season (May 31 to August 31). Arrow indicates date of pruning.1.0Figure 3.4b: Maize, cassava and Leucaena heights in unpruned plots for the 1991 maizecropping season (May 31 to August 31). Arrow indicates date of pruning.04 8Weeks after planting‘43.02.52.01.50.50Weeks after planting14242.5j1 199119922.0 -F;’jl.5E>) 1.0I-io__0.52 4 6 8 10 unprunedPruning interval (weeks)Figure 3.5: Mean Leucaena foliage pruning biomass (tfha) over the 1991/1992 maizecropping seasons (May 31 to August 31; May 6 to August 16).25100—- 10-weelç, mid-alley10-week, hedge /80 - unpruned, mid-alley .//. - -unpruned, hedge //200•6 •8 “ 10 12Weeks after plantingFigure 3 .6a: Light transmission (%) to maize ear level in the middle of the alleys and adjacent toLeucaena hedgerow during the 1991 cropping season (May 31 to August 31) under a10-week pruning interval and no pruning. Arrow indicates date of pruning.1 (‘ii—4-week a.m.o 4-week p.m.80 - __unpruneda.m.-- unprunedp.m.b04 -0 I6 —p8 10 -“2 14Weeks after plantingFigure 3.6b: Light transmission (%) to maize ear level adjacent to Leucaena hedgerow during the1992 cropping season (May 6 to August 16) under a 4-week pruning interval and nopruning. For each treatment light transmission in the morning (8 a.m.) and at noonare given. Arrows indicate dates of pruning.26When light transmission was related to the difference in height between Leucaena and maize asignificant relationship was detected (r2=0.80, P=0.0002). Light transmission approached 100% asthe difference between Leucaena and maize heights decreased (Figure 3.7). An increase in lighttransmission to maize was also related to a decrease in hedgerow LAI as Figure 3.8 illustrates(r2=0.89, P=O.0001).Similar light transmission patterns to maize, were observed at the cassava canopy under 4and 10 week pruning intervals. Low light transmission levels were consistent throughout the periodof measurement in the unpruned plots. When hedgerows were cut every 10 weeks (Figure 3.9a)light transmission decreased until pruning allowed for an increase in light transmission whichreached 100% after maize harvest. After pruning, more light was transmitted adjacent to the hedgecompared in the middle of the alleys where shading by both maize and cassava plants occurred.Similarly, when hedgerows were pruned every 4 weeks, shading to cassava decreased after pruning(Figure 3 .9b).Light transmission to the cassava canopy was related to the difference in height between thecrop and the hedgerow (r2=0.57, P=0.0002)(Figure 3.10). Furthermore this light transmission wasin turn related to LAI of the canopy above cassava (r2=0.89, P=0.0001)(Figure 3.11). Bothrelationships point to a decrease in light transmission to cassava with increasing hedgerow biomass.3.3.5. Soil MoistureSoil moisture distribution was not significantly affected by pruning interval or by distancefrom the hedgerows during the 1991 and 1992 maize growing seasons. After maize harvest andtoward the end of the 1991 rainy season, however, unpruned plots were 20% drier (10% vs. 13%moisture content) than the mean value of pruned treatments. Furthermore, differences in soilmoisture content between the area adjacent to hedgerows and the middle of the alleys indicategenerally wetter conditions adjacent to the hedgerow in the 4-week pruning interval during October27(Figure 3.12). In contrast, unpruned plots generally had drier conditions adjacent to the hedgerowcompared to the middle of the alleys. This phenomenon was particularly notable after the lastrainfall for which samples were collected.28Figure 3.7: Relationship between % light transmission to maize ear level and the difference inheight (cm) between maize and Leucaena during the 1991 maize cropping season(May 6 to September 1, 1991).Figure 3.8: Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % lighttransmission to maize cob during the 1992 cropping season (May 6 to August 16).I0 0.2 0.4 0.6 0.8 1.0 1.2Height difference (m)-O.65xy4.64eC-4I50403020 -10 -0...1 2 3LAI429100—- 10-week, mid-alley ,‘. 80 10-week, hedgeunpruned, mid-alley / /•unpruned, hedge [60Ii.140—2:468710121416 18Weeks after plantingFigure 3.9a: Light transmission (%) to cassava canopy in the middle of the alleys and adjacent toLeucaena hedgerow during the 1991 cropping season (May 31 to August 26) under a10-week pruning interval and unpruned plots. Arrow indicates date of pruning.1004-week, a.m.O 80 4-week, p.m.—- unpruned, a.m.unpruned, p.m.6O402:14Weeks after plantingFigure 3.9b: Light transmission (%) to cassava canopy adjacent to Leucaena hedgerow during the1992 cropping season (May 6 to August 16) under a 4-week pruning interval andunpruned plots. For each treatment light transmission in the morning (8 a.m.) and atnoon are given. Arrow indicates date of pruning.30Figure 3.11:CIRelationship between Leucaena hedgerow canopy LAI (leaf area index) and % lighttransmission to cassava canopy during the 1992 cropping season (May 6 to August16).0 0.5 1.0Height difference (m)1.5 2.0 2.510080604°200Figure 3.10: Relationship between % light transmission to the cassava canopy and the difference inheight (cm) between cassava and Leucaena during the first 4 months of cassavagrowth (May 6 to September 1, 1991).60 -50 -40 -30 -20100_____________________.;O.70xy=4.55e..1.2 3LAI3125-60-8040-20Figure 3.12: Differences in gravimetric soil moisture content adjacent to Leucaena hedgerows andmiddle of the alleys in the 4-week pruning and unpruned plots during the month fOctober 1991. Arrows indicate dates of pruning.20i15• 10500-20-40200-405 10October 1991323.4. DiscussionPruning Leucaena only at maize harvest reduced maize yield significantly. Cassava rootyield was not affected under long pruning intervals, although lateral shoot growth was higher inthese treatments. Growth characteristics of both crops were also influenced by pruning interval butnot consistently. Furthermore, distance from Leucaena hedgerows affected both yield and growthcharacteristics. Although effects varied with crop and year of the experiment, growth responsesand yield declines in both years were attributable to light limitations, while soil moisture had noclear effect under different pruning intervals.It is well known that shade affects maize yield, the severity of the effect depending on thestage of maize growth at which shade is applied. Mbewe and Hunter (1986) observed a decrease inmaize grain yield when light to the crop was reduced by 65% during its reproductive stage.Apparently environmental stress before and during flowering reduce grain number and final grainyield (Fagena et al., 1981; Lawson, 1975). When Kiniry and Ritchie (1985) applied shade stressduring the grain filling period, final kernel number and therefore grain yield was significantlyreduced. This latter phase in the development of maize is considered to be the most important indetermining final grain and total yield (Johnson and Tanner (1972b) in NeSmith and Ritchie (1992)).In my study, yield reductions were significant after the 8 week pruning in 1992 and 10 weekpruning in 1991, suggesting that shading has detrimental effects between 10 weeks after planting andmaize harvest. This 10 week point corresponds approximately to the beginning of the grain fillingperiod. Furthermore, I found that delaying pruning to 10 weeks after planting maize affects grainyield in plants grown adjacent to the hedgerows. This underlines the importance of environmentaleffects at this stage in maize growth. As Schussler and Westgate (1991) observed, shading duringthe grainfilling period had a more marked effect on kernel loss than when shading was applied atpollination. Since the upper maize canopy contributes a large portion of its assimilates to the cob,reduced photosynthetic capacity will lead to fewer and lighter kernels and consequently lower final33grain yield (Edmeades et al., 1979). Fewer kernels and lower kernel weights under unprunedLeucaena in 1992 accounted for the reduced grain yield I observed in this experiment.Maize stover yield was not as dramatically affected by pruning interval as grain yield.Stover was reduced by 30% in unpruned plots compared to pruned treatments in 1992. Mbewe andHunter (1986) observed similar reductions (25%) in stover yield when shade was applied either atthe vegetative stage or during grain filling, but found no differences when plants were shaded duringthe reproductive period. Generally maize grain yield exhibits a stronger response to limited solarradiation than stover yield (Scarsbrook and Doss, 1973; Earley et a!., 1966). A less sensitiveresponse by stover production to light limitations, in conjunction with high variability, may explainwhy no difference was observed in the first year of the experiment.Maize plants were shorter with smaller diameters adjacent to Leucaena hedgerows than inthe middle of the alleys. I expected to see etiolation under the shade of Leucaena. However,shading for the first 4 weeks after planting may have reduced assimilate contribution to vegetativegrowth enough to suppress vertical growth and allow the plants in the middle of the alleys to growtaller (Tetio-Kagho and Gardner, 1988). A reduction in assimilates could also explain why leaf areadid not differ significantly under different pruning intervals.Limited light transmission to maize had detrimental effects on maize growth and final yieldin this study. Similar findings were reported by Lawson and Kang (1990) who associated decreasedmaize yields with increased Leucaena biomass; a result they attributed to excessive shading by thehedgerow. Shade effects, more than any other factor, were used to explain low maize yields underAcacia albida, where the hedgerow was pruned only once during the growing season (Jama andGetahun, 1991). Increasing light transmission gradients with increasing distance from the hedgerowwere also observed by Kang et al., (1985) when Leucaena hedgerows were pruned at long intervals.Decreasing distance from hedgerows also had detrimental effects on maize grain yield (Kang andLawson, 1991; Haggar and Beer, 1993).34Were reduced light conditions solely responsible for the observed decline in maize yield?Another possible limiting factor, soil moisture, did not exhibit any clear trends during the maizecropping season. Nevertheless, other studies indicate that extended drought stress during thegrowing season, particularly at the time of grain-filling could seriously decrease yield (NeSmith andRitchie, 1992; Schussler and Westgate, 1991; Begg and Turner, 1976). Competition for water wasunlikely since the soil water requirements of maize are generally satisfied in rainfed systems (Kling,Maize program, IITA; personal communication).Cassava productivity was not markedly affected by any pruning interval in either year.From the early growth differences between unpruned and pruned plots, however, it is likely thatsome effect of continuous shading beyond 10 weeks after planting would be reflected in a decreasein final yield. Cassava etiolated under longer pruning intervals (8-10 wks) until the crop outgrewthe hedgerow and shade was no longer important to vegetative growth while etiolation continuedwhen Leucaena was not pruned. Kasele (1983) related a decline in cassava dry matter yield toincreased height and a concurrent decrease in stem diameter with increasing shade. Since cassavapartitions assimilates to root and shoot simultaneously, a greater proportion of assimilates arediverted to shoot growth under limited light conditions (Splittstoesser and Tenya, 1989; Cock, 1983;Sreekumari et al., 1988). This response was reflected in the significant increase in lateral shootyield under longer pruning frequencies observed in this experiment (Cock et al., 1979).An effect of soil moisture on cassava productivity could not be established for pruningintervals of 10 weeks or less. Higher soil moisture in the middle of the alleys in unpruned plotsmay be due to an ‘umbrella’ effect caused by the nature of the canopy. Wetter conditions adjacentto the hedgerow under the 4-week pruning interval may be the result of moisture conservation byshading of the hedgerows, a suggestion also made by (Lawson and Kang, 1991). However, the soilmoisture pattern in the unpruned plots at the end of the rainy season (5 months after planting)suggest the possibility of soil moisture depletion. Indeed Baker et al. (1989) working in Australia,35observed that with the application of drought stress at 6-8 months, cassava yield was markedlyreduced. Others have found that prolonged moisture stress can result in reductions in total biomassand root yield (Sharkaway et al., 1992; Lal, 1981).On the basis of this study, I can only make recommendations for Leucaena hedgerowpruning with respect to maize. Delaying pruning beyond 10 weeks after the initial cut back causeda decline in maize yield attributable to shading during the grain-filling stage. Timely pruning at 10weeks after planting maize is therefore advisable, in order to maintain crop productivity and toderive the benefits of alley cropping. The effects of delayed pruning (ie. more than 10 weeks) oncassava need to be investigated further, through tuberization and growth studies, in order torecommend a pruning interval that optimizes both maize and cassava yields.363.5. ReferencesBaker GR, Fukai S and Wilson GL (1989) The response of cassava to water deficits at variousstages of growth in the subtropics. Australian Journal of Agricultural Research 40: 517-528Begg JE and Turner NC (1976) Crop water deficits. Advances in Agronomy 28: 161-207Black TA, Chen 3M, Lee X and Sagar RM (1991) Characteristics of shortwave and Iongwaveirradiances under a Douglas-fir forest stand. Canadian Journal of Forest Research 21: 1020-1028Buck MG (1986) Concepts of resource sharing in agroforestry systems. Agroforestry Systems 4:191-203Cock JH (1983) Cassava. In: Cock JH, ed, Potential productivity of field crops under differentenvironment. pp 33-42. IIRI, PhilippinesCock JH, Franidin D, Sandoval G and Jun P (1979) The ideal cassava plant for maximum yield.Crop Science 19: 271-279Conover WJ and Iman RL (1981) Rank transformations as a bridge between parametrics andnonparametric statistics. American Statistician 35(3). 124-133.Duguma B, Kang BT and Okali DUU (1988) Effect of pruning intensities of three woodyleguminous species grown in alleycropping with maize and cowpea on an affisol.Agroforestry Systems 6: 67-80Earley EB, Miller RI, Reichert GC, Hageman RH and Seif RD (1966) Effects of shade on maizeproduction under field conditions Crop Science 6: 1-7Edmeades GO and Daynard TB (1979) The relationship between final yield and photosythesis atflowering in individual maize plants. Canadian Journal of Plant Science 59: 577-584El-Sharkaway MA, Hernandez ADP and Hershey C (1992) Yield stability of cassava duringprolonged mid-season water stress. Experimental Agriculture 28: 165-174Fagena NK, Bahgar VC and Jones CA (199 1),eds, Growth and mineral nutrition of field crops.Chapter 7: Corn. Marcel Dekker Inc., New York.Field, SP and OeMatan SS (1990) The effect of cutting height and pruning frequency of Leucaenaleucocephala hedgerows on maize production. Leucaena Research Reports 11:68-69.Gichuru MP and Kang BT (1990) Calliandra calothyrsus (Meissn.) in an alley cropping system withsequentially cropped maize and cowpea in southwestern Nigeria. Agroforestry Systems 9:191-203Haggar JP and Beer JW (1993) Effect on maize growth of the interactions between increasednitrogen availability and competition with trees in alley cropping. Agroforestry Systems 21:239-24937Huxley PA (1983) Plant research and agroforestry. Proceedings of a consultative meeting inNairobi, April 8-15, 1981, ICRAF, Nairobi, KenyaJama B and Getahun A (1991) Intercropping Acacia albida with maize (Zea mays) and green gram(Phaseolus aureus) at Mtwapa, Coast Province, Kenya. Agroforestry Systems 14: 193-205Kang BT, Wilson GF and Sipkens L (1981) Alley cropping maize (Zea mays L.) and leucaena(Leucaena leucocephala Lam) in southern Nigeria. Plant and Soil 63: 165-179Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpeawith Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277Kasele IN (1983) Studies on the effects os some environmental factors on cassava (Manihotesculenta Crantz) tuberization. Master of Philosophy Thesis, University of Thadan, Ibadan,NigeriaKiniry JR and Ritchie JT (1985) Shade-sensitive interval of kernel number of maize. AgronomyJournal 77: 711-715.Lal R (1981) Effects of soil moisture and bulk density on growth and development of two cassavacultivars. In: Tropical Root Crops: Research Strategies for the 1980’s, Proceedings of thefirst root crops symposium, International Society for Tropical Root Crops, Sept. 8-12, 1980,Ibadan, Nigeria.Lawson TL and Kang BT (1983) Resource use in alley cropping. In: International Institute ofTropical Agriculture Annual Report 1983. pp 181-182Lawson TL and Kang BT (1990) Yield of maize and cowpea in an alley cropping system in relationto available light. Agricultural and Forest Metereology 52: 347-357Mbewe DMN and Hunter RB (1986) The effect of shade stress on the performance of corn forsilage versus grain. Canadian Journal of Plant Science 66: 53-60NeSmith DS and Ritchie JT (1992) Maize (Zea mays L.) response to a severe soil water-deficitduring grain-filling. Field Crops Research 29: 23-35Nair, PKR (1984) Soil productivity aspects of agroforestry. Science and Practice of AgroforestrySeries 1. ICRAF, Nairobi, Kenya.Ong KC, Rao MR and Mathuva M (1990) Trees and crops: Competition for resources above andbelow the ground. Agroforestry Today 4(2): 4-5Rosecrance RC, Brewbaker JL and Fownes JH (1992) Alley cropping maize with nine leguminoustrees. Agroforestry Systems 17: 159-168SAS Institute Inc., (1985) SAS: User’s guide, Version 5 Edition, SAS Institute Inc., Cary NC,USA, 9S6p38Scarsbrook CE and Doss BD (1973) Leaf area index and radiation as related to corn yield.Agronomy Journal 65: 459-461Schussler JR and Westgate ME (1991) Maize kernel set at low water potential: II. Sensitivity toreduced assimilates at pollination. Crop Science 31: 1196-1203Singh RP, Ong KC and Saharan N (1989) Above and below ground interactions in alley-cropping insemi-arid India. Agroforestry Systems 9: 259-274Splittstoesser WE and Tunya GO (1988) Crop physiology of cassava. In: Janick, J, ed, HorticulturalReviews. Volume 13. pp.105-29Sreekumari MT, Abraham K and Ramanujam T (1988) The performance of cassava under shade.Journal of Root Crops 14: 43-53Tetio-Kagho, F and Gardner FP (1988) Responses of maize to plant population density. I. Canopydevelopment, light relationships and vegetative growth. Agronomy Journal 80: 930-935Young A (1989) Agroforestry for soil conservation. Science and Practice of Agroforestry Series No.4. ICRAF/CAB International, Nairobi, Kenya394.0. Nutrient contribution of Leucaena leucocephala to maize and cassava underdifferent pruning intervals4.1. IntroductionFood production systems such as alley cropping rely on biological means to maintain soilfertility and to contribute to sustainable crop production. Thus, where soil fertility is decliningand/or high-input agriculture is not possible, alley cropping may be an alternative for the resource-poor farmer (Kang et al., 1981). This agroforestry practice has been shown to improve soilchemical properties, particularly when nitrogen-fixing species such as Leucaena leucocephala areused (Brewbaker, 1987, Yamoah et a!., 1986; Nair, 1984). These improvements have beenattributed to the addition of organic nitrogen, carbon and phosphorus from prunings of fast-growinghedgerows (Kang and Balasubramian, 1990; Nair, 1984). Large inputs of foliage biomass andconsequently nutrients have been recorded with some alley cropping species (Yamoah et al., 1986).In addition to maintaining long-term soil fertility, prunings of hedgerows can act as directnutrient sources to associated crops (Read et al., 1985). Readily-available nutrients from rapidlydecomposing prunings may be taken up by associated crops (Tian et a!., 1992; Mulongoy andAkobundu, 1988). There may also be a transfer of nutrients by root-turnover of nitrogen fixingtrees (Yamoah et al., 1986). The soil ameliorating and/or direct crop nutrition effects associatedwith alley cropping have been reflected in sustained crop yields compared to the yield declines oftenobserved under continuous cultivation (Nair, 1984, Kang et al., 1981).The potential for hedgerow prunings to maintain soil fertility and/or contribute to cropnutrition is influenced by the method and timing of hedgerow pruning application, decompositionrate of prunings and crop phenology (Mulongoy and van der Meersch, 1988; Kang et al., 1981).Pruning every 4 or 6 weeks, as recommended from alley cropping experiments does not necessarilyconsider these factors. Furthermore if hedgerow prunings can contribute to crop nutrition, howlong can pruning be delaying before the contribution becomes negligible? Identifying a pruning40interval that considers these factors is a necessary step in realizing the benefits of alley cropping.Clearly this is also an important factor in the adoption of the technology.In this chapter I will examine the effect of different pruning intervals of Leucaena on itsnutrient yield and its potential contribution to alley cropped maize and cassava. Are pruningapplications reflected in enhanced crop productivity? Furthermore, is there any evidence of short-term soil fertility amelioration under alley cropping? I will answer these questions in an effort toidentify pruning intervals that optimize the benefits of Leucaena prunings.4.2. Materials and Methods4.2.1. Leucaena foliage and crop samplesI collected Leucaena pruning data in both years of the experiment. At every pruningLeucãena foliage biomass was weighed and subsamples taken for dry matter determination from a20 m2 area. Only Leucaena foliage and green, tender stems were sampled. I took furthersubsamples for nutrient analysis from every pruning date at which more than one treatment waspruned in order to make nutrient yield comparisons. Cassava leaf samples were collected at the endof the 1991 rainy season by taking the 3rd and 4th leaves from the apex of 10 plants in each plot(Porto, M., Tuber and Root Improvement Program, IITA; personal communication). During thesilking period in 1992, maize ear leaf samples were collected from 20 plants adjacent to thehedgerow and in the middle of the alley for the 4, 6- week pruned and unpruned plots.All plant samples were dried to constant weight at 65°C for dry matter determination. Plantmaterial was digested for subsequent nutrient analysis using the Parkinson-Allen method (Parkinsonand Allen, 1975). A Technicon autoanalyzer was used for N and P determinations while basecations were determined with a Perkin-Elmer 306 atomic absorption spectrometer. I calculatednutrient contents for maize and cassava on a leaf dry matter (weight of leaves sampled) basis.414.2.2. Soil analysisSoil samples were collected from 0-15 cm at the beginning of the 1991 and 1992 croppingperiods for characterization of each site. In 1991 I took composites of 20 cores (2 cm diameter) foreach block, while in 1992 40 cores from each block were taken; 20 from the area adjacent to thehedgerows (0 - 0.80 m) and 20 from the middle of the alleys 1.6 - 2.4 m). Soil samples were alsocollected in October, 1991, using of 10 cores from each treatment in every block. Bulk densitysamples were taken 24 weeks after planting in 1991 and 4 weeks after planting in the followingseason. I also determined soil texture for the site characterization samples using the hydrometermethod.A 2:1 soil-water suspension was used to measure pH. Phosphorus was extracted using theBray-Pt method with an extraction time of 5 minutes and P was subsequently determined using aGilford spectrophotometer. Total carbon was determined with the Leco carbon analyzer. Basecations were extracted using neutral 1M ammonium acetate and concentrations determined with aPerkin-Elmer 306 atomic absorption spectrometer. Total nitrogen was determined from an H2SO4extract with a Technicon autoanalyzer.4.2.3. Data analysesData were subjected to ANOVA and regression analysis with backward selection using SASGLM and REG procedures, respectively (SAS, 1985). Where data were not normally distributedand variances were nonhomogeneous, appropriate transformations were made. Ranks wereemployed when log or square-root transformations did not correct non-normality or heterogeneity(Conover and Iman, 1981).424.3. Results4.3.1. Crop nutrient concentrations and contentsDifferences were apparent in crop nutrient contents under different pruning intervals. Maizeear leaf N at silking was similar for the 4- and 6-week pruning intervals but significantly lower inunpruned plots compared to a 4-week pruning interval. Phosphorus contents were significantlyhigher in the 4-week pruning interval compared to 6-week and no-pruning (Table 4. la).Furthermore plants adjacent to the hedgerow in all treatments contained less N, P. K, Ca and Mgcompared to the middle of the plot in all pruning intervals (Table 4. ib). Neither pruning intervalnor location within the plots affected nutrient concentrations in maize ear leaves indicating thatdifferences in leaf nutrient content were due to significant differences in leaf dry matter (F= 12.28;P = 0.0008). Average nutrient concentrations for maize ear leaf were 29.6 g N/kg, 3.6 g P/kg, 23.0g K/kg, 3.0 g Ca/kg and 1.6 g Mg/kg.Cassava leaf nutrient concentrations varied significantly between unpruned plots and otherpruning intervals. Phosphorus and Mg concentrations were lower in cassava leaves where Leucaenawas not pruned (Table 4.2). In contrast, K concentration was on average higher in unprunedtreatments. When nutrient concentrations were converted to leaf content basis, cassava leaves inunpruned plots contained consistently less N, P. K, Mg and Ca than other treatments (Table 4.3).Cassava leaf dry weights were also significantly lower in unpruned Leucaena plots compared to anypruning interval.43Table 4. la. Maize ear leaf nutrient content at silking, 8 weeks after planting (July 5,1992) under 4- and 6- pruning intervals and unpruned plots.Pruning interval Nitrogen Phosphorus Potassium(weeks) mg/leaf DM4 10.33(0.60)la* 1.27(0.07)a 4.0(0.2)a6 9.64(0.75)ab l.13(0.06)b 3.7(0.3)aunpruned 8.60(0.31)b 1.06(O.06)b 3.5(0.l)a‘standard error of the mean in parenthesis*valueS with different letters differ within columns at the 0.05 significance levelusing Duncan’s multiple range test.Table 4. lb. Maize ear leaf nutrient content at silking, 8 weeks after planting (July 5, 1992)adjacent to the hedgerow and in the middle of the alleys.Nitrogen Phosphorus Potassiummg/leaf DMMiddle of the alley l0.8(0.6)la* 1.26(0.06)a 4.2(0.02)aAdjacent to the hedgerow 8.5(0.5)b 1.04(0.05)b 3.3(0.02)b1standard error of the mean in parenthesis*values with different letters differ within columns at the 0.05 significance level usingDuncan’s multiple range test.44Table 4.2. Cassava leaf nutrient concentrations under 4- and 6- week pruning intervals, andunpruned plots.Pruning interval Nitrogen Phosphorus Potassium Calcium Magnesium(weeks) (g/kg)4 43.8(0.5)la* 29.0(0. 1)a 2.6(1 .0)a 14.8(0.3)a 7.9(0. 1)a6 46.0(1.3)a 29.0(0.1)a 2.7(1.0)a 14.3(0.3)a 8.4(0.7)aunpruned 42.9(0.6)b 25.0(0.01)b 3.6(0.1)b 16.0(0.1)b 6.3(0.3)b1 standard error of the mean in parenthesis*values with different letters differ within columns at the 0.05 significance level using Duncan’smultiple range test.Table 4.3. Cassava leaf nutrient content under 4- and 6- week pruning intervals, and unprunedplots.Pruning interval Nitrogen Phosphorus Potassium Calcium Magnesium(weeks) mg/leaf DM4 105.5(4.8)la* 7.1(O.41)a 63.6(3.8)a 35.5(2.7)a 19.1(0.8)a6 111.6(14.3)a 7.1(1.11)a 66.7(10.0)a 34.9(5.1)a 20.3(2.7)aunpruned 50.5(4.82)b 2.9(0.29)b 42.4(4.2)b 18.8(1.9)b 7.5(1.2)b1standard error of the mean in parenthesis*values with different letters differ within within columns at the 0.05 significance level usingDuncan’s multiple range test.454.3.2. Leucaena nutrient yieldBoth nutrient concentration and yield of Leucaena foliage differed significantly with pruninginterval. In general, pruning intervals of more than 8 weeks yielded greater quantities of nutrients,although nutrient concentrations, particularly N and P, were generally lower (Table 4.4). Greaterbiomass, however, accounted for the differences observed in nutrient yields among pruning intervals(see Figure 3.8 in Chapter 1). For instance, although N and P concentrations were significantlylower in the 8-week pruning interval than the 2- and 4-week pruning intervals (Table 4.4), theformer yielded significantly more N, P and K at the same pruning date (Figure 4.1). As expected,Leucaena cut every two weeks in 1991 yielded lower amounts of nutrients at subsequent pruningdates due to decreasing biomass produced (Figure 4.1). In contrast, Leucaena pruned every 4weeks maintained a relatively constant nutrient contribution after the initial dropoff. In 1992, thesame trend was apparent with the 8-week supplying considerably more N, P and K than the monthlypruning interval at the same pruning date (Figure 4.2). The concentration of Ca and Mg did notvary with pruning interval in general, yet yields of these nutrients increased with increasing pruningintervals.Total nutrient yields of Leucaena prunings differed with pruning intervals depending on thetime period. For instance, prior to maize ear leaf sampling greater quantities of nutrients wereapplied with the 4- and 6- week pruning intervals compared to the 8 week pruning interval (Figure4.3a) yet over the whole growing season, nutrient yields were similar among these pruning intervals(Figure 4.3b). However, when Leucaena nutrient yields for different pruning intervals arecompared over a longer period (June to November, 1991), pruning every 10-week yields higherquantities of nutrients, particularly N and K, than other pruning intervals (Figure 4.4).46Table 4.4. Leucaena nitrogen, phosphorus and potassiumconcentrations under 2, 4 and 8 week pruning intervals.Pruning interval Nitrogen Phosphorus Potassium(weeks) (glkg)2 52.6(l.6)la* 3.6(O.2)a 15.7(1.7)4 55.6(2.2)a 3.9(O.2)a 17.4(3.3)8 46.4(2.2)b 2.7(O.1)b 21.6(0.6)1 standard error of the mean in parenthesis*al with different letters differ within columns at the 0.05significance level using Duncan’s multiple range test.47.I3020ECl)I’C08Weeks after plantingFigure 4.1: Nitrogen, phosphorus and potassium yield of Leucaena prunings under 2-, 4- and 8-week pruning intervals at 8, 16 and 24 weeks after planting during the 1991 growingseason.NZI 8-week— 4-week2-week60402043210H N16 2448504-week40-8-week‘—‘ 30 -.20Z\10_____0_\____ ___ _ __________________Nitrogen Potassium PhosphorusFigure 4.2. Nitrogen, phosphorus and potassium yield of Leucaena prunings under 4- and 8- weekpruning intervals at 8 weeks after planting during the 1992 growing season.49Figure 4.3a:Figure 4.3b:1:Nitrogen, phosphorus and potassium yield of Leucaena prunings prior to maize earleaf sampling in the 1992 growing season.1)0Nitrogen, phosphorus and potassium yield of Leucaena prunings during the 1992maize growing season.Nitrogen Potassium Phosphorus20015010050Nitrogen Potassium Phosphorus50100Figure 4.4: Total nitrogen, phosphorus and potassium yield of Leucaena during the 1991 growingseason (June to November).300250200150Eti).sz500Nitrogen Potassium Phosphorus514.3.3. Relationships between Leucaena prunings and crop productivityI tested several relationships to determine effects of Leucaena prunings on crop nutrient contents andyields. Hence, regressions were done with and without data from unpruned piots to determine theirinfluence on the relationships. Inclusion of unpruned plot data gave several significant relationships(Table 4.5). Leucaena N yield was associated with maize leaf N and grain yield. Furthermore, Nfrom Leucaena prunings was associated with maize ear leaf N status in the 4 and 6-week pruningintervals, but accounted for only 50% of the variation observed (Table 4.5). Maize grain and stoveryields were associated with N and K from Leucaena prunings. When data from unpruned plots wasdropped from the analysis, none of the above-mentioned relationships were significant, suggestingreductions in biomass in unpruned plots were responsible for the relationships I observed. When1992 maize yields were related to Leucaena pruning nutrient yields, soil moisture and light todetermine the most important factor/s, light transmission accounted for 75% of the variation. Thiswas also the case in 1992 where a decrease in available light to maize was associated with themajority of the decline in grain yield. Leucaena N, P and K from prunings were significantlyrelated to cassava leaf nutrient contents (Table 4.6). However, when all measured variables wererelated to cassava dry matter yield, only light transmission was a significant factor accounting for90% of the variation observed (Table 4.6).52Table 4.5. Association of maize yield and ear leaf nitrogen with nitrogen andpotassium from Leucaena prunings, and light transmission under Leucaena.Relationship r2 F P Regression equationy=maize leaf N, x=Leucaena N 0.52 9.60 0.012 y8.46+O.000lxy=maize grain, x=Leucaena N 0.86 67.21 0.001 y=2.18+0.02xy=maize stover, x=Leucaena K 0.61 17.53 0.015 y4.42+0.03xy=maize grain, xlight 0.75 12.23 0.025 y=-0.15+0.04xtransmission (1991)y=maize grain, x=light 0.68 21.56 0.001 y=1.33+0.13xtransmission (1992)Table 4.6. Association of cassava leaf nutrient contents and dry matter yield with nitrogen,potassium and phosphorus from Leucaena prunings.Relationship R2 F P Regression equationy=cassava leaf N, xLeucaena N 0.74 11.39 0.027 y=66.0+0.29xy=cassava leaf K, x=Leucaena K 0.67 8.02 0.047 y4.82+0.03xy=cassava leaf P. x=Leucaena P 0.76 12.42 0.024 y=3.89+0.40xy=cassava root DM yield, 0.92 33.04 0.0 10 y=-0.48+0.03xx = light transmissiony=cassava total DM yield, 0.88 21.90 0.018 y=0.16+0.05xx = light transmission534.3.4. Soil Fertility StatusI summarized surface soil chemical characteristics for each site in Table 2.1 of the generalexperimental layout. There were significant differences in fertility between soil taken adjacent to thehedge and the middle of the alley at the 1992 site prior to planting (Table 4.7). Phosphorus wasalmost twice as high adjacent to the hedgerows compared to the middle of the alleys (F= 19.15;P=0.049). Furthermore, significantly higher levels of ammonium were also found closer to thehedgerow than in the middle of the plots (F=21.82, P=O.02)(l’able 4.7). Total nitrogen andorganic carbon were marginally higher as well (F =7.55, P=0.071; F=9.0O, P=0.058,).At the end of the 1991 rainy season, only nitrate levels were affected by the different pruningintervals. The 10-week pruning interval, which was pruned 1 week prior to soil sampling, hadhigher nitrate levels compared to all other treatments.54Table 4.7. Soil surface (0-15 cm) chemical properties in the middle of alleys and adjacent toLeucaena hedgerows after 18 months of Leucaena fallow.pH Org. C Total N Available N Bray-i P K Ca Mg(1120) (Leco) NH4 NO3- mg/kg cmol/i00gg/kg g/kg mg/kgMiddle of 5.381 8.7 0.8 i.44a 0.56 i9.4a 0.31 2.10 0.39alley (0.07) (0.7) (0.04) (0.09) (0.02) (1.10) (0.02) (0.29) (0.03)Adjacent to 5.74 10.0 0.9 i.78b 0.63 38.4b 0.29 1.85 0.37hedgerow (0.06) (0.9) (0.04) (0.06) (0.03) (1.77) (0.02) (0.24) (0.04)1 standard error of the mean in parenthesis*values with different letters differ within columns at the 0.05 significance level using Duncan’smultiple range test.554.4. DiscussionWhen Leucaena hedgerows are not pruned at least once a season lower nutrient contents in maizeand cassava were observed. This decrease is exacerbated in maize plants adjacent to the hedge.Lower crop nutrients were related to yields and Leucaena pruning applications, yet theserelationships were largely determined by differences between pruned and unpruned treatments.The positive relationships suggest some nutrient contribution by Leucaena prunings application,yet such a conclusion is premature without first considering a number of confounding factors. Thenutritional status of the crops prior to sampling is important. Nutrient concentrations for maize earleaf did not differ significantly and were generally within the sufficiency range for maize nutritionalrequirements (Fagena et at., 1991). This suggests that adequate nutrients were supplied by thefertilizer (45 kg N/ha, 13 kg P/ha and 25 kg K/ha) and/or the initial prunings of the season(supplying approximately 100 kg N/ha, 5 kg P/ha and 70 kg K/ha). It has been observed thatapplying more than 60 kg/ha of N, does not elicit a significant maize yield response (Yamoah et a!.,1986). Thus, as was seen in this study, no yield differences would be expected with subsequentprunings.Moreover, light limitations to crops and the consequent detrimental effects on growth couldhave obscured an effect of Leucaena pruning applications. The difference in maize ear leaf nutrientcontents between pruned and unpruned treatments likely reflects lower dry matter production in thelatter. Lower dry matter production is associated with either limited nutrient uptake and/orphotosynthetic capacity (Fagena et a!., 1991). The relatively lower dry matter accumulation at thesilking stage resulted in lower crop yields in unpruned plots. According to data from my study,light limitation was the prevailing influence on crop growth and yield. Furthermore, I found nosignificant relationship between Leucaena nutrients applied, and crop yields and nutrient contentswhen data from unpruned plots were dropped. This suggests applying prunings 4 to 8 weeks afterplanting had no significant effect on the nutritional status of maize while pruning applications at 2 to5610 week intervals were negligible to cassava nutrition.Thus, the crop response relationships I established are not necessarily due to a direct responseof Leucaena nutrients applied. Read et al. (1985) also found that with the application of inorganicfertilizer, there was no crop response to Leucaena pruning applications. Still, many researchershave found strong positive correlations between N from Leucaena prunings and grain yields(Rosecrance et a!., 1992; Yamoah et a!., 1985) and ear leaf N (Kayode, 1986). Such a response isdependent on the synchronization of pruning application and crop nutrient demands (Mulongoy,1988; Pinney, 1986).The period of tropical maize maximum nutrient uptake occurs between 14 to 45 days afterplanting (Kling, 1990). Leucaena releases 50% of its N, P and K by 30 to 45 days after pruning(Mulongoy, 1988; Kang et a!., 1985). Thus, in my study, it is likely that only the initial pruning ofthe season, and the first 4-week pruning could have had a significant impact on maize nutrition.However, even pruning at 4 weeks after planting did not appear to have an effect on maize ear leafnutrients nor maize grain yields. Pruning at 6 weeks after planting occurred 3 days prior tosampling and is thus unlikely to have had an effect on ear leaf nutrient status while the 8 weekpruning occurred well after the sampling period. These observations suggest that application ofprunings after a critical period will have a lesser effect on crop growth than if applied before. Inagreement, Mulongoy and van der Meersch (1988) found surprisingly low maize uptake efficiencies(30%) of Leucaena pruning nitrogen despite large quantities available. Similarly, in studies withother hedgerow species, uptake rates of the associated crops have been lower than expected(Yamoah et a!, 1985; Mulongoy and Akobundu, 1988).Cassava exhibited a similar response to Leucaena pruning application, although it was lessmarked than for maize. Lower P and Mg leaf concentrations in cassava leaves in the unprunedtreatment may have reflected a soil deficiency and/or competition by Leucaena. On the other handhigher K and Ca leaf concentrations in the same treatment could be due to stemfiow and throughfall57contributions from Leucaena. This is an important mechanism of nutrient addition in forestecosystems (Parker, 1989). However, a significant reduction in cassava leaf dry matter undercontinuous shade at the time of sampling resulted in lower leaf nutrient contents compared to allother pruning intervals.Leaf concentrations fell below the sufficiency range for cassava (Howeler, 1981); thus anutrient response might be expected. The positive correlation between Leucaena pruning applicationand cassava leaf nutrient contents suggests a potential to enhance cassava nutrition. It is known thatcassava responds to N and K application in particular during its period of maximum growth rate, upto 7 months after planting (Cock, 1983; Fagena et al., 1991). However, multiple regressionanalysis of the factors investigated in this study indicated that available light, not nutrients, is theprincipal factor responsible for variation in cassava dry matter yield. My data are consistent withnumerous studies which have investigated environmental stresses on cassava yield and found light tobe limiting where there there is adequate soil moisture and a moderate level of soil fertility (Cock,1983).Since the role of Leucaena prunings in crop nutrition is unclear from my study, their capacityto enhance soil fertility and thus contribute to crop productivity in subsequent cropping seasons maybe more important. Mulongoy and Van der Meersch (1988) suggest that the residual effects ofapplying prunings and thus building the soil organic N pool is a significant benefit of alley cropping.Thus from the data in this study, longer pruning intervals can contribute larger quantities over aperiod of 6 months. Nutrient yield of Leucaena prunings increase with longer pruning intervalswhile nutrient concentrations actually decrease compared to more frequently cut hedgerows. Thiscan be attributed to greater pruning biomass in the former. Nutrient yield followed the samegeneral pattern as biomass yield. The relationship between nutrient yield and biomass production iswell documented for Leucaena Kang et al., 1981; Guevarra et al., 1987; Duguma et al. 1988;Karim et al., 1991). A decrease in nutrient concentration is expected with increasing growth as58more assimilates are used for woody matter production. Duguma et al., (1988) also found higher Nconcentrations in monthly Leucaena prunings compared to tn-monthly prunings.The carbon content of Leucaena prunings changes very little with time, remaining around 45%(Tian, 1992). Thus, with N concentrations ranging from 4 to almost 6 %, C:N ratios fall below 12,suggesting rapid decomposition of prunings from any pruning interval in this study. The increase insoil N03 after the 10 week pruning application also confirms that rapid mineralization occurs withLeucaena foliage. Hence pruning interval is important, not only in terms of nutrient availability butin the timing of application.The increase in soil NH4 and P adjacent to the hedgerow prior to 1992 cropping points to thesoil enhancing properties of Leucaena fallows. Numerous authors have noted soil fertilityimprovement under alley cropping with higher organic matter, exchangeable bases, P and pH (Kang et al., 1985; Siaw et al., 1991). Mulongoy and Akobundu (1988) and Gutteridge (1991) alsocommented on the residual fertility effects of pruning applications. Despite enhanced soil propertiesadjacent to the hedgerow, maize leaf nutrient contents and grain yields were lower here, reiteratingthe overriding effect of shading by Leucaena.Given that fertilizer may not be available to the resource-poor farmer, Leucaena pruningscould contribute to the nutrition of associated crops. As Pinney (1991) and Mulongoy andAkobundu (1990) suggest, pruning at or just after planting is most likely to have an effect on cropnutrition. Thus, subsequent prunings are primarily aimed at improving the fertility of the soilthrough continuous application of organic matter. A number of long-term studies have shown thatthe addition of Leucaena prunings is instrumental in maintaining high soil organic matter andnutrient status. Leucaena, as a nitrogen-fixing species, has potential to contribute large quantities ofnutrients (Kang et a!., 1986; Duguma, 1985). Hence, pruning only once a season between 4 and 8weeks after crop planting, may offer the most desirable scenario by supplying moderate amounts oforganic material while not unduly increasing the labour requirements of the farmer.594.5. ReferencesCock JR (1983) Cassava. In: Cock, JH, ed, Potential productivity of field crops under differentenvironment. pp 33-42. IRRJ, PhilippinesConover WJ and Iman RL (1981) Rank transformations as a bridge between parametrics andnonparametric statistics. American Statistician 35(3): 124-133Brewbaker JL (1987) Significant nitrogen fixing trees in agroforestry systems. In: Gholz, HL, ed,Agroforestry: Realities, Possibilities and Potentials. pp 3 1-35. Martinus Nijhoff Publishers,The NetherlandsDuguma B, Kang BT and Okali DUU (1988) Effect of pruning intensities of three woodyleguminous species grown in alley cropping with maize and cowpea on an alfisol. AgroforestrySystems 6: 67-80Fagena NK, Bahgar VC and Jones CA (199 1),eds, Growth and mineral nutrition of field crops.Chapter 7: Corn, Marcel Dekker Inc., New YorkHoweler RH and Cadavid LF (1983) Accumulation and distribution of dry matter and nutrientsduring a 12-month growing cycle of cassava (Manihot esculenta). Field Crops Research 7(2):123-129Kang BT, Sipkens L, Wilson GF and Nangju D (1981) Leucaena (Leucaena leucocephala (Lam) dewit) prunings as nitrogen sources for maize (Zea mays L.). Fertilizer Research 2: 279-287Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpeawith Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277Karim AB, Rhodes ER and Savill PS (1991) Effect of cutting height and cutting interval on drymatter yield of Leucaena leucocephala (Lam) De Wit. Agroforestry Systems 16:129-137Kayode GO (1986) Further studies on the response of maize to K fertilizer in the tropics. Journal ofAgricultural Science (Cambridge) 106:141-147.Matthews RB, Lungu 5, Volk J, Holden ST and Solberg K (1992) The potential of alley cropping inimprovement of cultivation systems in the high rainfall areas of Zambia II. Maize production.Agroforestry Systems 17:241-261Mulongoy K and Meersch MK van der (1988) Nitrogen contribution by Leucaena (Leucaenaleucocephala) prunings to maize in an alley cropping system. Biology and Fertility of Soils6:282-285Nair PKR (1984) Soil productivity aspects of agroforestry. Science and Practice of AgroforestrySeries No.1. ICRAF/CAB International, Nairobi, KenyaParker GG (1983) Throughfall, stemfiow in forest nutrition. In: Advances in Geological Research,pp 100-12160Parkinson JA and Allen SE (1975) A wet oxidation procedure for the determination of nitrogen andmineral nutrients in biological material. Communications Soil Science and Plant Analysis 6: 1-11Pinney AJ (1986) Alley cropping: A consideration of some tree/crop interfaces. MAgr.Sc. Thesis,University of Reading, UKRead MD, Kang BT and Wilson GF (1985) Use of Leucaena leucocephala (Lam) de Wit leaves as anitrogen source for crop production. Fertilizer Research 8(2): 107-111Rosecrance RC, Brewbaker JL and Fownes JH (1992) Alley cropping maize with nine leguminoustrees. Agroforestry Systems 17: 159-168SAS Institute Inc., (1985) SAS: User’s guide, Version 5 Edition, SAS Institute Inc., Cary NC,USA, 956pSiaw, DKA, Kang BT and Okali DUU (1991) Alley cropping with Leucaena leucocephala (Lam.)de Wit and Acioa barterii (Hook.f.) Engi. Agroforestry Systems 14:219-23 1.Tian G, Kang BT and Brussaard L (1992) Biological effect of plant residues with contrastingchemical composition under humid tropical conditions - decomposition and nutrient release.Soil Biology and Biochemistry 24: 1051-1060Yamoah CH, Agboola AA and Mulongoy K (1986) Decomposition, nitrogen release and weedcontrol by prunings of selected alley cropping shrubs. Agroforestry Systems 4:234-246615.0. Labour costs of different pruning intervals of Leucaena leucocephala in analley cropping system.5.1. IntroductionThe potential benefits of alley cropping in some areas of the subhumid tropics have been amplydemonstrated (Kang et al., 1981; Atta-Krah, 1988). Soil fertility and crop productivity can bemaintained over long periods and are appealing features of the practice. Yet in order to be readilyadopted, alley cropping must also be economically attractive.A major cost of alley cropping in humid and sub-humid environments is labour for pruning.Some suggest that alley cropping might increase labour demands by at least 50% compared totraditional farming systems (Ngambeki, 1985). This conclusion is based on several prunings duringa growing season of approximately six months. Such frequent pruning may not be suitable for smallholder farmers who face time, labour and economic constraints. Aside from the direct labour costinvolved in pruning hedgerows, delayed pruning can impose costs from yield losses because of tree-crop competition for light, nutrients and/or water (Lawson and Kang, 1991). Such costs haveimplications for adoption of the technology. For example, Indonesian farmers have indicated thatthey would be reluctant to adopt a technology that would reduce maize yields and increase labourdemands (Field and OeMatan, 1991). Hence, pruning management must balance the costs of labourwhile avoiding yield losses.There has also been interest in the potential of alley cropping as a means to control weeds(Boehringer, 1991). If this were the case, weed control might offset some of the increased costsassociated with alley cropping since weeding represents a major labour component during thecropping season and often conflicts with pruning in the same time period (Budelman, 1988).Data on the costs and benefits of the alley cropping are few and have seldom been collected inassociation with crop yield data. Thus, as part of an alley cropping experiment, I collected labourand weed biomass data for different pruning intervals of Leucaena. Labour and maize yield data62were compared in a partial economic analysis to determine desirable pruning intervals.5.2. Materials and MethodsThe pruning schedule is outlined in Table 5.1. During the second year of the experimentpruning intervals were chosen that were consistent with pruning intervals of the previous year andalso reflected situations encountered in on-farm trials (Dvorak, Resource and Crop ManagementProgram, JITA; personal communication). Pruning approximately every 6 weeks after plantingrepresents the case where the farmer prunes midway through the season and at maize harvest. Thethird treatment simulates the situation where the farmer prunes only at maize harvest (pruning atapproximately 12-14 weeks after planting). The 4 and 8-week pruning intervals represent commonon-station, experimental pruning intervals. The last treatment was an unpruned control.Prior to pruning the whole length of hedgerows, a 5 m section was pruned for determininghedgerow biomass and a subsample was taken for dry matter determination and nutrient analysis.At every pruning, I only counted Leucaena stems greater than 1 cm in diameter and measured thediameter of every tenth stem. Pruning of hedgerows was done by machete by field staff who werepaid a task wage upon completion (Naira 20). The time to prune 55m (less 5 m of hedgerow forbiomass determination) of hedgerow was recorded and subsequently converted to days per hectareusing 6 hour work days.For the initial pruning, field staff rotated through blocks. For subsequent prunings, one personpruned all treatments in a block. Prunings were coarsely chopped and spread relatively evenlythroughout the field. Stems greater than 2 cm in diameter were removed from the field.I assessed weed infestation under the 4- and 6- week pruning intervals, and the unpruned plots.Total weed biomass from 0.80 x 1.40 m quadrats was collected prior to every weeding (twiceduring the 1992 maize season and once after maize harvest) and dried at 65°C for dry matterdetermination.63I analyzed data from the initial pruning and subsequent prunings separately. No treatmenteffects were in place for the initial pruning. Labour measurements were only made during the 1992maize growing season and cassava was not considered. Analysis of covariance and regressionanalysis was carried out to determine important relationships between labour time and variablesmeasured using SAS (SAS, 1985).64Table 5.1. Pruning schedule by treatment for the 1992 maize growingseason, Ibadan, Nigeria.Week 4 week 6 week maize harvest 8 week unpruned0 Initial pruning for all treatments - April 14-15123 All treatments planted to maize - May 4-54 All treatments planted to cassava - May 14-15567 Pruning #18910 Pruning #111 Pruning #2 Pruning #112131415 Pruning #31617 Harvest maize from all treatments August 12-1318 Pruning #2 Pruning #119 Pruning #4 Pruning #2655.3. ResultsTo compare different costs of different pruning intervals, it was useful to ascertain what factorsinfluenced pruning labour. It is hypothesized that labour for pruning hedgerows at any given timedepends on the number and size of trees, tree species and the staff or “operator” performing thepruning or (Dvorak, 1992).L = g1{c, Xd, zS}where L = labour for the jth pruning of the ith treatment, hours/hag1 = denotation for ‘a function of..’c = number of trees per lOOm= mean stem diameter (cm)z = operatorS = tree speciesIn this study, I measured tree number and stem diameter, while I disregarded tree species,because only Leucaena was present. For the initial pruning, tree count for 55 m of hedgerowranged from 186 (8455 trees/ha) to 339 (15, 409 trees/ha); mean stem diameter, x, ranged from2.25 to 3.14 cm among blocks. Tree/shrub species would be expected to affect labour times due todifferences in hardness of wood and rates of growth.When data from the first pruning was analyzed, I found that operator effects accounted formost of the variation in pruning time. An analysis of variance showed significant differences amongoperators, with pruning time ranging from 2.4 to 3.7 days/ha. I expected this with the variability inworker endurance. Subsequently, an analysis of covariance was used to test the following model forthe initial pruning:L=BO+Blc+B2xd B3z6+4758where operator 5 (z5) is the reference, and z6, z7 and z8 are dummy variables equal to 1, 2 and 3 foroperator 6,7 and 8 respectively, and equal to 0 otherwise. Neither stand count nor stem diameterwere significant factors in determining time to prune.66I could not use stem diameter and stand counts for analysis of subsequent pruning data, sincemuch of the regrowth from the more frequently pruned treatments was less than 1 cm in diameter(see Materials and Methods). Therefore, time elapsed between prunings was used as a proxy forhedgerow regrowth.L1, = g2{t, z S}whereg2 = denotation for ‘a function of..’= time elapsed since previous pruningPruning labour prior to maize harvest increased relative to time elapsed since the previous pruning(Figure 5.1). Also notable was the drop in pruning time after maize harvest. Thus to determine theeffect of a standing crop in the field on pruning time, the following model was tested:L = B0 + (B1+2h)t + B3z2 + B4z3 + B5z4whereh = 0 if pruning took place before maize harvesth = 1 if pruning took place after maize harvestwhere operator 1 is the reference and z2, z3 and z4 are dummy variables for operators 2,3 and 4.The estimation results (Table 5.2) support the model. Pruning time increased with pruning intervaland rose sharply when maize was in the field and was growing.What effect did longer intervals between prunings have on pruning labour and on maize grainyields? Time elapsed between prunings accounted for 95% of the variation in pruning labour priorto maize harvest (Table 5.3); This relationship was less significant after maize harvest, againpointing to the importance of a standing crop in the field. Maize grain yield was also correlated tomean time elapsed between prunings (Table 5.3). As time between prunings increased so didpruning labour while maize yield decreased. This effect reflects the large differences between maizeyields in treatments that were pruned at least once a season and those that were not (see Table 3 .3ain Chapter 1). Mean grain yield in the latter was 2.1 t/ha compared to 4.6 t/ha with at least one inseason pruning.6716• before harvest14 o after harvest1210SC4. .•02 o0020 40 60 80 100 120Time elapsed between prunings (days)Figure 5.1: Relationship of pruning labour (days/ha) to time elapsed between prunings (days)before and after maize harvest.685.3.1. Comparing costs of treatmentsLabour for pruning at least once a season ranged from 11 to 15 days/ha with respectivecosts ranging from N220/ha to N300/ha. Pruning at harvest only, took an average of 4 days/ha andcost N80/ha at N20/day. There were significant differences in pruning labour times with within-season treatments using more labour than at the end of the season (F= 129.40; P=0.0001)(Table5.4). When I compared total pruning times for different intervals, pruning every 4 or 8 weeksrequired similar labour inputs while pruning at around 6 weeks after planting and at maize harvestonly, required less (Table 5.4).A partial budgeting approach using differences in labour and maize yield was employedto compare the costs and benefits of different pruning treatments.net benefits - net costs = p(Y1-.) - w(L1-L)wherei = pruning treatmentp = price of output, N*ItY = yield of treatment i, t/haY1. = yield of treatment i’, t/haw = wage, N/h andL1 = labour for pruning treatment i, days/ha= labour for pruning treatment i’, days/ha* N = Naira, the Nigerian currency approximately = $0.O3OCANThe average net gain of pruning at least once a season was N59001ha. Pruning once at6-7 weeks after planting and at harvest appears to give the best gain with N883/ha and Nl2OIhamore over pruning every 4 and 8 weeks respectively. Pruning every 4 weeks gave the lowestreturn, with a N900/ha loss compared to the other two in-season treatments.5.3.2. Weed biomassWhile weeding labour time was not recorded, weed biomass differences under variouspruning intervals may indicate some trends. I observed the highest weed dry matter productionduring the maize growing season under the 4-week pruning interval while the lowest was inunpruned plots (Table 5.5). At 4 weeks after planting, weed biomass was low in all treatments after69the application of a herbicide. Weed biomass decreased as the season progressed (Figure 5.2).Weeding labour requirements taken from Ruthenberg (1980) and Boehringer (1991) allow for anestimate of the requirements and costs in this study (Table 5.5). Apparently labour costs could bereduced substantially when hedgerows are not pruned at all; but this strategy has yield costs.Pruning once a season rather than twice may provide a small economic advantage in terms ofreduced weeding labour costs.Table 5.2. Estimation results determining the effect of time elapsed between prunings(days), operator and standing maize crop in alleys on labour for pruning hedgerowsduring the 1992 maize season, Ibadan, Nigeria.Variable Coefficient T-value SE of estimatetime elapsed(h=0)a 0.648 13.47 0.048time elapsed(h=1) 0.113 5.37 0.021operator 1 17.843 3.76 4.751operator 2 13.945 3.12 4.469operator 3 13.834 3.10 4.469operator 4 12.390 2.77 4.469a h=0 when pruning occurred with maize in the alleys, h= 1 whenpruning occurred after maize harvest.Table 5.3. Relationship of pruning labour (days/ha) and maize yield (t/ha) to pruning biomass andtime elapsed between prunings (days) for Leucaena prunings during the 1992 maize growing season,Ibadan, Nigeria.Relationship Equation PPruning labour y=137+3.8x-41x2 0.95 0.0001vs. time elapsedMaize grain yield y=0.01+0.15x-0.001x 0.75 0.0001vs. time elapsed70Table 5.4. Pruning labour (days/ha) for different pruning intervals.Treatment Labour for successive prunings In-season Totallabour labour1-every 4 weeks 5.0 4.0 4.0 2.0 13.Oa 15.Oab(O.11)* (0.23) (0.27) (0.26) (0.20) (0.21)2-at weeding 8.0 3.0 8.Ob 11.Oband after harvest (0.17) (0.54) (0.17) (0.35)3-after harvest 6.0 6.Oc(0.77) (0.77)4-every 8 weeks 14.0 3.0 14.Oa 17.Oa(0.94) (0.49) (0.94) (0.70)5-no pruning none none*standard error in brackets71Table 5.5. Total weed biomass (t/ha) and estimated labour and costrequirements under 4 and 6-week pruning intervals and unpruned plotsduring the 1992 maize growing season.Pruning interval Weed dry matter Labour Cost(weeks) (tlha) (daylha) (Naira)4 1.74(0.20)la* 47 9446 1.53(0.20)a 41 830unpruned 1.13(0.12)b 31 6131 standard error of the mean in parenthesis*values with different letters differ within columns at the 0.05 significancelevel using Duncan’s multiple range test.722.0Figure 5.2: Weed dry matter under 4- and 6- week pruning intervals and in unpruned plots duringthe 1992 maize growing season.1.51.00.504WAP 1OWAP 17WAPWeeks after planting735.4. DiscussionLabour requirements varied significantly with pruning intervals. Pruning at least once duringthe season required more labour and cost between two to three times more than pruning after maizeharvest. Yet the penalty in terms of yield losses when pruning is delayed until after maize harvest islarge at N5900. Thus, the costs of pruning up to 8 weeks after planting are relatively smallcompared to the potential loss of yield and income.Given that maize yields were not significantly lower at 10 weeks, pruning could be delayedto this point, yet this also means greater woody biomass production. Presumably, as therelationships between time elapsed between prunings and pruning labour show, there would be aconsequent increase in labour at 10 weeks. Pruning at 6 weeks after planting gave the mostfavourable economic gains, in terms of labour and maize yield. However, this may coincide withweeding and/or other farm operations, making it an unacceptable time to prune. Pruning later, at 8weeks after planting, has the disadvantage of more cumbersome manoeuvering among tall maize andcassava plants. Pruning every 4 weeks had the advantage of distributing the required labour overthe season but resulted in similar total pruning labour.Pruning later in the maize growing season when the crop is established and manouveringbecomes difficult, is more time-consuming than pruning when there is no crop (as in the initial orpost-harvest prunings). This appeared to be an important factor in determining pruning times,perhaps even more so than actual biomass to be cut. Practically, this difference in pruning timesimplies that economic evaluations of alley cropping should take into account a standing crop andintercrops.Weeding adds another economic consideration to an alley cropping system and while labourfor this activity was not measured and herbicide was applied, the biomass differences suggest someof the benefits and disadvantages of pruning at different times. While weed dry matter and groundcoverage in the post-harvest treatment were lower than in the other pruning intervals, the reduction74in weeding labour is unlikely to offset the loss of yield. A study by Boehringer (1988) on the weedsuppressing effect of different alley cropping species concluded that Leucaena increased rather thandecreased weed populations due to the rapid decomposition of the foliage and release of available N.Similar studies also showed no significant effects of Leucaena mulches on weeds in alleycropped plots, but suggested shade rather than mulch may be important in weed control in alleycropping (Jama et al., 1991; Kang et al., 1988). While a 6 week pruning interval did not reduceweed biomass markedly, the associated labour costs may be reduced substantially to make this aneconomical option for the farmer.This study suggests that once a farmer adopts alley cropping, the costs of not pruning withinthe maize season are large and that costs for pruning within the season are necessary to minimizeyield losses. Yields and costs for pruning once a season are not significantly different from pruningmore than once a season. Hence, pruning once a season, preferably by 8 weeks after planting, willavoid yield losses. If the fanner is able to prune hedgerows at around 6 weeks after planting, theactual labour costs will be lower than at either 4 or 8 weeks after planting.755.5. ReferencesBoehringer A (1991) The potential of alley cropping as a labour efficient management option tocontrol weeds: A hypothetical case. Journal of Agriculture in the Tropics and Subtropics92:3-12Budelman A (1988) The performance of the leaf mulches of Leucaena leucocephala, Flemingiamacrophylla and Gliricidia sepium in weed control. Agroforestry Systems 6:137-145Field SP and OeMatan SS (1990) The effect of cutting height and pruning frequency of Leucaenaleucocephala hedgerows on maize production. Leucaena Research Reports 11:68-69Kang BT, GF Wilson and L Sipkens (1981) Alley cropping maize (Zea mays L.) and leucaena(Leucaena leucocephala Lam) in southern Nigeria. Plant and Soil 63: 165-179Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpeawith Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277Lawson TL and Kang BT (1990) Yield of maize and cowpea in an alley cropping system in relationto available light. Agricultural and Forest Metereology 52: 347-357Ngambeki DS (1985) Economic evaluation of alley cropping Leucaena with maize-maize and maizecowpeas in Southern Nigeria. Agricultural Systems 17:243-258SAS Institute Inc., (1987) SAS: GLM Procedures, Version 5 Edition, SAS Institute Inc., Cary NC,USA, 956p.Sumberg JE and Atta-Krah AN (1988) The potential of alley farming in humid West Africa- a reevaluation. Agroforestry Systems 6:163-168Torres F (1983) Potential contribution of Leucaena hedgerows intercropped with maize to theproduction of organic nitrogen and fuelwood in the lowland tropics. Agroforestry Systems1:323-33376ConclusionsThe results of Chapter 3.0 support earlier work on resource competition between Leucaenahedgerows and associated crops. This systematic study of pruning intervals identified a period inmaize growth where shading by hedgerows was detrimental. Pruning by 10 weeks after planting hadnegligible effects on maize yield, while delaying to maize harvest resulted in 50% yield reductions.By recording both light transmission and soil moisture data over two growing seasons, I was able toisolate light as the limiting factor to maize productivity.In general, the effects of limited light were exacerbated directly adjacent to the hedgerow,particularly for longer pruning intervals. This indicates an inevitable loss in yield when pruning isdelayed beyond 8 weeks after planting. In my experiment, this yield loss adjacent to the hedge didnot reduce overall plot yields, yet under realistic farm conditions (ie. no fertilizer, competition fromweeds, poorer soils), yield declines could be significant. Indeed, large discrepancies exist in theperformance of alley cropped maize and cassava under experimental conditions and on farmer’sfields.Due to the defoliation of cassava under unpruned Leucaena the effects of continuous shading oncassava productivity could not be determined. Yet, even under farm conditions, it is unlikely thathedgerows would not be pruned at least once during the growing period of cassava. Thus, cassavaintercropped with maize, receives the benefits of pruning management that considers only maize.Also since cassava has an extended growing season effects of shading may be “diluted”. Clearly,though, more studies are needed to concentrate on the resource limitations and economicconsequences of intercropped cassava in the search for appropriate pruning intervals for both crops.An effect of applying Leucaena prunings was less clear than light limitations in my study.However, maize nutrient contents under unpruned Leucaena and adjacent to hedgerows followed thesame trend as grain yields. Presumably, under circumstances where nutrients are in short supply, acontribution by Leucaena would be noticeable. For cassava, I might expect an even greater77response to Leucaena prunings because of its extended period of nutrient uptake and longer growingperiod relative to maize.If pruning is delayed beyond the period of maximum crop uptake, Leucaena prunings willprovide longer term benefits rather than conferring immediate nutritional benefits to the crop.Evidence from other studies has shown that applications of prunings near crop planting is mosteffective in terms of crop uptake. Thus, only the initial pruning of the season can not be delayed,while a subsequent one can be at any other time during the maize season. Clearly, a pruninginterval that balances light limitations with crop nutritional and soil fertility benefits is achievable foralley cropped maize.In chapter 5, I conclude that pruning at least once during the maize season is also desirable ineconomic terms. While a decline in economic gain was expected, knowing the relative magnitude isuseful. Furthermore, my data suggests a potential advantage to pruning Leucaena at around 6weeks after planting. This may also be beneficial for reducing weeding labour somewhat.While the results of my thesis indicate a 6 week pruning interval as desirable in terms ofminimizing resource competition, deriving benefits from Leucaena prunings and avoiding economiclosses, any pruning interval must be adapted to the constraints of the farmer. For instance, themiddle of the maize growing season is often compromised by a short supply of labour. Thus, thefarmer has options to delay hedgerow pruning to a period between the middle of the growing seasonand 10 weeks after planting, before she or he encounters losses.My thesis points to a need for further integrative studies on pruning management of Leucaenafor alley crops. Collecting data on several aspects of the system provides holistic information that isessential in promoting the technology. Furthermore, given that on-farm conditions can varydramatically from experimental ones, more trials should be conducted under the former. Integratedand realistic alley cropping trials will aid in the successful adoption of the technology.78AppendicesAppendix AANOVA tables for maize height measurementsANOVA table for maize height, 4 weeks after planting, June 29, 1991.Source DF Type III SS Mean Square F-value PBlock 2 994.6667 497.3333 7.58 0.0074Treat 5 479.8125 95.9625 0.37 0.8549Block*Treat 10 2560.3333 9256.0333 3.90 0.0145Row 1 21.0069 21.0069 0.32 0.5819Treat*Row 5 25.2014 5.0403 0.08 0.9947ANOVA table for maize height, 6 weeks after planting, July 14, 1991.Source DF Type III SS Mean Square F-value PBlock 2 3795.6875 1897.8438 11.36 0.0027Treat 5 1355.5313 271.1063 0.59 0.7109BlOck*Treat 10 3693.1458 461.6432 2.76 0.0673Row 1 1873.3393 1873.3393 11.22 0.0074Treat*Row 5 2535.7005 507.1401 3.04 0.0636ANOVA table for maize height, 8 weeks after planting, July 28, 1991.Source DF Type III SS Mean Square F-value PBlock 2 4297.7260 1432.5753 9.43 0.0022Treat 5 2359.4010 471.8802 1.38 0.3264Block*Treat 10 2738.8257 342.3520 2.25 0. 1059Row 1 1081.1250 1081.1250 7.12 0.0219Treat*Row 5 807.7377 161.5474 1.06 0.4305ANOVA table for maize height, 3 weeks after planting, May 30, 1992Source DF Type ifi SS Mean Square F-value PBlock 3 0.0264 0.0088 1.06 0.3967Treat 4 0.0158 0.0039 0.57 0.6864Block*Treat 12 0.0823 0.0069 0.82 0.6285Row 1 0.0154 0.0154 1.85 0.1939Treat*Row 4 0.0132 00033 0.40 0. 808879ANOVA table for maize height, 5 weeks after planting, June 10, 1992.Source DF Type III 55 Mean Square F-value PBlock 3 0.0543 0.0181 0.85 0.4861Treat 4 0.0798 0.0199 0.43 0.78 10Block*Treat 12 0.5501 0.0458 2.16 0.0799Row 1 0.0774 0.0774 3.65 0.0753Treat*Row 4 0.1278 0.0320 1.51 0.2498ANOVA table for maize height, 6 weeks after planting, June 20, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0501 0.0167 1.53 0.2473Treat 4 0.0218 0.0054 0.51 0.7297Block*Treat 12 0. 1285 0.0107 0.98 0.5051Row 1 0.1323 0.1323 12.13 0.0033Treat*Row 4 0.0068 0.0017 0.16 0.9575ANOVA table for maize height, 8 weeks after planting, July 1, 1992.Source DF Type III SS Mean Square F-value__J PBlock 3 5114.4188 1704.8063 5.07 0.0128Treat 4 3658.2500 914.5625 1.24 0.3458Block*Treat 12 8854.8000 737.9000 2.19 0.0763Row 1 5917.0563 5917.0563 17.59 0.0008Treat*Row 4 1223.9750 306.9938 0.91 0.4834ANOVA table for maize height, 10 weeks after planting, July 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0183 0.0061 2.50 0.0992Treat 4 0.0621 0.0155 2.87 0.0699Block*Treat 12 0.0648 0.0054 2.21 0.0744Row 1 0.0484 0.0484 19.79 0.0005Treat*Row 4 00039 0.0010 0.40 0.8047ANOVA table for maize height, 12 weeks after planting, July 27, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0145 0.0050 2.73 0.0804Treat 4 0. 1220 0.0305 17.73 0.0001Block*Treat 12 0.0207 0.0017 0.95 0.5292Row 1 0.0134 0.0134 7.40 0.0158Treat*Row 4 0.0089 0.0022 1.23 0.339680ANOVA table for maize stem diameter, 8 weeks after planting, July 1, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.1052 0.0351 1.68 0.2146Treat 4 0.1234 0.0308 0.66 0.6329Block*Treat 12 0.5629 0.0469 2.24 0.0707Row 1 0.6669 0.6669 31.90 0.0001Treat*Row 4 0.1490 0.0373 1.78 0.1850ANOVA table for maize stem diameter, 10 weeks after planting, July 16, 1992.Source DF Type ifi SS Mean Square F-value PBlock 3 0.0022 0.0011 0.06 0.9378Treat 4 0.0764 0.0191 2.36 0. 1402Block*Treat 12 0.0647 0.0081 0.47 0.8505Row 1 0.4296 0.4296 25.03 0.0005Treat*Row 4 0.0600 0.0150 0.87 0.5134ANOVA table for maize stem diameter, 12 weeks after planting, July 27, 1992.Source DF Type ifi SS Mean Square F-valueBlock 3 9.2775 3.0925 1.50 0.2539Treat 4 26.4075 6.6021 2.69 0.0824Block*Treat 12 29.4462 2.4538 1.19 0.3674Row 1 48.8412 48.8412 23.76 0.0002Treat*Row 4 2.6259 0.6565 0.32 0. 8606ANOVA table for maize stem diameter, 13 weeks after planting, August 10, 1992._Source DF Type III SS Mean Square F-value PBlock 3 0.0211 0.0070 2.16 0.1357Treat 4 0. 1429 0.0357 5.95 0.0071Block*Treat 12 0.0721 0.0060 1.85 0.1308Row 1 0.1405 0.1405 43.19 0.0001Treat*Row 4 0.0188 0.0047 1.44 0.268382ANOVA tables for maize leaf numberANOVA table for maize leaf number, 3 weeks after planting, May 30, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0145 0.0048 0.78 0.5218Treat 4 0.0378 0.0094 0.97 0.4591Block*Treat 12 0.1168 0.0097 1.58 0.2006Row 1 0.0257 0.0257 4.16 0.0594Treat*Row 4 0.0490 0.0123 1.99 0. 1485ANOVA table for maize leaf number, 5 weeks after planting, June 10, 1992.Source DF Type Ill SS Mean Square F-value PBlock 3 0.0107 0.0036 1.53 0.2469Treat 4 0.0195 0.0049 0.99 0.4486Block*Treat 12 0.0589 0.0049 2.12 0.0853Row 1 0.0128 0.0128 5.52 0.0329Treat*Row 4 0.0200 0.0005 2.16 0.1232ANOVA table for maize leaf number, 6 weeks after planting, June 20, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0076 0.0025 1.33 0.3030Treat 4 0.0044 0.0011 0.09 0.9853Block*Treat 12 0. 1538 0.0128 6.68 0.0005Row 1 0.0666 0.0666 34.76 0.0001Treat*Row 4 0.0074 0.0019 0.97 0.4540ANOVA table for maize leaf number, 8 weeks after planting, July 1, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0073 0.0024 2.29 0.1199Treat 4 0.0032 0.0008 0.34 0.8464Block*Treat 12 0.0284 0.0024 2.22 0.0728Row 1 0.0059 0.0059 5.58 0.0321Treat*Row 4 0.0059 0.0015 1.40 0.282983ANOVA table for maize leaf number, 10 weeks after planting, July 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0024 0.0012 0.34 0.7213Treat 4 0.0532 0.0133 2.19 0.1603Block*Treat 12 0.0486 0.0061 1.68 0.2180Row 1 0.0326 0.0326 9.02 0.0133Treat*Row 4 0.0236 0.0059 1.63 0.2420ANOVA table for maize leaf number, 12 weeks after planting, July 27, 1992.Source DF Type ifi SS Mean Square F-value PBlock 3 0.0079 0.0026 1.10 0.3784Treat 4 0.0072 0.0018 0.94 0.4763Block*Treat 12 0.0232 0.0019 0.81 0.6376Row 1 0.0059 0.0059 2.49 0.1354Treat*Row 4 0.0153 0.0038 1.60 0.2246ANOVA table table for maize leaf number, 13 weeks after planting, August 10, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0362 0.0121 8.94 0.0012Treat 4 0.0376 0.0094 1.96 0. 1653Block*Treat 12 0.0575 0.0048 3.55 0.0116Row 1 0.0090 0.0090 6.66 0.0209Treat*Row 4 0.0065 0.0016 1.20 0.3523ANOVA tables for maize LAIANOVA table for maize LAI, 6 weeks after planting, July 11, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.0052 0.0026 0.12 0.8843Treat 5 0.0167 0.0033 0.16 0.9722ANOVA table for maize LAI, 8 weeks after planting, July 26, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.0824 0.0165 1.28 0.3008Treat 5 0.0020 0.0020 0.16 0.695484ANOVA table for maize LAI 4 weeks after planting, June 5, 1992.Source DF Type III SS Mean Square F-value P jBlock 3 1723.3799 574.4604 9.60 0.0013Treat 4 366.2712 91.5685 1.24 0.3464Block*Treat 12 887.6654 73.9722 1.24 0.3538Row 1 18.5512 18.5513 0.31 0.5871Treat*Row 4 930.7711 232.6939 3.89 0.0273ANOVA table for maize LAI, 6 weeks after planting, June 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 332.5505 110.8503 0.71 0.5610Treat 4 341.7135 85.4286 0.62 0.6560Block*Treat 12 1649.8888 137.4918 0.88 0.5819Row 1 87.0253 87.0253 0.56 0.4669Treat*Row 4 796.2887 199.0727 1.28 0.3232ANOVA table for maize LAI, 8 weeks after planting, July 1, 1992.Source DF Type III SS Mean Square F-value PBlock 3 1824.4044 608.1357 1.66 0.2237Treat 4 1368.4417 342.1108 1.28 0.3336Block*Treat 12 3219.4338 268.2865 0.73 0.7017Row 1 17.9175 17.9179 0.05 0.8284Treat*Row 4 1366.9699 341.7425 0.93 0.4742ANOVA table for maize LAI 12 weeks after planting, August 6, 1992.Source DF Type III SS Mean Square F-value PBlock 3 1426.0312 475.3446 1.54 0.2712Treat 4 421.2715 210.6358 0.41 0.6798Block*Treat 12 3051.8137 508.6356 1.65 0.2402Row 1 243.8449 243.8449 0.79 0.3978Treat*Row 4 76.688 38.3449 0.12 0.885985ANOVA tables for maize reproductive stage measurementsANOVA table for number of maize plants shedding pollen.Source DF Type III SS Mean Square F-value PBlock 3 299.7972 99.932 1 0.53 0.6702Treat 4 1544.0573 386.0142 3.06 0.0603Block*Treat 12 1515.6564 126.3053 0.67 0.7574Row 1 566.5072 566.5074 2.99 0.1044Treat*Row 4 83.1394 20.7853 0.11 0.9772ANOVA table for number of maize plants tasseling.Source DF Type III SS Mean Square F-value PBlock 3 188.8812 62.9602 0.57 0.6455Treat 4 1387.1583 346.7894 3.33 0.0476Block*Treat 12 1248.6344 104.0534 0.94 0.5384Row 1 492.4535 492.4533 4.44 0.0526Treat*Row 4 116.7124 29.1782 0.26 0.8978ANOVA table for number of maize plants silking.Source DF Type III SS Mean Square F-value PBlock 3 292.0555 97.3522 0.79 0.5215Treat 4 6588.2626 1647.0654 18.17 0.0001Block*Treat 12 1088.9937 90.6667 0.73 0.7045Row 1 1829.9323 1892.9338 14.76 0.0026Treat*Row 4 428.9282 107.2325 0.87 0.5077ANOVA tables for maize grain yieldANOVA table for 1991 maize grain yield.Source DF Type III SS Mean Square F-value PBlock 2 1.4474 0.7233 27.39 0.0001Treat 5 5.2201 1.0440 3.25 0.0530Block*Treat 10 3.2082 0.3208 12.15 0.0001Row 1 0.2922 0.2922 11.06 0.0018Treat*Row 5 0.2129 0.0426 1.61 0.177886ANOVA table for 1991 maize stover yield.Source DF Type ifi SS Mean Square F-value PBlock 2 0.0219 0.0109 0.42 0.6582Treat 5 0.5261 0.1052 0.94 0.4932Block*Treat 10 1.1135 0.1113 4.30 0.0004Row 1 0.0008 0.0008 0.03 0.8583Treat*Row 5 0.3155 0.0631 2.44 0.0500ANOVA table table for 1991 maize harvest index.Source DF Type Ill SS Mean Square F-value P jBlock 2 0.7567 0.3784 25.30 0.0001Treat 5 2.2804 0.4561 2.27 0. 1259Block*Treat 10 2.0051 0.2005 13.41 0.0001Row 1 0.0795 0.0796 5.32 0.0261Treat*Row 5 0.2418 0.0430 2.87 0.0256ANOVA table table for 1992 maize grain yield.Source DF Type III SS Mean Square F-value PBlock 3 1.4048 0.4683 5.27 0.0110Treat 4 57.8472 14.4621 27.19 0.0001Block*Treat 12 6.3824 0.5319 5.99 0.0009Row 1 0.5832 0.5832 6.56 0.0217Treat*Row 4 0.8658 0.2164 2.44 0.0926ANOVA table table for 1992 maize stover yield.Source DF Type III SS Mean Square F-value PBlock 3 21.5731 7.1909 10.64 0.0005Treat 4 69.9993 17.5002 11.54 0.0001Block*Treat 12 18.2012 1.5168 2.24 0.0706Row 1 2.2563 2.2563 3.34 0.0877Treat*Row 4 0.5200 0.1300 0.19 0.9387ANOVA table table for 1992 maize harvest index.Source DF Type III SS Mean Square F-value PBlock 3 0.0178 0.0059 6.48 0.0050Treat 4 0.0416 0.0104 4.54 0.0183Block*Treat 12 0.0274 0.0023 2.50 0.0482Row 1 0.0001 0.0001 0.15 0.7029Treat*Row 4 0.0038 00010 1.05 0.415287ANOVA table table for maize cob length at harvest, August 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 263.5331 87.8442 4.73 0.0162Treat 4 4637.8792 1159.4701 19.64 0.0001Block*Treat 12 708.3713 59.0312 3.18 0.0194Row 1 29.0701 29.0704 1.56 0.2303Treat*Row 4 183.3814 45.8451 2.47 0.0901ANOVA table table for maize cob width at harvest, August 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 7058.0001 2352.6671 2.65 0.0872Treat 4 248158. 1302 62039.5332 24.01 0.0001Block*Treat 12 31005.7481 2583.8121 2.91 0.0271Row 1 9711.0302 9711.0302 10.94 0.0052Treat*Row 4 9428. 1281 2357.0323 2.65 0.0741ANOVA table table for maize kernel number at harvest, August 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0. 1942 0.0652 3.21 0.0531Treat 4 3.1403 0.7853 22.07 0.0001Block*Treat 12 0.4272 0.0364 1.77 0. 1483Row 1 0.1104 0.1102 5.45 0.0342Treat*Row 4 0.1353 0.0343 1.68 0.2072ANOVA table table for maize kernel weight at harvest, August 16, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0173 0.0053 2.41 0. 1082Treat 4 0.8962 0.2242 22.49 0.000 1Block*Treat 12 0. 1204 0.0014 4.59 0.0034Row 1 0.0424 0.0423 19.21 0.0013Treat*Row 4 0.0553 0.0142 6.38 0.003488ANOVA tables for cassava height measurementsANOVA table for cassava height at 5 weeks after planting, July 7, 1991.Source DF Type III SS Mean Square F-value PBlock 2 164.1806 82.0903 4.52 0.0343Treat 5 925.2847 185.0569 3.99 0.0298Block*Treat 10 463.2361 46.3236 2.55 0.0635Row 1 333.0625 333.0625 18.35 0.0011Treat*Row 5 237.5625 47.5125 2.62 0.0798ANOVA table for cassava height at 6 weeks after planting, July 14, 1991.Source DF Type ifi SS Mean Square F-value PBlock 2 182.0972 91.0486 2.18 0.1559Treat 5 3292.0347 685.4069 11.66 0.0006Block*Treat 10 564.7361 56.4736 1.35 0.3065Row 1 845.8403 845.8403 20.24 0.0007Treat*Row 5 522.5347 104.5069 2.50 0.0898ANOVA table for cassava height at 8 weeks after planting, July 27, 1991.Source DF Type Ill SS Mean Square F-value PBlock 2 710.6806 355.3403 2.88 0.0950Treat 5 4872. 1389 974.4278 14.46 0.0003Block*Treat 10 673.6528 67.3653 0.55 0.8267Row 1 56.2500 56.2500 0.46 0.5121Treat*Row 5 598.8333 119.7667 0.97 0.4729ANOVA table for cassava height at 10 weeks after planting, August 10, 1991.Source DF Type III SS Mean Square F-value PBlock 2 350.0972 175.0486 0.50 0.6194Treat 5 2620.8056 524.1611 1.86 0.1880Block*Treat 10 2811.9861 281.1986 0.80 0.6324Row 1 4.0000 4.0000 0.01 0.9168Treat*Row 5 1580.8333 316.1667 0.90 0.511589ANOVA table for cassava height at 12 weeks after planting, August 23, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.0276 0.0138 0.40 0.6808Treat 5 0.7405 0.1481 4.50 0.0207Block*Treat 10 0.3288 0.0329 0.94 0.5291Row 1 0.0039 0.0039 0.11 0.7433Treat*Row 5 0.1107 0.0221 0.64 0.6763ANOVA table for cassava height at 14 weeks after planting, September 7, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.1136 0.0568 1.38 0.2890Treat 5 0.4190 0.0864 4.09 0.0277Block*Treat 10 0.2110 0.0211 0.51 0.8512Row 1 0.0140 0.0139 0.34 0.5711Treat*Row 5 0.0249 0.0050 0.12 0.9850ANOVA table for cassava height at 16 weeks after planting, September 20, 1991.Source DF Type III SS Mean Square F-value PBlock 2 445.3507 222.6753 0.39 0.6863Treat 5 6348.3299 1269.6660 6.42 0.0151Block*Treat 10 1284.7743 197.8249 0.35 0.9106Row 1 213.4222 213.4222 0.38 0.5548Treat*Row 5 642.8417 128.5683 0.23 0.9416ANOVA table for cassava height at 18 weeks after planting, October 10, 1991 (logged).Source DF Type III SS Mean Square F-value PBlock 2 0.1151 0.0576 2.88 0.0954Treat 5 0.1807 0.0361 1.28 0.3437Block*Treat 10 0.2816 0.0282 1.41 0.2837Row 1 0.0533 0.0533 2.66 0. 1285Treat*Row 5 0.0395 0.0079 0.39 0. 8433ANOVA table for cassava height at 20 weeks after planting, October 28, 1991.Source DF Type Ill SS Mean Square F-value PBlock 2 0.4018 0.2009 0.00 0.9997Treat 4 3219.1287 643.8257 1.72 0.2166Block*Treat 8 3733.5625 373.3563 0.50 0.8595Row 1 3.2452 3.2452 0.00 0.9488Treat*Row 4 3047.7169 609.5434 0.81 0.565290ANOVA table for cassava height at 24 weeks after planting, November 20, 1991.Source DF Type III SS Mean Square F-value PBlock 2 3793.0556 1896.5278 9.52 0.0033Treat 4 4395. 1389 879.0278 2.56 0.0970Block*Treat 8 3440.2778 344.0278 1.73 0.1836Row 1 667.3611 667.3611 1.37 0.2154Treat*Row 4 1840.9722 368.1944 1.85 0.1776ANOVA table for cassava height at 4 weeks after planting, June 9, 1992.Source DF Type III SS Mean Square F-value PBlock 3 174.8188 58.2729 2.36 0.1125Treat 4 179.7875 44.9469 1.63 0.2292Block*Treat 12 329.9625 27.4969 1.11 0.4152Row 1 138.7563 138.7563 5.62 0.0316Treat*Row 4 55.5875 13.8969 0.56 0.6932ANOVA table for cassava height at 6 weeks after planting, June 23, 1992.Source DF Type Ill SS Mean Square F-value PBlock 3 929.7688 309.9229 8.92 0.0012Treat 4 1498.4375 374.6094 2.72 0.0804Block*Treat 12 1654.5125 137.8760 3.97 0.0070Row 1 381.3063 381.6063 10.97 0.0047Treat*Row 4 342.6625 85.6656 2.46 0.0899ANOVA table for cassava height at 10 weeks after planting, July 20, 1992.Source DF Type ifi SS Mean Square F-value PBlock 3 152.0688 50.6896 0.20 0.8928Treat 4 3969.8125 992.4531 2.73 0.0791Block*Treat 12 4354.8375 362.9031 1.45 0.2444Row 1 200.2563 200.2563 0.80 0.3848Treat*Row 4 1349.3375 337.3344 1.35 0.2974ANOVA table for cassava height at 14 weeks after planting, August 25, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0. 1382 0.0461 2.89 0.0792Treat 4 0.4197 0. 1049 18.03 0.0003Block*Treat 12 0.0524 0.0058 0.37 0.9308Row 1 0.1105 0.1105 6.94 0.0218Treat*Row 4 0.1140 0.0285 1.79 0.195891ANOVA tables for cassava stem diameterANOVA table for cassava stem diameter at 10 weeks after planting, August 12, 1991.Source DF Type HI SS Mean Square F-value PBlock 2 0.1745 0.0872 1.16 0.3218Treat 2 0.6961 0.3480 3.52 0.1312Block*Treat 4 0.3952 0.0988 1.31 0.2770Row 1 0.2895 0.2895 3.84 0.0548Treat*Row 2 0.43 10 0.2 155 2.85 0.0654ANOVA table for cassava stem diameter at 12 weeks after planting, August 23, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.2013 0.1006 1.23 0.2990Treat 2 0. 1508 0.0754 2.55 0. 1933Block*Treat 4 0.1183 0.0296 0.36 0.8346Row 1 0.1693 0.1693 2.07 0.1552Treat*Row 2 0.0125 0.0063 0.08 0.9263ANOVA table for cassava stem diameter at 14 weeks after planting, September 7, 1991.Source DF Type HI SS Mean Square__[__F-value__j PBlock 2 4.5843 2.2918 0.50 0.6066Treat 2 49.4446 24.7222 3.71 0. 1226Block*Treat 4 26.6382 6.6596 1.47 0.2254Row 1 7.5561 7.5561 1.66 0.2027Treat*Row 2 11.7821 5.8911 1.30 0.2818ANOVA table for cassava stem diameter at 16 weeks after planting, September 20,1991.Source DF Type Ill SS Mean Square F-value PBlock 2 45.6168 22.8048 6.23 0.0038Treat 2 145.7016 72.8508 52.35 0.0014Block*Treat 4 5.5668 1.3917 0.38 0.8218Row 1 15.9078 15.9078 4.35 0.0421Treat*Row 2 1.6117 0.8058 0.22 0.8032ANOVA table for cassava stem diameter at 18 weeks after planting, October 9,1991.Source DF Type III SS Mean Square F-value PBlock 2 21.5394 10.7697 2.90 0.0642Treat 2 394.8935 197.4468 42.45 0.0020Block*Treat 4 18.6046 4.6512 1.25 0.3010Row 1 2.3229 2.3229 0.63 0.4327Treat*Row 2 16.8488 8.4244 2.27 0.113992ANOVA table for cassava stem diameter at 20 weeks after planting, October 28,1991.Source DF Type Ill SS Mean Square F-value PBlock 2 0.0252 0.0126 0.73 0.4887Treat 2 4.1165 2.0582 71.36 0.0007Block*Treat 4 0.1154 0.0288 1.66 0.1729Row 1 0.0779 0.0779 4.49 0.0390Treat*Row 2 0.0614 0.0307 1.77 0.1804ANOVA table for cassava stem diameter at 24 weeks after planting, November 20,1991.Source DF Type III SS Mean Square F-value__J PBlock 2 1.7791 0.8896 0.16 0.8497Treat 2 605.6722 302.8361 13.97 0.0157Block*Treat 4 86.7095 21.6774 3.98 0.0069Row 1 23.9279 23.9279 4.39 0.0411Treat*Row 2 34.8911 17.4456 3.20 0.0489ANOVA table for cassava stem diameter at 8 weeks after planting, July 9, 1992.Source DF Type III SS Mean Square F-value PBlock 3 2.5187 0.8396 2.34 0.1147Treat 4 1.4321 0.3580 1.00 0.4391Block*Treat 12 16.2429 1.3536 3.77 0.0088Row 1 0.1626 0.1626 0.45 0.5111Treat*Row 4 3.8509 0.9627 2.68 0.0721ANOVA table for cassava stem diameter at 10 weeks after planting, July 20, 1992._Source DF Type III SS Mean Square F-value PBlock 3 2.0833 0.6944 1.02 0.4105Treat 4 8.2609 2.0652 3.05 0.0599Block*Treat 12 8.1311 0.6776 1.00 0.4935Row 1 0.1000 0.1000 0.15 0.7066Treat*Row 4 3.6544 0.9136 1.35 0.2991ANOVA table for cassava stem diameter at 14 weeks after planting, August 25, 1992.Source DF Type ifi SS Mean Square F-value PBlock 3 1.0741 0.3580 0.61 0.6208Treat 4 0.7496 0.1834 0.50 0.7346Block*Treat 12 3.3491 0.3721 0.63 0.7489Row 1 1.5729 1.5729 2.68 0.1274Treat*Row 4 3.1411 0.7853 1.34 0.311393ANOVA tables for cassava node numberANOVA table for cassava node number at 9 weeks after planting, August 4, 1991.Source DF Type ifi 55 Mean Square F-value PBlock 2 0.0924 0.0462 3.44 0.1349Treat 1 0.5760 0.5761 24.33 0.0387Block*Treat 2 0.0474 0.0237 1.77 0.2821Row 1 0.0002 0.0002 0.02 0.9069Treat*Row 1 0.0476 0.0476 3.55 0.1328ANOVA table for cassava node number at 11 weeks after planting, August 17, 1991.Source DF Type ifi SS Mean Square F-value PBlock 2 17.5833 8.7917 0.77 0.5024Treat 2 324.0833 162.0417 141.42 0.0002Block*Treat 4 4.5833 1.1458 0.11 0.9781Row 1 29.3889 29.3889 2.59 0.1589Treat*Row 2 40.1944 20.0972 1.77 0.2489ANOVA table for cassava node number at 13 weeks after planting, August 30, 1991.Source DF Type III SS Mean Square F-value PBlock 2 13.0833 6.5417 0.55 0.6034Treat 2 334.0833 167.0417 25.62 0.0052Block*Treat 4 26.0833 6.5208 0.55 0.7080Row 1 1.3889 1.3889 0.12 0.7442Treat*Row 2 37.5278 18.7639 1.58 0.2814ANOVA table for cassava node number at 17 weeks after planting, September 27, 1991._Source DF Type III SS Mean Square F-value PBlock 2 0.4332 0.2166 1.13 0.3832Treat 2 13.3485 6.6742 10.95 0.0239Bloek*Treat 4 2.4381 0.6095 3.18 0. 1000Row 1 0.2027 0.2027 1.06 0.3434Treat*Row 2 1.7011 0.8506 4.44 0.0656ANOVA table for cassava node number at 20 weeks after planting, October 28, 1991.Source DF Type III SS J Mean Square F-value PBlock 2 17.3315 8.6658 0.97 0.4209Treat 3 793.0784 264.3595 9.85 0.0098Block*Treat 6 161.0195 26.8365 2.99 0.0772Row 1 9.6845 9.6845 0.12 0.5984Treat*Row 3 69.3265 23.1088 0.29 0.245794ANOVA table for cassava node number at 4 weeks after planting, June 9, 1992.Source DF Type III SS Mean Square F-value PBlock 3 21.8750 7.2917 2.11 0.1414Treat 4 27.5250 6.8813 1.49 0.2658Block*Treat 12 55.3750 4.6146 1.34 0.2934Row 1 0.2250 0.2250 0.07 0.8019Treat*Row 4 1.5250 0.3813 0.11 0.9769ANOVA table for cassava node number at 6 weeks after planting, June 23, 1992.Source DF Type III SS Mean Square F-value PBlock 3 16.6500 5.5500 7.70 0.0024Treat 4 58.6625 14.6656 6.28 0.0058Block*Treat 12 28.0375 2.3365 3.24 0.0172Row 1 18.2250 18.2250 25.28 0.0010Treat*Row 4 16.2125 4.0531 5.62 0.0057ANOVA table for cassava node number at 8 weeks after planting, July 9, 1992.Source DF Type III SS Mean Square F-value PBlock 3 699.3688 233.1229 2.51 0.0984Treat 4 6734.6875 1683.6719 9.76 0.0009Block*Treat 12 2069.4125 172.4510 1.85 0. 1291Row 1 85.5563 85.5563 0.92 0.3527Treat*Row 4 588.2875 147.0719 1.58 0.2304ANOVA table for cassava node number at 10 weeks after planting, July 20, 1992.Source DF Type Ill SS Mean Square F-value PBlock 3 20.8188 6.9396 1.92 0.1694Treat 4 16.0875 4.0219 1.15 0.3799Block*Treat 12 41.9625 3.4969 0.97 0.5 147Row 1 1.0563 1.0563 0.29 0.5965Treat*Row 4 14.1625 3.5406 0.98 0.4474ANOVA tables for cassava LAIANOVA table for cassava LAI at 5 weeks after planting, July 7, 1991.Source DF Type III SS Mean Square__[__F-value PBlock 2 0.0055 0.0028 1.03 0.2138Treat 5 0.0086 0.0017 2.70 0.092095ANOVA table for cassava LAI at 8 weeks after planting, July 24, 1991._Source j DF Type III SS Mean Square F-value PBlock 2 0.0027 0.0013 1.65 0.3292Treat 5 0.0094 0.0019 2.65 0.0887Block*Treat 10 0.0071 0.0007 0.87 0.6255Row 5 0.0028 0.0006 0.82 0.6616Treat*Row 1 0.0003 0.0003 0.34 0.5989ANOVA table for cassava LAI at 10 weeks after planting, August 7, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.0027 0.0013 0.27 0.7719Treat 5 0.0655 0.0013 0.27 0.2286Block*Treat 10 0.0505 0.0051 0.87 0. 1255Row 1 0.0002 0.0002 0.00 0.9489Treat*Row 5 0.0037 0.0007 0.12 0.7014ANOVA table for cassava LAI at 12 weeks after planting, August 21, 1991.Source DF Type HI SS Mean Square F-value PBlock 2 0.0198 0.0099 0.47 0.7180Treat 5 0.0465 0.0093 3.57 0.0635Block*Treat 10 0.0182 0.0018 0.27 0.8751Row 1 0.0007 0.0007 0.03 0.8871Treat*Row 5 0.0001 0.0000 0.00 0.9620ANOVA table for cassava LAI at 14 weeks after planting, September 5, 1991.Source DF Type III SS Mean Square F-value__J PBlock 2 0.2894 0.1447 85.78 0.0001Treat 5 4.4434 0.8887 5.72 0.0204Block*Treat 7 1.0877 0.1554 92.13 0.0001Row 1 0.1093 0.1093 64.78 0.0001Treat*Row 3 0.9607 0.3202 189.86 0.0001ANOVA table for cassava LAI at 18 weeks_after_planting, October 10, 1991._Source DF Type III SS Mean Square F-value PBlock 2 0.7164 0.3582 16.35 0.0001Treat 5 4.9318 0.9864 4.78 0.0322Block*Treat 7 1.4447 0.2064 9.42 0.0001Row 1 0.5532 0.5532 25.25 0.0001Treat*Row 2 0.6761 0.3381 15.43 0.000196ANOVA table for cassava LAI at 20 weeks after planting, October 28, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.2894 0.1447 85.78 0.0001Treat 5 4.4434 0.8887 5.72 0.0204Block*Treat 7 1.0876 0.1554 92.13 0.0001Row 1 0.1093 0.1093 64.78 0.0001Treat*Row 3 0.9607 0.3202 189.86 0.0001ANOVA table for cassava LAI at 5 weeks after planting, June 20, 1992.Source DF Type ifi SS Mean Square F-value PBlock 3 0.0017 0.0006 3.40 0.0455Treat 4 0.0006 0.0001 0.89 0.4999Block*Treat 12 00020 0.0002 1.02 0.4790Row 1 0.0006 0.0006 3.96 0.0652Treat*Row 4 0.0012 0.0003 1.91 0.1611ANOVA table for cassava LAI at 8 weeks after planting, July 10, 1992.Source DF Type Ill SS Mean Square F-value PBlock 3 0.0010 0.0003 1.75 0.1996Treat 4 0.0005 0.0001 0.52 0.7225Block*Treat 12 0.0028 0.0002 1.26 0.3290Row 1 0.0002 0.0002 1.10 0.3110Treat*Row 4 0.0004 0.0001 0.52 0.7207ANOVA tables for cassava pre-harvest measurementsANOVA table for cassava total node number prior to harvest.Source DF Type III SS Mean Square F-value PBlock 2 0.2010 0. 1005 3.45 0.0724Treat 4 0.2224 0.0556 1.99 0.1891Block*Treat 8 0.2236 0.0279 0.96 0.5134Row 1 0.0661 0.0661 2.27 0. 1627Treat*Row 4 0.2285 0.0571 1.96 0.1765ANOVA table for number of forking levels in cassava prior to harvest.Source DF Type III SS Mean Square__J__F-value PBlock 2 0.0647 0.0324 1.08 0.3751Treat 4 0.1793 0.0448 1.90 0.2034Block*Treat 8 0. 1884 0.0236 0.79 0.6245Row 1 0.0228 0.0228 0.76 0.4027Treat*Row 4 0.1238 0.0310 1.04 0.435397ANOVA table for total number of forks in cassava prior to harvest.Source DF Type UI SS Mean Square F-value PBlock 2 0.2642 0.1321 1.07 0.3797Treat 4 0.4534 0.1133 1.04 0.4440Block*Treat 8 0.8724 0.1090 0.88 0.5621Row 1 0.1761 0.1761 1.42 0.2602Treat*Row 4 0.5028 0.1257 1.02 0.4440ANOVA tables for cassava yieldANOVA table for cassava total yield (roots, main and lateral shoot).Source DF Type III SS Mean Square F-value PBlock 2 99.6955 49.8478 1.85 0.2270Treat 4 430.2757 107.5689 4.02 0.0530Block*Treat 7 187.5106 26.7872 0.99 0.5039Row 1 10.7756 10.7756 0.40 0.5476Treat*Row 4 513.6667 128.4167 4.76 0.0359ANOVA table for cassava lateral shoot yield (stem and leaves).Source DF Type ifi SS Mean Square F-value PBlock 2 261.3978 130.6989 10.38 0.0080Treat 4 635.5191 158.8798 7.01 0.0135Block*Treat 7 158.5508 22.6501 1.80 0.2282Row 1 2.8269 2.8269 0.22 0.6500Treat*Row 4 73.4063 18.3516 1.46 0.3107ANOVA table for cassava harvest index.Source DF Type III SS Mean Square F-value PBlock 2 572.0000 286.0000 17.58 0.0019Treat 4 343.1059 85.7765 3.69 0.0636Block*Treat 7 162.5692 23.2242 1.43 0.3251Row 1 12.1298 12. 1298 0.75 0.4164Treat*Row 4 23.2604 5.8151 0.36 0.831598ANOVA tables for 1992 soil moisture samplesANOVA table for gravimetric soil moisture content at 4 weeks after planting, June 3, 1992Source DF Type III SS Mean Square F-value PBlock 3 0.5824 0.1941 24.67 0.0001Treat 2 0.2295 0.0786 1.58 0.0015Block*Treat 6 0.3339 0.0557 7.07 0.0051Row 1 0.0773 0.0773 9.83 0.0120Treat*Row 2 0.0124 0.0062 0.79 0.4842ANOVA table for gravimetric soil moisture content at 5 weeks after planting, June 9, 1992Source DF Type Ill SS Mean Square F-value PBlock 3 0.0514 0.0171 2.56 0.1284Treat 2 0.0839 0.0419 2.14 0. 1992Block*Treat 6 0.1178 0.0196 2.93 0.0810Row 1 0.0060 00060 0.89 0.3722Treat*Row 2 0.0442 0.0221 3.30 0.0900ANOVA table for gravimetric soil moisture content at 5 weeks after planting, June 10, 1992_Source DF Type III SS Mean Square F-value PBlock 3 0.0242 0.0242 3.14 0.2185Treat 2 0.0005 0.0005 0.06 0.8314Block*Treat 6 0.0007 0.0007 0.09 0.7902Row 1 0.0070 0.0035 0.46 0.6870Treat*Row 2 0. 1550 0.0775 9.69 0.0539ANOVA table for_gravimetric soil moisture content at 8 weeks after planting, June 29, 1992Source DF_[ Type III SS Mean Square F-value PBlock 3 0.2041 0.0680 0.64 0.6156Treat 2 0.0839 0.0140 0.13 0.9879Block*Treat 6 0.0006 0.0006 0.01 0.9420Row 1 0. 1496 0.0748 0.70 0.5289Treat*Row 2 0.1027 0.0514 3.68 0.0908ANOVA table for gravimetric soil moisture content at 11 weeks after planting, July 22, 1992Source DF Type III SS Mean Square J__F-value PBlock 3 0.1119 0.0373 10.93 0.0023Treat 2 0.2274 0.1137 2.86 0.1342Block*Treat 6 0.2386 0.0389 11.66 0.0008Row 1 0.0618 0.0618 18.13 0.0021Treat*Row 2 0.0174 0.0087 2.87 0. 132199ANOVA table for gravimetric soil moisture content at 11 weeks after planting, July 23, 1992_Source DF Type III SS Mean Square F-value PBlock 3 0.0141 0.0047 1.18 0.3723Treat 2 0.2510 0.1255 4.67 0.0599Block*Treat 6 0.1614 0.0369 9.20 0.0142Row 1 0.0369 0.0034 0.85 0.4601Treat*Row 2 0.0068 0.0269 6.71 0.0062ANOVA table for gravimetric soil moisture content at 12 weeks after planting, July 31, 1992Source DF Type ifi SS Mean Square F-value PBlock 3 0.1451 0.0484 1.03 0.4303Treat 2 0.3385 0. 1693 2.24 0.1874Block*Treat 6 0.4529 0.0754 1.60 0.2619Row 1 0.0027 0.0027 0.06 0.8166Treat*Row 2 0.0164 0.0082 0.17 0.8434ANOVA table for gravimetric soil moisture content at 12 weeks after planting, August 3,1992.Source DF Type III SS Mean Square F-value P ]Block 3 9.525 3.1749 0.96 0.4516Treat 2 0.3358 0. 1679 0.02 0.9833Block*Treat 6 59.5442 9.9240 3.01 0.0673Row 1 3.1538 3.1538 0.96 0.3538Treat*Row 2 8.9275 4.4638 1.35 0.3064ANOVA table for gravimetric soil moisture content at 12 weeks after planting, August 4, 1992Source DF Type III SS Mean Square F-value PBlock 3 16.1146 5.3715 10.48 0.0027Treat 2 7.0758 3.5379 0.87 0.4649Block*Treat 6 24.3242 4.0540 7.91 0.0035Row 1 14.8838 14.8838 29.03 0.0004Treat*Row 2 1.1775 0.5888 1.15 0.3596ANOVA table for gravimetric soil moisture content, 13 weeks after planting, August 7, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0245 0.0082 5.75 0.0177Treat 2 0.0297 0.0148 0.76 0.5081Block*Treat 6 0.1173 0.0195 13.75 0.0004Row 1 0.0372 0.0372 26.18 0.0006Treat*Row 2 0.0034 0.0017 1.19 0.3478100ANOVA table for gravimetric soil moisture content 13 weeks after planting, August 12, 1992.Source DF_J Type ifi SS Mean Square F-value PBlock 3 0.0528 0.0175 14.59 0.0008Treat 2 0.0543 0.0271 2.68 0.1473Block*Treat 6 0.0607 0.0101 8.38 0.0028Row 1 0.0935 0.0935 77.45 0.0001Treat*Row 2 0.0110 0.0055 4.57 0.0427ANOVA table for gravimetric soil moisture content, 15 weeks after planting, August 26, 1992Source DF Type ifi SS Mean Square j__F-value PBlock 3 0.3795 0. 1265 4.24 0.0399Treat 2 0.2588 0.1294 2.92 0.1300Block*Treat 6 0.2657 0.0443 1.48 0.2851Row 1 0.4099 0.4099 13.74 0.0049Treat*Row 2 0. 1515 0.0757 2.54 0.1337ANOVA table for gravimetric soil moisture content, 16 weeks after planting, September 1, 1992Source DF Type III SS Mean Square F-value PBlock 3 31.4779 10.4926 3.68 0.0560Treat 2 12.4233 6.2112 2.49 0.1628Block*Treat 6 14.9433 2.4906 0.87 0.5492Row 1 15.5204 15.5204 5.45 0.0445Treat*Row 2 23.0233 11.5117 4.04 0.0560ANOVA tablesfor crop nutrient concentration and contentANOVA table for maize ear leaf N content.Source DF [ Type III SS Mean Square F-value pBlock 3 0.0674 0.0225 1.52 0.2753Treat 2 0. 1407 0.0703 5.96 0.0376Block*Treat 6 0.0709 0.0118 0.80 0.5949Row 1 0.3073 0.3073 20.75 0.0014Treat*Row 2 0.0156 0.0078 0.53 0.6078101ANOVA table for maize ear leaf P content.Source DF Type ifi SS Mean Square F-value PBlock 3 0.0482 0.0161 1.12 0.3925Treat 2 0.1561 0.0781 23.47 0.0015Block*Treat 6 0.0200 0.0033 0.23 0.9558Row 1 0.2431 0.2431 16.88 0.0026Treat*Row 2 0.0375 0.0188 1.30 0.3185ANOVA table for maize ear leaf Ca content.Source DF Type ifi SS Mean Square F-value__} ‘Block 3 0.2490 0.0830 4.38 0.0368Treat 2 0.1375 0.0688 2.40 0.1714Block*Treat 6 0.1718 0.0286 1.51 0.2773Row 1 0.3657 0.3657 19.28 0.0017Treat*Row 2 0.0832 0.0416 2.19 0. 1676ANOVA table for maize ear leaf K content.Source DF Type III SS Mean Square F-value PBlock 3 0.0557 0.0186 1.75 0.2260Treat 2 0.0787 0.0393 2.84 0.1354Block*Treat 6 0.0830 0.0138 1.30 0.3453Row 1 0.4197 0.4197 39.57 0.0001Treat*Row 2 0.0049 0.0025 0.23 0.7979ANOVA table for maize ear leaf Mg content.Source DF Type III SS J Mean_Square__J__F-value PBlock 3 0.0265 0.0088 1.45 0.2915Treat 2 0.0355 0.0178 1.34 0.3313Block*Treat 6 0.0798 0.0133 2.18 0.1409Row 1 0.3621 0.3621 59.42 0.0001Treat*Row 2 0.0192 0.0096 1.58 0.2590ANOVA table for maize ear leaf N concentration.Source [_DF Type III SS Mean Square F-value pBlock 3 0.0975 0.0325 1.75 0.2264Treat 4 0.0606 0.0303 2.11 0.2019Block*Treat 12 0.0860 0.0143 0.77 0.6108Row 1 0.0038 0.0038 0.20 0.6638Treat*Row 4 0.0068 0.0034 0.18 0.8352102ANOVA table for maize ear leaf P concentration.Source J DF Type III SS Mean Square F-value PBlock 3 0.0336 0.0112 1.66 0.2442Treat 4 00053 0.0026 0.63 0.5627Block*Treat 12 0.0249 0.0042 0.61 0.7155Row 1 0.0020 0.0020 0.29 0.6019Treat*Row 4 0.01 15 0.0058 0.85 0.4587ANOVA table for maize ear leaf Ca concentration._Source DF Type III SS Mean Square F-value PBlock 3 0.01 14 0.0038 13.76 0.0010Treat 4 0.0003 0.0001 0.24 0.7908Block*Treat 12 0.0032 0.0005 1.91 0.1830Row 1 0.0003 0.0003 1.22 0.2978Treat*Row 4 0.0024 0.0012 4.39 0.0468ANOVA table for maize ear leaf K concentration.Source DF Type III SS Mean Square F-value PBlock 3 0.0265 0.0088 5.03 0.0256Treat 4 0.0296 0.0148 3.70 0.0898Block*Treat 12 0.0240 0.0040 2.28 0. 1280Row 1 0.0152 0.0151 8.64 0.0165Treat*Row 4 0.007 1 0.0036 2.03 0.1872ANOVA table for maize ear leaf Mg concentration.Source DF Type III SS Mean Square F-value PBlock 3 0.0118 0.0039 1.21 0.3623Treat 4 0.0830 0.0415 3.96 0.0800Block*Treat 12 0.0629 0.0105 3.21 0.0570Row 1 0.0025 0.0025 0.77 0.4020Treat*Row 4 0.0103 0.0052 1.58 0.2576ANOVA table for maize ear leaf weight.Source DF Type Ill SS Mean Square F-value PBlock 3 0.0283 0.0094 0.73 0.5618Treat 2 0.1887 0.0944 12.28 0.0076Block*Treat 6 0.0461 0.0077 0.59 0.7309Row 1 0.2770 0.2770 21.32 0.0013Treat*Row 2 0.0188 0.0094 0.72 0.5117103ANOVA table for cassava leaf N content._Source OF Type III SS Mean Square F-value PBlock 2 0.0765 0.0382 1.25 0.3272Treat 5 1.7534 0.3508 11.48 0.0007ANOVA table for cassava leaf P content.Source OF Type III SS Mean Square F-value PBlock 2 0.1150 0.0575 1.69 0.2326Treat 5 2.3512 0.4702 13.85 0.0003ANOVA table for cassava leaf Ca content.Source DF Type III SS Mean Square F-value PBlock 2 0.0606 0.0303 0.71 0.3272Treat 5 1.3264 0.2653 6.22 0.0007ANOVA table for cassava leaf K content.Source OF_[ Type III SS Mean Square F-value pBlock 2 0.0551 0.0275 0.89 0.4413Treat 5 0.7329 0. 1466 4.73 0.0177ANOVA table for cassava leaf Mg content.Source OF Type III SS Mean Square F-value PBlock 2 0.0380 0.0190 0.49 0.6284Treat 5 2.6284 0.5257 13.47 0.0004ANOVA table for cassava leaf N concentration.Source DF Type III SS Mean Square F-value PBlock 2 0.0802 0.0401 3.06 0.0919Treat 5 0. 1816 0.0363 2.77 0.0800ANOVA table for cassava leaf P concentration.Source OF Type III SS Mean Square F-value PBlock 2 0.0040 0.0020 1.19 0.3436Treat 5 0. 1014 0.0203 12.15 0.0005104ANOVA table for cassava leaf Ca concentration.Source DF Type III SS Mean Square F-value PBlock 2 0.0046 0.0023 1.14 0.3587Treat 5 0.0314 0.0063 3.14 0.0584ANOVA table for cassava leaf K concentration.Source DF Type ifi SS Mean Square F-value PBlock 2 0.0019 0.0009 0.48 0.6338Treat 5 0.1972 0.0394 20.15 0.0001ANOVA table for cassava leaf Mg concentration.Source [_DF Type III SS Mean Square F-value pBlock 2 0.0513 0.0257 2.73 0.1130Treat 5 0.1653 0.0331 3.52 0.0428ANOVA table for cassava leaf weight.Source [_DF Type III SS Mean Square F-value PBlock 2 0.0606 0.0384 1.04 0.3890Treat 5 1.3264 0.3156 8.53 0.0022ANOVA tables for Leucaena pruning nutrient concentration and yieldANOVA table for mean Leucaena Ca concentration for 2-, 4- and 8- week pruning intervals._Source DF Type III SS Mean Square F-value PBlock 2 37.3333 18.6667 2.84 0.0945Treat 2 357.3333 178.6667 27.22 0.0001ANOVA table for mean Leucaena Mg concentration for 2-, 4- and 8- week pruning intervals.Source DF Type III SS Mean Square F-value PBlock 2 105.3333 52.6667 2.50 0. 1202Treat 2 81.3333 40.6667 1.93 0.1839ANOVA table for mean Leucaena K concentration for 2-, 4- and 8- week pruning intervals.Source DF Type III SS Mean Square F-value PBlock 2 208.0000 104.0000 7.24 0.0077Treat 2 85.3333 42.6667 2.97 0.0865105ANOVA table for mean Leucaena N concentration for 2-, 4- and 8- week pruning intervals.Source DF Type III SS Mean Square F-value PBlock 2 85.3333 42.6667 2.97 0.0865Treat 2 208.0000 104.0000 7.24 0.0077ANOVA table for mean Leucaena P concentration for 2-, 4- and 8- week pruning intervals.Source DF Type Ill SS Mean Square F-value__[ pBlock 2 1.3333 0.6667 0.22 0.8022Treat 2 432.0000 216.0000 72.62 0.0001ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July25, 1991.Source DF Type III SS Mean Square F-value PBlock 2 15.3612 7.6806 1.05 0.4295Treat 2 277.1817 138.5908 18.98 0.0091ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 8 weeks after planting,July 25, 1991.Source DF Type III SS Mean Square F-value PBlock 2 1.0500 0.5250 1.14 0.4050Treat 2 25.0146 12.5073 27.22 0.0047ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July25, 1991.Source DF Type III SS Mean Square F-value PBlock 2 59.8974 29.9487 1.57 0.3134Treat 2 1930.5833 965.2917 50.68 0.0014ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July25, 1991.Source DF Type III SS Mean Square F-value PBlock 2 153.8034 76.9017 1.20 0.3907Treat 2 5968.8167 2984.4084 46.55 0.0017ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 8 weeks after planting,July 25, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.0938 0.0469 0.64 0.5738Treat 2 7.0876 3.5438 48.39 0.0016106ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 16 weeks after planting,Source DF Type III SS Mean Square F-value PBlock 2 1.3308 0.6654 7.23 0.0469Treat 2 3 1.5956 15.7978 171.69 0.0001ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 16 weeks after planting,September 18, 1991.Source DF Type III SS Mean Square F-value PBlock 2 1.1219 0.5610 3.51 0.1316Treat 2 29.4576 14.7288 92.25 0.0005ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 16 weeks after planting,September 18, 1991.Source DF_J Type III SS Mean Square F-value PBlock 2 387.2336 193.6168 1.20 0.3912Treat 2 8219.7811 4109.8905 25.42 0.0053ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 16 weeks after planting,September 18, 1991.Source DF Type III SS Mean Square F-value PBlock 2 893.9507 446.9754 1.83 0.2724Treat 2 42832.2768 21416. 1384 87.76 0.0005ANOVA table for Leucaena P yield for 2-, 4- and 8- week intervals at 16 weeks after planting,September 18, 1991.Source DF Type ifi SS Mean Square F-value PBlock 2 3.4021 1.7010 1.53 0.3212Treat 2 149.9640 74.9820 67.40 0.0008ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 24 weeks after planting,November 14, 1991.Source DF Type III SS [ Mean Square F-value PBlock 2 0.3045 0.1522 0.16 0.8568Treat 2 71.8549 23.9516 24.95 0.0009September 18, 1991.107ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 24 weeks after planting,November 14, 1991.Source DF Type III SS Mean Square F-value__] pBlock 2 0.2094 0.1047 0.33 0.7326Treat 2 21.5555 7.1852 22.51 0.0012ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 24 weeks after planting,November 14, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.3061 0.1530 0.40 0.6862Treat 2 24.2221 8.0746 21.17 0.0014ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 24 weeks after planting,November 14, 1991.Source DF Type Ill SS Mean Square__[__F-value pBlock 2 32.8380 16.4190 0.77 0.5028Treat 2 1714.2456 571.4152 26.89 0.0007ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 24 weeks after planting,November 14, 1991._Source DF Type Ill SS Mean Square F-value PBlock 2 0.0372 0.0186 1.34 0.3312Treat 2 2.0205 0.6735 48.44 0.0001ANOVA tables for soil analysisANOVA table for differences in K from soil samples taken prior to planting in 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.1872 0.0624 21.74 0.0154Row 1 0.0157 0.0157 5.45 0. 1017ANOVA table for differences in K from soil samples taken prior to planting in 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.2061 0.0687 2.03 0.2875Row 1 0.0062 0.0062 0.18 0.6968108ANOVA table for differences in Ca from soil samples taken prior to planting in 1992.Source DF Type Ill SS Mean Square F-value PBlock 3 0.8334 0.2778 8.23 0.0585Row 1 0.0588 0.0588 1.74 0.2786ANOVA table for differences in Mg from soil samples taken prior to planting in 1992.Source J_DF Type III SS J Mean Square F-value__J PBlock 3 0.4358 0. 1453 22.28 0.0149Row 1 0.0286 0.0286 4.39 0.1272ANOVA table for differences in pH from soil samples taken prior to planting in 1992._Source DF Type ifi SS Mean Square F-value PBlock 3 0.0063 0.002 1 13.74 0.0294Row 1 0.0010 0.0010 6.57 0.0830ANOVA table for differences in total N from soil samples taken prior to planting in 1992._Source DF Type Ill SS Mean Square F-value PBlock 3 0.1561 0.0520 11.91 0.0357Row 1 0.0330 0.0330 7.55 0.0709ANOVA table for differences in P from soil samples taken prior to planting in 1992.Source DF Type III SS [ Mean Square F-value__[ p 1Block 3 0.0404 0.0135 1.16 0.4946Row 1 0.2230 0.2230 19.15 0.0485ANOVA table for differences in NH4 from soil samples taken prior to planting in 1992.Source DF Type ifi SS Mean Square j__F-valueBlock 3 0.6214 0.3157 9.84 0.0462Row 1 0.2363 0.2363 22.10 0.0182ANOVA table for differences in NO3 from soil samples taken prior to planting in 1992.Source DF Type III SS Mean Square F-valueBlock 3 0.2529 0.0843 2.74 0.2147Row 1 0.0245 0.0245 2.39 0.2195109ANOVA table for differences in K from soil samples taken at the end of the rainy season, 1991.Source DF Type ifi SS Mean Square F-value PBlock 2 0.0697 0.0348 1.54 0.2617Treat 5 0.3525 0.0705 3.11 0.0597ANOVA table for differences in Na from soil samples taken at the end of the rainy season, 1991.Source DF Type III SS Mean Square F-value PBlock 2 00003 0.0002 7.57 0.0100Treat 5 0.0003 0.0000 3.35 0.0490ANOVA table for differences in Ca from soil samples taken at the end of the rainy season, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.8278 0.4139 1.81 0.2133Treat 5 3.1242 0.6248 2.73 0.0826ANOVA table for differences in Mg from soil samples taken at the end of the rainy season, 1991.Source DF Type Ill SS Mean Square F-value PBlock 2 0.0720 0.0360 1.46 0.2777Treat 5 0.1894 0.0379 1.54 0.2628ANOVA table for differences in pH from soil samples taken at the end of the rainy season, 1991.Source DF Type ifi SS Mean Square F-value PBlock 2 0.0013 0.0006 3.51 0.0699Treat 5 0.0023 0.0005 2.48 0. 1041ANOVA table for differences in P from soil samples taken at the end of the rainy season, 1991.Source DF Type III SS Mean Square F-value__[ pBlock 2 0.0006 0.0003 0.02 0.98 16Treat 5 0.2025 0.0405 2.41 0.1114ANOVA table for differences in total N from soil samples taken at the end of the rainy season,1991.Source DF f Type Ill s [ Mean_Square__j__F-value PBlock 2 0.1447 0.0723 1.01 0.3989Treat 5 0.4499 0.0900 1.25 0.3542110ANOVA table for differences in total organic C from soil samples taken at the end of the rainyseason, 1991.Source DF Type Ill SS Mean Square F-value PBlock 2 0.0421 0.0211 0.71 0.5152Treat 5 0.1289 0.0258 0.87 0.5348ANOVA table for differences in bulk density from soil samples taken at the end of the rainy season,1991.Source DF Type Ill SS Mean Square F-value PBlock 2 23244.4444 11622.2222 2.62 0.1219Treat 5 14444.4444 2888.8889 0.65 0.6683ANOVA table for differences in NH4 from soil samples taken at the end of the rainy season, 1991.Source DF Type III SS Mean Square F-value PBlock 2 0.45 16 0.2258 0.47 0.6352Treat 5 3.3960 0.6792 0.57 0.7211ANOVA table for differences in NO3- from soil samples taken at the end of the rainy season, 1991.Source DF Type ifi SS Mean Square F-value__[ pBlock 2 0.0162 0.0081 1.12 0.3637Treat 5 0.0340 0.0068 3.74 0.0361ANOVA tables for pruning labour requirementANOVA table for differences in pruning labour for the initial pruning of the season, April 14/15,1992.Source J_DF Type III SS Mean Square F-value PBlock 3 64.2500 21.4167 6.12 0.9439Treat 3 7498.2500 2499.4167 14.41 0.0009ANOVA table for differences in total in-season pruning requirements.Source DF Type Ill SS Mean Square F-value PBlock 3 25.1667 8.3889 0.14 0.9300Treat 3 2278. 1667 759.3889 12.46 0.0010111ANOVA tables for weed biomass assessmentANOVA table for differences in total weed biomass over the 1992 maize season.ANOVA table for differences in weed biomass at 4 weeks after planting, June 3, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0216 0.0072 1.35 0.3438Treat 2 0.0127 0.0063 1.19 0.3678ANOVA table for differences in weed biomass at 10 weeks after planting, July 14, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.3356 0.1119 0.92 0.4867Treat 2 0.9904 0.4952 4.06 0.0766ANOVA table for differences in weed biomass at 17 weeks after planting, August 31, 1992.Source DF Type III SS Mean Square F-value PBlock 3 0.0356 0.0119 1.27 0.3671Treat 2 0.9038 0.4519 48.20 0.0002Source DF Type Ill SS Mean Square F-value PBlock 3 0.4092 0.1364 1.02 0.5673Treat 2 2.9231 1.4616 10.89 0.0500112Appendix BRegression outputfor Leucaena LAI vs. light transmission to the cassava canopy.Analysis of VarianceSource DF SS MS F Value Prob> FModel 1 2.59599 2.59599 70.994 0.0001Error 12 0.43879 0.03657C Total 13 3.03478Root MSE 0.19122 R-fsquare 0.8554Dep Mean 2.97217 Adj R-sq 0.8434C.V. 6.43378Parameter Standard T for HO:Variable DF Estimate Error Parameter= 0 Prob > I TIINTERCEP 1 4.551187 0.19424625 23.430 0.0001LAI 1 -0.698020 0.08284296 -8.426 0.0001Regression outputfor Leucaena LAI vs. light transmission to the maize ear level.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 2.38646 2.38646 59.401 0.0001Error 12 0.48211 0.04018C Total 13 2.86857Root MSE 0.20044 R-square 0.8319Dep Mean 3.36162 Adj R-sq 0.8179C.V. 5.96255Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > I TIINTERCEP 1 4.635266 0. 17371950 26.682 0.0001MAIZE LAI 1 -0.650291 0.08437460 -7.707 0.0001113Regression outputfor maize!Leucaena height difference vs light transmission.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 2242.11475 2242.11475 29.502 0.0004Error 9 683.99434 75.99937C Total 10 2926.10909Root MSE 8.71776 R-square 0.7662Dep Mean 37.99091 Adj R-sq 0.7403C.V. 22.94697Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > TINTERCEP 1 29.381764 3.06941977 9.572 0.0001DIFF2 1 38.477722 7.0841 1231 5.432 0.0004Regression outputfor cassava/Leucaena height difference vs light transmission to cassava canopy.Analysis of VarianceSource DF SS MS F Value Prob > FModel 2 12526.42109 6263.21054 21.288 0.0001Error 16 4707.41996 294.21375C Total 18 17233.84105Root MSE 17.15266 R-square 0.7269Dep Mean 34.26842 Adj R-sq 0.6927C.V. 50.05384Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > TIINTERCEP 1 63.607054 10.39000858 6.122 0.0001DIFF 1 -0.309482 0.07014247 -4.412 0.0004DIFF(sq) 1 46. 169469 69.39186166 0.665 0.5153114Regression outputfor Leucaena foliage N vs. maize ear leaf 1VAnalysis of VarianceSource DF SS MS F Value Prob > FRegression 1 5.52543471 5.52543471 6.35 0.0284Error 11 9.56687299 0.86971573Total 12 15.09230769Parameter Standard Type IIVariable Estimate Error Sum of Squares F Prob > FINTERCEP 8.45993635 0.45261989 303.83951010 349.35 0.0001SQN 0.00006261 0.00002484 5.52543471 6.35 0.0284Regression outputfor Leucaena foliage N vs. maize grain yield.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 16.06833 16.06833 67.205 0.0001Error 11 2.63004 0.23909C Total 12 18.69837Root MSE 0.48897 R-square 0.8593Dep Mean 3.82846 Adj R-sq 0.8466C.V. 12.77206Parameter Standard T for HO:Variable DF Estimate Error Parameter 0 Prob > TIINTERCEP 1 2.180189 0.24252344 8.990 0.0001LEUCN 1 0.016259 0.00198331 8.198 0.0001115Regression outputfor Leucaena foliage K vs. maize stover yield.Analysis of VarianceSource DF SS MS F Value Prob> FModel 1 20.91215 20.91215 17.527 0.0015Error 11 13.12477 1.19316C Total 12 34.03692Root MSE 1.09232 R-square 0.6144Dep Mean 6.28462 Adj R-sq 0.5793C.V. 17.38084Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > TIINTERCEP 1 4.417371 0.53917774 8.193 0.0001LEUCK 1 0.027149 0.00648498 4.186 0.0015Regression outputfor mean light transmission to maize ear level during the growing 1991 season vs.maize grain yield.Analysis of VarianceSource DF SS MS F Value Prob> FModel 1 1.27067 1.27067 12.229 0.0250Error 4 0.41561 0.10390C Total 5 1.68628Root MSE 0.32234 R-square 0.7535Dep Mean 2.18833 Adj R-sq 0.6919C.V. 14.72993Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > IT IINTERCEP 1 -0.148038 0.68093384 -0.217 0.8385LIGHT 1 0.043173 0.01234550 3.497 0.0250116Regression outputfor mean light transmission to maize ear level during the growing 1991 season vs.maize grain yield.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 11.50135 11.50135 21.564 0.0009Error 10 5.33354 0.53335C Total 11 16.83489Root MSE 0.73031 R-square 0.6832DepMean 3.71917 AdjR-sq 0.6515C.V. 19.63641Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > I TINTERCEP 1 1.326613 0.55668709 2.383 0.0384LIGHT 1 0.126479 0.02723644 4.644 0.0009Regression outputfor Leucaena foliage P vs. cassava leafP content.Analysis of VarianceSource DF SS MS F Value Prob>FModel 1 16.02162 16.02162 12.423 0.0243Error 4 5. 15873 1.28968C Total 5 21.18035Root MSE 1.13564 R-square 0.7564Dep Mean 6. 82500 Adj R-sq 0.6955C.V. 16.63943Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > I TIINTERCEP 1 3.889130 0.95329496 4.080 0.0151LEUCP 1 0.401258 0.11384436 3.525 0.0243117Regression outputfor Leucaena foliage N vs. cassava leafN content.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 2960.74346 2960.74346 11.391 0.0279Error 4 1039.65862 259.91465C Total 5 4000.40208Root MSE 16.12187 R-square 0.7401Dep Mean 102.71167 Adj R-sq 0.675 1C.V. 15.69624Parameter Standard T for HO:Variable DF Estimate Error Parameter 0 Prob > (TINTERCEP 1 66.007932 12.71151241 5.193 0.0065LEUCN 1 0.293630 0.08699920 3.375 0.0279Regression outputfor Leucaena foliage K vs. cassava leaf K content.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 5.67454 5.67454 8.010 0.0473Error 4 2.83374 0.70844C Total 5 8.50828Root MSE 0.84169 R-square 0.6669Dep Mean 6.43833 Adj R-sq 0.5837C.V. 13.07305Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > TINTERCEP 1 4.824878 0.66563742 7.249 0.0019LEUCK 1 0.027882 0.00985175 2.830 0.0473118Regression outputfor mean light transmission to the cassava canopy during the first 4 months ofgrowth vs. cassava root yield.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 0.07231 0.07231 33.044 0.0105Error 3 0.00657 0.002 19C Total 4 0.07888Root MSE 0.04678 R-square 0.9 168Dep Mean 0.47200 Adj R-sq 0.8890C.V. 9.91117Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > TINTERCEP 1 -0.480899 0. 16708278 -2.878 0.0636LIGHT 1 0.030699 0.00534046 5.748 0.0105Regression outputfor nwan light transmission to the cassava canopy during the first 4 months ofgrowth vs. cassava total dry matter yield.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 0.18744 0.18744 21.927 0.0184Error 3 0.02564 0.00855C Total 4 0.21308Root MSE 0.09246 R-square 0. 8796Dep Mean 1.69800 Adj R-sq 0.8395C.V. 5.44502Parameter Standard T for HO:Variable DF Estimate Error Parameter 0 Prob > T IINTERCEP 1 0.163880 0.33021877 0.496 0.6538LIGHT 1 0.049424 0.01055476 4.683 0.0184119Regression outputfor Leucaena stem diameter, count and operator (person performing the pruning)vs. pruning time.R-square = 0.50983341 C(p) = 2.01564260Source DF SS MS F Value Prob > FRegression 2 297.23287904 148.61643952 6.76 0.0097Error 13 285.76712096 21.98208623Total 15 583.00000000Parameter Standard Type IIVariable Estimate Error Sum of Squares F Prob > FINTERCEP -15.68089379 11.37994362 41.73787295 1.90 0.1915COUNT 0.05656893 0.02868866 85.46817316 3.89 0.0703OPERATOR 3.86799348 1.15002097 248.67312440 11.31 0.0051Regression outputfor pruning labour vs. time elapsed between prunings.R-square = 0.95536886 C(p) = 2.3 1690796Source DF SS MS F Value Prob > FRegression 2 17481.14827261 8740.57413630 181.95 0.0001Error 17 816.65172739 48.03833691Total 19 18297.80000000Parameter Standard Type IIVariable Estimate Error Sum of Squares F Prob > FINTERCEP 28.79550184 9.61275136 431.06409314 8.97 0.0081TIME -0.31637895 0.36573470 35.94767375 0.75 0.3991SQTIME 0.01158640 0.00294085 745.65977484 15.52 0.0011120Regression outputfor pruning labour vs. Leucaena biomass pruned.R-square = 0.64089331 C(p) = 2.00019672Source DF SS MS F Value Prob > FRegression 2 11726.93765775 5863.46882888 15.17 0.0002Error 17 6570.86234225 386.52131425Total 19 18297.80000000Parameter Standard Type IIVariable Estimate Error Sum of Squares F Prob > FINTERCEP 69.36403277 31.81612728 1837. 16213696 4.75 0.0436BIOMASS 86.40163224 40.21357755 1784.31661293 4.62 0.0464SQBIOM -126.33478494 80.54930334 950.81442324 2.46 0. 1352Regression outputfor Leucaena biomass vs. time elapsed between prunings.Analysis of VarianceSource DF SS MS F Value Prob > FModel 2 18.18500 9.09250 161.047 0.0001Error 17 0.95980 0.05646C Total 19 19.14480Root MSE 0.23761 R-square 0.9499Dep Mean 1.39000 Adj R-sq 0.9440C.V. 17.09428Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > I TIINTERCEP 1 -2.585861 0.32954846 -7.847 0.0001TIME 1 0. 120443 0.01253827 9.606 0.0001SQTIME 1 -0.000708 0.00010082 -7.024 0.0001121Regression outputfor pruning labour vs. time elapsed between prunings.Analysis of VarianceSource DF SS MS F Value Prob > FModel 1 69.24000 69.24000 368.301 0.0001Error 18 3.38397 0.18800C Total 19 72.62397Root MSE 0.43359 R-square 0.9534Dep Mean 3.39570 Adj R-sq 0.9508C.V. 12.76872Parameter Standard T for HO:Variable DF Estimate Error Parameter = 0 Prob > I TIINTERCEP 1 1.305870 0.14580156 8.956 0.0001SQTIME 1 0.000572 0.00002979 19. 191 0.0001122

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