Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

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

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-ubc_1994-0100.pdf [ 2.02MB ]
Metadata
JSON: 831-1.0087369.json
JSON-LD: 831-1.0087369-ld.json
RDF/XML (Pretty): 831-1.0087369-rdf.xml
RDF/JSON: 831-1.0087369-rdf.json
Turtle: 831-1.0087369-turtle.txt
N-Triples: 831-1.0087369-rdf-ntriples.txt
Original Record: 831-1.0087369-source.json
Full Text
831-1.0087369-fulltext.txt
Citation
831-1.0087369.ris

Full Text

PRUNING MANAGEMENT OF LEUCAENA LEUCOCEPHALA ALLEYCROPPED WITH MAIZE AND CASSAVA by SYLVIA ELIESABETH WELKE B.Sc., The University of Waterloo, 1988 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF TIlE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Soil Science)  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA December 1993 ©  Sylvia Eliesabeth Welke, 1993  In  presenting  this thesis  in  partial  fulfilment of the  degree at the University of British Columbia,  requirements  for an  advanced  I agree that the Library shall make it  freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.  (Signature)  Department of  8o/ Sczeiice  The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  Abstract An experiment was carried out to determine suitable pruning intervals for Leucaena leucocephala in an alley cropping system with maize and cassava in Southwestern Nigeria. I considered light and soil moisture limitations to crops in the system, in addition to nutrient contributions by Leucaena prunings to both crops and the soil. Pruning labour was also taken into account to provide an economic perspective. Marked reductions in maize yield were recorded when hedgerow pruning was delayed beyond 10 weeks after crop planting while cassava economic yield was not affected. I observed a general trend of taller plants with thinner stems when Leucaena hedgerows were not pruned or pruned at intervals of 8 weeks or less. Plants adjacent to the hedgerows were usually shorter than those in the middle of the alleys. I attributed the yield declines and growth effects to light limitations rather than soil moisture depletion by the hedgerows, although the potential for the latter could exist in drought. While productivity was affected by light reductions, there was no clear indication that Leucaena prunings contributed to crop growth. Differences in leaf nutrient content were obvious between treatments where hedgerows were pruned at least once a season and where they were not. Maize nutrition was likely satisfied by inorganic fertilizer and initial application of Leucaena pruning, but the same could not be established for cassava where nutrient concentrations  were 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 different pruning intervals were calculated, it was clear that pruning at least once during the maize growing season was advantageous. I briefly discuss some possible economic advantages and disadvantages of pruning every 4 and 8 weeks, or mid-season and at harvest. Upon integrating the biophysical and economic data gathered in the study, it is clear that hedgerow pruning can be delayed up to 10 weeks after planting for maize. For cassava, further studies are necessary in order to recommend pruning intervals for a maize/cassava intercrop in an alley cropping system. 11  Table of Contents ii  Abstract  iii  Table of Contents List of Figures  V  List of Tables  vii ix  Acknowledgements 1.0. General Introduction  1  2.0. Experimental Layout  5  3.0. Effect of Leucaena leucocephala (Lam de Wit) pruning frequency on alley cropped 9 maize/cassava 3.1 Introduction .9 • 10 3.2. Materials and Methods 10 3.2.1. Crop Growth Characteristics and Yield 3.2.2. Leucaena growth and pruning biomass • 11 • 12 3.2.4. Soil Moisture 3.2.5. Data analyses • 12 • 12 3.3 Results • 12 3.3.1. Crop growth characteristics • 16 3.3.2. Crop yields • 22 3.3.3. Leucaena growth and pruning biomass 3.3.4. Incident light 3.3.5. Soil Moisture 3.4. Discussion 3.5. References 4.0. Nutrient contribution of Leucaena leucocephala to maize and cassava under dVferent pruning intervals 4.1. Introduction 4.2. Materials and Methods 4.2.1. Leucaena foliage and crop samples 4.2.2. Soil analysis 4.2.3. Data analyses 4.3. Results 4.3.1. Crop nutrient concentrations and contents 4.3.2. Leucaena nutrient yield 4.3.3. Relationships between Leucaena prunings and crop productivity 4.3.4. Soil Fertility Status 4.4. Discussion 4.5. References  111  40 41 41 42 42 43 43 46 52 54 56 60  5.0.  Labour costs of different pruning intervals of Leucaena leucocephala in an alley cropping system 5.1. Introduction 5.2. Materials and Methods 5.3. Results 5.3.1. Comparing costs of treatments 5.3.2. Weed biomass 5.4. Discussion 5.5. References  Conclusions Appendices Appendix A ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables ANOVA tables Appendix B  77  for for for for for for for for for for for for for for for for  maize height measurements maize stem diameter maize LAI maize reproductive stage measurements maize grain yield cassava height measurements cassava stem diameter cassava node number cassava LAI cassava pre-harvest measurements cassava yield 1992 soil moisture samples crop nutrient concentration and content Leucaena pruning nutrient concentration and yield soil analysis pruning labour requirement  iv  99 105 108 111 113  List of Figures 2. 1: 2.2:  Cross-sectional view of an alley cropping plot with maize in 4 m alleys between Leucaena hedgerows  7  Plot layout indicating planting pattern of maize and cassava, as well as distance between crops and Leucaena hedgerows  7  Maize plant height as affected by distance from Leucaena hedgerows in the 8 week pruning interval and unpruned piots during the 1992 maize cropping season  15  Maize basal stem diameter as affected by distance from Leucaena hedgerows in the 8 week pruning interval and unpruned piots during the 1992 maize cropping season  15  Cassava internode lengths for the 2- and 8- week pruning intervals and unpruned plots during the first 18 weeks of cassava growth in 1991  18  Cassava plant height the 2-, 6- and 10- week pruning intervals and unpruned plots during the 1991 rainy season  18  3.3:  Cassava lateral shoot dry matter yield (kg/plant) harvested 13 months after planting  21  3.4a:  Maize, cassava and Leucaena heights under the 6-week pruning interval for the 1991 maize growing season  24  Maize, cassava and Leucaena heights in unpruned plots for the 1991 maize cropping season  24  Mean Leucaena foliage pruning biomass (tlha) over the 1991/1992 maize cropping seasons  25  Light transmission (%) to maize ear level in the middle of the alleys and adjacent to Leucaena hedgerow during the 1991 cropping season  26  Light transmission (%) to maize ear level adjacent to Leucaena hedgerow during the 1992 cropping season under a 4-week pruning interval and unpruned plots  26  Relationship between % light transmission to maize ear level and the difference in height (cm) between maize and Leucaena during the 1991 maize cropping season  29  Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % light transmission to maize cob during the 1992 cropping season  29  Light transmission (%) to cassava canopy in the middle of the alleys and adjacent to Leucaena hedgerow during the 1991 cropping season under a 10-week pruning interval and unpruned plots  30  3. la:  3. ib: 3.2a: 3.2b:  3.4b:  3.5: 3 .6a:  3.6b: 3.7: 3.8: 3 .9a:  v  3.9b: 3.10:  3.11: 3.12:  4.1:  4.2. 4.3a: 4.3b: 4.4: 5.1:  5.2:  Light transmission (%) to cassava canopy adjacent to Leucaena hedgerow during the 1992 cropping season under a 4-week pruning interval and unpruned plots  30  Relationship between % light transmission to the cassava canopy and the difference in height (cm) between cassava and Leucaena during the first 4 months of cassava growth  31  Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % light transmission to cassava canopy during the 1992 cropping season  31  Differences in gravimetric soil moisture content adjacent to Leucaena hedgerows and middle of the alleys in the 4-week pruning and unpruned plots during the month of October 1991  32  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 growing season  48  Nitrogen, phosphorus and potassium yield of Leucaena prunings under 4- and 8- week pruning intervals at 8 weeks after planting during the 1992 growing season  49  Nitrogen, phosphorus and potassium yield of Leucaena prunings prior to maize ear leaf sampling in the 1992 growing season  50  Nitrogen, phosphorus and potassium yield of Leucaena prunings during the 1992 maize growing season  50  Total nitrogen, phosphorus and potassium yield of Leucaena during the 1991 growing season  51  Relationship of pruning labour (days/ha) to time elapsed between prunings (days) before and after maize harvest  68  Weed dry matter under 4- and 6- week pruning intervals and in unpruned plots during the 1992 maize growing season  73  vi  List of Tables 2.1.  Soil physical and chemical characteristics before the 1991 and 1992 cropping season for the 0-15 cm surface soil layer  8  3.1  Maize reproductive stage measurements taken July 13,1993  14  3.2a.  Maize grain and stover yield (tlha) as affected by Leucaena pruning interval  19  3.2b.  Maize grain yields as affected by distance from Leucaena hedgerow  19  3.3.  Maize yield components as affected by pruning intervals for 1992  20  4. la.  Maize ear leaf nutrient content at silking under 4- and 6- pruning intervals and unpruned plots  44  Maize ear leaf nutrient content at silking adjacent to the hedgerow and in the middle of the alleys  44  Cassava leaf nutrient concentrations under 4- and 6- week pruning intervals, and unpruned plots  45  Cassava leaf nutrient content under 4- and 6- week pruning intervals and unpruned plots  45  Leucaena nitrogen, phosphorus and potassium concentrations under 4-, 6- and 8- week pruning intervals  47  Association of maize grain yield and ear leaf nitrogen to nitrogen and potassium from Leucaena prunings  53  Association of cassava leaf nutrient contents with nitrogen, potassium and phosphorus from Leucaena prunings  53  Soil surface (0-15 cm) chemical properties in the middle of alleys and adjacent to Leucaena hedgerows after 18 months of Leucaena fallow  55  5.1.  Pruning schedule by treatment for the 1992 maize growing season  65  5.2.  Estimation results determining the effect of time elapsed between prunings (days), operator and standing maize crop in alleys on labour for pruning hedgerows  70  Relationship of pruning labour (days/ha) and maize yield (t/ha) to pruning biomass and time elapsed between prunings (days) for Leucaena prunings  70  4. lb.  4.2. 4.3.  4.4. 4.5. 4.6.  4.7.  5.3.  vii  5.4.  Pruning labour (days/ha) for different pruning intervals  71  5.5.  Total weed biomass (tiha) and estimated labour and cost requirements under 4and 6-week pruning intervals and unpruned plots  72  viii  Acknowledgements A large number of people were involved in this project, directly and indirectly, and I am grateful to all of them. First, I could never have realized my dream of doing agroforestry research in the tropics if I didn’t have the financial support awarded by C.B.I.E. (CIDA award for young canadians). My advisor, Art Bomke, gave me belief in myself to do my best. I have no end of thanks for him. I also am indebted to my committee members who provided valuable advice and insights. Dr. B.T. Kang conceived the project and always available for consultation during the field research. Thanks to Karen Dvorak who was patient with all my late-night and early-morning economics questions. I could never have coped with all those measurements, crises and malaria attacks without Enoch Tanyi who was always there to help out. The same is true for Stefan Hauser and his workers in the first year of the project. I also am grateful to my four assistants who helped me despite the heat and rain. Special thanks go to Charity Nnaji who despite her overflowing work always had the time to print something for me. I am grateful to all the other special people at IITA who contributed to the project through their friendship and discussions. At UBC I couldn’t have completed much of the manuscript without the infinite computer knowledge of Rick Kettler or without the “light discussions” with Andy Black. And how could I have 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 one way or another. And there are not enough thanks for my mother who is always there.  ix  1.0. General Introduction Food production in sub-Saharan African countries has been declining over the past decade, in sharp contrast to other developing nations (Vergara, 1987). Rapid population growth, urbanization and global economic policies have, in large part, led to this decline. Consequently, pressure on both arable and marginal lands has increased leading to extensive degradation of the land resource base in the sub-Saharan region (Sanchez, 1987). Yet, these lands have been fanned for centuries under the traditional shifting cultivation or bush fallow system which allows for natural soil fertility restoration during the fallow phase and supplies subsistence farmer needs (Vergara, 1987). The sustainability of the system depends on relatively short (1 to 5 years) cropping periods compared to longer fallow phases (5 to >20 years) (Nair, 1985). However, with increased pressure on land for food production, traditional crop production systems have broken down as fallow period length decreases or is replaced by continuous cultivation in some areas (Okigbo, 1984). While intense cultivation is feasible on some of the more fertile soils of the subtropics, much of the area is dominated by highly weathered, low-activity clay soils such as Oxisols and Ultisols (ferralsols) (Nair, 1984; Kang et al., 1990). Many studies have shown that these 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 an affordable option for many farmers. Even with external inputs, continuous cropping is not sustainable 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 its maintenance in agricultural production in the humid and sub-humid tropics (Kang, 1991). One approach to the latter is through the application of organic materials from leafy shrubs or trees in agroforestry systems. Agroforestry is a land-use system in which woody perennials are planted together in space or time with crops and/or livestock (Vergara, 1987). The contribution of agroforestry tree/shrub species to soil fertility is multifold. Litter fall as well as deliberate manuring  1  with prunings has been shown to increase soil organic matter and, in some cases, base saturation of the soil (Nair, 1984). Including nitrogen-fixing trees in agroforestry systems can contribute to crop nutrition or provide protein-rich fodder (Brewbaker, 1987). Soil physical properties are also enhanced by the presence of trees; for instance, water infiltrability, pore size distribution and water transmissivity are favourably affected (Hulugalle and Kang, 1981; Lal, 1981). Agroforestry also seeks to provide economic security to the farmer by providing income from herbaceous and tree crops, and/or animals. Alley cropping is one example of an agroforestry practice in which arable crops are grown in rows between planted woody shrubs or trees. During the cropping season, the hedgerows are pruned periodically to prevent shading of the crops. The prunings can be used as mulch, livestock fodder or as fuelwood. Outside the cropping season, the hedgerow species acts as a bush fallow with soil restorative properties through litter fall and by tapping soil moisture and nutrients in lower soil horizons (Young, 1989; Nair, 1984). Thus, alley cropping permits an extension of the cropping period before returning land to long-term fallow. Research on process-oriented aspects of alley cropping has been conducted at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, since 1975 (Kang and Wilson, 1987). More recently, management and economic considerations of alley cropping are being addressed in order to encourage adoption of the technology. One important management aspect is the pruning of hedgerows, which must take into account both biophysical and economic considerations. “Optimal” hedgerow pruning intervals of 4 to 6 weeks have been established from on-station experiments for crop production (Kang et al., 1985). But are these intervals practical or even economical for the farmer who may adopt alley cropping? Observations from on-farms trials indicate that farmers will often delay pruning beyond the recommended intervals for various reasons. Small-scale farmers are usually faced with high labour costs and at times, labour shortages (Dvorak, unpublished). Furthermore, conflicts with other farm  2  activities could hinder pruning of hedgerows. How long can pruning be delayed before crop yields  are significantly affected? In an effort to identify appropriate pruning management for Leucaena leucocephala in an alley cropping system that incorporates biophysical and economic aspects, a study  was conducted: (1) to determine the effect of pruning intervals of Leucaena on the growth and yield of a maize/cassava intercrop, (2) to determine the nutrient yield of hedgerows under pruning intervals and effect of prunings on crop nutrient content and yield; and (3) to determine labour requirements of different Leucaena pruning intervals.  3  1.1. References Brewbaker 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 Netherlands Hulugalle and Kang (1981) Effect of hedgerow species in alley cropping systems on surface soil physical properties of an Oxic Paleustalf in southwestern Nigeria. Journal of Agricultural Science (Cambridge) 14(3): 301-307. Kang, BT and GF Wilson (1987) The development of alley cropping as a promising agroforstry technology. In: Steppler HA and Nair PKR, eds, Agroforestry: A decade of development. pp 24-45. ICRAF, Nairobi, Kenya Kang BT, GT Wilson and TL Lawson (1985) Alley cropping as a stable alternative to shifign cultivation. IITA, Thadan, Nigeria Kang BT (1989) Nutrient management for sustained crop production in the humid and subhumid tropics. In: van der Heide, J, ed, Nutrient management for food crop production in tropical farming systems. pp 1-28. Institute for Soil Fertility and 11TA, Haren, The Netherlands Lal R (1981) Clearing a tropical forest. II Effects on crop performance, deforestation, land preparation, growth and yield of maize, Nigeria. Field Crops Research 4(4): 345-354 Nair PKR (1985) Classification of agroforestry systems. Agroforestry Systems. 3: 97-128 Nair PKR (1984) Soil productivity aspects of agroforestry. ICRAF, Nairobi, Kenya. Okigbo B (1984) Cropping systems and rotations development for improving shifting cultivation and related intermittent production systems in tropical Africa. Soils Bulletin, FAO. 35: 121-140 Sanchez PA (1987) Soil productivity and sustainability in agroforestry systems. In: Steppler HA and Nair PKR, eds, Agroforestry: A decade of development. ICRAF, Nairobi, Kenya Sanchez PA (1976) Properties and management of soils in the tropics. John wiley and sons, New York Vergara, NT (1987) Agroforestry: A sustainable land use for fragile ecosystems in the humid tropics. In: Steppler HA and Nair PKR, eds, Agroforestry: A decade of development. ICRAF, Nairobi, Kenya Young A (1989) Agroforestry for soil conservation. Science and Practice of Agorforestry Series No. 4, ICRAF/CAB International, Nairobi, Kenya.  4  2.0. Experimental Layout I 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 mean annual rainfall at the research station is 1280 mm, which is bimodally distributed with a main rainy season 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 (M31m ) was 13.44 and 12.25 for 2 the 1991 and 1992 growing seasons, respectively. Different experimental sites were used for 1991 and 1992. Plot size in 1991 was 8 m x 4 m while I chose larger plots (30 m x 4 m) the following year to accomodate pruning labour measurements and to allow for cassava dry matter accumulation studies. Experimental plots were arranged 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 Egbeda and Ibadan series, in 1991 and 1992, respectively. The physical and chemical characteristics of these soils are summarized in Table 2.1. Leucaena leucocephala (Lam. de Wit)(K38) hedgerows were initially established in 1985, at both sites, at an interrow spacing of 4 m and intrarow spacing of 0.25 m. The 1991 site was under yam cultivation from 1986 to 1989 and left fallow thereafter. The 1992 site 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 control weeds. The plots were subsequently planted to maize (TZSR-W) on May 31, 1991 and May 6, 1992 at a spacing of 0.4 m x 0.8 m (31, 250 plants/ha). Cassava (TMS 30572) was planted one week later 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, the maize was sidedressed with 15 kg N as CAN (Calcium ammonium nitrate). Maize was harvested August 31, 1991 and August 16, 1992. Cassava was harvested June 15, 1992. 5  The 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 in 1992. Six- and 12- weekly pruning intervals simulated the situations where the farmer prunes once during the maize season or only at maize harvest, respectively. An unpruned treatment was included in both years.  6  4.0 m  Figure 2.1: Cross-sectional view of an alley cropping plot with maize in 4 m alleys between Leucaena hedgerows.  •  .  :* B.  B. m • Zea mays  .  •  EEl .  .  •  4.Om Manihot esculenta  Leucaena leucocephala  Figure 2.2: Plot layout indicating planting pattern of maize and cassava, as well as distance between crops and Leucaena hedgerows.  7  00  i222  .  5.6  6.1  (H 0 2 )  pH  9.0  10.0  0.9  1.2  Org. C Total N (Leco) g/kg g/kg  24.2  30.0  mg/kg  Bray-i P  0.30  0.39  1.98  4.03  0.38  1.10  OAc 4 NH extractable cations K Ca Mg (cmol /kg)  1.16  1.11  ) 3 (gfcm  Bulk Density  76.0  78.0  %sand  %silt  12.0 12.0 sandy loam  11.0 11.0 sandy loam  %clay  Texture  Table 2.1. Soil physical and chemical characteristics before the 1991 and 1992 cropping season for the 0-15 cm surface soil layer of an Oxic Paleustaif, IITA, Ibadan, Nigeria.  3.0. Effect of Leucaena leucocephala (Lam de Wit) pruning frequency on alley cropped maizelcassava. 3.1 Introduction Agroforestry systems are inherently complex. By definition, herbaceous crops are in close association with trees or shrubs in these systems. Consequently, resource pools are shared by both components and there exists the potential for competition between them. This is an important issue since the system aims to produce large amounts of tree biomass for mulch, fodder or fuelwood while simultaneously sustaining crop production (Huxley, 1983; Kang et aL, 1985). Since the goal of agroforestry practices is to minimize negative interactions and to optimize crop and tree productivity (Young, 1989), tree management becomes an important tool with which to allocate and control 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 have been 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 the rows of plants adjacent to infrequently pruned Leucaena compared to control plots. In other studies, 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 in grain 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. Alley cropping studies in the sub-humid regions of the tropics suggest that light interference by the hedgerow can severely limit crop productivity while research in semi-arid climates indicates competition for water between crop and tree (Singh et al., 1988). Competition for nutrients can also be a concern in alley cropping systems on inherently infertile soils (Gichuru and Kang, 1990) and/or when hedgerow prunings are exported rather than used as mulch in the field (Nair, 1984). Pruning  9  management 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 the growth and yield of maize and cassava. How long can hedgerow pruning be delayed before light and/or soil moisture resources become limiting to the crop? Are crops adjacent to the hedgerows more affected than those in the middle of the alleys? I will address these questions in order to determine suitable pruning intervals for production of maize and cassava.  3.2. Materials and Methods 3.2.1. Crop Growth Characteristics and Yield I measured growth characteristics for maize and cassava in both years for 4 plants adjacent to the hedgerow (80 cm from the trees) and in the middle of the alleys (160 cm from the trees). Maize height and leaf area were recorded three times during the 1991 cropping season and biweekly in 1992. 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 planting in 1992 to determine effects of pruning interval on maize reproductive stages. Cassava height, stem diameter, internode length and leaf area were measured on a biweekly to monthly basis during the 1991 cropping season. I repeated these measurements in 1992 but recorded them from May to August only, at which time the experiment was terminated. Whole plots (32 m 2 or 80 plants) were harvested in 1991 to determine maize and cassava yields while 20.5 m 2 (or 64 plants) were harvested for maize in 1992. Unfortunately, many cassava plants in unpruned plots were lost at maize harvest following the accidental application of a defoliating pesticide. Consequently, this treatment was not included in the analysis for cassava yield. At maize harvest, I determined stover and grain yields in both years. Cassava plants were separated into roots, main and lateral shoots at harvest. All plant material was dried at 65°C for three days for dry matter determination. 10  3.2.2. Leucaena growth and pruning biomass Leucaena height and width were measured at weekly intervals in 1991 and only prior to prunings in 1992. I determined pruned biomass at every pruning. Whole rows (8 m long) in 1991 and 5 m sections in 1992 were harvested for dry matter determination. When stems exceeded 2 cm diameter, I recorded foliage and stems weights separately. Approximately 500 g of foliage and stems were taken as subsamples for dry matter determination. These were subsequently weighed, oven-dried at 65°C for 3 days and reweighed.  3.2.3. Solar radiation Light transmission to maize and cassava was measured in both years of the experiment during the maize growing season (approximately 3 months). In 1991, I used a Li-Cor 1000 solarimeter tube to record light transmission. In 1992, due to equipment breakdown, a Li-Cor plant canopy analyzer was used instead, to measure LAI (leaf area index the ratio of leaf area to land area occupied by a -  given number of plants), as an indicator of direct light transmission. I converted LAI values from the plant canopy analyzer to light transmission values in order to be comparable to 1991 data (Black et al., 1992). In 1991, light transmission was measured for all treatments but only for the 4-weekly pruning and no-pruning interval in 1992. I recorded light readings or LAI between 11:00 a.m. and 1:00 p.m. at maize ear height, above the cassava canopy (until cassava was higher than Leucaena and harvested maize) and under the open sky. Light transmission was recorded adjacent to the hedge and the middle of the plot in 1991, but only adjacent to the hedge in 1992. I measured light at weekly and bi-weekly intervals during the first and second seasons, respectively. Transmission in 1992 refers to direct radiation (ie. only one component 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 of hedgerow shading.  11  3.2.4. Soil Moisture Soil moisture was determined gravimetrically for the 0-15 cm soil layer. I collected composite samples of 5 cores adjacent to the hedgerow and in the middle of the alleys in both years. Samples were taken before and after pruning for all treatments in 1991 and in 4, 6 and 12 weekly pruned plots in 1992. To obtain a soil moisture profile over time, samples were collected daily towards the end of the rainy season for 1991. In 1991, I sampled plots on a total of 21 dates from July to the end of October. In 1992, soil moisture samples were collected from the 4- and 6- week pruning intervals, and the unpruned plots for 13 dates during the maize growing season.  3.2.5. Data analyses Data were analyzed either as a completely randomized block one-way or split-plot design using PROC GLM in the SAS package (SAS, 1985). I analyzed medians rather means to overcome inconsistencies among observers recording growth measurements and slower growth in transplanted maize and cassava, in 1991 and 1992, respectively. When log or square root transformations did not correct non-normally distributed data or those with heterogeneous variances, rank transformations were used (Conover and Iman, 1981). Where differences between treatments were significant, I separated means using Duncan’s multiple range test.  3.3 Results 3.3.1. Crop growth characteristics Maize Distance 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 significant effect. Differences in growth were not consistent across years of the experiment. Poor germination of maize seeds in 1991 and subsequent transplanting may have contributed to the high variation observed (CV=30% compared to CV= 15% in 1992). In the second year of the study, maize plants 12  were significantly taller and had thinner stems in unpruned plots compared to pruned plots, but were of similar height to plants in the 4-week pruning interval. Yet, both height and stem diameter differences 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 hedge affected stem diameter and height by 5 and 6 weeks after planting, respectively. Maize was consistently taller with greater basal diameter in the middle of the alleys than those plants adjacent to the hedge in all treatments (Figure 3.la and 3.lb). Plants adjacent to the hedge also had fewer leaves. 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- week pruning intervals. Furthermore, a smaller percentage of maize plants adjacent to the hedge had silked compared to plants in mid-alley in the unpruned plots and the 8-week pruning interval.  13  Table 3.1 Maize reproductive stage measurements taken July 13,1993 (standard error in brackets). %plants silking  % plants tasseling  Pruning interval (weeks)  mid-alley  4 8 unpruned  85.0(0.6) 76.1(4.4) 70.5(4.7)  hedge  80.7(3.9) 78.7(10.0) 60.8(3.5)  whole plot  mid-alley  hedge  82.2(2.0)a*l 74.9(5. 1)a 65.6(3.3)b  94.5(O.8)a 91.6(4.2)a 93.l(2.1)a 96.8(1 .9)a 76.5(10.5)b 86.7(4.6)a 79.1(2.9)a 63.0(8.9)b 58.7(6.1)b  whole plot  *lwhole plot values with different letters within columns vary significantly at the 0.05 level using Duncan’s multiple range test. 9edge/mid-aIley values with different letters within rows vary significantly at the 0.05 level using Duncan’s multiple range test.  14  3.0 2.5  / 1/..  -  -7:..  I....  2.0  -  1.5  I.. 1/•  8-week, mid-alley 8-week, hedge —unpruned, mid-alley • unpruned, hedge -  —  1.0 0.5 0  Figure 3. la:  10 8 6 Weeks after planting  4  2  12  14  Maize plant height 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.  2.0 1.8  I  ‘L6 1.4  1.2  2  Figure 3. lb:  4  6  8 10 Weeks after planting  12  14  Maize basal stem diameter as affected by distance from Leucaena hedgerows in 8week pruning intervals and unpruned plots during the 1992 maize cropping season (May 6 to August 16). Vertical lines indicate standard error of the mean.  15  Cassava Cassava growth characteristics were also affected by pruning interval, but the effect of distance from hedgerow was unclear. Furthermore, growth differences were more consistent in 1991 than in 1992. At least 30% of cassava were replaced at 2 weeks after planting due to poor sprouting in 1992, contributing to the high variability (average CV = 30%) I observed in cassava growth characteristics in 1992. In 1991, cassava node lengths were most dramatically affected by pruning interval with longer nodes under longer pruning intervals and unpruned plots compared to shorter intervals (Figure 3.2a). Cassava plants in plots that were not pruned or pruned only every 10 weeks were also significantly taller compared to a 2- week pruning interval (Figure 3.2b). Plants were taller at the hedge compared to those in the middle of alleys, but only early in the season, while node length and stem diameter were generally not affected. Data collected one week prior to harvest yielded no significant differences among treatments or distance from the hedgerows in number of branches, total number of forks and total node number.  3.3.2. Crop yields Maize grain and stover yields differed between years but were significantly affected by pruning intervals in both years. (Table 3.2a). In plots where hedgerows were not pruned before maize harvest, maize grain yields were reduced by almost 50% compared to pruned hedgerows. Generally grain yields were lower adjacent to the hedge compared to the middle of the alleys in the longer pruning intervals and unpruned plots (Table 3.2b). Stover yields were unaffected by pruning interval in 1991, yet in 1992 stover production was significantly lower in unpruned plots compared to yields from pruned plots. All yield components differed significantly between pruned and unpruned treatments with fewer, lighter kernels and smaller cobs in the latter (Table 3.3). This effect was also apparent adjacent to the hedge in the 8week pruning interval and the unpruned plots. The harvest index (ratio of economic plant parts to  16  total 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 matter production. Only lateral shoot yield was significantly different among treatments. Cassava grown in plots that were pruned less frequently had higher lateral shoot yield than those grown under the more frequently pruned intervals (Figure 3.3). The position of cassava relative to the hedgerow was not a significant factor in determining cassava dry matter yields.  17  60  -  —-  50  I  40  30  2-week 8-week unpruned  -  -  -  20 8-”  14  12  10  18  -46  20  Weeks after planting Figure 3.2a:  Cassava internode lengths for the 2- and 8- week pruning intervals and unpruned plots 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 for the 8-week pruning interval.  2.5 —  —-  2.0  C)  •  .  .  2-week 10-week unpruned  1.  1.0 0.5 0 0  5  —‘i0  15  >20  25  Weeks after planting Figure 3.2b:  Cassava plant height for the 2-, 6- and 10- week pruning intervals and unpruned plots during the 1991 rainy season (May 31 to October 17). Vertical lines indicate standard errors of the mean. Arrows indicate dates of pruning for the 10-week pruning interval.  18  Table 3.2a. Maize grain and stover yield (t/ha) as affected by Leucaena pruning interval (standard error of the mean in brackets). Grain yield (t/ha)  Pruning interval (weeks)  1992  1.22! 3.12(0.18)a* 3.11(0.24)a 3.12(0.14)a 3.23(0.09)a 2.71(0.23)a  2 4 6 8 10 12 unpruned  grain  stover  grain  3.29(O.12)a 3.34(O.34)a 3.56(O.25)a 4.16(O.24)a 3.89(0.19)a  -  1.50(0.28)b  -  4.33(O.13)a 4.63(O.27)a 4.70(O.21)a  7.33(0.50)a 6.35(0.29)a 7.76(0.36)a  -  -  2.04(0.17)b 2.19(0.16)b  -  -  stover  3.20(0.17)a  4.65(0.51)b 4.57(0.46)b  *values with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  Table 3 .2b. Maize grain yields as affected by distance from Leucaena hedgerow (standard error of the mean in brackets). Grain yield (t/ha)  Pruning interval  (weeks)  4 6 8 10 12 unpruned  122Z  1221 hedge  mid-alley  hedge  2.96(0.45)a* 3.26(0.22)a 3.14(0.12)a 2.08(0.28)a  3.26(O.22)a 2.97(O.27)a 3.31(O.14)a 3.14(O.20)b  4.35(O.13)a 4.70(O.47)a 4.57(O.30)a  -  1.53(0.44)a  -  2.43(0.06)b  -  1.72(0.16)a 1.95(0.27)a  mid-alley  4.31(O.24)a 4.57(O.36)a 4.83(O.32)a -  2.36(0.22)b 1.48(0.38)b  *values with different letters differ within rows at the 0.05 significance level using Duncan’s multiple range test.  19  Table 3.3. Maize yield components as affected by pruning intervals for 1992 (standard error in brackets). Pruning interval Kernel # (weeks)  4 6 8 12 unpruned  473(9.8)a* 468(1O.4)a 495(11.8)a 319(21.7)b 319(21.1)b  wt./100 kernel(g)  77.9(1.6)a 77.5(2.3)a 77.8(2.2)a 53.8(2.6)b 58.1 (2 .6)b  Cob width Cob length (cm) (cm)  4.3(O.O)a 4.4(O.1)a 4.3(O.1)a 3.7(O.1)b 3.8(O.1)b  15.6(O.2)a 15.3(O.2)a 16.2(O.2)a 11.7(O.6)b 11.8(O.4)b  Harvest index  O.38ab O.41a O.38ab O.31c O.33bc  *al with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  20  0.40  0.30 Pd  0  0.20 C C  -z rJ2 0.10  0.-.  2  4  6  —  10  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.  21  3.3.3. Leucaena growth and pruning biomass  Figures 3.4a and 3.4b show the growth of Leucaena in relation to maize and cassava growth for the unpruned plot and 6-week pruning interval, respectively. When Leucaena was pruned every six weeks, maize outgrew the hedgerow at 6 weeks after planting while cassava only had a brief shadefree period between 6 and 8 weeks after planting. However, when Leucaena was not pruned throughout 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 is mean pruned biomass. A general increase in biomass is apparent with longer pruning intervals over the first 3 month period in both years (Figure 3.5).  3.3.4. Incident light  Maize and cassava were shaded by Leucaena hedgerows in both years and most markedly in plots where hedgerows were cut infrequently or not at all. Crops that were grown in plots where Leucaena 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 particularly noticeable in the first 2-3 months of growth of both crops when they were relatively shorter than Leucaena. It was also apparent that cassava received almost 50% less light than maize during this  period, due to a combination of hedgerow and maize light interception. As expected there was always greater light transmission at noon when light passed through a thin canopy directly overhead compared to early morning (Figure 3.6b). Light transmission to maize in plots with unpruned Leucaena decreased gradually over the season by more than 50% (Figures 3.6a and b). However, a different pattern is evident when Leucaena is pruned every 10 weeks a different pattern is evident. Prior to pruning, light  transmission 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, with  22  relatively little change until the end of the growing season (Figure 3.6b). Distance from the hedgerows also influenced light transmission to maize. In unpruned plots, crops adjacent to hedgerow 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 of alleys compared to light transmission at the hedge. After pruning, however, more light was transmitted adjacent to the hedge than in the middle of the alleys where shading by other maize plants contributed to a reduction in light transmission.  23  3.0 2.5 ,  2.0  1.5 -I  L0 0.5 0 8  4  ‘4  Weeks after planting  Figure 3.4a: Maize, cassava and Leucaena heights under the 6-week pruning interval for the 1991 maize cropping season (May 31 to August 31). Arrow indicates date of pruning.  3.0  2.5 2.0 1.5  1.0 0.5  0  14  Weeks after planting  Figure 3.4b: Maize, cassava and Leucaena heights in unpruned plots for the 1991 maize cropping season (May 31 to August 31). Arrow indicates date of pruning.  24  2.5  j1 1991 2.0  1992 -  F;’  jl.5  E >) I-i  1.0  0.5  o__ 2  4  6  8  10  unpruned  Pruning interval (weeks)  Figure 3.5:  Mean Leucaena foliage pruning biomass (tfha) over the 1991/1992 maize cropping seasons (May 31 to August 31; May 6 to August 16).  25  100 — -  80  -  .  10-weelç, mid-alley 10-week, hedge unpruned, mid-alley unpruned, hedge  / .  //  //  -  -  20 0 •8 “ 10 Weeks after planting  •6  12  Figure 3 .6a: Light transmission (%) to maize ear level in the middle of the alleys and adjacent to Leucaena hedgerow during the 1991 cropping season (May 31 to August 31) under a 10-week pruning interval and no pruning. Arrow indicates date of pruning. 1 (‘ii  —4-week a.m. 4-week p.m.  o 80  -  __unpruneda.m. unprunedp.m. -  -  40 b0  -  0  I  6  —p8  10  -“2  14  Weeks after planting Figure 3.6b: Light transmission (%) to maize ear level adjacent to Leucaena hedgerow during the 1992 cropping season (May 6 to August 16) under a 4-week pruning interval and no pruning. For each treatment light transmission in the morning (8 a.m.) and at noon are given. Arrows indicate dates of pruning.  26  When light transmission was related to the difference in height between Leucaena and maize a = 0.80, P=0.0002). Light transmission approached 100% as 2 significant relationship was detected (r the difference between Leucaena and maize heights decreased (Figure 3.7). An increase in light transmission to maize was also related to a decrease in hedgerow LAI as Figure 3.8 illustrates =0.89, P=O.0001). 2 (r Similar light transmission patterns to maize, were observed at the cassava canopy under 4 and 10 week pruning intervals. Low light transmission levels were consistent throughout the period of 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 which reached 100% after maize harvest. After pruning, more light was transmitted adjacent to the hedge compared 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 the =0.57, P=0.0002)(Figure 3.10). Furthermore this light transmission was 2 crop and the hedgerow (r =0.89, P=0.0001)(Figure 3.11). Both 2 in turn related to LAI of the canopy above cassava (r relationships point to a decrease in light transmission to cassava with increasing hedgerow biomass.  3.3.5. Soil Moisture Soil moisture distribution was not significantly affected by pruning interval or by distance from the hedgerows during the 1991 and 1992 maize growing seasons. After maize harvest and toward 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 soil moisture content between the area adjacent to hedgerows and the middle of the alleys indicate generally wetter conditions adjacent to the hedgerow in the 4-week pruning interval during October  27  (Figure 3.12). In contrast, unpruned plots generally had drier conditions adjacent to the hedgerow compared to the middle of the alleys. This phenomenon was particularly notable after the last rainfall for which samples were collected.  28  I  0  0.2  0.4  0.6  0.8  1.0  1.2  Height difference (m) Figure 3.7:  Relationship between % light transmission to maize ear level and the difference in height (cm) between maize and Leucaena during the 1991 maize cropping season (May 6 to September 1, 1991).  50 -O.65x  C -4  I  y4.64e  40 30 20  .  -  . .  10  -  0 1  3  2  4  LAI Figure 3.8:  Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % light transmission to maize cob during the 1992 cropping season (May 6 to August 16).  29  100 10-week, mid-alley 10-week, hedge unpruned, mid-alley unpruned, hedge  — -  .  80  •  ,‘  //  [  60 Ii .1  40 —  2:4 68710121416  18  Weeks after planting Figure 3.9a:  Light transmission (%) to cassava canopy in the middle of the alleys and adjacent to Leucaena hedgerow during the 1991 cropping season (May 31 to August 26) under a 10-week pruning interval and unpruned plots. Arrow indicates date of pruning. 100 O 80 — -  4-week, a.m. 4-week, p.m. unpruned, a.m. unpruned, p.m.  6O 40 2:  14 Weeks after planting Figure 3.9b:  Light transmission (%) to cassava canopy adjacent to Leucaena hedgerow during the 1992 cropping season (May 6 to August 16) under a 4-week pruning interval and unpruned plots. For each treatment light transmission in the morning (8 a.m.) and at noon are given. Arrow indicates date of pruning.  30  100  80 60 4° 20  0 0  0.5  1.0  1.5  2.0  2.5  Height difference (m) Figure 3.10:  Relationship between % light transmission to the cassava canopy and the difference in height (cm) between cassava and Leucaena during the first 4 months of cassava growth (May 6 to September 1, 1991).  60 50  -  ;O.70x  C  I  y=4.55e  -  .  40 30  -  -  .  .  20 .  10 0 1  2  3 LAI  Figure 3.11:  Relationship between Leucaena hedgerow canopy LAI (leaf area index) and % light transmission to cassava canopy during the 1992 cropping season (May 6 to August 16).  31  25 20  15 i •  10 5 0 0  -20 -40 -60 -80  40 20 0 -20 -40 10  5  October 1991 Figure 3.12:  Differences in gravimetric soil moisture content adjacent to Leucaena hedgerows and middle of the alleys in the 4-week pruning and unpruned plots during the month f October 1991. Arrows indicate dates of pruning.  32  3.4. Discussion Pruning Leucaena only at maize harvest reduced maize yield significantly. Cassava root yield was not affected under long pruning intervals, although lateral shoot growth was higher in these treatments. Growth characteristics of both crops were also influenced by pruning interval but not consistently. Furthermore, distance from Leucaena hedgerows affected both yield and growth characteristics.  Although effects varied with crop and year of the experiment, growth responses  and yield declines in both years were attributable to light limitations, while soil moisture had no clear effect under different pruning intervals. It is well known that shade affects maize yield, the severity of the effect depending on the stage of maize growth at which shade is applied. Mbewe and Hunter (1986) observed a decrease in maize 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 grain yield (Fagena et al., 1981; Lawson, 1975). When Kiniry and Ritchie (1985) applied shade stress during the grain filling period, final kernel number and therefore grain yield was significantly reduced. This latter phase in the development of maize is considered to be the most important in determining 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 week pruning in 1991, suggesting that shading has detrimental effects between 10 weeks after planting and maize harvest. This 10 week point corresponds approximately to the beginning of the grain filling period. Furthermore, I found that delaying pruning to 10 weeks after planting maize affects grain yield in plants grown adjacent to the hedgerows. This underlines the importance of environmental effects at this stage in maize growth. As Schussler and Westgate (1991) observed, shading during the grainfilling period had a more marked effect on kernel loss than when shading was applied at pollination. 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 final 33  grain yield (Edmeades et al., 1979). Fewer kernels and lower kernel weights under unpruned Leucaena 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 and Hunter (1986) observed similar reductions (25%) in stover yield when shade was applied either at the vegetative stage or during grain filling, but found no differences when plants were shaded during the reproductive period. Generally maize grain yield exhibits a stronger response to limited solar radiation than stover yield (Scarsbrook and Doss, 1973; Earley et a!., 1966). A less sensitive response by stover production to light limitations, in conjunction with high variability, may explain why no difference was observed in the first year of the experiment. Maize plants were shorter with smaller diameters adjacent to Leucaena hedgerows than in the 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 vegetative growth enough to suppress vertical growth and allow the plants in the middle of the alleys to grow taller (Tetio-Kagho and Gardner, 1988). A reduction in assimilates could also explain why leaf area did not differ significantly under different pruning intervals. Limited light transmission to maize had detrimental effects on maize growth and final yield in this study. Similar findings were reported by Lawson and Kang (1990) who associated decreased maize yields with increased Leucaena biomass; a result they attributed to excessive shading by the hedgerow. Shade effects, more than any other factor, were used to explain low maize yields under Acacia albida, where the hedgerow was pruned only once during the growing season (Jama and Getahun, 1991). Increasing light transmission gradients with increasing distance from the hedgerow were 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 and Lawson, 1991; Haggar and Beer, 1993).  34  Were 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 maize cropping season. Nevertheless, other studies indicate that extended drought stress during the growing season, particularly at the time of grain-filling could seriously decrease yield (NeSmith and Ritchie, 1992; Schussler and Westgate, 1991; Begg and Turner, 1976). Competition for water was unlikely 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 that some effect of continuous shading beyond 10 weeks after planting would be reflected in a decrease in final yield. Cassava etiolated under longer pruning intervals (8-10 wks) until the crop outgrew the hedgerow and shade was no longer important to vegetative growth while etiolation continued when Leucaena was not pruned.  Kasele (1983) related a decline in cassava dry matter yield to  increased height and a concurrent decrease in stem diameter with increasing shade. Since cassava partitions assimilates to root and shoot simultaneously, a greater proportion of assimilates are diverted 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 shoot yield 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 pruning intervals of 10 weeks or less. Higher soil moisture in the middle of the alleys in unpruned plots may be due to an ‘umbrella’ effect caused by the nature of the canopy. Wetter conditions adjacent to the hedgerow under the 4-week pruning interval may be the result of moisture conservation by shading of the hedgerows, a suggestion also made by (Lawson and Kang, 1991). However, the soil moisture 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,  35  observed that with the application of drought stress at 6-8 months, cassava yield was markedly reduced. Others have found that prolonged moisture stress can result in reductions in total biomass and root yield (Sharkaway et al., 1992; Lal, 1981). On the basis of this study, I can only make recommendations for Leucaena hedgerow pruning with respect to maize. Delaying pruning beyond 10 weeks after the initial cut back caused a decline in maize yield attributable to shading during the grain-filling stage. Timely pruning at 10 weeks after planting maize is therefore advisable, in order to maintain crop productivity and to derive the benefits of alley cropping. The effects of delayed pruning (ie. more than 10 weeks) on cassava need to be investigated further, through tuberization and growth studies, in order to recommend a pruning interval that optimizes both maize and cassava yields.  36  3.5. References Baker GR, Fukai S and Wilson GL (1989) The response of cassava to water deficits at various stages of growth in the subtropics. Australian Journal of Agricultural Research 40: 517-528 Begg JE and Turner NC (1976) Crop water deficits. Advances in Agronomy 28: 161-207 Black TA, Chen 3M, Lee X and Sagar RM (1991) Characteristics of shortwave and Iongwave irradiances under a Douglas-fir forest stand. Canadian Journal of Forest Research 21: 10201028 Buck MG (1986) Concepts of resource sharing in agroforestry systems. Agroforestry Systems 4: 191-203 Cock JH (1983) Cassava. In: Cock JH, ed, Potential productivity of field crops under different environment. pp 33-42. IIRI, Philippines Cock JH, Franidin D, Sandoval G and Jun P (1979) The ideal cassava plant for maximum yield. Crop Science 19: 271-279 Conover WJ and Iman RL (1981) Rank transformations as a bridge between parametrics and nonparametric statistics. American Statistician 35(3). 124-133. Duguma B, Kang BT and Okali DUU (1988) Effect of pruning intensities of three woody leguminous species grown in alleycropping with maize and cowpea on an affisol. Agroforestry Systems 6: 67-80 Earley EB, Miller RI, Reichert GC, Hageman RH and Seif RD (1966) Effects of shade on maize production under field conditions Crop Science 6: 1-7 Edmeades GO and Daynard TB (1979) The relationship between final yield and photosythesis at flowering in individual maize plants. Canadian Journal of Plant Science 59: 577-584 El-Sharkaway MA, Hernandez ADP and Hershey C (1992) Yield stability of cassava during prolonged mid-season water stress. Experimental Agriculture 28: 165-174 Fagena 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 Leucaena leucocephala hedgerows on maize production. Leucaena Research Reports 11:68-69. Gichuru MP and Kang BT (1990) Calliandra calothyrsus (Meissn.) in an alley cropping system with sequentially cropped maize and cowpea in southwestern Nigeria. Agroforestry Systems 9: 191-203 Haggar JP and Beer JW (1993) Effect on maize growth of the interactions between increased nitrogen availability and competition with trees in alley cropping. Agroforestry Systems 21: 239-249  37  Huxley PA (1983) Plant research and agroforestry. Proceedings of a consultative meeting in Nairobi, April 8-15, 1981, ICRAF, Nairobi, Kenya Jama 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: 193-205 Kang 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: 165-179 Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpea with Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277 Kasele IN (1983) Studies on the effects os some environmental factors on cassava (Manihot esculenta Crantz) tuberization. Master of Philosophy Thesis, University of Thadan, Ibadan, Nigeria Kiniry JR and Ritchie JT (1985) Shade-sensitive interval of kernel number of maize. Agronomy Journal 77: 711-715.  Lal R (1981) Effects of soil moisture and bulk density on growth and development of two cassava cultivars. In: Tropical Root Crops: Research Strategies for the 1980’s, Proceedings of the first 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 of Tropical Agriculture Annual Report 1983. pp 181-182 Lawson TL and Kang BT (1990) Yield of maize and cowpea in an alley cropping system in relation to available light. Agricultural and Forest Metereology 52: 347-357 Mbewe DMN and Hunter RB (1986) The effect of shade stress on the performance of corn for silage versus grain. Canadian Journal of Plant Science 66: 53-60 NeSmith DS and Ritchie JT (1992) Maize (Zea mays L.) response to a severe soil water-deficit during grain-filling. Field Crops Research 29: 23-35 Nair, PKR (1984) Soil productivity aspects of agroforestry. Science and Practice of Agroforestry Series 1. ICRAF, Nairobi, Kenya. Ong KC, Rao MR and Mathuva M (1990) Trees and crops: Competition for resources above and below the ground. Agroforestry Today 4(2): 4-5 Rosecrance RC, Brewbaker JL and Fownes JH (1992) Alley cropping maize with nine leguminous trees. Agroforestry Systems 17: 159-168 SAS Institute Inc., (1985) SAS: User’s guide, Version 5 Edition, SAS Institute Inc., Cary NC, USA, 9S6p  38  Scarsbrook CE and Doss BD (1973) Leaf area index and radiation as related to corn yield. Agronomy Journal 65: 459-461 Schussler JR and Westgate ME (1991) Maize kernel set at low water potential: II. Sensitivity to reduced assimilates at pollination. Crop Science 31: 1196-1203 Singh RP, Ong KC and Saharan N (1989) Above and below ground interactions in alley-cropping in semi-arid India. Agroforestry Systems 9: 259-274 Splittstoesser WE and Tunya GO (1988) Crop physiology of cassava. In: Janick, J, ed, Horticultural Reviews. Volume 13. pp. 129 105 Sreekumari MT, Abraham K and Ramanujam T (1988) The performance of cassava under shade. Journal of Root Crops 14: 43-53 Tetio-Kagho, F and Gardner FP (1988) Responses of maize to plant population density. I. Canopy development, light relationships and vegetative growth. Agronomy Journal 80: 930-935 Young A (1989) Agroforestry for soil conservation. Science and Practice of Agroforestry Series No. 4. ICRAF/CAB International, Nairobi, Kenya  39  4.0. Nutrient contribution of Leucaena leucocephala to maize and cassava under different pruning intervals 4.1. Introduction Food production systems such as alley cropping rely on biological means to maintain soil  fertility and to contribute to sustainable crop production. Thus, where soil fertility is declining and/or high-input agriculture is not possible, alley cropping may be an alternative for the resourcepoor farmer (Kang et al., 1981). This agroforestry practice has been shown to improve soil chemical properties, particularly when nitrogen-fixing species such as Leucaena leucocephala are used (Brewbaker, 1987, Yamoah et a!., 1986; Nair, 1984). These improvements have been attributed to the addition of organic nitrogen, carbon and phosphorus from prunings of fast-growing hedgerows (Kang and Balasubramian, 1990; Nair, 1984). Large inputs of foliage biomass and consequently 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 direct nutrient sources to associated crops (Read et al., 1985). Readily-available nutrients from rapidly decomposing prunings may be taken up by associated crops (Tian et a!., 1992; Mulongoy and Akobundu, 1988). There may also be a transfer of nutrients by root-turnover of nitrogen fixing trees (Yamoah et al., 1986). The soil ameliorating and/or direct crop nutrition effects associated with alley cropping have been reflected in sustained crop yields compared to the yield declines often observed under continuous cultivation (Nair, 1984, Kang et al., 1981). The potential for hedgerow prunings to maintain soil fertility and/or contribute to crop nutrition is influenced by the method and timing of hedgerow pruning application, decomposition rate 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 necessarily consider these factors. Furthermore if hedgerow prunings can contribute to crop nutrition, how long can pruning be delaying before the contribution becomes negligible? Identifying a pruning  40  interval 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 its nutrient yield and its potential contribution to alley cropped maize and cassava. Are pruning applications reflected in enhanced crop productivity? Furthermore, is there any evidence of shortterm soil fertility amelioration under alley cropping? I will answer these questions in an effort to identify pruning intervals that optimize the benefits of Leucaena prunings.  4.2. Materials and Methods 4.2.1. Leucaena foliage and crop samples I collected Leucaena pruning data in both years of the experiment. At every pruning Leucãena foliage biomass was weighed and subsamples taken for dry matter determination from a  20 m 2 area. Only Leucaena foliage and green, tender stems were sampled. I took further subsamples for nutrient analysis from every pruning date at which more than one treatment was pruned in order to make nutrient yield comparisons. Cassava leaf samples were collected at the end of 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 the silking period in 1992, maize ear leaf samples were collected from 20 plants adjacent to the hedgerow 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. Plant material was digested for subsequent nutrient analysis using the Parkinson-Allen method (Parkinson and Allen, 1975). A Technicon autoanalyzer was used for N and P determinations while base cations were determined with a Perkin-Elmer 306 atomic absorption spectrometer. I calculated nutrient contents for maize and cassava on a leaf dry matter (weight of leaves sampled) basis.  41  4.2.2. Soil analysis  Soil samples were collected from 0-15 cm at the beginning of the 1991 and 1992 cropping periods for characterization of each site. In 1991 I took composites of 20 cores (2 cm diameter) for each block, while in 1992 40 cores from each block were taken; 20 from the area adjacent to the hedgerows (0 0.80 m) and 20 from the middle of the alleys 1.6 2.4 m). Soil samples were also -  -  collected in October, 1991, using of 10 cores from each treatment in every block. Bulk density samples were taken 24 weeks after planting in 1991 and 4 weeks after planting in the following season. I also determined soil texture for the site characterization samples using the hydrometer method. A 2:1 soil-water suspension was used to measure pH. Phosphorus was extracted using the Bray-Pt method with an extraction time of 5 minutes and P was subsequently determined using a Gilford spectrophotometer. Total carbon was determined with the Leco carbon analyzer. Base cations were extracted using neutral 1M ammonium acetate and concentrations determined with a SO 2 H Perkin-Elmer 306 atomic absorption spectrometer. Total nitrogen was determined from an 4 extract with a Technicon autoanalyzer.  4.2.3. Data analyses  Data were subjected to ANOVA and regression analysis with backward selection using SAS GLM and REG procedures, respectively (SAS, 1985). Where data were not normally distributed and variances were nonhomogeneous, appropriate transformations were made. Ranks were employed when log or square-root transformations did not correct non-normality or heterogeneity (Conover and Iman, 1981).  42  4.3. Results 4.3.1. Crop nutrient concentrations and contents Differences were apparent in crop nutrient contents under different pruning intervals. Maize ear leaf N at silking was similar for the 4- and 6-week pruning intervals but significantly lower in unpruned plots compared to a 4-week pruning interval. Phosphorus contents were significantly higher 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 Mg compared to the middle of the plot in all pruning intervals (Table 4. ib). Neither pruning interval nor location within the plots affected nutrient concentrations in maize ear leaves indicating that differences 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, 23.0 g K/kg, 3.0 g Ca/kg and 1.6 g Mg/kg. Cassava leaf nutrient concentrations varied significantly between unpruned plots and other pruning intervals. Phosphorus and Mg concentrations were lower in cassava leaves where Leucaena was not pruned (Table 4.2). In contrast, K concentration was on average higher in unpruned treatments. When nutrient concentrations were converted to leaf content basis, cassava leaves in unpruned 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 any pruning interval.  43  Table 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 (weeks) 4 6 unpruned  Nitrogen 10.33(0.60)la* 9.64 (0.75)ab 8.60(0.31)b  Phosphorus mg/leaf DM  Potassium  1.27(0.07)a  4.0(0.2)a  l.13(0.06)b  3.7(0.3)a 3.5(0.l)a  1.06(O.06)b  ‘standard error of the mean in parenthesis *valueS with different letters differ within columns at the 0.05 significance level using 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.  Middle of the alley Adjacent to the hedgerow  Nitrogen  Phosphorus mg/leaf DM  Potassium  l0.8(0.6)la*  1.26(0.06)a  4.2(0.02)a  8.5(0.5)b  1.04(0.05)b  3.3(0.02)b  standard error of the mean in parenthesis 1 *values with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  44  Table 4.2. Cassava leaf nutrient concentrations under 4- and 6- week pruning intervals, and unpruned plots. Pruning interval (weeks)  Nitrogen  Phosphorus  Potassium (g/kg)  4 6 unpruned  43.8(0.5)la* 46.0(1.3)a 42.9(0.6)b  29.0(0. 1)a 29.0(0.1)a 25.0(0.01)b  2.6(1 .0)a 2.7(1.0)a 3.6(0.1)b  Calcium  14.8(0.3)a 14.3(0.3)a 16.0(0.1)b  Magnesium  7.9(0. 1)a 8.4(0.7)a 6.3(0.3)b  1 standard error of the mean in parenthesis *values with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  Table 4.3. Cassava leaf nutrient content under 4- and 6- week pruning intervals, and unpruned plots. Pruning interval  Nitrogen  Phosphorus  Calcium  Magnesium  35.5(2.7)a 34.9(5.1)a 18.8(1.9)b  19.1(0.8)a 20.3(2.7)a 7.5(1.2)b  mg/leaf DM  (weeks) 4 6 unpruned  Potassium  105.5(4.8)la* 111.6(14.3)a 50.5(4.82)b  7.1(O.41)a 7.1(1.11)a 2.9(0.29)b  63.6(3.8)a 66.7(10.0)a 42.4(4.2)b  standard error of the mean in parenthesis 1 *values with different letters differ within within columns at the 0.05 significance level using Duncan’s multiple range test.  45  4.3.2. Leucaena nutrient yield Both nutrient concentration and yield of Leucaena foliage differed significantly with pruning interval. 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). Greater biomass, 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 significantly lower in the 8-week pruning interval than the 2- and 4-week pruning intervals (Table 4.4), the former 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 pruning dates due to decreasing biomass produced (Figure 4.1). In contrast, Leucaena pruned every 4 weeks maintained a relatively constant nutrient contribution after the initial dropoff. In 1992, the same trend was apparent with the 8-week supplying considerably more N, P and K than the monthly pruning interval at the same pruning date (Figure 4.2). The concentration of Ca and Mg did not vary with pruning interval in general, yet yields of these nutrients increased with increasing pruning intervals. Total nutrient yields of Leucaena prunings differed with pruning intervals depending on the time period. For instance, prior to maize ear leaf sampling greater quantities of nutrients were applied with the 4- and 6- week pruning intervals compared to the 8 week pruning interval (Figure 4.3a) 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 are compared over a longer period (June to November, 1991), pruning every 10-week yields higher quantities of nutrients, particularly N and K, than other pruning intervals (Figure 4.4).  46  Table 4.4. Leucaena nitrogen, phosphorus and potassium concentrations under 2, 4 and 8 week pruning intervals. Pruning interval (weeks) 2 4 8  Nitrogen  Phosphorus (glkg)  Potassium  52.6(l.6)la*  3.6(O.2)a 3.9(O.2)a 2.7(O.1)b  15.7(1.7) 17.4(3.3) 21.6(0.6)  55.6(2.2)a 46.4(2.2)b  1 standard error of the mean in parenthesis *al with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  47  60  NZI 8-week 4-week 2-week  —  40 .  20  I  4 3 2  1 0  30  E  20  Cl) I’  C  0  H 8  N  16 24 Weeks after planting Figure 4.1: Nitrogen, phosphorus and potassium yield of Leucaena prunings under 2-, 4- and 8week pruning intervals at 8, 16 and 24 weeks after planting during the 1991 growing season.  48  50 4-week 8-week  40 -  ‘—‘  30  -  .  20  Z\  10_ 0_\  Nitrogen  Figure 4.2.  Potassium  Phosphorus  Nitrogen, phosphorus and potassium yield of Leucaena prunings under 4- and 8- week pruning intervals at 8 weeks after planting during the 1992 growing season.  49  1: Nitrogen  Potassium  Phosphorus  Figure 4.3a: Nitrogen, phosphorus and potassium yield of Leucaena prunings prior to maize ear leaf sampling in the 1992 growing season.  200  150 1)  100  50  0  Nitrogen  Potassium  Phosphorus  Figure 4.3b: Nitrogen, phosphorus and potassium yield of Leucaena prunings during the 1992 maize growing season.  50  300  250  E  200  150 ti)  .s  100  z 50  0  Nitrogen  Potassium  Phosphorus  Figure 4.4: Total nitrogen, phosphorus and potassium yield of Leucaena during the 1991 growing season (June to November).  51  4.3.3. Relationships between Leucaena prunings and crop productivity  I tested several relationships to determine effects of Leucaena prunings on crop nutrient contents and yields. Hence, regressions were done with and without data from unpruned piots to determine their influence 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, N  from Leucaena prunings was associated with maize ear leaf N status in the 4 and 6-week pruning intervals, but accounted for only 50% of the variation observed (Table 4.5). Maize grain and stover yields were associated with N and K from Leucaena prunings. When data from unpruned plots was dropped from the analysis, none of the above-mentioned relationships were significant, suggesting reductions in biomass in unpruned plots were responsible for the relationships I observed. When 1992 maize yields were related to Leucaena pruning nutrient yields, soil moisture and light to determine the most important factor/s, light transmission accounted for 75% of the variation. This was also the case in 1992 where a decrease in available light to maize was associated with the majority of the decline in grain yield. Leucaena N, P and K from prunings were significantly related to cassava leaf nutrient contents (Table 4.6). However, when all measured variables were related to cassava dry matter yield, only light transmission was a significant factor accounting for 90% of the variation observed (Table 4.6).  52  Table 4.5. Association of maize yield and ear leaf nitrogen with nitrogen and potassium from Leucaena prunings, and light transmission under Leucaena. P  Regression equation  2 r  F  y=maize leaf N, x=Leucaena N  0.52  9.60  0.012  y8.46+O.000lx  y=maize grain, x=Leucaena N  0.86  67.21  0.001  y=2.18+0.02x  y=maize stover, x=Leucaena K  0.61  17.53  0.015  y4.42+0.03x  y=maize grain, xlight transmission (1991)  0.75  12.23  0.025  y=-0.15+0.04x  y=maize grain, x=light transmission (1992)  0.68  21.56  0.001  y=1.33+0.13x  Relationship  Table 4.6. Association of cassava leaf nutrient contents and dry matter yield with nitrogen, potassium and phosphorus from Leucaena prunings. 2 R  F  P  Regression equation  y=cassava leaf N, xLeucaena N  0.74  11.39  0.027  y=66.0+0.29x  y=cassava leaf K, x=Leucaena K  0.67  8.02  0.047  y4.82+0.03x  y=cassava leaf P. x=Leucaena P  0.76  12.42  0.024  y=3.89+0.40x  y=cassava root DM yield, x = light transmission  0.92  33.04  0.0 10  y=-0.48+0.03x  y=cassava total DM yield, x = light transmission  0.88  21.90  0.018  y=0.16+0.05x  Relationship  53  4.3.4. Soil Fertility Status I summarized surface soil chemical characteristics for each site in Table 2.1 of the general experimental layout. There were significant differences in fertility between soil taken adjacent to the hedge and the middle of the alley at the 1992 site prior to planting (Table 4.7). Phosphorus was almost 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 the  hedgerow than in the middle of the plots (F=21.82, P=O.02)(l’able 4.7). Total nitrogen and organic 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 pruning intervals. The 10-week pruning interval, which was pruned 1 week prior to soil sampling, had higher nitrate levels compared to all other treatments.  54  Table 4.7. Soil surface (0-15 cm) chemical properties in the middle of alleys and adjacent to Leucaena hedgerows after 18 months of Leucaena fallow. pH  Org. C  Total N  Available N  Bray-i P  (1120)  (Leco) g/kg  mg/kg  g/kg  NH 4 3 NO mg/kg  K  Ca  Mg  cmol/i00g  Middle of alley  (0.07)  8.7 (0.7)  0.8 (0.04)  i.44a (0.09)  0.56 (0.02)  i9.4a (1.10)  0.31 (0.02)  2.10 (0.29)  0.39 (0.03)  Adjacent to hedgerow  5.74 (0.06)  10.0 (0.9)  0.9 (0.04)  i.78b (0.06)  0.63 (0.03)  38.4b (1.77)  0.29 (0.02)  1.85 (0.24)  0.37 (0.04)  1  5.381  standard error of the mean in parenthesis  *values with different letters differ within columns at the 0.05 significance level using Duncan’s  multiple range test.  55  4.4. Discussion When Leucaena hedgerows are not pruned at least once a season lower nutrient contents in maize and 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 these relationships 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. The nutritional status of the crops prior to sampling is important. Nutrient concentrations for maize ear leaf did not differ significantly and were generally within the sufficiency range for maize nutritional requirements (Fagena et at., 1991).  This suggests that adequate nutrients were supplied by the  fertilizer (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 that applying 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 subsequent prunings. Moreover, light limitations to crops and the consequent detrimental effects on growth could have obscured an effect of Leucaena pruning applications. The difference in maize ear leaf nutrient contents between pruned and unpruned treatments likely reflects lower dry matter production in the latter. Lower dry matter production is associated with either limited nutrient uptake and/or photosynthetic capacity (Fagena et a!., 1991). The relatively lower dry matter accumulation at the silking 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 no significant relationship between Leucaena nutrients applied, and crop yields and nutrient contents when data from unpruned plots were dropped. This suggests applying prunings 4 to 8 weeks after planting had no significant effect on the nutritional status of maize while pruning applications at 2 to  56  10 week intervals were negligible to cassava nutrition. Thus, the crop response relationships I established are not necessarily due to a direct response  of Leucaena nutrients applied. Read et al. (1985) also found that with the application of inorganic fertilizer, there was no crop response to Leucaena pruning applications. Still, many researchers have 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 is dependent 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 after planting (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 of the 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 leaf nutrients nor maize grain yields. Pruning at 6 weeks after planting occurred 3 days prior to sampling and is thus unlikely to have had an effect on ear leaf nutrient status while the 8 week pruning occurred well after the sampling period. These observations suggest that application of prunings after a critical period will have a lesser effect on crop growth than if applied before. In agreement, Mulongoy and van der Meersch (1988) found surprisingly low maize uptake efficiencies (30%) of Leucaena pruning nitrogen despite large quantities available. Similarly, in studies with other 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 less marked than for maize. Lower P and Mg leaf concentrations in cassava leaves in the unpruned treatment may have reflected a soil deficiency and/or competition by Leucaena. On the other hand higher K and Ca leaf concentrations in the same treatment could be due to stemfiow and throughfall  57  contributions from Leucaena. This is an important mechanism of nutrient addition in forest ecosystems (Parker, 1989). However, a significant reduction in cassava leaf dry matter under continuous shade at the time of sampling resulted in lower leaf nutrient contents compared to all other pruning intervals. Leaf concentrations fell below the sufficiency range for cassava (Howeler, 1981); thus a nutrient response might be expected. The positive correlation between Leucaena pruning application and cassava leaf nutrient contents suggests a potential to enhance cassava nutrition. It is known that cassava responds to N and K application in particular during its period of maximum growth rate, up to 7 months after planting (Cock, 1983; Fagena et al., 1991).  However, multiple regression  analysis of the factors investigated in this study indicated that available light, not nutrients, is the principal factor responsible for variation in cassava dry matter yield. My data are consistent with numerous studies which have investigated environmental stresses on cassava yield and found light to be 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 capacity to enhance soil fertility and thus contribute to crop productivity in subsequent cropping seasons may be more important. Mulongoy and Van der Meersch (1988) suggest that the residual effects of applying 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 a period of 6 months. Nutrient yield of Leucaena prunings increase with longer pruning intervals while nutrient concentrations actually decrease compared to more frequently cut hedgerows. This can be attributed to greater pruning biomass in the former. Nutrient yield followed the same general pattern as biomass yield. The relationship between nutrient yield and biomass production is well 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 as  58  more assimilates are used for woody matter production. Duguma et al., (1988) also found higher N concentrations 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 in soil N0 3 after the 10 week pruning application also confirms that rapid mineralization occurs with Leucaena foliage. Hence pruning interval is important, not only in terms of nutrient availability but  in the timing of application. 4 and P adjacent to the hedgerow prior to 1992 cropping points to the The increase in soil NH soil enhancing properties of Leucaena fallows. Numerous authors have noted soil fertility improvement 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) also commented on the residual fertility effects of pruning applications. Despite enhanced soil properties adjacent to the hedgerow, maize leaf nutrient contents and grain yields were lower here, reiterating the overriding effect of shading by Leucaena. Given that fertilizer may not be available to the resource-poor farmer, Leucaena prunings could contribute to the nutrition of associated crops. As Pinney (1991) and Mulongoy and Akobundu (1990) suggest, pruning at or just after planting is most likely to have an effect on crop nutrition. Thus, subsequent prunings are primarily aimed at improving the fertility of the soil through continuous application of organic matter.  A number of long-term studies have shown that  the addition of Leucaena prunings is instrumental in maintaining high soil organic matter and nutrient status. Leucaena, as a nitrogen-fixing species, has potential to contribute large quantities of nutrients (Kang et a!., 1986; Duguma, 1985). Hence, pruning only once a season between 4 and 8 weeks after crop planting, may offer the most desirable scenario by supplying moderate amounts of organic material while not unduly increasing the labour requirements of the farmer.  59  4.5. References Cock JR (1983) Cassava. In: Cock, JH, ed, Potential productivity of field crops under different environment. pp 33-42. IRRJ, Philippines Conover WJ and Iman RL (1981) Rank transformations as a bridge between parametrics and nonparametric statistics. American Statistician 35(3): 124-133 Brewbaker 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 Netherlands Duguma B, Kang BT and Okali DUU (1988) Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol. Agroforestry Systems 6: 67-80 Fagena NK, Bahgar VC and Jones CA (199 1),eds, Growth and mineral nutrition of field crops. Chapter 7: Corn, Marcel Dekker Inc., New York Howeler RH and Cadavid LF (1983) Accumulation and distribution of dry matter and nutrients during a 12-month growing cycle of cassava (Manihot esculenta). Field Crops Research 7(2): 123-129 Kang BT, Sipkens L, Wilson GF and Nangju D (1981) Leucaena (Leucaena leucocephala (Lam) de wit) prunings as nitrogen sources for maize (Zea mays L.). Fertilizer Research 2: 279-287 Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpea with Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277 Karim AB, Rhodes ER and Savill PS (1991) Effect of cutting height and cutting interval on dry matter yield of Leucaena leucocephala (Lam) De Wit. Agroforestry Systems 16:129-137 Kayode GO (1986) Further studies on the response of maize to K fertilizer in the tropics. Journal of Agricultural Science (Cambridge) 106:141-147. Matthews RB, Lungu 5, Volk J, Holden ST and Solberg K (1992) The potential of alley cropping in improvement of cultivation systems in the high rainfall areas of Zambia II. Maize production. Agroforestry Systems 17:241-261 Mulongoy K and Meersch MK van der (1988) Nitrogen contribution by Leucaena (Leucaena leucocephala) prunings to maize in an alley cropping system. Biology and Fertility of Soils 6:282-285 Nair PKR (1984) Soil productivity aspects of agroforestry. Science and Practice of Agroforestry Series No.1. ICRAF/CAB International, Nairobi, Kenya Parker GG (1983) Throughfall, stemfiow in forest nutrition. In: Advances in Geological Research, pp 100-121  60  Parkinson JA and Allen SE (1975) A wet oxidation procedure for the determination of nitrogen and mineral nutrients in biological material. Communications Soil Science and Plant Analysis 6: 111 Pinney AJ (1986) Alley cropping: A consideration of some tree/crop interfaces. MAgr.Sc. Thesis, University of Reading, UK Read MD, Kang BT and Wilson GF (1985) Use of Leucaena leucocephala (Lam) de Wit leaves as a nitrogen source for crop production. Fertilizer Research 8(2): 107-111 Rosecrance RC, Brewbaker JL and Fownes JH (1992) Alley cropping maize with nine leguminous trees. Agroforestry Systems 17: 159-168 SAS Institute Inc., (1985) SAS: User’s guide, Version 5 Edition, SAS Institute Inc., Cary NC, USA, 956p Siaw, 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 contrasting chemical composition under humid tropical conditions decomposition and nutrient release. Soil Biology and Biochemistry 24: 1051-1060 -  Yamoah CH, Agboola AA and Mulongoy K (1986) Decomposition, nitrogen release and weed control by prunings of selected alley cropping shrubs. Agroforestry Systems 4:234-246  61  5.0. Labour costs of different pruning intervals of Leucaena leucocephala in an alley cropping system. 5.1. Introduction The potential benefits of alley cropping in some areas of the subhumid tropics have been amply demonstrated (Kang et al., 1981; Atta-Krah, 1988). Soil fertility and crop productivity can be maintained over long periods and are appealing features of the practice. Yet in order to be readily adopted, 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 to traditional farming systems (Ngambeki, 1985). This conclusion is based on several prunings during a growing season of approximately six months. Such frequent pruning may not be suitable for small holder farmers who face time, labour and economic constraints. Aside from the direct labour cost involved in pruning hedgerows, delayed pruning can impose costs from yield losses because of treecrop competition for light, nutrients and/or water (Lawson and Kang, 1991). Such costs have implications for adoption of the technology. For example, Indonesian farmers have indicated that they would be reluctant to adopt a technology that would reduce maize yields and increase labour demands (Field and OeMatan, 1991). Hence, pruning management must balance the costs of labour while 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 costs associated with alley cropping since weeding represents a major labour component during the cropping 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 in association with crop yield data. Thus, as part of an alley cropping experiment, I collected labour and weed biomass data for different pruning intervals of Leucaena. Labour and maize yield data  62  were compared in a partial economic analysis to determine desirable pruning intervals.  5.2. Materials and Methods The pruning schedule is outlined in Table 5.1. During the second year of the experiment pruning intervals were chosen that were consistent with pruning intervals of the previous year and also reflected situations encountered in on-farm trials (Dvorak, Resource and Crop Management Program, JITA; personal communication). Pruning approximately every 6 weeks after planting represents the case where the farmer prunes midway through the season and at maize harvest. The third treatment simulates the situation where the farmer prunes only at maize harvest (pruning at approximately 12-14 weeks after planting). The 4 and 8-week pruning intervals represent common on-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 determining hedgerow 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 the diameter of every tenth stem. Pruning of hedgerows was done by machete by field staff who were paid a task wage upon completion (Naira 20). The time to prune 55m (less 5 m of hedgerow for biomass determination) of hedgerow was recorded and subsequently converted to days per hectare using 6 hour work days. For the initial pruning, field staff rotated through blocks. For subsequent prunings, one person pruned all treatments in a block. Prunings were coarsely chopped and spread relatively evenly throughout 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 (twice during the 1992 maize season and once after maize harvest) and dried at 65°C for dry matter determination. 63  I analyzed data from the initial pruning and subsequent prunings separately. No treatment effects were in place for the initial pruning. Labour measurements were only made during the 1992 maize growing season and cassava was not considered. Analysis of covariance and regression analysis was carried out to determine important relationships between labour time and variables measured using SAS (SAS, 1985).  64  Table 5.1. Pruning schedule by treatment for the 1992 maize growing season, Ibadan, Nigeria. Week  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19  4 week  6 week  maize harvest  Initial pruning for all treatments  -  8 week  April 14-15  All treatments planted to maize May 4-5 All treatments planted to cassava May 14-15 -  -  Pruning #1  Pruning #1 Pruning #2  Pruning #1  Pruning #3 Harvest maize from all treatments August 12-13 Pruning #1 Pruning #2 Pruning #2 Pruning #4  65  unpruned  5.3. Results To compare different costs of different pruning intervals, it was useful to ascertain what factors influenced pruning labour. It is hypothesized that labour for pruning hedgerows at any given time depends on the number and size of trees, tree species and the staff or “operator” performing the pruning or (Dvorak, 1992). L  =  {c, 1 g  Xd,  zS}  where L = labour for the jth pruning of the ith treatment, hours/ha 1 = denotation for ‘a function of..’ g c = number of trees per lOOm = mean stem diameter (cm) z = operator S = tree species In 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 hedgerow ranged from 186 (8455 trees/ha) to 339 (15, 409 trees/ha); mean stem diameter, x, ranged from 2.25 to 3.14 cm among blocks. Tree/shrub species would be expected to affect labour times due to differences in hardness of wood and rates of growth. When data from the first pruning was analyzed, I found that operator effects accounted for most of the variation in pruning time. An analysis of variance showed significant differences among operators, with pruning time ranging from 2.4 to 3.7 days/ha. I expected this with the variability in worker endurance. Subsequently, an analysis of covariance was used to test the following model for the initial pruning:  B d+B 5 x 2 L=BO+Blc+B 6 3 + 7 4 8 z 8 are dummy variables equal to 1, 2 and 3 for ,z 6 7 and z ) is the reference, and z 5 where operator 5 (z operator 6,7 and 8 respectively, and equal to 0 otherwise. Neither stand count nor stem diameter were significant factors in determining time to prune.  66  I could not use stem diameter and stand counts for analysis of subsequent pruning data, since much 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 for hedgerow regrowth. , 1 L  {t, z 2 g  =  2 whereg  S}  denotation for ‘a function of..’ time elapsed since previous pruning  =  =  Pruning 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 the effect of a standing crop in the field on pruning time, the following model was tested: L  =  3 + B z 4 4 z 5 2 + B z 3 +)t 1 (B h B + B 0 + 2 B  whereh = 0 if pruning took place before maize harvest h = 1 if pruning took place after maize harvest , z 2 3 and z 4 are dummy variables for operators 2,3 and 4. where operator 1 is the reference and z The estimation results (Table 5.2) support the model. Pruning time increased with pruning interval and 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 grain yields? Time elapsed between prunings accounted for 95% of the variation in pruning labour prior to maize harvest (Table 5.3); This relationship was less significant after maize harvest, again pointing to the importance of a standing crop in the field. Maize grain yield was also correlated to mean time elapsed between prunings (Table 5.3). As time between prunings increased so did pruning labour while maize yield decreased. This effect reflects the large differences between maize yields in treatments that were pruned at least once a season and those that were not (see Table 3 .3a in Chapter 1). Mean grain yield in the latter was 2.1 t/ha compared to 4.6 t/ha with at least one in season pruning.  67  16 • before harvest o after harvest  14 12 10  S C  4.  •.  2  o  0  0  0 20  120 100 80 60 40 Time elapsed between prunings (days)  Figure 5.1: Relationship of pruning labour (days/ha) to time elapsed between prunings (days) before and after maize harvest.  68  5.3.1. Comparing costs of treatments  Labour for pruning at least once a season ranged from 11 to 15 days/ha with respective costs ranging from N220/ha to N300/ha. Pruning at harvest only, took an average of 4 days/ha and cost N80/ha at N20/day. There were significant differences in pruning labour times with withinseason treatments using more labour than at the end of the season (F= 129.40; P=0.0001)(Table 5.4). When I compared total pruning times for different intervals, pruning every 4 or 8 weeks  required similar labour inputs while pruning at around 6 weeks after planting and at maize harvest only, required less (Table 5.4). A partial budgeting approach using differences in labour and maize yield was employed to compare the costs and benefits of different pruning treatments. net benefits  -  net costs  =  -Y p(Y . 1 ) 1 -L w(L ) -  where i = pruning treatment p = price of output, N*It Y = yield of treatment i, t/ha . = yield of treatment i’, t/ha 1 Y w = wage, N/h and 1 = labour for pruning treatment i, days/ha L = labour for pruning treatment i’, days/ha *  N  =  Naira, the Nigerian currency approximately  =  $0.O3OCAN  The average net gain of pruning at least once a season was N59001ha. Pruning once at 6-7 weeks after planting and at harvest appears to give the best gain with N883/ha and Nl2OIha more over pruning every 4 and 8 weeks respectively. Pruning every 4 weeks gave the lowest return, with a N900/ha loss compared to the other two in-season treatments.  5.3.2. Weed biomass  While weeding labour time was not recorded, weed biomass differences under various pruning intervals may indicate some trends. I observed the highest weed dry matter production during the maize growing season under the 4-week pruning interval while the lowest was in unpruned plots (Table 5.5). At 4 weeks after planting, weed biomass was low in all treatments after  69  the 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 an estimate of the requirements and costs in this study (Table 5.5). Apparently labour costs could be reduced 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 of reduced 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 hedgerows during the 1992 maize season, Ibadan, Nigeria. Coefficient  Variable time elapsed(h=0)a time elapsed(h=1) operator 1 operator 2 operator 3 operator 4 a  0.648 0.113 17.843 13.945 13.834 12.390  T-value 13.47 5.37 3.76 3.12 3.10 2.77  SE of estimate 0.048 0.021 4.751 4.469 4.469 4.469  h=0 when pruning occurred with maize in the alleys, h= 1 when pruning occurred after maize harvest.  Table 5.3. Relationship of pruning labour (days/ha) and maize yield (t/ha) to pruning biomass and time elapsed between prunings (days) for Leucaena prunings during the 1992 maize growing season, Ibadan, Nigeria. Relationship Pruning labour vs. time elapsed Maize grain yield vs. time elapsed  Equation  P  2 y=137+3.8x-41x  0.95  0.0001  2 y=0.01+0.15x-0.001x  0.75  0.0001  70  Table 5.4. Pruning labour (days/ha) for different pruning intervals. Treatment  Labour for successive prunings  1-every 4 weeks  5.0 (O.11)*  4.0 (0.23)  weeding 2-at and after harvest  8.0 (0.17)  3.0 (0.54)  3-after harvest  6.0 (0.77)  4-every 8 weeks  14.0 (0.94)  5-no pruning *  4.0 (0.27)  2.0 (0.26)  In-season labour  Total labour  13.Oa (0.20)  15.Oab (0.21)  8.Ob (0.17)  11.Ob (0.35) 6.Oc (0.77)  14.Oa (0.94)  3.0 (0.49)  none  none  standard error in brackets  71  17.Oa (0.70)  Table 5.5. Total weed biomass (t/ha) and estimated labour and cost requirements under 4 and 6-week pruning intervals and unpruned plots during the 1992 maize growing season. Pruning interval (weeks)  Weed dry matter (tlha)  4 6 unpruned  1.74(0.20)la* 1.53(0.20)a 1.13(0.12)b  Labour (daylha)  47 41 31  Cost (Naira)  944 830 613  1 standard error of the mean in parenthesis *values with different letters differ within columns at the 0.05 significance level using Duncan’s multiple range test.  72  2.0  1.5  1.0  0.5  0 4WAP  1OWAP  17WAP  Weeks after planting Figure 5.2: Weed dry matter under 4- and 6- week pruning intervals and in unpruned plots during the 1992 maize growing season.  73  5.4. Discussion Labour requirements varied significantly with pruning intervals. Pruning at least once during the season required more labour and cost between two to three times more than pruning after maize harvest. Yet the penalty in terms of yield losses when pruning is delayed until after maize harvest is large at N5900. Thus, the costs of pruning up to 8 weeks after planting are relatively small compared to the potential loss of yield and income. Given that maize yields were not significantly lower at 10 weeks, pruning could be delayed to this point, yet this also means greater woody biomass production. Presumably, as the relationships between time elapsed between prunings and pruning labour show, there would be a consequent increase in labour at 10 weeks. Pruning at 6 weeks after planting gave the most favourable economic gains, in terms of labour and maize yield. However, this may coincide with weeding and/or other farm operations, making it an unacceptable time to prune. Pruning later, at 8 weeks after planting, has the disadvantage of more cumbersome manoeuvering among tall maize and cassava plants. Pruning every 4 weeks had the advantage of distributing the required labour over the season but resulted in similar total pruning labour. Pruning later in the maize growing season when the crop is established and manouvering becomes difficult, is more time-consuming than pruning when there is no crop (as in the initial or post-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 times implies that economic evaluations of alley cropping should take into account a standing crop and intercrops. Weeding adds another economic consideration to an alley cropping system and while labour for this activity was not measured and herbicide was applied, the biomass differences suggest some of the benefits and disadvantages of pruning at different times. While weed dry matter and ground coverage in the post-harvest treatment were lower than in the other pruning intervals, the reduction 74  in weeding labour is unlikely to offset the loss of yield.  A study by Boehringer (1988) on the weed  suppressing effect of different alley cropping species concluded that Leucaena increased rather than decreased 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 alley cropped plots, but suggested shade rather than mulch may be important in weed control in alley cropping (Jama et al., 1991; Kang et al., 1988). While a 6 week pruning interval did not reduce weed biomass markedly, the associated labour costs may be reduced substantially to make this an economical option for the farmer. This study suggests that once a farmer adopts alley cropping, the costs of not pruning within the maize season are large and that costs for pruning within the season are necessary to minimize yield losses. Yields and costs for pruning once a season are not significantly different from pruning more than once a season. Hence, pruning once a season, preferably by 8 weeks after planting, will avoid yield losses. If the fanner is able to prune hedgerows at around 6 weeks after planting, the actual labour costs will be lower than at either 4 or 8 weeks after planting.  75  5.5. References Boehringer A (1991) The potential of alley cropping as a labour efficient management option to control weeds: A hypothetical case. Journal of Agriculture in the Tropics and Subtropics 92:3-12 Budelman A (1988) The performance of the leaf mulches of Leucaena leucocephala, Flemingia macrophylla and Gliricidia sepium in weed control. Agroforestry Systems 6:137-145 Field SP and OeMatan SS (1990) The effect of cutting height and pruning frequency of Leucaena leucocephala hedgerows on maize production. Leucaena Research Reports 11:68-69 Kang 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: 165-179 Kang BT, Grimme H and Lawson TL (1985) Alley cropping sequentially cropped maize and cowpea with Leucaena on a sandy soil in Southern Nigeria. Plant and Soil 85: 267-277  Lawson TL and Kang BT (1990) Yield of maize and cowpea in an alley cropping system in relation to available light. Agricultural and Forest Metereology 52: 347-357 Ngambeki DS (1985) Economic evaluation of alley cropping Leucaena with maize-maize and maize cowpeas in Southern Nigeria. Agricultural Systems 17:243-258 SAS 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 re evaluation. Agroforestry Systems 6:163-168 -  Torres F (1983) Potential contribution of Leucaena hedgerows intercropped with maize to the production of organic nitrogen and fuelwood in the lowland tropics. Agroforestry Systems 1:323-333  76  Conclusions The results of Chapter 3.0 support earlier work on resource competition between Leucaena hedgerows and associated crops. This systematic study of pruning intervals identified a period in maize growth where shading by hedgerows was detrimental. Pruning by 10 weeks after planting had negligible 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 to isolate 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 is delayed beyond 8 weeks after planting. In my experiment, this yield loss adjacent to the hedge did not reduce overall plot yields, yet under realistic farm conditions (ie. no fertilizer, competition from weeds, poorer soils), yield declines could be significant. Indeed, large discrepancies exist in the performance of alley cropped maize and cassava under experimental conditions and on farmer’s fields. Due to the defoliation of cassava under unpruned Leucaena the effects of continuous shading on cassava productivity could not be determined. Yet, even under farm conditions, it is unlikely that hedgerows would not be pruned at least once during the growing period of cassava. Thus, cassava intercropped 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 economic consequences 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 the same trend as grain yields. Presumably, under circumstances where nutrients are in short supply, a contribution by Leucaena would be noticeable. For cassava, I might expect an even greater 77  response to Leucaena prunings because of its extended period of nutrient uptake and longer growing period relative to maize. If pruning is delayed beyond the period of maximum crop uptake, Leucaena prunings will provide 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 most effective 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 pruning interval that balances light limitations with crop nutritional and soil fertility benefits is achievable for alley cropped maize. In chapter 5, I conclude that pruning at least once during the maize season is also desirable in economic terms. While a decline in economic gain was expected, knowing the relative magnitude is useful. Furthermore, my data suggests a potential advantage to pruning Leucaena at around 6 weeks 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 of minimizing resource competition, deriving benefits from Leucaena prunings and avoiding economic losses, any pruning interval must be adapted to the constraints of the farmer. For instance, the middle of the maize growing season is often compromised by a short supply of labour. Thus, the farmer has options to delay hedgerow pruning to a period between the middle of the growing season and 10 weeks after planting, before she or he encounters losses. My thesis points to a need for further integrative studies on pruning management of Leucaena for alley crops. Collecting data on several aspects of the system provides holistic information that is essential in promoting the technology. Furthermore, given that on-farm conditions can vary dramatically from experimental ones, more trials should be conducted under the former. Integrated and realistic alley cropping trials will aid in the successful adoption of the technology.  78  Appendices Appendix A ANOVA tables for maize height measurements ANOVA table for maize height, 4 weeks after planting, June 29, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 994.6667 479.8125 2560.3333 21.0069 25.2014  Mean Square  F-value  497.3333 95.9625 9256.0333 21.0069 5.0403  7.58 0.37 3.90 0.32 0.08  P 0.0074 0.8549 0.0145 0.5819 0.9947  ANOVA table for maize height, 6 weeks after planting, July 14, 1991. Source  DF  Block Treat BlOck*Treat Row Treat*Row  2 5 10 1 5  Type III SS 3795.6875 1355.5313 3693.1458 1873.3393 2535.7005  Mean Square  F-value  1897.8438 271.1063 461.6432 1873.3393 507.1401  11.36 0.59 2.76 11.22 3.04  P 0.0027 0.7109 0.0673 0.0074 0.0636  ANOVA table for maize height, 8 weeks after planting, July 28, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 4297.7260 2359.4010 2738.8257 1081.1250 807.7377  Mean Square  F-value  P  1432.5753 471.8802 342.3520 1081.1250 161.5474  9.43 1.38 2.25 7.12 1.06  0.0022 0.3264 0. 1059 0.0219 0.4305  F-value  P  ANOVA table for maize height, 3 weeks after planting, May 30, 1992 Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type ifi SS  Mean Square  0.0264 0.0158 0.0823 0.0154 0.0132  0.0088 0.0039 0.0069 0.0154 00033  79  1.06 0.57 0.82 1.85 0.40  0.3967 0.6864 0.6285 0.1939 0. 8088  ANOVA table for maize height, 5 weeks after planting, June 10, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type III 55 0.0543 0.0798 0.5501 0.0774 0.1278  0.0181 0.0199 0.0458 0.0774 0.0320  F-value 0.85 0.43 2.16 3.65 1.51  P 0.4861 0.78 10 0.0799 0.0753 0.2498  ANOVA table for maize height, 6 weeks after planting, June 20, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0501 0.0218 0. 1285 0.1323 0.0068  0.0167 0.0054 0.0107 0.1323 0.0017  F-value 1.53 0.51 0.98 12.13 0.16  P 0.2473 0.7297 0.5051 0.0033 0.9575  ANOVA table for maize height, 8 weeks after planting, July 1, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  5114.4188 3658.2500 8854.8000 5917.0563 1223.9750  1704.8063 914.5625 737.9000 5917.0563 306.9938  F-value__J 5.07 1.24 2.19 17.59 0.91  P 0.0128 0.3458 0.0763 0.0008 0.4834  ANOVA table for maize height, 10 weeks after planting, July 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0183 0.0621 0.0648 0.0484 00039  0.0061 0.0155 0.0054 0.0484 0.0010  F-value 2.50 2.87 2.21 19.79 0.40  P 0.0992 0.0699 0.0744 0.0005 0.8047  ANOVA table for maize height, 12 weeks after planting, July 27, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 0.0145 0. 1220 0.0207 0.0134 0.0089  80  Mean Square  F-value  0.0050 0.0305 0.0017 0.0134 0.0022  2.73 17.73 0.95 7.40 1.23  P 0.0804 0.0001 0.5292 0.0158 0.3396  ANOVA table for maize stem diameter, 8 weeks after planting, July 1, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 0.1052 0.1234 0.5629 0.6669 0.1490  Mean Square  F-value  0.0351 0.0308 0.0469 0.6669 0.0373  1.68 0.66 2.24 31.90 1.78  P 0.2146 0.6329 0.0707 0.0001 0.1850  ANOVA table for maize stem diameter, 10 weeks after planting, July 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type ifi SS  Mean Square  0.0022 0.0764 0.0647 0.4296 0.0600  0.0011 0.0191 0.0081 0.4296 0.0150  F-value 0.06 2.36 0.47 25.03 0.87  P 0.9378 0. 1402 0.8505 0.0005 0.5134  ANOVA table for maize stem diameter, 12 weeks after planting, July 27, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type ifi SS 9.2775 26.4075 29.4462 48.8412 2.6259  Mean Square  F-value  3.0925 6.6021 2.4538 48.8412 0.6565  1.50 2.69 1.19 23.76 0.32  0.2539 0.0824 0.3674 0.0002 0. 8606  ANOVA table for maize stem diameter, 13 weeks after planting, August 10, 1992. _Source Block Treat Block*Treat Row Treat*Row  DF 3 4 12 1 4  Type III SS  Mean Square  0.0211 0. 1429 0.0721 0.1405 0.0188  0.0070 0.0357 0.0060 0.1405 0.0047  82  F-value 2.16 5.95 1.85 43.19 1.44  P 0.1357 0.0071 0.1308 0.0001 0.2683  ANOVA tables for maize leaf number ANOVA table for maize leaf number, 3 weeks after planting, May 30, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  F-value  0.0048 0.0094 0.0097 0.0257 0.0123  0.0145 0.0378 0.1168 0.0257 0.0490  0.78 0.97 1.58 4.16 1.99  P 0.5218 0.4591 0.2006 0.0594 0. 1485  ANOVA table for maize leaf number, 5 weeks after planting, June 10, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type Ill SS  Mean Square  0.0107 0.0195 0.0589 0.0128 0.0200  F-value 1.53 0.99 2.12 5.52 2.16  0.0036 0.0049 0.0049 0.0128 0.0005  P 0.2469 0.4486 0.0853 0.0329 0.1232  ANOVA table for maize leaf number, 6 weeks after planting, June 20, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0076 0.0044 0. 1538 0.0666 0.0074  F-value  0.0025 0.0011 0.0128 0.0666 0.0019  1.33 0.09 6.68 34.76 0.97  P 0.3030 0.9853 0.0005 0.0001 0.4540  ANOVA table for maize leaf number, 8 weeks after planting, July 1, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0073 0.0032 0.0284 0.0059 0.0059  0.0024 0.0008 0.0024 0.0059 0.0015  83  F-value 2.29 0.34 2.22 5.58 1.40  P 0.1199 0.8464 0.0728 0.0321 0.2829  ANOVA table for maize leaf number, 10 weeks after planting, July 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type III SS  0.0012 0.0133 0.0061 0.0326 0.0059  0.0024 0.0532 0.0486 0.0326 0.0236  F-value 0.34 2.19 1.68 9.02 1.63  P 0.7213 0.1603 0.2180 0.0133 0.2420  ANOVA table for maize leaf number, 12 weeks after planting, July 27, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type ifi SS  0.0026 0.0018 0.0019 0.0059 0.0038  0.0079 0.0072 0.0232 0.0059 0.0153  F-value 1.10 0.94 0.81 2.49 1.60  P 0.3784 0.4763 0.6376 0.1354 0.2246  ANOVA table table for maize leaf number, 13 weeks after planting, August 10, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type III SS 0.0362 0.0376 0.0575 0.0090 0.0065  0.0121 0.0094 0.0048 0.0090 0.0016  F-value 8.94 1.96 3.55 6.66 1.20  P 0.0012 0. 1653 0.0116 0.0209 0.3523  ANOVA tables for maize LAI  ANOVA table for maize LAI, 6 weeks after planting, July 11, 1991. Source  DF  Type III SS  Block Treat  2 5  0.0052 0.0167  Mean Square 0.0026 0.0033  F-value 0.12 0.16  P 0.8843 0.9722  ANOVA table for maize LAI, 8 weeks after planting, July 26, 1991. Source  DF  Type III SS  Block Treat  2 5  0.0824 0.0020  Mean Square 0.0165 0.0020  84  F-value 1.28 0.16  P 0.3008 0.6954  ANOVA table for maize LAI 4 weeks after planting, June 5, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 1723.3799 366.2712 887.6654 18.5512 930.7711  Mean Square  F-value  574.4604 91.5685 73.9722 18.5513 232.6939  9.60 1.24 1.24 0.31 3.89  P 0.0013 0.3464 0.3538 0.5871 0.0273  ANOVA table for maize LAI, 6 weeks after planting, June 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 332.5505 341.7135 1649.8888 87.0253 796.2887  Mean Square  F-value  110.8503 85.4286 137.4918 87.0253 199.0727  0.71 0.62 0.88 0.56 1.28  P 0.5610 0.6560 0.5819 0.4669 0.3232  ANOVA table for maize LAI, 8 weeks after planting, July 1, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 1824.4044 1368.4417 3219.4338 17.9175 1366.9699  Mean Square  F-value  608.1357 342.1108 268.2865 17.9179 341.7425  1.66 1.28 0.73 0.05 0.93  P 0.2237 0.3336 0.7017 0.8284 0.4742  ANOVA table for maize LAI 12 weeks after planting, August 6, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 1426.0312 421.2715 3051.8137 243.8449 76.688  85  Mean Square  F-value  475.3446 210.6358 508.6356 243.8449 38.3449  1.54 0.41 1.65 0.79 0.12  P 0.2712 0.6798 0.2402 0.3978 0.8859  j  ANOVA tables for maize reproductive stage measurements ANOVA table for number of maize plants shedding pollen. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 299.7972 1544.0573 1515.6564 566.5072 83.1394  Mean Square  F-value  99.932 1 386.0142 126.3053 566.5074 20.7853  0.53 3.06 0.67 2.99 0.11  Mean Square  F-value  62.9602 346.7894 104.0534 492.4533 29.1782  0.57 3.33 0.94 4.44 0.26  Mean Square  F-value  97.3522 1647.0654 90.6667 1892.9338 107.2325  0.79 18.17 0.73 14.76 0.87  Mean Square  F-value  0.7233 1.0440 0.3208 0.2922 0.0426  27.39 3.25 12.15 11.06 1.61  P 0.6702 0.0603 0.7574 0.1044 0.9772  ANOVA table for number of maize plants tasseling. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 188.8812 1387.1583 1248.6344 492.4535 116.7124  P 0.6455 0.0476 0.5384 0.0526 0.8978  ANOVA table for number of maize plants silking. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 292.0555 6588.2626 1088.9937 1829.9323 428.9282  P 0.5215 0.0001 0.7045 0.0026 0.5077  ANOVA tables for maize grain yield ANOVA table for 1991 maize grain yield. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 1.4474 5.2201 3.2082 0.2922 0.2129  86  P 0.0001 0.0530 0.0001 0.0018 0.1778  ANOVA table for 1991 maize stover yield.  Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Mean Square  Type ifi SS  0.0219 0.5261 1.1135 0.0008 0.3155  0.0109 0.1052 0.1113 0.0008 0.0631  F-value 0.42 0.94 4.30 0.03 2.44  P 0.6582 0.4932 0.0004 0.8583 0.0500  ANOVA table table for 1991 maize harvest index. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type Ill SS  Mean Square  0.7567 2.2804 2.0051 0.0795 0.2418  0.3784 0.4561 0.2005 0.0796 0.0430  F-value 25.30 2.27 13.41 5.32 2.87  P 0.0001 0. 1259 0.0001 0.0261 0.0256  ANOVA table table for 1992 maize grain yield. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 1.4048 57.8472 6.3824 0.5832 0.8658  Mean Square  F-value  0.4683 14.4621 0.5319 0.5832 0.2164  5.27 27.19 5.99 6.56 2.44  Mean Square  F-value  7.1909 17.5002 1.5168 2.2563 0.1300  10.64 11.54 2.24 3.34 0.19  P 0.0110 0.0001 0.0009 0.0217 0.0926  ANOVA table table for 1992 maize stover yield. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 21.5731 69.9993 18.2012 2.2563 0.5200  P 0.0005 0.0001 0.0706 0.0877 0.9387  ANOVA table table for 1992 maize harvest index. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  0.0178 0.0416 0.0274 0.0001 0.0038  87  Mean Square  F-value  0.0059 0.0104 0.0023 0.0001 00010  6.48 4.54 2.50 0.15 1.05  P  0.0050 0.0183 0.0482 0.7029 0.4152  j  ANOVA table table for maize cob length at harvest, August 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 263.5331 4637.8792 708.3713 29.0701 183.3814  Mean Square  F-value  87.8442 1159.4701 59.0312 29.0704 45.8451  4.73 19.64 3.18 1.56 2.47  P 0.0162 0.0001 0.0194 0.2303 0.0901  ANOVA table table for maize cob width at harvest, August 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 7058.0001 248158. 1302 31005.7481 9711.0302 9428. 1281  Mean Square  F-value  2352.6671 62039.5332 2583.8121 9711.0302 2357.0323  2.65 24.01 2.91 10.94 2.65  P 0.0872 0.0001 0.0271 0.0052 0.0741  ANOVA table table for maize kernel number at harvest, August 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0. 1942 3.1403 0.4272 0.1104 0.1353  0.0652 0.7853 0.0364 0.1102 0.0343  F-value 3.21 22.07 1.77 5.45 1.68  P 0.0531 0.0001 0. 1483 0.0342 0.2072  ANOVA table table for maize kernel weight at harvest, August 16, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0053 0.2242 0.0014 0.0423 0.0142  0.0173 0.8962 0. 1204 0.0424 0.0553  88  F-value 2.41 22.49 4.59 19.21 6.38  P 0. 1082 0.000 1 0.0034 0.0013 0.0034  ANOVA tables for cassava height measurements ANOVA table for cassava height at 5 weeks after planting, July 7, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 164.1806 925.2847 463.2361 333.0625 237.5625  Mean Square  F-value  82.0903 185.0569 46.3236 333.0625 47.5125  4.52 3.99 2.55 18.35 2.62  P 0.0343 0.0298 0.0635 0.0011 0.0798  ANOVA table for cassava height at 6 weeks after planting, July 14, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type ifi SS 182.0972 3292.0347 564.7361 845.8403 522.5347  Mean Square  F-value  91.0486 685.4069 56.4736 845.8403 104.5069  2.18 11.66 1.35 20.24 2.50  P 0.1559 0.0006 0.3065 0.0007 0.0898  ANOVA table for cassava height at 8 weeks after planting, July 27, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type Ill SS 710.6806 4872. 1389 673.6528 56.2500 598.8333  Mean Square  F-value  355.3403 974.4278 67.3653 56.2500 119.7667  2.88 14.46 0.55 0.46 0.97  P 0.0950 0.0003 0.8267 0.5121 0.4729  ANOVA table for cassava height at 10 weeks after planting, August 10, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 350.0972 2620.8056 2811.9861 4.0000 1580.8333  89  Mean Square  F-value  175.0486 524.1611 281.1986 4.0000 316.1667  0.50 1.86 0.80 0.01 0.90  P 0.6194 0.1880 0.6324 0.9168 0.5115  ANOVA table for cassava height at 12 weeks after planting, August 23, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS  Mean Square  0.0276 0.7405 0.3288 0.0039 0.1107  0.0138 0.1481 0.0329 0.0039 0.0221  F-value  0.40 4.50 0.94 0.11 0.64  P 0.6808 0.0207 0.5291 0.7433 0.6763  ANOVA table for cassava height at 14 weeks after planting, September 7, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS  Mean Square  0.1136 0.4190 0.2110 0.0140 0.0249  0.0568 0.0864 0.0211 0.0139 0.0050  F-value 1.38 4.09 0.51 0.34 0.12  P 0.2890 0.0277 0.8512 0.5711 0.9850  ANOVA table for cassava height at 16 weeks after planting, September 20, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 445.3507 6348.3299 1284.7743 213.4222 642.8417  Mean Square  F-value  222.6753 1269.6660 197.8249 213.4222 128.5683  0.39 6.42 0.35 0.38 0.23  P 0.6863 0.0151 0.9106 0.5548 0.9416  ANOVA table for cassava height at 18 weeks after planting, October 10, 1991 (logged). Source  DF  Type III SS  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  0.1151 0.1807 0.2816 0.0533 0.0395  Mean Square  F-value  0.0576 0.0361 0.0282 0.0533 0.0079  2.88 1.28 1.41 2.66 0.39  P 0.0954 0.3437 0.2837 0. 1285 0. 8433  ANOVA table for cassava height at 20 weeks after planting, October 28, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 4 8 1 4  Type Ill SS 0.4018 3219.1287 3733.5625 3.2452 3047.7169  90  Mean Square  F-value  0.2009 643.8257 373.3563 3.2452 609.5434  0.00 1.72 0.50 0.00 0.81  P 0.9997 0.2166 0.8595 0.9488 0.5652  ANOVA table for cassava height at 24 weeks after planting, November 20, 1991. Source  Block Treat Block*Treat Row Treat*Row  DF  2 4 8 1 4  Type III SS  3793.0556 4395. 1389 3440.2778 667.3611 1840.9722  Mean Square  F-value  1896.5278 879.0278 344.0278 667.3611 368.1944  9.52 2.56 1.73 1.37 1.85  P  0.0033 0.0970 0.1836 0.2154 0.1776  ANOVA table for cassava height at 4 weeks after planting, June 9, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 174.8188 179.7875 329.9625 138.7563 55.5875  Mean Square  F-value  58.2729 44.9469 27.4969 138.7563 13.8969  2.36 1.63 1.11 5.62 0.56  P 0.1125 0.2292 0.4152 0.0316 0.6932  ANOVA table for cassava height at 6 weeks after planting, June 23, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type Ill SS 929.7688 1498.4375 1654.5125 381.3063 342.6625  Mean Square  F-value  309.9229 374.6094 137.8760 381.6063 85.6656  8.92 2.72 3.97 10.97 2.46  P 0.0012 0.0804 0.0070 0.0047 0.0899  ANOVA table for cassava height at 10 weeks after planting, July 20, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type ifi SS  152.0688 3969.8125 4354.8375 200.2563 1349.3375  Mean Square  F-value  50.6896 992.4531 362.9031 200.2563 337.3344  0.20 2.73 1.45 0.80 1.35  P  0.8928 0.0791 0.2444 0.3848 0.2974  ANOVA table for cassava height at 14 weeks after planting, August 25, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0. 1382 0.4197 0.0524 0.1105 0.1140  0.0461 0. 1049 0.0058 0.1105 0.0285  91  F-value 2.89 18.03 0.37 6.94 1.79  P 0.0792 0.0003 0.9308 0.0218 0.1958  ANOVA tables for cassava stem diameter ANOVA table for cassava stem diameter at 10 weeks after planting, August 12, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 2 4 1 2  Mean Square  Type HI SS 0.1745 0.6961 0.3952 0.2895 0.43 10  0.0872 0.3480 0.0988 0.2895 0.2 155  F-value 1.16 3.52 1.31 3.84 2.85  P 0.3218 0.1312 0.2770 0.0548 0.0654  ANOVA table for cassava stem diameter at 12 weeks after planting, August 23, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Mean Square  Type III SS 0.2013 0. 1508 0.1183 0.1693 0.0125  0.1006 0.0754 0.0296 0.1693 0.0063  F-value 1.23 2.55 0.36 2.07 0.08  P 0.2990 0. 1933 0.8346 0.1552 0.9263  ANOVA table for cassava stem diameter at 14 weeks after planting, September 7, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Type HI SS  Mean Square__[__F-value__j 2.2918 24.7222 6.6596 7.5561 5.8911  4.5843 49.4446 26.6382 7.5561 11.7821  0.50 3.71 1.47 1.66 1.30  P 0.6066 0. 1226 0.2254 0.2027 0.2818  ANOVA table for cassava stem diameter at 16 weeks after planting, September 20,1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Type Ill SS 45.6168 145.7016 5.5668 15.9078 1.6117  Mean Square  F-value  22.8048 72.8508 1.3917 15.9078 0.8058  6.23 52.35 0.38 4.35 0.22  P 0.0038 0.0014 0.8218 0.0421 0.8032  ANOVA table for cassava stem diameter at 18 weeks after planting, October 9,1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 2 4 1 2  Type III SS 21.5394 394.8935 18.6046 2.3229 16.8488  92  Mean Square  F-value  10.7697 197.4468 4.6512 2.3229 8.4244  2.90 42.45 1.25 0.63 2.27  P 0.0642 0.0020 0.3010 0.4327 0.1139  ANOVA table for cassava stem diameter at 20 weeks after planting, October 28,1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Type Ill SS  Mean Square  0.0252 4.1165 0.1154 0.0779 0.0614  0.0126 2.0582 0.0288 0.0779 0.0307  F-value 0.73 71.36 1.66 4.49 1.77  P 0.4887 0.0007 0.1729 0.0390 0.1804  ANOVA table for cassava stem diameter at 24 weeks after planting, November 20,1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Type III SS  Mean Square  1.7791 605.6722 86.7095 23.9279 34.8911  0.8896 302.8361 21.6774 23.9279 17.4456  F-value__J 0.16 13.97 3.98 4.39 3.20  P 0.8497 0.0157 0.0069 0.0411 0.0489  ANOVA table for cassava stem diameter at 8 weeks after planting, July 9, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  2.5187 1.4321 16.2429 0.1626 3.8509  0.8396 0.3580 1.3536 0.1626 0.9627  F-value 2.34 1.00 3.77 0.45 2.68  P 0.1147 0.4391 0.0088 0.5111 0.0721  ANOVA table for cassava stem diameter at 10 weeks after planting, July 20, 1992. _Source Block Treat Block*Treat Row Treat*Row  DF 3 4 12 1 4  Type III SS 2.0833 8.2609 8.1311 0.1000 3.6544  Mean Square  F-value  0.6944 2.0652 0.6776 0.1000 0.9136  1.02 3.05 1.00 0.15 1.35  P 0.4105 0.0599 0.4935 0.7066 0.2991  ANOVA table for cassava stem diameter at 14 weeks after planting, August 25, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type ifi SS  Mean Square  1.0741 0.7496 3.3491 1.5729 3.1411  0.3580 0.1834 0.3721 1.5729 0.7853  93  F-value 0.61 0.50 0.63 2.68 1.34  P 0.6208 0.7346 0.7489 0.1274 0.3113  ANOVA tables for cassava node number ANOVA table for cassava node number at 9 weeks after planting, August 4, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 1 2 1 1  Type ifi 55  Mean Square  0.0924 0.5760 0.0474 0.0002 0.0476  0.0462 0.5761 0.0237 0.0002 0.0476  F-value 3.44 24.33 1.77 0.02 3.55  P 0.1349 0.0387 0.2821 0.9069 0.1328  ANOVA table for cassava node number at 11 weeks after planting, August 17, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 2 4 1 2  Type ifi SS 17.5833 324.0833 4.5833 29.3889 40.1944  Mean Square  F-value  8.7917 162.0417 1.1458 29.3889 20.0972  0.77 141.42 0.11 2.59 1.77  P 0.5024 0.0002 0.9781 0.1589 0.2489  ANOVA table for cassava node number at 13 weeks after planting, August 30, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 2 4 1 2  Type III SS 13.0833 334.0833 26.0833 1.3889 37.5278  Mean Square  F-value  6.5417 167.0417 6.5208 1.3889 18.7639  0.55 25.62 0.55 0.12 1.58  P 0.6034 0.0052 0.7080 0.7442 0.2814  ANOVA table for cassava node number at 17 weeks after planting, September 27, 1991. _Source Block Treat Bloek*Treat Row Treat*Row  DF 2 2 4 1 2  Type III SS 0.4332 13.3485 2.4381 0.2027 1.7011  Mean Square  F-value  0.2166 6.6742 0.6095 0.2027 0.8506  1.13 10.95 3.18 1.06 4.44  P 0.3832 0.0239 0. 1000 0.3434 0.0656  ANOVA table for cassava node number at 20 weeks after planting, October 28, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 3 6 1 3  Type III SS  J  17.3315 793.0784 161.0195 9.6845 69.3265  94  Mean Square  F-value  8.6658 264.3595 26.8365 9.6845 23.1088  0.97 9.85 2.99 0.12 0.29  P 0.4209 0.0098 0.0772 0.5984 0.2457  ANOVA table for cassava node number at 4 weeks after planting, June 9, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type III SS  7.2917 6.8813 4.6146 0.2250 0.3813  21.8750 27.5250 55.3750 0.2250 1.5250  F-value 2.11 1.49 1.34 0.07 0.11  P 0.1414 0.2658 0.2934 0.8019 0.9769  ANOVA table for cassava node number at 6 weeks after planting, June 23, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type III SS  5.5500 14.6656 2.3365 18.2250 4.0531  16.6500 58.6625 28.0375 18.2250 16.2125  F-value 7.70 6.28 3.24 25.28 5.62  P 0.0024 0.0058 0.0172 0.0010 0.0057  ANOVA table for cassava node number at 8 weeks after planting, July 9, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 699.3688 6734.6875 2069.4125 85.5563 588.2875  Mean Square  F-value  233.1229 1683.6719 172.4510 85.5563 147.0719  2.51 9.76 1.85 0.92 1.58  P 0.0984 0.0009 0. 1291 0.3527 0.2304  ANOVA table for cassava node number at 10 weeks after planting, July 20, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type Ill SS  6.9396 4.0219 3.4969 1.0563 3.5406  20.8188 16.0875 41.9625 1.0563 14.1625  F-value 1.92 1.15 0.97 0.29 0.98  P 0.1694 0.3799 0.5 147 0.5965 0.4474  ANOVA tables for cassava LAI  ANOVA table for cassava LAI at 5 weeks after planting, July 7, 1991. Source  DF  Type III SS  Block Treat  2 5  0.0055 0.0086  Mean Square__[__F-value  0.0028 0.0017  95  1.03 2.70  P 0.2138 0.0920  ANOVA table for cassava LAI at 8 weeks after planting, July 24, 1991. _Source Block Treat Block*Treat Row Treat*Row  j  DF 2 5 10 5 1  Type III SS 0.0027 0.0094 0.0071 0.0028 0.0003  Mean Square  F-value  0.0013 0.0019 0.0007 0.0006 0.0003  1.65 2.65 0.87 0.82 0.34  P 0.3292 0.0887 0.6255 0.6616 0.5989  ANOVA table for cassava LAI at 10 weeks after planting, August 7, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type III SS 0.0027 0.0655 0.0505 0.0002 0.0037  Mean Square  F-value  0.0013 0.0013 0.0051 0.0002 0.0007  0.27 0.27 0.87 0.00 0.12  P 0.7719 0.2286 0. 1255 0.9489 0.7014  ANOVA table for cassava LAI at 12 weeks after planting, August 21, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 10 1 5  Type HI SS  Mean Square  0.0198 0.0465 0.0182 0.0007 0.0001  0.0099 0.0093 0.0018 0.0007 0.0000  F-value 0.47 3.57 0.27 0.03 0.00  P 0.7180 0.0635 0.8751 0.8871 0.9620  ANOVA table for cassava LAI at 14 weeks after planting, September 5, 1991. Source  DF  Block Treat Block*Treat Row Treat*Row  2 5 7 1 3  Type III SS  Mean Square  0.2894 4.4434 1.0877 0.1093 0.9607  0.1447 0.8887 0.1554 0.1093 0.3202  F-value__J 85.78 5.72 92.13 64.78 189.86  P 0.0001 0.0204 0.0001 0.0001 0.0001  ANOVA table for cassava LAI at 18 weeks_after_planting, October 10, 1991. _Source Block Treat Block*Treat Row Treat*Row  DF 2 5 7 1 2  Type III SS 0.7164 4.9318 1.4447 0.5532 0.6761  96  Mean Square  F-value  0.3582 0.9864 0.2064 0.5532 0.3381  16.35 4.78 9.42 25.25 15.43  P 0.0001 0.0322 0.0001 0.0001 0.0001  ANOVA table for cassava LAI at 20 weeks after planting, October 28, 1991. Source Block Treat Block*Treat Row Treat*Row  DF 2 5 7 1 3  Mean Square  Type III SS  0.1447 0.8887 0.1554 0.1093 0.3202  0.2894 4.4434 1.0876 0.1093 0.9607  F-value 85.78 5.72 92.13 64.78 189.86  P 0.0001 0.0204 0.0001 0.0001 0.0001  ANOVA table for cassava LAI at 5 weeks after planting, June 20, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Mean Square  Type ifi SS  0.0006 0.0001 0.0002 0.0006 0.0003  0.0017 0.0006 00020 0.0006 0.0012  F-value 3.40 0.89 1.02 3.96 1.91  P 0.0455 0.4999 0.4790 0.0652 0.1611  ANOVA table for cassava LAI at 8 weeks after planting, July 10, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type Ill SS 0.0010 0.0005 0.0028 0.0002 0.0004  Mean Square  F-value  0.0003 0.0001 0.0002 0.0002 0.0001  1.75 0.52 1.26 1.10 0.52  P 0.1996 0.7225 0.3290 0.3110 0.7207  ANOVA tables for cassava pre-harvest measurements ANOVA table for cassava total node number prior to harvest. Source Block Treat Block*Treat Row Treat*Row  DF 2 4 8 1 4  Type III SS 0.2010 0.2224 0.2236 0.0661 0.2285  Mean Square  F-value  0. 1005 0.0556 0.0279 0.0661 0.0571  3.45 1.99 0.96 2.27 1.96  P 0.0724 0.1891 0.5134 0. 1627 0.1765  ANOVA table for number of forking levels in cassava prior to harvest. Source Block Treat Block*Treat Row Treat*Row  DF 2 4 8 1 4  Type III SS  Mean Square__J__F-value 0.0324 0.0448 0.0236 0.0228 0.0310  0.0647 0.1793 0. 1884 0.0228 0.1238  97  1.08 1.90 0.79 0.76 1.04  P 0.3751 0.2034 0.6245 0.4027 0.4353  ANOVA table for total number of forks in cassava prior to harvest. Source Block Treat Block*Treat Row Treat*Row  DF 2 4 8 1 4  Mean Square  Type UI SS  0.1321 0.1133 0.1090 0.1761 0.1257  0.2642 0.4534 0.8724 0.1761 0.5028  F-value 1.07 1.04 0.88 1.42 1.02  P 0.3797 0.4440 0.5621 0.2602 0.4440  ANOVA tables for cassava yield ANOVA table for cassava total yield (roots, main and lateral shoot). Source Block Treat Block*Treat Row Treat*Row  DF 2 4 7 1 4  Type III SS 99.6955 430.2757 187.5106 10.7756 513.6667  Mean Square  F-value  49.8478 107.5689 26.7872 10.7756 128.4167  1.85 4.02 0.99 0.40 4.76  P 0.2270 0.0530 0.5039 0.5476 0.0359  ANOVA table for cassava lateral shoot yield (stem and leaves). Source  DF  Block Treat Block*Treat Row Treat*Row  2 4 7 1 4  Type ifi SS 261.3978 635.5191 158.5508 2.8269 73.4063  Mean Square  F-value  130.6989 158.8798 22.6501 2.8269 18.3516  10.38 7.01 1.80 0.22 1.46  Mean Square  F-value  286.0000 85.7765 23.2242 12. 1298 5.8151  17.58 3.69 1.43 0.75 0.36  P 0.0080 0.0135 0.2282 0.6500 0.3107  ANOVA table for cassava harvest index. Source Block Treat Block*Treat Row Treat*Row  DF 2 4 7 1 4  Type III SS 572.0000 343.1059 162.5692 12.1298 23.2604  98  P 0.0019 0.0636 0.3251 0.4164 0.8315  ANOVA tables for 1992 soil moisture samples ANOVA table for gravimetric soil moisture content at 4 weeks after planting, June 3, 1992 Source Block Treat Block*Treat Row Treat*Row  DF  Type III SS  3 2 6 1 2  0.5824 0.2295 0.3339 0.0773 0.0124  Mean Square 0.1941 0.0786 0.0557 0.0773 0.0062  P  F-value 24.67 1.58 7.07 9.83 0.79  0.0001 0.0015 0.0051 0.0120 0.4842  ANOVA table for gravimetric soil moisture content at 5 weeks after planting, June 9, 1992 Source Block Treat Block*Treat Row Treat*Row  DF  Type Ill SS  3 2 6 1 2  0.0514 0.0839 0.1178 0.0060 0.0442  Mean Square 0.0171 0.0419 0.0196 00060 0.0221  F-value 2.56 2.14 2.93 0.89 3.30  P 0.1284 0. 1992 0.0810 0.3722 0.0900  ANOVA table for gravimetric soil moisture content at 5 weeks after planting, June 10, 1992 _Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Type III SS  Mean Square  0.0242 0.0005 0.0007 0.0035 0.0775  0.0242 0.0005 0.0007 0.0070 0. 1550  F-value 3.14 0.06 0.09 0.46 9.69  P 0.2185 0.8314 0.7902 0.6870 0.0539  ANOVA table for_gravimetric soil moisture content at 8 weeks after planting, June 29, 1992 Source Block Treat Block*Treat Row Treat*Row  DF_[ 3 2 6 1 2  Mean Square  Type III SS  0.0680 0.0140 0.0006 0.0748 0.0514  0.2041 0.0839 0.0006 0. 1496 0.1027  F-value 0.64 0.13 0.01 0.70 3.68  P 0.6156 0.9879 0.9420 0.5289 0.0908  ANOVA table for gravimetric soil moisture content at 11 weeks after planting, July 22, 1992 Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Mean Square  Type III SS  0.0373 0.1137 0.0389 0.0618 0.0087  0.1119 0.2274 0.2386 0.0618 0.0174  99  J__F-value 10.93 2.86 11.66 18.13 2.87  P 0.0023 0.1342 0.0008 0.0021 0. 1321  ANOVA table for gravimetric soil moisture content at 11 weeks after planting, July 23, 1992 _Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Type III SS  Mean Square  0.0141 0.2510 0.1614 0.0369 0.0068  0.0047 0.1255 0.0369 0.0034 0.0269  F-value 1.18 4.67 9.20 0.85 6.71  P 0.3723 0.0599 0.0142 0.4601 0.0062  ANOVA table for gravimetric soil moisture content at 12 weeks after planting, July 31, 1992 Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Type ifi SS  Mean Square  0.1451 0.3385 0.4529 0.0027 0.0164  0.0484 0. 1693 0.0754 0.0027 0.0082  F-value 1.03 2.24 1.60 0.06 0.17  P 0.4303 0.1874 0.2619 0.8166 0.8434  ANOVA table for gravimetric soil moisture content at 12 weeks after planting, August 3,1992. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Type III SS  Mean Square  9.525 0.3358 59.5442 3.1538 8.9275  3.1749 0. 1679 9.9240 3.1538 4.4638  F-value 0.96 0.02 3.01 0.96 1.35  P 0.4516 0.9833 0.0673 0.3538 0.3064  ANOVA table for gravimetric soil moisture content at 12 weeks after planting, August 4, 1992 Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Type III SS 16.1146 7.0758 24.3242 14.8838 1.1775  Mean Square  F-value  5.3715 3.5379 4.0540 14.8838 0.5888  10.48 0.87 7.91 29.03 1.15  P 0.0027 0.4649 0.0035 0.0004 0.3596  ANOVA table for gravimetric soil moisture content, 13 weeks after planting, August 7, 1992. Source  DF  Block Treat Block*Treat Row Treat*Row  3 2 6 1 2  Type III SS 0.0245 0.0297 0.1173 0.0372 0.0034  100  Mean Square  F-value  0.0082 0.0148 0.0195 0.0372 0.0017  5.75 0.76 13.75 26.18 1.19  P 0.0177 0.5081 0.0004 0.0006 0.3478  ]  ANOVA table for gravimetric soil moisture content 13 weeks after planting, August 12, 1992. Source  DF_J  Block Treat Block*Treat Row Treat*Row  3 2 6 1 2  Mean Square  Type ifi SS  0.0175 0.0271 0.0101 0.0935 0.0055  0.0528 0.0543 0.0607 0.0935 0.0110  F-value 14.59 2.68 8.38 77.45 4.57  P 0.0008 0.1473 0.0028 0.0001 0.0427  ANOVA table for gravimetric soil moisture content, 15 weeks after planting, August 26, 1992 Source Block Treat Block*Treat Row Treat*Row  DF  Type ifi SS  3 2 6 1 2  0.3795 0.2588 0.2657 0.4099 0. 1515  Mean Square 0. 1265 0.1294 0.0443 0.4099 0.0757  j__F-value 4.24 2.92 1.48 13.74 2.54  P 0.0399 0.1300 0.2851 0.0049 0.1337  ANOVA table for gravimetric soil moisture content, 16 weeks after planting, September 1, 1992 Source  DF  Block Treat Block*Treat Row Treat*Row  3 2 6 1 2  Type III SS  Mean Square  F-value  10.4926 6.2112 2.4906 15.5204 11.5117  3.68 2.49 0.87 5.45 4.04  31.4779 12.4233 14.9433 15.5204 23.0233  P 0.0560 0.1628 0.5492 0.0445 0.0560  ANOVA tables for crop nutrient concentration and content ANOVA table for maize ear leaf N content. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  [  Mean Square  Type III SS  0.0225 0.0703 0.0118 0.3073 0.0078  0.0674 0. 1407 0.0709 0.3073 0.0156  101  F-value 1.52 5.96 0.80 20.75 0.53  p 0.2753 0.0376 0.5949 0.0014 0.6078  ANOVA table for maize ear leaf P content. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Mean Square  Type ifi SS  0.0161 0.0781 0.0033 0.2431 0.0188  0.0482 0.1561 0.0200 0.2431 0.0375  F-value 1.12 23.47 0.23 16.88 1.30  P 0.3925 0.0015 0.9558 0.0026 0.3185  ANOVA table for maize ear leaf Ca content. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Mean Square  Type ifi SS  0.0830 0.0688 0.0286 0.3657 0.0416  0.2490 0.1375 0.1718 0.3657 0.0832  F-value__} 4.38 2.40 1.51 19.28 2.19  ‘ 0.0368 0.1714 0.2773 0.0017 0. 1676  ANOVA table for maize ear leaf K content. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Mean Square  Type III SS  0.0186 0.0393 0.0138 0.4197 0.0025  0.0557 0.0787 0.0830 0.4197 0.0049  F-value 1.75 2.84 1.30 39.57 0.23  P 0.2260 0.1354 0.3453 0.0001 0.7979  ANOVA table for maize ear leaf Mg content. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  J  Type III SS  Mean_Square__J__F-value 0.0088 0.0178 0.0133 0.3621 0.0096  0.0265 0.0355 0.0798 0.3621 0.0192  1.45 1.34 2.18 59.42 1.58  P 0.2915 0.3313 0.1409 0.0001 0.2590  ANOVA table for maize ear leaf N concentration. Source Block Treat Block*Treat Row Treat*Row  [_DF 3 4 12 1 4  Mean Square  Type III SS  0.0325 0.0303 0.0143 0.0038 0.0034  0.0975 0.0606 0.0860 0.0038 0.0068  102  F-value 1.75 2.11 0.77 0.20 0.18  p 0.2264 0.2019 0.6108 0.6638 0.8352  ANOVA table for maize ear leaf P concentration. Source Block Treat Block*Treat Row Treat*Row  J  DF 3 4 12 1 4  Mean Square  Type III SS  0.0112 0.0026 0.0042 0.0020 0.0058  0.0336 00053 0.0249 0.0020 0.01 15  F-value 1.66 0.63 0.61 0.29 0.85  P 0.2442 0.5627 0.7155 0.6019 0.4587  ANOVA table for maize ear leaf Ca concentration. _Source Block Treat Block*Treat Row Treat*Row  DF 3 4 12 1 4  Mean Square  Type III SS 0.01 14 0.0003 0.0032 0.0003 0.0024  0.0038 0.0001 0.0005 0.0003 0.0012  F-value 13.76 0.24 1.91 1.22 4.39  P 0.0010 0.7908 0.1830 0.2978 0.0468  ANOVA table for maize ear leaf K concentration. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS  Mean Square  0.0088 0.0148 0.0040 0.0151 0.0036  0.0265 0.0296 0.0240 0.0152 0.007 1  F-value 5.03 3.70 2.28 8.64 2.03  P 0.0256 0.0898 0. 1280 0.0165 0.1872  ANOVA table for maize ear leaf Mg concentration. Source  DF  Block Treat Block*Treat Row Treat*Row  3 4 12 1 4  Type III SS 0.0118 0.0830 0.0629 0.0025 0.0103  Mean Square  F-value  0.0039 0.0415 0.0105 0.0025 0.0052  1.21 3.96 3.21 0.77 1.58  P 0.3623 0.0800 0.0570 0.4020 0.2576  ANOVA table for maize ear leaf weight. Source Block Treat Block*Treat Row Treat*Row  DF 3 2 6 1 2  Mean Square  Type Ill SS  0.0094 0.0944 0.0077 0.2770 0.0094  0.0283 0.1887 0.0461 0.2770 0.0188  103  F-value 0.73 12.28 0.59 21.32 0.72  P 0.5618 0.0076 0.7309 0.0013 0.5117  ANOVA table for cassava leaf N content. _Source Block Treat  OF  Type III SS  2 5  0.0765 1.7534  Mean Square 0.0382 0.3508  F-value 1.25 11.48  P 0.3272 0.0007  ANOVA table for cassava leaf P content. Source  OF  Type III SS  Block Treat  2 5  0.1150 2.3512  Mean Square  0.0575 0.4702  F-value 1.69 13.85  P 0.2326 0.0003  ANOVA table for cassava leaf Ca content. Source  DF  Type III SS  Block Treat  2 5  0.0606 1.3264  Mean Square 0.0303 0.2653  F-value 0.71 6.22  P 0.3272 0.0007  ANOVA table for cassava leaf K content. Source Block Treat  OF_[ 2 5  Mean Square  Type III SS  0.0275 0. 1466  0.0551 0.7329  F-value 0.89 4.73  p 0.4413 0.0177  ANOVA table for cassava leaf Mg content. Source  OF  Type III SS  Block Treat  2 5  0.0380 2.6284  Mean Square 0.0190 0.5257  F-value 0.49 13.47  P 0.6284 0.0004  ANOVA table for cassava leaf N concentration. Source  DF  Type III SS  Block Treat  2 5  0.0802 0. 1816  Mean Square 0.0401 0.0363  F-value  3.06 2.77  P 0.0919 0.0800  ANOVA table for cassava leaf P concentration. Source  OF  Type III SS  Block Treat  2 5  0.0040 0. 1014  Mean Square 0.0020 0.0203  104  F-value 1.19 12.15  P 0.3436 0.0005  ANOVA table for cassava leaf Ca concentration. Source  DF  Type III SS  Block Treat  2 5  0.0046 0.0314  Mean Square 0.0023 0.0063  F-value 1.14 3.14  P 0.3587 0.0584  ANOVA table for cassava leaf K concentration. Source  DF  Type ifi SS  Block Treat  2 5  0.0019 0.1972  Mean Square  0.0009 0.0394  F-value 0.48  20.15  P 0.6338 0.0001  ANOVA table for cassava leaf Mg concentration. Source Block Treat  [_DF 2 5  Mean Square  Type III SS  0.0257 0.0331  0.0513 0.1653  F-value 2.73 3.52  p 0.1130 0.0428  ANOVA table for cassava leaf weight. Source Block Treat  [_DF 2 5  Type III SS  Mean Square 0.0384 0.3156  0.0606 1.3264  F-value  1.04 8.53  P 0.3890 0.0022  ANOVA tables for Leucaena pruning nutrient concentration and yield ANOVA table for mean Leucaena Ca concentration for 2-, 4- and 8- week pruning intervals. _Source Block Treat  DF  2 2  Type III SS  37.3333 357.3333  Mean Square  F-value  18.6667 178.6667  2.84 27.22  P  0.0945 0.0001  ANOVA table for mean Leucaena Mg concentration for 2-, 4- and 8- week pruning intervals. Source  DF  Block Treat  2 2  Type III SS 105.3333 81.3333  Mean Square  F-value  52.6667 40.6667  2.50 1.93  P 0. 1202 0.1839  ANOVA table for mean Leucaena K concentration for 2-, 4- and 8- week pruning intervals. Source  DF  Block Treat  2 2  Type III SS 208.0000 85.3333  105  Mean Square  F-value  104.0000 42.6667  7.24 2.97  P 0.0077 0.0865  ANOVA table for mean Leucaena N concentration for 2-, 4- and 8- week pruning intervals. Source  DF  Block Treat  2 2  Type III SS 85.3333 208.0000  Mean Square  F-value  42.6667 104.0000  2.97 7.24  P 0.0865 0.0077  ANOVA table for mean Leucaena P concentration for 2-, 4- and 8- week pruning intervals. Source  DF  Block Treat  2 2  Mean Square  Type Ill SS  0.6667 216.0000  1.3333 432.0000  F-value__[ 0.22 72.62  p 0.8022 0.0001  ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July 25, 1991. Source  DF  Block Treat  2 2  Type III SS 15.3612 277.1817  Mean Square  F-value  7.6806 138.5908  1.05 18.98  P 0.4295 0.0091  ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July 25, 1991. Source  DF  Block Treat  2 2  Type III SS 1.0500 25.0146  Mean Square  F-value  0.5250 12.5073  1.14 27.22  P 0.4050 0.0047  ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July 25, 1991. Source  DF  Block Treat  2 2  Type III SS 59.8974 1930.5833  Mean Square  F-value  29.9487 965.2917  1.57 50.68  P 0.3134 0.0014  ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July 25, 1991. Source  DF  Block Treat  2 2  Type III SS 153.8034 5968.8167  Mean Square  F-value  76.9017 2984.4084  1.20 46.55  P 0.3907 0.0017  ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 8 weeks after planting, July 25, 1991. Source  DF  Block Treat  2 2  Mean Square  Type III SS  0.0469 3.5438  0.0938 7.0876 106  F-value  0.64 48.39  P 0.5738 0.0016  ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 16 weeks after planting, September 18, 1991. Source  DF  Block Treat  2 2  Mean Square  Type III SS  0.6654 15.7978  1.3308 3 1.5956  F-value 7.23 171.69  P 0.0469 0.0001  ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 16 weeks after planting, September 18, 1991. Source  DF  Block Treat  2 2  Type III SS 1.1219 29.4576  Mean Square  F-value  0.5610 14.7288  3.51 92.25  P 0.1316 0.0005  ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 16 weeks after planting, September 18, 1991. Source Block Treat  DF_J 2 2  Type III SS 387.2336 8219.7811  Mean Square  F-value  193.6168 4109.8905  1.20 25.42  P 0.3912 0.0053  ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 16 weeks after planting, September 18, 1991. Source  DF  Block Treat  2 2  Type III SS 893.9507 42832.2768  Mean Square  F-value  446.9754 21416. 1384  1.83 87.76  P  0.2724 0.0005  ANOVA table for Leucaena P yield for 2-, 4- and 8- week intervals at 16 weeks after planting, September 18, 1991. Source  DF  Block Treat  2 2  Type ifi SS 3.4021 149.9640  Mean Square  F-value  1.7010 74.9820  1.53 67.40  P 0.3212 0.0008  ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 24 weeks after planting, November 14, 1991. Source  DF  Block Treat  2 2  Type III SS  [  0.3045 71.8549  107  Mean Square  F-value  0.1522 23.9516  0.16 24.95  P  0.8568 0.0009  ANOVA table for Leucaena Mg yield for 2-, 4- and 8- week intervals at 24 weeks after planting, November 14, 1991. Source  DF  Block Treat  2 2  Mean Square  Type III SS  0.1047 7.1852  0.2094 21.5555  F-value__] 0.33 22.51  p 0.7326 0.0012  ANOVA table for Leucaena K yield for 2-, 4- and 8- week intervals at 24 weeks after planting, November 14, 1991. Source  DF  Block Treat  2 2  Mean Square  Type III SS  0.1530 8.0746  0.3061 24.2221  F-value  0.40 21.17  P 0.6862 0.0014  ANOVA table for Leucaena N yield for 2-, 4- and 8- week intervals at 24 weeks after planting, November 14, 1991. Source  DF  Block Treat  2 2  Mean Square__[__F-value  Type Ill SS  16.4190 571.4152  32.8380 1714.2456  0.77 26.89  p 0.5028 0.0007  ANOVA table for Leucaena Ca yield for 2-, 4- and 8- week intervals at 24 weeks after planting, November 14, 1991. _Source Block Treat  DF 2 2  Mean Square  Type Ill SS  0.0186 0.6735  0.0372 2.0205  F-value 1.34 48.44  P 0.3312 0.0001  ANOVA tables for soil analysis ANOVA table for differences in K from soil samples taken prior to planting in 1992. Source  DF  Block Row  3 1  Mean Square  Type III SS  0.0624 0.0157  0.1872 0.0157  F-value 21.74 5.45  P 0.0154 0. 1017  ANOVA table for differences in K from soil samples taken prior to planting in 1992. Source  DF  Block Row  3 1  Mean Square  Type III SS  0.0687 0.0062  0.2061 0.0062  108  F-value 2.03 0.18  P 0.2875 0.6968  ANOVA table for differences in Ca from soil samples taken prior to planting in 1992. Source  DF  Block Row  3 1  Type Ill SS  Mean Square  0.2778 0.0588  0.8334 0.0588  P  F-value  8.23 1.74  0.0585 0.2786  ANOVA table for differences in Mg from soil samples taken prior to planting in 1992. Source Block Row  J_DF 3 1  Type III SS  J  Mean Square 0. 1453 0.0286  0.4358 0.0286  P  F-value__J 22.28 4.39  0.0149 0.1272  ANOVA table for differences in pH from soil samples taken prior to planting in 1992. _Source Block Row  DF 3 1  Mean Square  Type ifi SS  0.002 1 0.0010  0.0063 0.0010  P  F-value 13.74 6.57  0.0294 0.0830  ANOVA table for differences in total N from soil samples taken prior to planting in 1992. _Source Block Row  DF 3 1  Mean Square  Type Ill SS  0.0520 0.0330  0.1561 0.0330  F-value 11.91 7.55  P 0.0357 0.0709  ANOVA table for differences in P from soil samples taken prior to planting in 1992. Source  DF  Block Row  3 1  Type III SS  [  Mean Square 0.0135 0.2230  0.0404 0.2230  F-value__[ 1.16 19.15  p  0.4946 0.0485  4 from soil samples taken prior to planting in 1992. ANOVA table for differences in NH Source  DF  Type ifi SS  Block Row  3 1  0.6214 0.2363  Mean Square  0.3157 0.2363  j__F-value 9.84 22.10  0.0462 0.0182  3 from soil samples taken prior to planting in 1992. ANOVA table for differences in NO Source  DF  Type III SS  Block Row  3 1  0.2529 0.0245  Mean Square 0.0843 0.0245  109  F-value 2.74 2.39  0.2147 0.2195  1  ANOVA table for differences in K from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Mean Square  Type ifi SS  0.0348 0.0705  0.0697 0.3525  F-value 1.54 3.11  P 0.2617 0.0597  ANOVA table for differences in Na from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Mean Square  Type III SS  0.0002 0.0000  00003 0.0003  F-value 7.57 3.35  P 0.0100 0.0490  ANOVA table for differences in Ca from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Type III SS  Mean Square 0.4139 0.6248  0.8278 3.1242  F-value 1.81 2.73  P 0.2133 0.0826  ANOVA table for differences in Mg from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Type Ill SS 0.0720 0.1894  Mean Square  F-value  0.0360 0.0379  1.46 1.54  P 0.2777 0.2628  ANOVA table for differences in pH from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Mean Square  Type ifi SS  0.0006 0.0005  0.0013 0.0023  F-value 3.51 2.48  P 0.0699 0. 1041  ANOVA table for differences in P from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Mean Square  Type III SS  0.0003 0.0405  0.0006 0.2025  F-value__[ 0.02 2.41  p 0.98 16 0.1114  ANOVA table for differences in total N from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  f  Type Ill s  [  Mean_Square__j__F-value 0.0723 0.0900  0.1447 0.4499  110  1.01 1.25  P 0.3989 0.3542  ANOVA table for differences in total organic C from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Mean Square  Type Ill SS  0.0211 0.0258  0.0421 0.1289  F-value 0.71 0.87  P  0.5152 0.5348  ANOVA table for differences in bulk density from soil samples taken at the end of the rainy season, 1991. Source  DF  Block Treat  2 5  Type Ill SS 23244.4444 14444.4444  Mean Square  F-value  11622.2222 2888.8889  2.62 0.65  P 0.1219 0.6683  4 from soil samples taken at the end of the rainy season, 1991. ANOVA table for differences in NH Source  DF  Type III SS  Block Treat  2 5  0.45 16 3.3960  Mean Square 0.2258 0.6792  F-value 0.47 0.57  P  0.6352 0.7211  - from soil samples taken at the end of the rainy season, 1991. 3 ANOVA table for differences in NO Source  DF  Type ifi SS  Block Treat  2 5  0.0162 0.0340  Mean Square  0.0081 0.0068  F-value__[  1.12 3.74  p 0.3637 0.0361  ANOVA tables for pruning labour requirement ANOVA table for differences in pruning labour for the initial pruning of the season, April 14/15, 1992. Source Block Treat  J_DF 3 3  Type III SS 64.2500 7498.2500  Mean Square  F-value  21.4167 2499.4167  6.12 14.41  P 0.9439 0.0009  ANOVA table for differences in total in-season pruning requirements. Source  DF  Block Treat  3 3  Type Ill SS 25.1667 2278. 1667  111  Mean Square  F-value  8.3889 759.3889  0.14 12.46  P 0.9300 0.0010  ANOVA tables for weed biomass assessment ANOVA table for differences in total weed biomass over the 1992 maize season. Source  DF  Block Treat  3 2  Type Ill SS  Mean Square 0.1364 1.4616  0.4092 2.9231  F-value 1.02 10.89  P 0.5673 0.0500  ANOVA table for differences in weed biomass at 4 weeks after planting, June 3, 1992. Source  DF  Block Treat  3 2  Mean Square  Type III SS  0.0072 0.0063  0.0216 0.0127  F-value 1.35 1.19  P 0.3438 0.3678  ANOVA table for differences in weed biomass at 10 weeks after planting, July 14, 1992. Source  DF  Block Treat  3 2  Mean Square  Type III SS  0.1119 0.4952  0.3356 0.9904  F-value 0.92 4.06  P 0.4867 0.0766  ANOVA table for differences in weed biomass at 17 weeks after planting, August 31, 1992. Source  DF  Block Treat  3 2  Mean Square  Type III SS  0.0119 0.4519  0.0356 0.9038  112  F-value 1.27 48.20  P 0.3671 0.0002  Appendix B Regression outputfor Leucaena LAI vs. light transmission to the cassava canopy. Analysis of Variance DF  Source  0.19122 2.97217 6.43378  Root MSE Dep Mean C.V.  Variable DF INTERCEP 1 LAI  2.59599 0.43879 3.03478  1 12 13  Model Error C Total  SS  MS  F Value  2.59599 0.03657  R-fsquare Adj R-sq  70.994  4.551187 0.19424625 -0.698020 0.08284296  0.0001  0.8554 0.8434  Standard T for HO: Parameter Error Parameter = 0 Estimate 1  Prob> F  Prob >  I TI  0.0001 23.430 -8.426 0.0001  Regression output for Leucaena LAI vs. light transmission to the maize ear level. Analysis of Variance  DF  Source  Model Error C Total  1 12 13  Root MSE Dep Mean C.V.  Variable DF  SS 2.38646 0.48211 2.86857  0.20044 3.36162 5.96255  MS  F Value  2.38646 0.04018 R-square Adj R-sq  59.401  4.635266 -0.650291  0.0001  0.8319 0.8179  Standard T for HO: Parameter Error Parameter = 0 Estimate  INTERCEP 1 MAIZE LAI 1  Prob > F  26.682 -7.707  0. 17371950 0.08437460  113  Prob >  I TI  0.0001 0.0001  Regression outputfor maize!Leucaena height difference vs light transmission. Analysis of Variance SS  DF  Model Error C Total  1 2242.11475 2242.11475 75.99937 9 683.99434 10 2926.10909  8.71776 Root MSE 37.99091 Dep Mean 22.94697 C.V. Variable DF  R-square Adj R-sq  Prob > F  F Value  MS  Source  29.502  0.0004  0.7662 0.7403  Standard T for HO: Parameter Error Parameter = 0 Estimate  Prob >  0.0001 0.0004  9.572 5.432  INTERCEP 1 29.381764 3.06941977 1 38.477722 7.0841 1231 DIFF2  T  Regression outputfor cassava/Leucaena height difference vs light transmission to cassava canopy. Analysis of Variance Source Model Error C Total Root MSE Dep Mean C.V.  DF  SS  21.288  2 12526.42109 6263.21054 16 4707.41996 294.21375 18 17233.84105 17.15266 34.26842 50.05384  R-square Adj R-sq  0.0001  0.7269 0.6927  Parameter Standard T for HO: Error Parameter = 0 Estimate Variable DF INTERCEP 1 63.607054 10.39000858 1 DIFF -0.309482 0.07014247 46. 169469 69.39186166 DIFF(sq) 1  Prob > F  F Value  MS  6.122 -4.412 0.665  114  Prob >  TI  0.0001 0.0004 0.5153  Regression outputfor Leucaena foliage N vs. maize ear leaf 1V Analysis of Variance DF  Source Regression Error Total  11 12  Standard Error  Parameter Estimate  Variable INTERCEP SQN  5.52543471 0.86971573  5.52543471 9.56687299 15.09230769  1  F Value Prob > F  MS  SS  6.35  0.0284  F  Prob > F  Type II Sum of Squares  0.45261989 8.45993635 0.00002484 0.00006261  349.35 0.0001 303.83951010 5.52543471 6.35 0.0284  Regression outputfor Leucaena foliage N vs. maize grain yield. Analysis of Variance Source  DF  SS  Model Error C Total  1 11 12  16.06833 2.63004 18.69837  Root MSE Dep Mean C.V.  Variable DF  0.48897 3.82846 12.77206  MS  F Value  16.06833 0.23909  R-square Adj R-sq  Prob > F  67.205  0.8593 0.8466  Parameter Standard T for HO: Error Parameter 0 Estimate  INTERCEP 1 1 LEUCN  0.0001  8.990 8.198  2.180189 0.24252344 0.016259 0.00198331  115  Prob >  TI  0.0001 0.0001  Regression outputfor Leucaena foliage K vs. maize stover yield. Analysis of Variance Source  DF  SS  Model Error C Total  1 11 12  20.91215 13.12477 34.03692  Root MSE Dep Mean C.V.  1.09232 6.28462 17.38084  Estimate  INTERCEP 1 1 LEUCK  17.527  20.91215 1.19316  R-square Adj R-sq  Prob> F 0.0015  0.6144 0.5793  T for HO: Error Parameter = 0  Standard  Parameter Variable DF  F Value  MS  8.193 4.186  4.417371 0.53917774 0.027149 0.00648498  Prob >  TI  0.0001 0.0015  Regression outputfor mean light transmission to maize ear level during the growing 1991 season vs. maize grain yield. Analysis of Variance Source  DF  SS  Model Error C Total  1 4 5  1.27067 0.41561 1.68628  Root MSE Dep Mean C.V.  Variable DF  0.32234 2.18833 14.72993  MS  F Value  1.27067 0.10390  R-square Adj R-sq  12.229  0.0250  0.7535 0.6919  Parameter Standard T for HO: Error Parameter = 0 Estimate  INTERCEP 1 1 LIGHT  Prob> F  -0.217 3.497  -0.148038 0.68093384 0.043173 0.01234550  116  Prob > IT I 0.8385 0.0250  Regression outputfor mean light transmission to maize ear level during the growing 1991 season vs. maize grain yield. Analysis of Variance Source  DF  SS  Model Error C Total  1 10 11  11.50135 5.33354 16.83489  Root MSE DepMean C.V.  0.73031 3.71917 19.63641  F Value  MS 11.50135 0.53335  R-square AdjR-sq  21.564  0.0009  0.6832 0.6515  Standard T for HO: Parameter Error Parameter = 0 Estimate Variable DF INTERCEP 1 1 LIGHT  Prob > F  2.383 4.644  1.326613 0.55668709 0.126479 0.02723644  Prob >  IT  0.0384 0.0009  Regression output for Leucaena foliage P vs. cassava leaf P content. Analysis of Variance Source  DF  SS  Model Error C Total  1 4 5  16.02162 5. 15873 21.18035  Root MSE Dep Mean C.V.  Variable DF  1.13564 6. 82500 16.63943  F Value  MS 16.02162 1.28968  R-square Adj R-sq  12.423  0.0243  0.7564 0.6955  Standard T for HO: Parameter Error Parameter = 0 Estimate  INTERCEP 1 1 LEUCP  Prob>F  4.080 3.525  3.889130 0.95329496 0.401258 0.11384436  117  Prob >  I TI  0.0151 0.0243  Regression outputfor Leucaena foliage N vs. cassava leaf N content. Analysis of Variance MS  DF  Model Error C Total  1 2960.74346 2960.74346 4 1039.65862 259.91465 5 4000.40208  Root MSE Dep Mean C.V.  Variable DF  SS  16.12187 102.71167 15.69624  R-square Adj R-sq  0.0279  11.391  0.7401 0.675 1  Standard T for HO: Parameter Error Parameter 0 Estimate 66.007932 12.71151241 0.293630 0.08699920  INTERCEP 1 1 LEUCN  Prob > F  F Value  Source  5.193 3.375  Prob > (T 0.0065 0.0279  Regression outputfor Leucaena foliage K vs. cassava leaf K content. Analysis of Variance Source  DF  SS  Model Error C Total  1  5.67454 2.83374 8.50828  4 5  Root MSE Dep Mean C.V.  Variable DF  0.84169 6.43833 13.07305  MS  F Value 8.010  5.67454 0.70844  R-square Adj R-sq  0.0473  0.6669 0.5837  Parameter Standard T for HO: Error Parameter = 0 Estimate  INTERCEP 1 1 LEUCK  Prob > F  7.249 2.830  4.824878 0.66563742 0.027882 0.00985175  118  Prob >  T  0.0019 0.0473  Regression outputfor mean light transmission to the cassava canopy during the first 4 months of growth vs. cassava root yield. Analysis of Variance Source  DF  SS  Model  1  0.07231  Error C Total  3 4  0.00657 0.07888  Root MSE Dep Mean C.V.  0.04678 0.47200 9.91117  MS 0.07231 0.002 19  R-square Adj R-sq  F Value  Prob > F  33.044  0.0105  0.9 168 0.8890  Standard T for HO: Parameter Error Parameter = 0 Estimate Variable DF INTERCEP 1 1 LIGHT  -2.878 5.748  -0.480899 0. 16708278 0.030699 0.00534046  Prob >  T  0.0636 0.0105  Regression outputfor nwan light transmission to the cassava canopy during the first 4 months of growth vs. cassava total dry matter yield. Analysis of Variance Source  DF  SS  Model Error C Total  1 3 4  0.18744 0.02564 0.21308  Root MSE Dep Mean C.V.  Variable DF  0.09246 1.69800 5.44502  MS 0.18744 0.00855  R-square Adj R-sq  F Value  Prob > F  21.927  0.0184  0. 8796 0.8395  Standard T for HO: Parameter Error Parameter 0 Estimate  INTERCEP 1 1 LIGHT  0.496 4.683  0.163880 0.33021877 0.049424 0.01055476  119  Prob >  TI  0.6538 0.0184  Regression output for Leucaena stem diameter, count and operator (person performing the pruning) vs. pruning time. R-square DF  Source  Variable  Parameter Estimate  INTERCEP COUNT OPERATOR  Standard Error  2.01564260 F Value Prob > F  Type II Sum of Squares  11.37994362 0.02868866 1.15002097  -15.68089379 0.05656893 3.86799348  =  148.61643952 21.98208623  297.23287904 285.76712096 583.00000000  13 15  C(p)  MS  SS  2  Regression Error Total  0.50983341  =  6.76  F  41.73787295 85.46817316 248.67312440  0.0097  Prob > F  1.90 0.1915 3.89 0.0703 11.31 0.0051  Regression outputfor pruning labour vs. time elapsed between prunings. R-square Source Regression Error Total  Variable  DF 2 17 19  =  0.95536886  17481.14827261 816.65172739 18297.80000000 Standard Error  =  2.3 1690796 F Value Prob > F  MS  SS  Parameter Estimate  C(p)  8740.57413630 48.03833691  Type II Sum of Squares  181.95  F  0.0001  Prob > F  8.97 0.0081 9.61275136 431.06409314 INTERCEP 28.79550184 0.75 0.3991 0.36573470 35.94767375 -0.31637895 TIME 15.52 0.0011 0.00294085 745.65977484 0.01158640 SQTIME  120  Regression outputfor pruning labour vs. Leucaena biomass pruned. R-square  Parameter Estimate  Variable INTERCEP BIOMASS SQBIOM  Standard Error  =  2.00019672 F Value Prob > F  5863.46882888 386.52131425  Type II Sum of Squares  31.81612728 40.21357755 80.54930334  69.36403277 86.40163224 -126.33478494  C(p)  MS  11726.93765775 6570.86234225 18297.80000000  2 17 19  Regression Error Total  0.64089331  SS  DF  Source  =  15.17  F  0.0002  Prob > F  4.75 0.0436 4.62 0.0464 2.46 0. 1352  1837. 16213696 1784.31661293 950.81442324  Regression outputfor Leucaena biomass vs. time elapsed between prunings. Analysis of Variance Source  DF  SS  MS  Model Error C Total  2 17 19  18.18500 0.95980 19.14480  9.09250 0.05646  Root MSE Dep Mean C.V.  0.23761 1.39000 17.09428  R-square Adj R-sq  F Value 161.047  0.0001  0.9499 0.9440  Standard T for HO: Parameter Error Parameter = 0 Estimate Variable DF INTERCEP 1 1 TIME 1 SQTIME  Prob > F  -7.847 9.606 -7.024  -2.585861 0.32954846 0. 120443 0.01253827 -0.000708 0.00010082  121  Prob >  I TI  0.0001 0.0001 0.0001  Regression outputfor pruning labour vs. time elapsed between prunings. Analysis of Variance Source  DF  SS  Model Error C Total  1 18 19  69.24000 3.38397 72.62397  Root MSE Dep Mean C.V.  0.43359 3.39570 12.76872  F Value  MS 69.24000 0.18800  R-square Adj R-sq  368.301  0.0001  0.9534 0.9508  Standard T for HO: Parameter Estimate Error Parameter = 0 Variable DF INTERCEP 1 SQTIME 1  Prob > F  1.305870 0.14580156 0.000572 0.00002979  8.956 19. 191  122  Prob >  I TI  0.0001 0.0001  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0087369/manifest

Comment

Related Items