Growth and yield of eight agroforestry tree species in line plantings in Western Kenya and their effect on maize yields and soil properties

Between October 1988 and August 1992, field experiments were carried out in West Kenya to evaluate the suitability of Leucaena leucocephala, L. collinsii, Gliricidia sepium, Calliandra calothyrsus, Sesbania sesban, S. grandiflora, Senna siamea and S. spectabilis to provide a range of agroforestry products and services. The initial objective was to establish the growth rates and wood and leaf yields of these tree species, when planted in single rows. After the initial evaluation, it was evident that valuable additional information could be collected if the trees were converted to hedges and their effect on intercropped maize and soils was studied. At 21 months after planting, different species and provenances ranged in height between 3.5 and 6 m and varied considerably in phenotypic appearance. Wood production (1988–1990) varied from 3 to 33.8 t ha⁻¹ and leaf production varied from 0.62 to 10.1 t ha⁻¹. During intercropping (1990–1992), leaf production varied from 0 to 10.9 t ha⁻¹. Maize yields were higher in association with Leucaena and Gliricidia than with Calliandra, Sesbania and Senna. Cumulative maize grain and stover yields over four seasons were positively correlated with the total amount of tree leaves applied (r² range, 0.70–0.95). The effect of tree leaf mulch on crop yields decreased over time for all species. Leaves with high nutrient contents, which decompose fast (Leucaena, Gliricidia, Sesbania) are likely to have been more effective in sustaining crop yields than leaves with lower nutrient contents (Senna) or more complex decomposition patterns (Calliandra). Simple “leaf input-crop output” budgets to calculate the reserves for N, P and K in different systems explained crop yield differences in some cases. Compared to the fertility status of “zero-mulch” control plots, the status of soil C, N, P, K, Ca, Mg and S was to varying degrees improved under Leucaena, Gliricidia and Sesbania, much less under Calliandra but not under Senna. First season grain yields were related to the soil fertility status at the end of the tree fallow. The results of these experiments suggest that under subhumid tropical conditions with soils of relatively poor nutrient status, where light and water are not likely to be the major limiting factors to crop production, the application of sufficient quantities of high quality tree mulch may positively influence maize yields. When agroforestry tree species with contrasting decomposition and nutrient release patterns are evaluated jointly, it is more difficult to demonstrate a general relationship between quantities of mulch applied and improvements in crop yields and soil fertility levels. Therefore, further chemical, physiological and phenotypic characterization of free species with potential for fallow and intercropping systems is required.     

The agronomic and economic performance of banana,bean and tree intercropping in the highlands of Burundi: an interim assessment

To meet their wood, fodder and fruit needs, resource-poor farmers with only small land holdings are forced to mix trees in their food crop plots. An experiment was conducted to study the effect of nine tree species planted at 312.5 trees ha^–1 (4×8 m) on the yield of bananas planted at 625 stools ha^–1 (4×4 m) and beans (80000 plants ha^–1) as well as the wood production of the trees when intercropped. In addition, an economic analysis was done to compare the different tree/banana/bean associations.After three and one-half years, wood volume (in m³ ha^–1) ofGrevillea robusta (18.1), was highest and that ofErythrina poeppigiana (2.7),Cedrela odorata (2.4) orMarkhamia lutea (0.8) was the lowest. Volume ofCedrela serrata (13.7) was not significantly different from that ofAlbizia chinensis (12.8) but was significantly higher than that ofLeucaena diversifolia (6.8),Acrocarpus fraxinifolius (6.7) orCalliandra calothyrsus (6.0).None of the tree species had a significant influence on the yields of the bananas and none affected the yield of the bean crops until the seventh cropping season, three years after the trees were planted. In that year, Grevillea reduced bean yield by 29%, Albizia by 34% and Leucaena by 36%. From the economic analyses, all the treatments except Leucaena and Markhamia had positive net benefits relative to the control (banana/bean) but the results were highly variable.C. serrata was found to be the best tree to be intercropped in a banana/bean system.     

Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol

Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly).For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania.The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena.The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height.IITA Journal paper number 335     

Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol

Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly). For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania. The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena. The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height. IITA Journal paper number 335     

Growth of four tree species managed as hedgerows in response to liming on an acid soil in West Sumatra,Indonesia

A hedgerow intercropping study was conducted for 7 years in West Sumatra, Indonesia on an acid and highly Al-saturated soil to determine growth and yield responses of tree hedgerows and upland rice and cowpea intercrops. Three tree species,Paraserianthes falcataria, Calliandra calothyrsus, andGliricidia sepium and a no-tree control were planted at three lime rates with low annual fertilizer inputs of 20 kg P and 50 kg K ha^–1.Paraserianthes andCalliandra grew vigorously, whileGliricidia grew poorly and was replaced after four years withFlemingia macrophylla. After four years,Paraserianthes yields declined due to tree mortality, probably due to intensive pruning.Calliandra andFlemingia were well adapted to intensive pruning (4 to 6 times per year). Gliricidia growth was especially limited by low soil Ca availability and high soil acid saturation.Calliandra andFlemingia yields increased with liming only in the last several years of the study whileParaserianthes did not respond to lime. The species can be tentatively ranked in response to lime as:Gliricidia > Calliandra > Flemingia > Paraserianthes.     

Alley cropping of maize with nine leguminous trees

A maize-leguminous tree alley cropping system was studied on N-deficient soils in Hawaii to determine mulch effects on maize yields. Calliandra calothyrsus, Cajanus cajan, Cassia siamea, Gliciridia sepium, KX1 — Leucaena hybrid (L. pallida X L. diversifolia), L. leucocephala, L. pallida, L. salvadorensis, and Sesbania sesban were evaluated for green manure and yield of intercropped maize. S. sesban, G. sepium, L. pallida, and KX1 produced between 5 and 12 dry t/ha/yr green manure with nitrogen yields between 140 and 275 kg N/ha in 4 prunings. Maize yields responded linearly to nitrogen applied as green manure. Maize yield increased 12 kg for each kg of nitrogen applied. Additions of prunings from hedge rows were able to support maize grain yields at about 1800 kg/ha for two consecutive cropping seasons, while control plot yields averaged less than 600 kg/ha. Maize yields reflected the amount of nitrogen applied as green manure, regardless of tree species from which the nitrogen was derived. In March, maize yields decreased 34% in the row spaced 40 cm from the hedge, relative to the one spaced 110 cm away. In July, increasing the distance away from the hedge to 60 cm and coppicing the hedge earlier in maize growth, significantly improved grain yield. Grain yields decreased only 10% in the row closest to the trees.     

Calliandra calothyrsus (Meissn.) in an alley cropping system with sequentially cropped maize and cowpea in southwestern Nigeria

Alley cropping is increasingly becoming accepted as an appropriate technology with the potential to provide stable and sustainable food production in the tropics. However, only a few of the potential trees/shrubs have been tested. The performance of Calliandra calothyrsus (Meissn) as an alley cropping species was evaluated on an Oxic Paleustalf. The treatments were: prunings removal, prunings application; and three N levels, 0,45, and 90 kg N ha^–1, in a factorial arrangement. The cropping sequence was maize (main season) follwed by cowpea (minor season). Nitrogen fertilizer treatments were applied to the maize crop only. Four annual prunings of Calliandra hedgerows produced a total of 6 t ha^–1 of dry matter prunings containing about 200 kg ha^–1 of N. Maize yields were increased by the application of prunings but no benefits were obtained by supplementing the prunings with inorganic N. An average maize grain yield of 3.1 t ha^–1 per year was maintained without any chemical fertilizer input. However, without any prunings, maize yields were substantially increased by the application of inorganic N. Cowpea yield did not respond to application of prunings but plants grown adjacent to the hedgerows had reduced yield probably due to shading. Our results suggest that six rows (0.57 m inter-row spacing) between Calliandra hedgerows spaced at 4 m are optimum for this cowpea variety. The performance of Calliandra was comparable to that of Leucaena which has been widely shown to be effective in alley cropping systems of the region.     

Stepwise approach to alley cropping technology development and transfer in the forest zone of Cameroon

Two projects on alley cropping research and development have been implemented in the Forest zone of Cameroon (FZC) since 1988. Their goal was to identify the main agricultural constraints in the FZC and to introduce alley cropping in the farming systems to improve soil fertility and crop yields. The first step in the implementation process was the participatory surveys which revealed that (a) the main agricultural constraint in the FZC is low soil fertility; (b) alley cropping is an agroforestry technology which may solve the problem; (c) alley cropping should be first targetted to farmers who own inherited or purchased lands. The second step was the on-station tree screening activity from which Leucaena leucocephala, Gliricidia sepium, Calliandra calothyrsus and Paraserianthes falcataria were identified as promising tree species. The third activity was to test alley cropping with three promising tree species (Leucaena, Gliricidia and Calliandra) on farmers' fields. Results from the first year testing on farmers' fields showed that: (1) the direct seeding method used was ineffective: seedling emergence rate was 45% for Leucaena and 52% for Gliricidia; (2) Cassava suppressed the growth of Leucaena and Gliricidia by 57 and 45%, respectively; (3) three-month-old Calliandra seedlings planted 1 m away from cassava plants had 96% survival rate. Based on these third step findings, all new farms were established with Calliandra seedlings using maize as a test-crop in the year of establishment and the subsequent year. After two years of cropping, maize grain yield in alley plots was 52% higher than maize grown on no-tree plots. In 1993, 52 farmers who had witnessed the alley farm maize growth in 1992 requested to join the project. This sudden interest of farmers to start their own alley farms was considered as a positive sign for adoption and therefore a success in alley cropping (AC) introduction in the zone.     

Assessing farmers’ interest in agroforestry in two contrasting agro-ecological zones of Rwanda

Uptake and management of agroforestry technologies differs among farms in Rwanda and needs to be documented as a basis for shaping future research and development programs. The objective of this study was to investigate current agroforestry practices, farmers’ preferences, tree management and perspectives for agroforestry technologies. The study consisted of a combination of a formal survey, a participatory tree testing, farmer evaluation and focus group discussions in the Central Plateau (moderate altitude) and the Buberuka (high altitude) agro-ecological zones. A survey and a tree testing exercise with a range of species: (timber species—Eucalyptus urophyla, Grevillea robusta; legume shrubs - Calliandra calothyrsus, Tephrosia vogelii; and fruit species—Persea americana and Citrus sinensis) were carried out in Simbi (Central Plateau) and Kageyo (Buberuka) with farmers from different wealth status who received tree seedlings for planting, managing, and evaluating. Simbi had more tree species farm^?1 (4.5) than Kageyo (2.9). Fruit trees occurred most frequently in Simbi. Grevillea robusta, Calliandra calothyrsus and Tephrosia vogelii were mostly established along contours, fruit trees in homefields and Eucalyptus urophyla trees in woodlots. Survival was better on contours for Grevillea robusta (58–100 %) and Calliandra calothyrsus (50–72 %). Tree growth was strongly correlated with the total tree lop biomass in Eucalyptus urophyla (R ² = 0.69). Grevillea robusta was most preferred in Simbi and Eucalyptus urophyla and Calliandra calothyrsus in Kageyo. The study provided information useful for revising the national agroforestry research and extension agenda and has important implications for other countries in the highlands of Africa.     

Fodder production of some shrubs and trees under two harvest intervals in subhumid southern Ghana

The study was undertaken to determine the relative performance of 13 fodder trees and shrubs in herbage production and quality under two forage regrowth periods six and 12 weeks. In primary growth assessment it was found that the species which achieved the most height growth were Cajanus cajan, Sesbania sesban and Gliricidia sepium. In terms of herbage dry matter production the species which performed best were Cajanus cajan, Flemingia macrophylla, Calliandra calothrysus, Codariocalyx gyroidesand Gliricidia sepium. In crude protein content the superior species were Albizia lebbeck, Cajanus cajan, Leucaena leucocephala and Sesbania sesban. Regrowth harvests in the second year showed Gliricidia sepium, Calliandra calothrysus and Flemingia macrophylla achieve the greatest herbage yields with yields in excess of 1 t/ha obtaining at the first 12 week regrowth harvest. Albizia lebbeck, Cajanus cajan, Leucaena leucocephala and Samanean saman produced consistently very high crude protein levels (more than 20%) in the regrowth harvests. Calcium contents of herbage of all test species in the regrowth harvests were in excess of the critical minimum requirement of 0.44% for ruminant feeding. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry systems and soil surface management of a tropical alfisol: I: Soil moisture and crop yields

Field experiments were conducted on a tropical Alfisol at Ibadan, Nigeria, to evaluate the effects on soil moisture and crop yields of three agroforestry systems. Effects of agroforestry treatments involving two perennial shrubs (Leucaena leucocephala and Gliricidia sepium), each at 2-m and 4-m row spacings, were compared with no-till and plow-till systems of seedbed preparation. Measurements were made for soil properties, runoff and erosion, nutrient losses in runoff, and crop growth and yield for a uniform maize (Zea mays) and cowpea (Vigna unguiculata) rotation. All of the six plots, each measuring 70 × 10m, were established on a natural slope of about 7%. Alterations in soil properties and effects on crop growth were evaluated for six consecutive years from 1982 through 1987.Seed germination and seedling establishment of Leucaena hedgerows were satisfactory while establishment of Gliricidia from stem cuttings was unsatisfactory. Maize germination and crop stand were normal while that of cowpea were suppressed by both Leucaena and Gliricidia. Maize growth and yield were suppressed only in the vicinity of hedgerows. Maize grain yield in agroforestry systems averaged about 10 percent lower than that of the control. In contrast with maize, agroforestry systems drastically suppressed cowpea grain yield. The average cowpea yield in agroforestry systems was 30 to 50% of the control. Regardless of the mangement system, grain yields declined over time at the rate of 340 and 96 kg ha^–1yr^–1 for maize and cowpea, respectively.Hedgerows of Leucaena and Gliricidia acted as windbreaks. Consequently, soil moisture content in the top 0–5 cm layer in agroforestry systems was generally higher than that in the control during both wet and dry seasons.     

Composted shrub-prunings and other organic manures for smallholder farming systems in southern Rwanda

Organic manures are the primary source of crop nutrients in many African farming systems. The quantity of such materials that are available on farms and their quality are therefore important issues, especially in countries with limited land resources, such as Rwanda. In this study, different types of compost (including composted shrub-prunings) were compared with farmyard manure (FYM) and green manure (Calliandra calothyrsus) using beans (Phaseolus vulgaris) as test crops. The study confirmed the farmers’ general opinion that FYM has high manurial value for crop yields. Composts with P- and Ca-rich Tithonia diversifolia prunings were of similar quality as FYM or dung composts and had a higher fertilizer value than Calliandra ‘green manure’ (biomass transfer). However, the farmers’ perception of trees and shrubs as biomass and nutrient sources is still very low in Rwanda. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of intercropping maize and closely spacedLeucaena hedgerows on soil conservation and maize yield on a steep slope at Ntcheu,Malawi

A six-year soil conservation trial was conducted on a steep slope, 44%, with a subhumid climate, based on very closely spaced (90 cm) hedgerows, using three intraspecific hybrids ofLeucaena leucocephala. Soil loss averaged 2.0 t/ha per year on theLeucaena plots compared with an initial 80 t/ha per year on the unprotected control plot, falling to 27 t/ha per year after the top soil had been eroded. After 6 years, micro terraces of 35 cm high and 81 cm wide had developed on the intercropped plots, with substantially improved soil properties. Maize yield (unfertilized) were maintained at 1.5–2.0 t/ha on the protected plots, compared with a progressive fall from 0.8 to 0.5 t/ha on the sole maize control.     

Phosphorus uptake and maize response to organic and inorganic fertilizer inputs in Rubona,Southern Province of Rwanda

Green manure of multipurpose trees is known to be a good source of nutrients to crop. However, most agroforestry species do not have adequate phosphorus (P) in their leaves. Supplementing green manure with moderate dose of P is a beneficial strategy to improve food security in Rwanda. This study examines the effects of Calliandra calothyrsus Meissner, Tithonia diversifolia Hensley A.Gray and Tephrosia vogelii Hook.f. green manure applied independently or in combination with triple super phosphate (TSP) and lime on maize yield and P uptake in the Oxic Tropudalf of Rubona, Rwanda. The treatments were the control, lime at 2.5 t ha⁻¹, TSP at 25 and 50 kg P ha⁻¹, leaf of C. calothyrsus, T. diversifolia, and T. vogelii each at 25 and 50 kg P ha⁻¹, respectively. Leaf shrubs biomass, TSP and lime were applied for four consecutive seasons (2001–2004). The results showed that the combination of green manure with TSP at a rate of 50 kg P ha⁻¹ significantly increased maize yield from 24 to 508% when compared to the control and T. divesifolia combined with TSP was leading (508%). Equally, the same treatments as indicated above showed higher P uptake (15.6–18. 6 kg P ha⁻¹) than the control (5 kg P ha⁻¹) and 65% of maize yields variation was explained by total P uptake. The plant residues quality such as C:N ratio, total plant N, and P significantly influenced the variability of maize grain yields.     

Growth of ten multipurpose tree species on acid soils in Sangmelima,Cameroon

Ten multipurpose tree species were planted both in monoculture and intercropped withArachis hypogea (groundnut) in a randomized complete block with three replications. The vigrou, biomass, nutrient content, and coppicing percentage of the trees were evaluated. Intercropping with groundnuts during the establishment phase did not affect subsequent growth and development of the species.Acacia mangium, Acacia auriculiformis, Cassia siamea, Calliandra calothyrsus andParaserianthes falcataria established well, when compared toGliricidia sepium, Leucaena leucocephala, Dialum guineense, Dubocia macrocarpa andMilicia excelsa. A. mangium, A. auriculiformis, C. calothyrsus, C. siamea andP. falcataria produced the highest leaf (4 to 20 t ha^–1) and wood (12 to 37 t ha^–1) biomass yield (primary growth) at one to three years after planting. Coppicing percentage ofA. mangium A. auriculiformis andP. falcataria were relatively low (35 to 50%).C. calothyrsus andC. siamea showed the highest coppicing percentage (95 to 100%) and produced the greatest coppice biomass (9 to 13 t ha^–1). Total nitrogen and organic matter percentage of soils from under the stands of these two species were also significantly higher than that of the rest. The two species may thus be considered for use in agroforestry technologies for soil improvement on acid soils, which are typical of the moist tropics.     

The potential of alley cropping im improvement of cultivation systems in the high rainfall areas of Zambia II. Maize production

Theee trials to evaluat the potential of alley cropping in maize production on the low fertility, acidic soils in Northern Zambia are described. Leucaena leucocephala, Gliricidia sepium, Sesbania sesban, Albizia falcataria, Fleminga congesta, and Cassia spectabilis, were grown in alley crops with hybrid maize and soybean. All trials received recommended rates of P and K fertiliser; N fertiliser was applied at three rates as a subplot treatment. One trial received lime before establishment.Only in the limed trial was there a significant improvement in maize yields through alley cropping; when no N fertiliser was applied, incorporation of Leucaena leucocephala prunings resulted in an increase of up to 95% in yields, with a smaller improvement being produced by Flemingia congesta. There was a significant correlation between the quantity of prunings biomass applied and the proportional increase in maize yields over the control treatment. It is suggested that the lack of effect of most of the tree species on crop yields was due to low biomass production.An economic analysis showed that alley cropping with limed Leucaena was only profitable when fertiliser costs were high in relation to maize prices. However, lime is both expensive and difficult to obtain and transport for most small scale farmers in the region, and is therefore not a practical recommendation. It is suggested that future alley cropping research should focus on screening a wider range of tree species, including other species of Leucaena, for acid tolerance and higher biomass production.     

The effect of young Leucaena leucocephala (Lam) De Wit hedges on the growth and yield of maize,sweet potato and cowpea in an agroforestry system in Sierra Leone

An investigation was undertaken at Senehun — Kamajei, a high rainfall region in Sierra Leone, to assess the effects of Leucaena leucocephala, on the growth and productivity of maize, cowpea and sweet potato. The experiment was laid out in a completely randomised design with four replicates of each treatment. The treatments and controls were: (i) pure crops of maize, cowpea, sweet potato, Leucaena clean weeded and unweeded and (ii) intercrops of Leucaena with the food crops, both (iii) with and without applied fertilizers after the first year.The growth of Leucaena was slow but nevertheless tended to reduce grain yields of maize, and tuber and vine yields of sweet potato in the rows in the immediate vicinity of the trees, especially in the nitrogen-treated plots. The maize, in particular, caused an improvement in the early height growth of the trees.     

A study of the potential of hedgerow intercropping in semi-arid India using a two-way systematic design

The potential of hedgerow intecrropping with Leucaena leucocephala was explored on vertic Inceptisols over 4 years at ICRISAT Center, Patancheru, India. The study was conducted using a systematic layout involving different alley widths ranging from 1.35 to 4.95 m and with varying distances between hedge and crops. The alleys were cropped with alternate rows of sorghum and pigeonpea. Hedges composed double Leucaena hedgerows 60 cm apart were periodically harvested for fodder. Sole crops of all components and a sorghum/pigeonpea intercrop were included in all four replications of the study.Starting in the second year, Leucaena was progressively more competitive to annual crops, causing substantial yield reduction. Competition (primarily for moisture) was most severe in narrow alleys and was greatest on pigeonpea.The growth of Leucaena was not sufficient to compensate for reduced crop yields. Land equivalent ratios (LERs) calculated on the basis of grain yield of crops and Leucaena fodder yields showed that hedgerow intercropping (HI) was advantageous over sole crops only during the first two years using wide alleys, but disadvantegeous in the last two years. LERs calculated on the basis of total dry matter indicated only a small advantage for HI (13–17 percent) over sole crops in wider (>4 m) alleys. Average returns per year from HI exceeded those of the most productive annual crop system (sorghum/pigeonpea intercropping) by 8 percent in 4.05 m alleys, and by 16 percent in 4.95 m alleys. Fodder production during the dry season was 40 percent of the annual total in these alley widths. Thus hedgerow intercropping at 4–5 m alley width is not very attractive for farmers in semi-arid India, which has 600–700 mm of annual rainfall. There is a need to examine the potential of HI in wider alleys. The merits and limitations of the systematic design are discussed.     

Incidence and Severity of Bean Rust (Uromyces appendiculatus) in Alleys between Leucaena Hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala (Lam.) de Wit in an alley cropping system on the incidence and severity of rust (Uromyces appendiculatus (Pers.) Unger) on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over 2 years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m, 4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at 2–3 months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Rust on beans was assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Bean growth and yield were also measured. Rust increased with increasing alley width and was less severe in bean rows adjacent to hedgerows. Bean yield was highest in the treeless control plots and declined with decreasing alley width. Beans in 2 m alleys had significantly lower (p < 0.05) yields than 8 m alleys and treeless control plots. Bean growth was greatly modified in 2 m alleys and close to hedgerows. Light availability and diurnal temperature increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had marked effect on microclimate. The changes in yield, rust incidence and severity were examined in relation to microclimate, inoculum survival and dispersal.     

Tree species and pruning regime affect crop yield on bench terraces in SW Uganda

Integration of trees on farms may exert complementary or competitive effects on crop yield. This 4 year study examined novel systems in which Alnus acuminata (alnus), Calliandra calothyrsus (calliandra), Sesbania sesban (sesbania) or a mixture of all three were grown on the degraded upper part of bench terraces in Uganda; beans or maize were grown on the more fertile lower terrace during the short and long rains. Three pruning treatments (shoot, root or shoot + root pruning) were applied to the tree rows adjacent to the crops; shoot prunings were applied as green manure to the woodlot from which they came. Pruning increased survival in calliandra and reduced survival in sesbania; alnus was unaffected. Pruning reduced tree height and stem diameter in alnus, but did not affect calliandra or sesbania. Maize yield adjacent to unpruned calliandra, alnus and sesbania or a mixture of all three was reduced by 48, 17, 6 and 24% relative to sole maize. Shoot pruning initially sustained crop performance but shoot + root pruning became necessary when tree age exceeded 2 years; shoot + root pruning increased maize yield by 88, 40, 11 and 31% in the calliandra, alnus, sesbania and tree mixture systems relative to unpruned trees. Bean yield adjacent to unpruned calliandra, alnus, sesbania and the tree mixture was 44, 31, 33 and 22% lower than in sole crops and pruning had no significant effect on crop yield. The results suggest that sesbania fallows may be used on the upper terrace without reducing crop yield on the lower terrace, whereas pruning of alnus is needed to sustain yield. Calliandra woodlots appear to be unsuitable as crop yield was reduced even after pruning.