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     

Alley cropping with Leucaena leucocephala (Lam.) De Wit and Acioa barteri (Hook.f.) Engl.

The effect of alley cropping with seven combinations of Acioa and Leucaena hedgerows and a control (no hedgerow) treatment on sequentially cropped maize and cowpea was studied in 1985 and 1986. The trial was carried out on an Alfisol in the humid zone of southwestern Nigeria. Hedgerows were established in 1983, using 4 m inter-hedgerow spacing and pruned to 25 cm height during cropping. Highest dry matter, wood, and nutrient yields of prunings of Acioa and Leucaena hedgerows were obtained with sole cropping. Growing Leucaena and Acioa in the same hedgerow suppressed dry matter production and nutrient yield of Acioa more than of Leucaena owing to the latter's faster growth. Total pruning dry matter yield was reduced as the proportion of Acioa increased in the combination. Leucaena prunings had higher nutrient yield than Acioa. Under 22-month old uncut hedgerows, weed biomass declined in the presence of Leucaena, either alone or in combination with Acioa. Weed weight under sole Leucaena hedgerows was about a third of that in the control plot. There was no significant effect of alley cropping on weed biomass, although alley cropping with Acioa and Leucaena hedgerows resulted in the dominance of broadleaf weeds while the control had a mixture of broadleaves and grasses. Alley cropping with various combinations of Acioa and Leucaena hedgerows increased maize and cowpea yields compared to control. Nitrogen application in both years increased maize grain yield. Mean yield increase due to N application in both years was highest in the control (47.2%) followed by the sole Acioa hedgerow (25.2%) and less in hedgerows with Leucaena. The results of observations over two years do not show any advantage for the tested Leucaena and Acioa combinations on maize and cowpea crops as compared to the sole hedgerows. B.T. Kang (IITA), c/o Miss Maureen Larkin     

Nutrient contribution and maize performance in alley cropping systems

Dry matter yield and potential contribution of N, P and K of some woody perennials as well as performance of maize were assessed in an alley cropping system at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Dry matter yield was highest forCassia, followed byGliricidia and theFlemingia. Whereas dry matter yields ofCassia varied significantly at the various pruning times, those ofGliricidia andFlemingia were relatively uniform.Gliricidia contributed the highest amount of N from the cutback (first pruning) and three subsequent prunings. Dry wood yield at cutback was 14.5, 6.8 and 29.7 tonnes/ha forGliricidia, Flemingia andCassia respectively. Coppicing rate was faster inGliricidia thanFlemingia andCassia. Maize height, stover and cob weights were reduced though insignificantly, for the maize rows close to the shrub hedgerows compared to those in the middle of the alleys. For the plots without N application and prunings removed, the maize near the hedgerows showed better performance than those in the middle of the alleys. The results indicate that N supplementation is needed in the alley cropping systems to optimize yield. The amount of N required is higher inFlemingia alleys than forGliricidia andCassia. Root growth of maize was found to be restricted in control plots without hedges; uptake of the major nutrients (N, P and K) was also found to be similarly affected in those plots.     

Influence of root pruning and cutting interval ofLeucaena hedgerows on performance of alley croppedrabi sorghum

The influence of root pruning and cutting interval ofLeucaena hedgerows on alley croppedrabi sorghum was investigated. Paired (60 cm)Leucaena hedgerows spaced 6.6 m wide were subject to either root pruning, using a country plough during mid-kharif season, or no root pruning. The cutting frequency ofLeucaena hedgerows ranged from one month to six months during therabi cropping period. The effect on soil moisture, crop growth, yield and yield components ofrabi sorghum was examined.Root pruning ofLeucaena hedgerows increased grain and stover yields of the alley croppedrabi sorghum by 33 and 17%, respectively, over root not pruned hedgerows. Similarly, shorter cutting intervals (one and two months) increased crop yields as compared with longer cutting intervals (three and six months). The growth (height and dry matter) of the crop was similarly influenced. Soil moisture studies indicated that the competition between crop and hedgerows was considerably reduced by the root pruning. The results clearly showed that the competition between hedgerows and arable crop can be reduced considerably by root pruning and frequent cutting (at one to two months interval) of the hedgerows.     

Nitrogen fixation capacity in the component species of contour hedgerows: how important?

The choice of an appropriate hedgerow species is one of the most critical decisions in exploiting the value of a contour hedgerow system. The implications of hedgerow species with nitrogen (N)-fixation capacity on hedgerow-crop competition and crop productivity have been widely debated. We examined the agronomic significance of N-fixation by comparing the performance of species representing three classes of hedgerow vegetation: A nitrogen-fixing tree legumeGliricidia sepium), a non-nitrogen fixing tree (Senna spectabilis syn.Cassia spectabilis), and a forage grass (Pennisetum purpureum). The 4-year study investigated the hedgerow biomass and nutrient yields, and their relative effects on the performance of two annual crops commonly grown in alley farming systems, with emphasis on hedgerow-crop interference. The work was done on an Ultic Haplorthox (pH 4.8, organic C 1.9%, total N 0.18%).Senna produced 46% more pruning biomass on an annual basis than didGliricidia; N supplied to the alley crops was similar toGliricidia in the first year of observation, but 20–30% higher in the succeeding years. Upland rice and maize grain yields and total dry matter were unaffected by tree species, but the nitrogen-fixing tree exerted less competitive effects on the annual crops growing in adjacent rows. Grass hedgerows reduced maize yields 86% by the second year, indicating an unsustainable drawdown of nutrients and water. We conclude that hedgerow systems composed of a nitrogen-fixing tree did not exert significant advantages compared to a non-fixing tree species, and that factors other than N-fixation were more important determinants for the choice of hedgerow species.     

Effect of alley cropping with Leucaena leucocephala and fertilizer application on yield of vegetable crops

Field experiments were conducted to investigate the effect of alley cropping vegetable crops with Leucaena leucocephala (Lam.) de Wit for two seasons on a sandy loam Oxic paleustalf in southwestern Nigeria. Four vegetable crops (Amaranthus cruentus L.; Celosia argentea L.; Okra, Hibiscus esculentus L.; and tomato, Lycopersicon esculentum Mill.) were grown in control plots and in 4-m wide alleys between established Leucaena hedgerows without and with fertilizer (30 N-13 P-24 K kg ha^–1). Leucaena prunings yielded large dry biomass and nutrients during both seasons. Yield of four vegetable crops responded more to fertilizer in control than in alley cropped treatments. Better yield of vegetables in alley cropped plots was in part due to following effect of the Leucaena hedgerows. Fertilizer application increased mean yields of Amaranthus, Celosia, okra and tomato by 325, 164, 47 and 94% in control plots and by 36, 26, 4 and 20% in alley cropped plots, respectively. For both seasons, yields were not significantly different between alley cropped with and without fertilizer and the control with fertilizer treatments. Yield was least in control without fertilizer. Alley cropping with Leucaena can reduce fertilizer requirement for vegetable production. Cost and return analysis using 1988 prices indicated that alley cropping with vegetable crops can be profitable.c/o Miss Maureen Larkin, L. W. Lambourn & Company, 26 Dingwall Road, Croydon CR9 3EE, England     

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.     

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.     

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.     

Above and below ground interactions in alley-cropping in semi-arid India

The influence of micro-environment on the growth and yield of cowpea, castor and sorghum was investigated in a 10 m wide alley cropping system. The alleys were formed by Leucaena hedgerows pruned for both fodder and pole production. Below-ground interaction was examined by installing a polythene root barrier between the root systems of crops and Leucaena and by measurements of both soil moisture and root growth. Microclimate measurements included light, wind speed, humidity and temperature.Growth and yield of crops declined from 150 to 30% of sole crop as the distance from the hedgerows decreased from 5 to 0.3 m. The presence of the root barrier had a marked effect on crop growth and completely eliminated any reduction in crop yield, although shading by the hedgerows reached 30 to 85% of full sunlight. There was some modification of the microclimate in the alleys but the changes were not great enough to significantly influence crop yield. The substantial increase in crop yield in the middle of the alleys was explained by the residual effect of a previous hedgerow, removed 12 months previously, on probably the infiltration rate and nutrient status of the soil. These results clearly showed that alley cropping in the semi-arid tropics induces competition for moisture between the trees and crops which may severely reduce crop yield.     

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.     

Above- and below-ground biomass dynamics in a sole cropping and an alley cropping system withGliricidia sepium in the semi-deciduous rainforest zone of West Africa

A considerable amount of data is available about above-ground biomass production and turnover in tropical agroforestry systems, but quantitative information concerning root turnover is lacking. Above- and below-ground biomass dynamics were studied during one year in an alley cropping system withGliricidia sepium and a sole cropping system, on aPlinthic Lixisol in the semi-deciduous rainforest zone of the Côte d'Ivoire. Field crops were maize and groundnut. Live root mass was higher in agroforestry than in sole cropping during most of the study period. This was partly due to increased crop and weed root development and partly to the presence of the hedgerow roots. Fine root production was higher in the alleys and lower under the hedgerows compared to the sole cropping plots. Considering the whole plot area, root production in agroforestry and sole cropping systems was approximatly similar with 1000–1100 kg ha^–1 (dry matter with 45% C) in 0–50 cm depth; about 55% of this root production occured in the top 10 cm. Potential sources of error of the calculation method are discussed on the basis of the compartment flow model. Above-ground biomass production was 11.1 Mg ha^–1 in sole cropping and 13.6 Mg ha^–1 in alley cropping, of which 4.3 Mg ha^–1 were hedgerow prunings. The input of hedgerow root biomass into the soil was limited by the low root mass ofGliricidia as compared to other tree species, and by the decrease of live root mass of hedgerows and associated perennial weeds during the cropping season, presumably as a result of frequent shoot pruning.     

Yields of maize/cassava intercrops grown with hedgerows of three multipurpose trees on an acid Ultisol of Cameroon

Maize/cassava were intercropped between hedgerows of Senna spectabilis [(DC.) Irwin and Barneby], Flemingia macrophylla [(Willd.) Merrill] and Dactyladenia barteri [(Hook f ex Oliv.) Engl.] for five consecutive years on an Ultisol in southern Cameroon. Crop yields and hedgerow biomass production in the third to fifth year of cropping are reported. S. spectabilis produced more biomass than F. macrophylla and D. barteri in all years. Cumulative maize grain and cassava tuber yields were highest in F. macrophylla alley cropping, outyielding the no-tree control consistently by 42 to 67% (average 56%). Between hedgerows of D. barteri and S. spectabilis, crops yielded 17% and 16% more than the no-tree control, respectively. However, between S. spectabilis hedgerows, yields were highly variable between years (–15% to +35% compared to the no-tree control) and thus the system is at risk of failure. F. macrophylla is recommended for continuous alley cropping of maize/cassava intercrop. The use of D. barteri may require fallow phases for biomass accumulation followed by cropping phases with rigorous pruning. Although this may lead to lower cumulative yields, the products of the fallow phase, such as stakes and firewood, may provide some compensation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Volunteer biomass production between multipurpose tree hedgerows after two years of fallow in southern Cameroon

The ability of multipurpose hedgerow tree species to out-compete undesired regrowth during fallow phases was examined. Biomass and spatial distribution of grass and broad leaf volunteers was measured after two years of fallow, in two alley cropping systems planted at six m interrow distance, at the Humid Forest Ecoregional Centre Research Station, Mbalmayo, southern Cameroon. The two experiments had been continuously cropped for five and six years previously. In the experiment cropped for six years, the presence of Senna spectabilis [(DC.) Irwin and Barnaby] hedgerows reduced the biomass of the volunteer regrowth from 9.2 to 4.3 Mg ha⁻¹. Tillage during the previous cropping phase increased the broad leaf biomass from 3.0 to 4.4 Mg ha⁻¹, reduced the biomass of grasses from 3.4 to 2.7 Mg ha⁻¹ but had no effect on the total volunteer biomass. Volunteer biomass was significantly lower within 1.5 m of the S. spectabilis hedgerows than at positions further away. In the experiment cropped for five years, S. spectabilis reduced the volunteer regrowth biomass significantly. Two other hedgerow species, Dactyladenia barteri [(Hook f ex Oliv.) Engl.] and Flemingia macrophylla [(Willd.) Merrill] had no effect on the total amount of volunteer regrowth but did reduce volunteer biomass within 0.5 m of the hedgerows. S. spectabilis caused a stronger reduction of volunteer biomass than D. barteri and F. macrophylla at almost all distances from the hedgerows. The competitiveness of D. barteri and F. macrophylla is insufficient and their growth habit is unsuitable to out-compete undesired species in this alley cropping system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pattern of soil moisture depletion in alley cropping under semiarid conditions in Zambia

The pattern of soil moisture changes was studied during a cropping season in an alley cropping experiment of maize withLeucaena leucocephala andFlemingia macrophylla at the SADC/ICRAF Agroforestry Research Station in a semiarid region near Lusaka, Zambia (28°2956 East and 15°2132 South). Soil moisture potential was monitored at regular intervals using tensiometers installed at 15, 30 and 45 cm depths in fertilized and unfertilized alleys within the double hedgerow, and the first, second and third rows of maize in the alleys.Soil moisture moved mostly towards the top horizon during very dry conditions. Alleys that had received a combination of fertilizer and hedgerow prunings depleted more moisture than those that had only hedgerow prunings. There were no differences in moisture utilization pattern between leucaena and flemingia hedgerows. The hedgerows depleted the same amount of moisture as the maize plants. However, during dry conditions, there was a higher soil moisture content under the hedgerows than in maize rows, indicating that there was no apparent competition for moisture between the hedgerows and the maize plants.     

The effects of between-row (alley widths) and within-row spacings ofGliricidia sepium on alley-cropped maize in Sierra Leone

The effects of spacings between hedgerows (alley widths) and the spacings of trees within hedgerows ofGliricidia sepium on growth and grain yield of maize were investigated at Senehun in southern Sierra Leone. Four between-row spacings (2, 4, 6 and 8 m) were combined with three within-row spacings (0.25, 0.50 and 1.00 m) in a split block design. Maize, at densities of 20,000, 40,000 and 53,333 plants ha^–1, was established in the alleys and also as pure crops. N, P and K fertilizers were applied to all plots before pruning of the trees began. When pruning started, only the pure maize plots received fertilizer; prunings from the hedgerows were returned to the appropriate alleys in the other plots.Plots with the highest maize populations consistently gave the best yields before pruning started, but lower populations gave improved yields after pruning. Yields of maize increased with increasing alley widths before the start of pruning, after which the narrower alleys of 2 and 4 m outyielded the wider ones by almost double, probably because of the large amount of nutrients applied in prunings. Lack of light limited grain yields before the start of pruning, when there was some shading by the hedgerows. Alleys of 2–4 m wide, planted no closer than 0.50 m within rows, resulted in more than twice the yields of maize than in the 8-m alleys planted at 0.25 m within rows, once the hedgerows were well established and were being managed.     

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.     

Alley cropping Sesbania sesban (L) Merill with food crops in the highland region of Rwanda

Food production in the densely populated Rwandan highlands is impeded by soil erosion and loss in fertility. Alley cropping leguminous shrubs with food crops on contours is purported to minimize the problem and to provide wood and forage. This study reports the effect of Sesbania prunings plus moderate levels of N and P on bean (Phaseolus sp) and maize (Zea mays) yields in alley cropping. Experimental design was a randomized complete block with split-split plots. Main plots were alley width: 2, 4, 6 and 8 m. Phosphorus (P) at 0, 30 and 60 kg P₂O₅/ha occupied the subplot and nitrogen (N) at 0, 30 and 60 kg/ha were assigned at the sub-sub plot level. No P was applied to maize during the second cropping season. Crop yield in kg/ha included the land space taken by hedgerows. Bean yield in 6 m alleys (1100 kg/ha) was about twice that in 2 m alleys (500 kg/ha). Bean responded to N and P. Optimum alley width and N for bean yield were 6 m and 30 kg/ha, respectively. Cuttings from alley hedgerows provided stakes for climbing beans. Maize responded to N but not to residual P. The highest maize yield came from 8 m alleys with 40 kg/ha, but yields from 8 and 6 m alleys with the same N treatment were not significantly different. Maize plants in middle rows were significantly taller than plants in rows adjacent to hedgerows. Maize rust development showed significant alley width and row position effect. There were significantly fewer uredinia in the Sebania alleys relative to the control plots without shrub hedgerows. Rust development on maize in middle rows was significantly greater than development in border rows.     

Insect pests and beneficial arthropods population under different hedgerow intercropping systems in semiarid Kenya

Exploiting the principles of biological control of crop pests is an important management strategy for the resource-poor smallholder farmers of the tropics. The effects of nine hedgerow species on the abundance of major insect pests of beans and maize, and predatory/parasitic-arthropods were monitored over two cropping seasons and the intervening dry period. The tree/shrub species evaluated were Gliricidia sepium, Grevillea robusta, Senna siamea, Senna spectabilis, Flemingea congesta, Croton megalocarpus, Morus alba, Calliandra calothyrsus and Lantana camara. Arthropod abundance was monitored through counts of infested plants and using yellow pan and pitfall traps. Beanfly (Ophiomyia spp.) infestation was significantly higher in the presence of hedgerows (35%) than in their absence (25%). Hedgerows did not influence aphid (Aphis fabae) infestation of beans. In contrast, maize associated with hedgerows experienced significantly lower stalk borer (Busseola fusca and Chilo spp.) and aphid (Rhophalosiphum maidis) infestations than pure maize, the margin of difference being 13% and 11% respectively for the two pests. Ladybird beetles closely followed their prey, aphids, with significantly higher catches in sole cropped-plots than in hedgerow-plots and away from hedgerows. Activity of wasps was significantly greater close to hedgerows than away from them. Spider catches during maize season were 77% greater in the presence of hedgerows than in their absence, but catches during other seasons were similar between the two cropping systems. Differences among hedgerow species were not significant for most of the arthropods monitored, except that beanfly infestation was greater with Gliricidia hedgerows. The study indicates that the effect of hedgerows on pest infestations of crops and their role as refugia for predators cannot be generalized but depends on the specific arthropods.This revised version was published online in November 2005 with corrections to the Cover Date.     

Agroforestry systems and soil surface management of a tropical alfisol:

Field runoff plots, 70 x 10 m each, were established on a tropical Alifisol in southwestern Nigeria to monitor water runoff, soil erosion and nutrient loss in water runoff. The non-agroforestry control treatment (A) was established at two levels: plow-till and no-till systems of seedbed preparation. There were two agroforestry systems based on contour hedgerows of (B) Leucaena leucocephala and (C) Gliricidia sepium established at 4-m and 2-m spacings. Field plots were established in 1982 and hydrological measurements were made for uniform maize-cowpea rotation for 12 consecutive growing seasons from 1982 through 1987. Once established hedgerows of Leucaena at 2-m spacing were extremely effective in reducing water runoff and controlling erosion. Runoff, erosion and nutrient losses were generally more from maize grown in the first season than from cowpea grown in the second. Mean seasonal erosion from maize was 4.3, 0.10, 0.57, 0.10, 0.64 and 0.60 t/ha for plow-till, no-till, Leucaena-4m, Leucaena-2m, Gliricidia-2m treatments, respectively. Mean runoff in the first season from treatments listed in the order above was 17.0, 1.3, 4.9, 3.3, 4.3, and 2.4 percent of the rainfall received. There were high losses of Ca and K in water runoff from the plow-till treatment. In contrast to runoff and erosion, losses of bases in water runoff from agroforestry treatments were relatively high, high concentration of bases in runoff was probably due to nutrient recycling by the deep-rooted perennials.