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.     

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     

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.     

Productivity of annual cropping and agroforestry systems on a shallow Alfisol in semi-arid India

An experiment was conducted at ICRISAT Center, Patancheru, India from June 1984 to April 1988 on a shallow Alfisol to determine whether the productivity of annual crop systems can be improved by adding perennial species such as Leucaena leucocephala managed as hedgerows. Except in the first year, crop yields were suppressed by Leucaena due to competition for moisture. The severity of competition was high in years of low rainfall and on long-duration crops such as castor and pigeonpea. Based on total biomass, sole Leucaena was most productive; even on the basis of land productivity requiring both Leucaena fodder and annual crops, alley cropping had little or no advantage over block planting of both components. Application of hedge prunings as green manure or mulch on top of 60 kg N and 30 kg P ₂ O ₅ha⁻¹ to annual crops did not show any benefit during the experimental period, characterized by below average rainfall. Indications are that (i) alley cropping was beneficial in terms of soil and water conservation with less runoff and soil loss with 3 m alleys than with 5.4 m alleys, and (ii) root pruning or deep ploughing might be effective in reducing moisture competition.     

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.     

The potential of alley cropping in improvement of cultivation systems in the high rainfall areas of Zambia. III. Effects on soil chemical and physical properties

A detailed study of the soil chemical and physical properties in seven-year-old alley cropping trial containingLeucaena leucocephala andFlemingia congesta in Northern Zambia is described. There was a strong correlation between the maize yield and the total amount of nitrogen applied, both from prunings and fertiliser, suggesting that a major reason for the observed benefit from alley cropping, particularly withLeucaena, was due to an improvement in nitrogen supply.Leucaena produced significantly more biomass, and its leaves had higher concentrations of nitrogen, phosphorous and potassium and lower C/N and C/P ratios than did those ofFlemingia. There was also evidence that the trees had a beneficial effect on other soil chemical properties; under the hedgerows, particularly those ofLeucaena, there were higher levels of organic carbon, Mg, K and ECEC, and pH values were also highest.It is suggested that higher levels of organic carbon in the alley crop treatments were responsible for the improvements observed in soil physical properties. Lower bulk density, lower penetration resistance, and a higher infiltration rate and pore volume fraction were measured in the alley crops, although there was no significant change in the soil water release parameters.A deteriorating effect of constant applications of nitrogen fertiliser on soil fertility was observed; as the level of urea application increased, there were significant decreases in Mg, K and pH, increases in Al and soil acidity, and higher penetrometer resistance. These results highlight the urgent need for further research on biological methods of maintaining soil fertility.     

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.     

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.     

Intercropping field crops between rows of Leucaena leucocephala under rainfed conditions in northern India

A field study was conducted for six years (1981–1986) on sandy loam soil on intercropping hedgerows of Leucaena leucocephala (Lam) de Wit. with three field crops viz. maize (Zea mays L), black gram (Vigna mungo L) and cluster bean (Cyamopsis tetragonoloba L Taub.). In treatments 1 and 2 Leucaena hedges were planted as pure crops at close (25 cm × 75 cm) and wide (25 cm × 375 cm) spacings. In treatments 3, 4 and 5 the three field crops were intercropped between the hedgerows of Leucaena at the wide spacing, and in treatments 6, 7 and 8 the field crops were raised as pure crops. Leucaena was topped to 75 cm each time it attained a height of 175 cm. The pure crop of Leucaena at close spacing produced an average, over the six years, of 34 t ha⁻¹a⁻¹ of green fodder and 9.4 t ha⁻¹a⁻¹ of air dry fuelwood. The Leucaena at wide spacing produced 18.9 t ha⁻¹a⁻¹ of green fodder and 6.3 t ha⁻¹a⁻¹ of fuelwood. Intercropping with field crops decreased the yield of green fodder and fuelwood. The yield of all the field crops was less when raised as intercrops than as pure crops. Mean maximum net returns were obtained from intercrops of Leucaena and cluster bean (Rs 3540 ha⁻¹a⁻¹) which were significantly higher than the returns from pure crop of Leucaena at wide spacing but similar to the returns from pure crops of cluster bean. Leucaena with maize (Rs 3273 ha⁻¹a⁻¹) and black gram (Rs 3125 ha⁻¹a⁻¹) gave significantly higher net returns over pure crops of Leucaena at wide spacing, maize and black gram. ICRISAT = International Crops Research Institute for the Semi-Arid Tropics- Hyderabad, India. CIAT = Centro International de Agricultura Tropical - Cali - Columbia     

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     

A tree/crop interface design and its use for evaluating the potential of hedgerow intercropping

The paper describes a tree/crop interface (TCI) experiment designed to investigate the effects of row orientation using Leucaena leucocephala Lam. Each TCI plot consisted of a regularly pruned Leucaena hedge in the middle and 12 crop rows on either side. Eight such plots were arranged at 45° around a sole Leucaena plot with rows oriented in four compass directions viz., North-South, East-West, Northeast-Southwest and Northwest-Southeast.Results of four years from 1984 to 1987 did not show any effect of row orientation, and similarly, no effect was seen on crop rows due to their location on the windward or leeward side of the hedge. The TCI effect was positive on the first crop row in the first year because Leucaena grew slowly, but depressed the yield of the first 4 to 6 crop rows(1.8 to 2.7 m from hedge) in subsequent years. The negative effect of Leucaena was noted more on sunflower in a relatively dry year than on sorghum in other years.Results from the TCI plots were used to estimate the yield of five hedgerow intercropping (HI) systems with varying alley widths (2.7 to 9.9 m). Comparison with sole stands of Leucaena and crops indicated that HI was more productive particularly at close alley widths. For example, hedges spaced at 2.7 m and 3.6 m averaged 37% and 25% higher productivity than the respective sole stands; but this advantage may be an overestimation of the real potential.The relevance of TCI experiments for studying agroforestry systems, their merits and limitations, especially of the design employed in this study are discussed.     

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.     

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     

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.     

Canopy management possibilities for arboreal Leucaena in mixed sorghum and livestock small farm production systems in semi-arid India

A major problem for small farmers in the semi-arid tropics is the chronic shortage of fodder for draft animals. Leucaena leucocephala has improved productivity in many places in India and in various cropping systems, usually as either a pure crop or in a hedgerow alley-cropping configuration. Mixed cropping with arboreal forms is seldom seen. For off-season fodder production, hedgerows have the disadvantage of being open to unmanaged browsing when unfenced (as is usual). Arboreal forms are generally far less vulnerable. In this paper, the components of production of sorghum and arboreal Leucaena are measured under different intensities of canopy lopping. The most productive management system of those examined was pollarding of the Leucaena at the time of under-sowing with sorghum. In a year with less than 50% of average seasonal rainfall, this system gave a yield of 4.6 tonnes/ha/yr fresh wt fodder and 3.8 tonnes/ha/yr dry wt. of fuel harvests, while increasing the standing crop of wood by 1.8 t/ha/yr and retaining a yield of sorghum grain equivalent to 46% of pure sorghum cropping; the LER of this system was 1.35. Cash values of the alternative management systems were estimated, including the discounted Net Present Value of the standing crop of timber. Maximum value was attained with unlopped pure crop Leucaena followed by pollarded Leucaena with sorghum; pure crop sorghum achieved a lower value. These results demonstrate both the high productivity of Leucaena/sorghum based systems, and the stability of production even in poor rainfall conditions. Pollarding transferred the high future value of Leucaena timber to the present value of sorghum grain and fuelwood.     

Competition for light between hedgerows and maize in an alley cropping system in Hawaii, USA

Successful agroforestry systems depend on minimizing tree-cropcompetition. In this study, field experiments and a simulation model were usedto distinguish between tree-crop competition for light and belowgroundcompetition in an alley cropping system. Maize (Zea maysL.) was harvested periodically in three treatments: between vertical barriers ofshade cloth, hedgerows of Flemingia macrophylla (Willd.)Merr., and sole maize. Radiation intercepted by the maize was calculated using asimulation model based on measured values for direct and diffuse light, hedgerowdimensions and leaf area, and solar trajectory. Radiation use efficiency wascalculated as biomass production per unit of intercepted radiation. Maizebiomass and yield in both the alley crop and the shade cloth treatment weregreatest in the center of the alleys. Grain yield between hedgerows was 3.5Mg ha⁻¹ (averaged across the alley), significantlyless than in the shade cloth (7.4 Mg ha⁻¹) or thesole maize (7.7 Mg ha⁻¹) treatments. Lightintercepted by the maize in the alley crop was about half that intercepted bythe maize in the sole crop. The shade cloth intercepted less light than thehedgerows because it did not have an appreciable width. Radiation use efficiencyin the three treatments was 0.75 g mol⁻¹ PAR anddid not differ significantly among treatments. Tree-crop competition wasoverwhelmingly for light. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

Leaf quality of selected hedgerow species at two canopy ages in the derived savanna zone of West Africa

Prunings in hedgerow intercropping systems are a potential source of organic matter and their quality is an important characteristic driving decomposition and nutrient release. To determine the potential range of residue characteristics and the impact of canopy age on those, selected characteristics of Leucaena leucocephala, Gliricidia sepium, and Senna siamea hedgerow leaf residues were determined for young (5–10 weeks) and old (39–47 weeks) hedgerow canopies in six sites, representative in terms of soil for the derived savanna zone of West-Africa. The N content of the Leucaena and Senna residues decreased with age (from 4.8 to 3.9% and from 4.1 to 3.0%, respectively, while the N content of the Gliricidia residues remained constant (3.9%). The P content of all species decreased with age (from 0.30 to 0.20%, on average). The lignin content of the Leucaena residues increased, and their polyphenol content decreased with age, while for the Senna residues only an increase in polyphenol content with canopy age was evident. Neither the lignin nor the polyphenol content of the Gliricidia leaf residues was markedly affected by canopy age. For all species, the P and ADF content were positively correlated with the ash and lignin content, respectively. The N content of the Leucaena and Senna residues was positively correlated with their P content while the lignin content of the same species was negatively correlated with the polyphenol content. Because of the low variation in certain residue characteristics between sites, the presented data and equations could potentially be used to reasonably estimate those characteristics if no other information is available. For other characteristics, such as polyphenol contents, measurements are preferable in view of the relatively high variation encountered.This revised version was published online in November 2005 with corrections to the Cover Date.     

Early growth of alley shrubs in the Highland region of Rwanda

Early growth of some woody shrubs used in alley cropping were studied in the Buberuka Highland and Central Plateau region of Rwanda. The altitudinal ranges for the two agroecological zones are 1800–2400 m and 1500–1900 m respectively. First, early growth of Sesbania sesban (Sesbania) as affected by intercropped bean, potato, pea and wheat was studied. Second, effect of lime and manure applications on growth of Sesbania, Leucaena sp (Leucaena), Calliandra Calothyrsus (Calliandra) and Markhamia lutea (Markhamia) was investigated. Third, growth of Sesbania and Leucaena at selected locations were examined. Bean grown in association with Sesbania enhanced the growth of the shrub in the Central Plateau region. At both sites, growth of Sesbania was retarded by intercropped pea. Growth of Sesbania increased significantly during the dry season in June and July. Biomass and height after one years' growth of Sesbania were higher in the Buberuka than in the Central Plateau region. Growth of the shrubs is ranked as: sesbania > Leucaena > Calliandra > Markhamia in the Buberuka Highlands. Farmyard manure generally increased the growth rates of the shrubs. Calliandra and Leucaena were most responsive to liming. The response of Leucaena to liming decreased with manure application but no definite trend was observed for Calliandra, Sesbania and Markhamia. Sesbania and Markhamia were least influenced by application of lime. Their respective LRI's were 0.35 and 0.46. The average growth rates for Sesbania and Leucaena at selected locations ranged between 26.4–62.2 cm/month and 13.1–27.4 cm per month respectively.Contribution from the University of Arkansas' USAID supported Farming Systems Research Program (FSRP) in Rwanda (USAID 696-0110), BP 625, Kigali Rwanda