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.     

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 4. The economic return of ecological knowledge

We tested the economic value of ecological knowledge in a midwestern USA alley-cropping system where row crops are planted in alleys between fine hardwood trees grown for veneer. Economic models were constructed to compare among agroforestry designs as well as to compare agroforestry with traditional forest plantation culture and row crop monoculture and rotational management. The general modeling approach was to quantify production inputs and outputs, estimate costs and revenues, simulate tree growth and crop productivity in agroforestry configurations, and estimate discounted cash flows. We incorporated scenarios that controlled both above- and below-ground competition through appropriate management as found in our previous research. This research showed the importance of below-ground competition in determining crop yields and the period of time that crop income could be expected from the agroforestry interplanting. Net present values and internal rates of return showed that agroforestry systems were generally more favorable investments than traditional agriculture and forestry. More importantly, the use of simple management techniques targeted at reducing below-ground competition allowed longer cultivation of row crops, greatly increasing returns to the landowner. Thus, the economic benefit of understanding the ecological interactions within agroforestry plantings dictates that accurate assessment of agroforestry alternatives will require the modeling of agroforestry as an integrated, interactive system.This revised version was published online in November 2005 with corrections to the Cover Date.     

Residue management of a planted fallow on an acid soil in Cameroon: crop yields and soil organic matter fractions

A fallow management trial was initiated in March 1990 in Yaounde, Cameroon, with the objective of identifying an efficient method of managing residue derived from a planted fallow of Cajanus cajan. Ten months after establishment, the shrubs were slashed and residues were treated in one of the following ways: burnt, incorporated in the soil, mulched on soil surface or removed. Following that, maize and groundnut were planted. Soil organic matter was fractionated after the residue treatments, and elementary partial budgeting was conducted. After three cycles of fallow and cropping seasons, maize yield was similar, about 3 t ha^-1, in all plots except in the residue-removed plots, where it was 1.4 t ha^-1. Yield trend of groundnut was also similar. The residue management method did not affect either the nature of fractions or the total content of soil organic matter. The highest net return, US$5945 ha^-1 year^-1, was obtained from the residue incorporated treatment, whereas the highest return to labour, US$11 per manday^-1 was associated with burning of residues. In areas such as the forest zone of Cameroon where labour is a major constraint and climatic conditions allow vigorous vegetation growth, burning appears to be the best method of residues management, at least in the short run. This revised version was published online in June 2006 with corrections to the Cover Date.     

Performance of a maize/cassava intercrop in tilled and no-till Senna spectabilis alley cropping on an Ultisol in southern Cameroon

An intercrop of maize and cassava was cultivated for six consecutive years from 1990/91 to 1995/96. This paper reports on crop performance from the fourth to the sixth year in alley cropping with Senna spectabilis and in a no-tree control, with and without tillage. Maize grain yield increased significantly from 1993 to 1994 (P = 0.0032) and from 1994 to 1995 (P = 0.019). Tillage only had a significantly positive effect on maize grain yield in 1993. Alley cropping had no significant effect on maize grain yield in any year. Cassava root yield was neither affected by tillage nor by alley cropping in any year. Neither the cumulative yields over the three years nor the sum of maize grain and cassava root yield were significantly affected by alley cropping or tillage. No significant interactions were found between cropping system and tillage system.This revised version was published online in November 2005 with corrections to the Cover Date.     

Yield of plantain alley cropped with Leucaena leucocephala and Flemingia macrophylla in Kumasi, Ghana

The decline in yield of plantain has partly been attributed to inadequate soil moisture and pests, particularly nematodes. The objectives of the study therefore were to determine the effect of mulch from Leucaena leucocephala and Flemingia macrophylla (Willd.) Merr. grown as hedgerows on (i) soil moisture and temperature (ii) growth and yield of plantain and (iii) pathogenic nematode populations. The study was conducted from 1991 to 1994 in Kumasi, Ghana. Treatments comprised of leguminous plants, L. leucocephala and F. macrophylla, and a control (no leguminous plants), arranged in a randomised complete block design with four replications. The leguminous plants were planted in 1991 while the plantain was planted in 1992. Results indicated that the highest biomass yield was produced by F. macrophylla. Mulching with prunings of F. macrophylla resulted in significantly (P < 0.05) higher retention of soil moisture and lower soil temperatures than mulching with prunings of L. leucocephala. Growth of plantain determined by plant height, leaf production, pseudostem girth and yield were significantly greater in F. macrophylla mulched plots than L. leucocephala treatment and control plots where no mulch was applied. Plant parasitic nematodes isolated were Meloidogyne spp., Pratylenchus spp., Paratylenchus spp., Helicotylenchus spp., and Rotylenchus spp. Three years after planting of hedgerows, significantly (P < 0.05) higher populations of Meloidogyne spp. (367 per 100 g soil), Paratylenchus spp. (92 per 100 g soil), Helicotylenchus spp. (8 per 100 g soil), and Rotylenchus spp. (308 per 100 g soil) were associated with L. leucocephala hedgerow than with Flemingia macrophylla hedgerow (42.0, 83.0 per 100 g soil) and the control (74.50, 41.0 per 100 g soil). F. macrophylla has qualities that suppress nematode populations. The results clearly indicated the superiority of Flemingia macrophylla over Leucaena leucocephala as mulch for plantain production.This revised version was published online in November 2005 with corrections to the Cover Date.     

Leucaena + maize alley cropping in Malawi. Part 2: Residual P and leaf management effects on maize nutrition and soil properties

Agroforestry systems involving leaf removal for animal fodder may result in rapid depletion of soil fertility. The purpose of this research was to determine if the effects of leaf removal on soil fertility parameters and maize yield in a Leucaena leucocephala alley cropping system could be reversed. Three leaf management strategies in a Leucaena alley cropping trial that had been in effect from 1987 to 1991 were investigated: 1) leaves returned, 2) leaves removed, and 3) leaves removed, with 100 kg inorganic N ha⁻¹ added. In the 1990/91 season, a 3⁴ confounded factorial design was utilized to investigate the effects of leaf management strategy, N rate (0, 30 and 60 kg N ha⁻¹); maize plant population (14,800, 29,600, and 44,400 plants ha⁻¹); and P rate (0, 18, and 35 kg P ha⁻¹). In the 1991/92 and 1992/93 seasons, leaves were applied equally to all plots, and no P was applied. The N rate and plant population treatments were continued, and the same confounded factorial design was implemented to investigate residual leaf management strategy, residual P rate, n rate, and plant population. The yield gap between the plots where leaves had been returned vs. removed narrowed each season due to uniform leaf application. Application of N improved yields during both seasons. Residual effects of the initial P application decreased to only 10% of the total yield in 1992/93. Plant population affected yields only during the season of very good rainfall. Leaf additions resulted in a relative increase in soil pH, total N,and exchangeable Ca, Mg, and K and a decrease C/N ratio in plots that had not previously received leaves. Leaves supplied more K and Zn to the upper 15 cm of soil than were being extracted by the maize crop, but uniform leaf additions eliminated differences in K and Zn uptake. Plant Zn uptake decreased with increasing P rate and plant population, and increased with increasing N rate and a history of leaf return. The results show that applying leaves equilibrated yields within two seasons, and resulted in a relative improvement of several soil properties. The residual effect from P applications was not adequate to maximize yields.     

Alley cropping of sorghum with Leucaena during the post-rainy season on Vertisols in semi-arid India

A field experiment was conducted for two years (1989– 1991) on a Vertisol in Bijapur, India in a split-plot design, replicated four times, to evaluate the potential of alley cropping post-rainy season sorghum between Leucaena hedgerows. Leucaena produced on average 2.74 t per ha of prunings and 1.57 t per ha of wood annually. Alley cropping decreased sorghum yields by 28 to 45% when all Leucaena prunings were removed from the system and by 21 to 24%, when on average 1.92 t per ha prunings were applied to the soil annually. The reduction of sorghum yield increased as higher rates of N were applied to sorghum. Although alley cropping increased organic carbon by 21% and available N by 19% at the time of crop sowing, it did not result in increased crop yields because of competition for water between hedgerows and crops. Calculation of land equivalent ratios based on total Leucaena biomass indicated that alley cropping was more productive than sole cropping of sorghum only in one year, and that, too, when no N was applied to sorghum. Therefore, alley cropping of Vertisols with post-rainy season sorghum is not likely to have any advantage in the short term. This revised version was published online in June 2006 with corrections to the Cover Date.     

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     

Soil nitrogen dynamics in alley cropping and no-till systems on ultisols of the Georgia Piedmont, USA

On highly-weathered Ultisols of the Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping presents an option for rapidly increasing soil nitrogen availability while restoring long-term soil fertility. Three years after the establishment of Albizia julibrissin hedgerows and no-till agriculture trials, we measured inorganic soil nitrogen (NO₃ ^-–N and NH₄ ^-–N) and net nitrogen mineralization during a 4-month field study and a 14-day laboratory study . We also measured the influence of tree leaf amendments on grain sorghum production and N uptake. Soil nitrate increased four-fold within two weeks of adding Albizia leaf mulch. Soil ammonium did not increase as rapidly nor to the same extent after tree mulch addition. Averaged over the 4-month study, soil nitrate and ammonium were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till plots. Net nitrification and mineralization were no higher in the alley cropping plots, during either field or laboratory incubations. Tree mulch additions enhanced crop biomass production and N uptake 2 to 3.5 times under both high and low soil moisture conditions. Our study demonstrates the dramatic short-term impacts of Albizia mulch addition on plant available nitrogen. Combined with no-till practices, alley cropping with Albizia hedges offers Piedmont farmers an option for reducing reliance upon chemical N fertilizer while improving soil organic matter levels. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Effect of soil fertility on early growth of Leucaena and Gliricidia in alley farms

Young leucaena (Leucaena leucocephala (Lam) de Wit) and gliricidia (Gliricidia sepium (Jacq) Steud) alley-cropped with food crops on farmers' fields in southwestern Nigeria showed marked variability in growth and foliage coloration. A field study was undertaken to determine whether variability in soil fertility was responsible for the differential growth of the two tree species. Plant height of leucaena and gliricidia at 6 and 9 months after planting (MAP) were significantly correlated with soil organic C and total N. Dry matter yield at 12 MAP was also significantly correlated with plant height, soil organic C and total N for leucaena but not for gliricidia. Soil and plant N concentrations were significantly higher in farms with normal than those with chlorotic plants.     

Effects of no-tillage and alley cropping on soil properties and crop yields in a Typic Kandiudult of southern Cameroon

The effects of no-tillage and alley cropping withCassia spectabilis hedgerows on soil properties and crop yields in a Typic Kandiudult of the humid forest zone of Central Africa were studied over the period 1990–1992 in southern Cameroon. The experimental treatments were no-tillage and hand tillage, both of which were either alley cropped withC. spectabilis hedgerows at interhedgerow spacings of 6 m or not alley cropped (control). A maize + cassava intercrop was planted in all plots at the commencement of each growing season.No-tillage had no significant effects on soil physical properties except to decrease soil temperature. In comparison to hand tillage, no-tillage increased soil organic C and total N in both years and pH in 1991. Mean organic C and total N with no-tillage were 1.77% and 0.174%, respectively, whereas with hand tillage were 1.35% and 0.145%, respectively. Notillage also resulted in a greater proportion ofC. spectabilis roots occurring in the topsoil. Alley cropping caused significant reductions in dry season soil temperature, surface seal formation and cassava root growth, and increases in exchangeable Ca, effective CEC and water infiltration compared with non-alley cropped controls. Infiltration rate at 2 h after commencing measurements were greater by 75% with alley cropping. Lowest maize cob and cassava tuber yeilds were observed when no-tillage was combined with alley cropping whereas highest yields occurred with no-tillage alone.     

The effects of alley cropping withLeucaena leucocephala and of different management practices on the productivity of maize and soil chemical properties in lowland coastal Kenya

The effects of leucaena hedgerows, mulching with leucaena foliage (0,50 and 100% of harvested foliage), cowpea intercropping and adition of dairy cattle slurry (55 t ha^–1 per maize crop) on the yield of maize from a sandy soil were assessed. The four-year results from five maize crops are reported.Except in the first year, yields of maize grain and stover were significantly reduced by 30% in the presence of leucaena hedgerows. Use of leucaena mulch eliminated this effect; application of all the harvested leucaena mulch (100%) increased the total maize grain yield of the five crops by 44% over sole maize. Hedgerow and mulching management required an additional 36 mandays labour ha^–1 which was more than compensated by the increased maize yields. Furthermore leucaena hedgerows substantially depressed the growth of weeds between cropping seasons.Intercropping with cowpea significantly depressed yields of maize grain and stover when both crops were sown together, but not in later seasons when cowpea was sown four weeks after the maize. Application of slurry increased the total yields of maize grain and stover by 35 and 37%, respectively. The grain yield of maize in leucaena hedgerow treatments fertilized with slurry did not respond to application of more than 50% of leucaena foliage, which suggested that half of the foliage could be spared for feeding to livestock. The cumulative yield of maize grain from the highest yielding organic system was 85% of the yield from the fertilizer treatment.The study, which is continuing, demonstrates that large increases in agricultural productivity are possible through the intercropping of maize with woody forage and grain legumes and the integration of dairy cattle production into the system. It thus shows the importance of exploiting crop/livestock interactions.     

Leucaena + maize alley cropping in Malawi. Part 1: Effects of N, P, and leaf application on maize yields and soil properties

Yields under alley cropping might be improved if the most limiting nutrients not adequately supplied or cycled by the leaves could be added as an inorganic fertilizer supplement. Three historic leaf management strategies had been in effect for 3 years ina Leucaena leucocephala alley cropping trial on the Lilongwe Plain of central Malawi : 1) leaves returned; 2) leaves removed; and 3) leaves removed, with 100 kg inorganic N ha⁻¹ added. An initial soil analysis showed P status to be suboptimal under all strategies. A confounded 3⁴ factorial experiment was conducted with the following treatments: leaf management strategy (as above), N fertilizer rate (0, 30, and 60 kg N ha⁻¹), P fertilizer rate (0, 18, and 35 kg P ha⁻¹), and maize population (14,800, 29,600, and 44,400 plants ha⁻¹). Both N and P were yield limiting, and interacted positively to improve yields. The addition of 30 kg N and 18 kg P ha⁻¹ improved yields similarly under all leaf management strategies by an average of 2440 kg ha⁻¹. Increasing the rates to 60 kg N and 35 kg P ha⁻¹ improved yields an additional 1990 kg ha⁻¹ in the ‘leaves returned’ and leaves removed + N’ strategies, but did not improve yields under the ‘leaves removed’ strategy. Lower yields were related to lack of P response at the highest P rate in this treatment, which may have induced Zn deficiency. Plots receiving leaves had higher organic C, total N, pH, exchangeable Ca, Mg, K, and S, and lower C/N ratios in the 0–15 cm soil layer than did plots where leaves had been removed. Leaf removal with N addition was similar to leaf removal alone for all soil factors measured except for organic C and total N, which were higher where N had been added. The results show that N and P were the primary yield-limiting nutrients. Historic N application maintained the soil's ability to respond to N and P on par with leaf additions.     

Effect on maize growth of the interaction between increased nitrogen availability and competition with trees in alley cropping

Maize growing next toErythrina hedgerows had 44% lower biomass (p<0.01) and 35% lower N content (p<0.1) than maize growing in the middle of the alleys. Maize growing next toGliricidia hedgerows had the same biomass but 56% higher N content (p<0.1) than maize growing in the middle of the alleys. However these differences did not develop until 2 months after sowing of the maize.Spatial variability in soil nitrogen mineralization and mulch nitrogen release did not explain any of the differences in growth or N uptake of the maize with respect to distance from the trees. It is hypothesized that the slower growth of the maize next to theErythrina trees after 2 months is due to increasing light and/or nutrient competition from the trees as the trees recover from pollarding. The apparent lack of competition fromGlirigidia may be due to different rates of regrowth or different shoot and root architecture.A theoretical model is described demonstrating that if a crop is to take advantage of the higher nutrient availability under alley cropping it must complete the major part of its growth before the trees recover significantly from pollarding, and start competing strongly with the crop.     

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.     

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.     

毛竹主要营林措施技术经济效果分析

本文分析了毛竹主要营林措施松土、施肥和留养母竹及其综合技术的经济效果，分析表明，不同松土深度亩产值间具有极显著差异，松土以25cm为好，这时反应弹性大，纯收入高。施氮肥和有机肥可极显著增产产，尿素以每亩施20kg为佳；有机肥增产作用大小顺序是饼肥＞猪栏肥＞干稻草＞青草。母竹以留养四度为好，由于△NPV均大于零说明松土25cm、施尿素20kg／亩、留四度母竹及其综合技术都是可行的，可根据当地人、财、物资 况选用。从△NPVR值来看，投资效益以每亩施20kg尿素最好然后依次是松土25cm、综合技术和留四度母竹。