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.     

Evaluation of phytotoxic effects ofGliricidia sepium (Jacq.) Walp prunings on maize and cowpea seedlings

Phytotoxic effects ofGliricidia prunings were tested on maize seedlings in the laboratory and on maize and cowpea seedlings in the field. In the laboratory test, growth of maize seedlings was significantly depressed by addition of leachate ofGliricidia prunings. In the field, leaf, chlorosis of maize and cowpea seedlings occurred when mulched withGliricidia prunings; number of affected leaves increased with increasing mulch rate. Maize was more susceptible than cowpea. This phytotoxic effect, however, did not reduce growth of maize and cowpea seedlings in the field. ApplyingGliricidia mulch one week before planting eliminated the phytotoxic effects on maize.     

On-farm research in a silvopastoral project: a case study

The Silvopastoral Project is being implemented by CATIE in the Atlantic humid lowland of Costa Rica, in order to develop alternatives to the current destructive mode of livestock production. The overall approach is briefly described and two superimposed on-farm experiments are discussed in more detail. The main constraints for on-farm research within the project are analysed: the limited previous knowledge of the area and of the local species, the difficulty of achieving a common understanding about research with collaborating farmers, the need for additional staff supervision and the complexity of the statistical analyses. An attempt is made to draw lessons from the ongoing project regarding how to resolve the apparent contradiction between rigorous scientific requirements and questions of immediate value to extension, the compromises to be achieved between different types of evaluation (statistical, risk, etc.) and the potentials and limitations of farmers' participation in research.     

Cacao-coconut intercropping in Ghana: agronomic and economic perspectives

In Ghana, shade for cacao (Theobroma cacao L.) is becoming a critical issue because of extensive deforestation. Unlike in some other cacao-growing countries, cacao is not grown under the shade of coconut (Cocos nucifera) in Ghana. An experiment to compare the merits of four cacao-coconut intercropping systems with the traditional cultivation of cacao under Gliricidia sepium shade was undertaken at the Cocoa Research Institute of Ghana. Cacao seedling girth was not affected when intercropped with coconut but was significantly (P = 0.01) reduced when intercropped with G. sepium. High density cacao facilitated better early canopy formation. Yield of cacao spaced at 2.5 m triangular (1739 plants ha^–1) with coconut at 9.8 m triangular (105 plants ha^–1) was significantly higher (P = 0.05) than from the other treatments during 1993/94 to 1995/96. There were no major disease problems associated with intercropping cacao with coconuts. Widely spaced coconuts intercropped with cacao spaced at 3 m × 3 m showed better flowering and gave higher coconut yields, but cacao spaced at 2.5 m triangular under coconuts spaced at 9.8 m triangular was more profitable than the other treatments. Moisture stress was the greatest in cacao system with G. sepium shade and this could be responsible for the low yield of cacao in that treatment. It is suggested that properly arranged high density cacao under widely spaced coconuts can be a profitable intercrop system for adoption by cacao farmers in Ghana.This revised version was published online in November 2005 with corrections to the Cover Date.     

Studies withGliricidia sepium for crop/livestock production systems in West Africa

This paper reports for progress of research onGliricidia sepium conducted by the Humid Zone Programme (HZP) of the International Livestock Centre for Africa (ILCA) at Ibadan in Southwest Nigeria in the period 1982–1986. It examines the biological characteristics of the species, with respect to growth, flowering and seed production, and analyses its potential for improving crop production (through soil fertility maintenance) and livestock production (through production of improved fodder). Integration ofGliricidia into cropping systems is necessary for optimum realisation of its crop improvement quality. The alley farming system is presented in the paper as one means of achieving sustainability in crop production through integration of trees, such asGliricidia, into cropping systems. The use ofGliricidia in Intensive Feed Gardens, for production of leguminous fodder is also described as an alternative production system. The paper finally reports on experiences with local farmers in on-farm research and development for the integration ofGliricidia andLeucaena into local farming systems. It ends with a suggestion for more research, targetted specifically at improvement of the species and its utilisation.     

Tree leafing phenology and crop productivity in semi-arid agroforestry systems in Kenya

The hypothesis that temporal separation of resource use between trees and crops minimises competition for wa ter in agroforestry systems during the cropping period and increases utilisation of annual rainfall was tested at Machakos in semi-arid Kenya. Four popular tree species were chosen to provide a range of leafing phenologies. These included Melia volkensii, which sheds its leaves twice a year, Senna spectabilis and Gliricidia sepium, which shed their leaves during the long dry season, and the evergreen Croton megalocarpus. All four species retained their foliage during the long rains, offering little scope for temporal separation of resource use. Maize (Zea mays) yields were reduced by 50–70% in the agroforestry treatments. Reductions in crop yield were strongly correlated with tree growth (r ² =0.94) and available soil moisture (r ² =0.88). G. sepium remained leafless for much of the short rains despite the presence of available soil water, and was least competitive with the bean crops (Phaseolus vulgaris) grown at this time. Reductions in crop yield in the agroforestry treatments were closely correlated with tree growth (r ² =0.99) and available moisture (r ² =0.79) during the 1996/97 short rains (158 mm), but not during the much wetter 1997/98 season (608 mm). Shading by trees or shade nets reduced crop yield, in contrast to previous studies in the semi-arid tropics. Low off-season rainfall during the study period (9% of annual rainfall compared to the long-term average of 20%) limited the potential for temporal separation of growing periods. Where the prospects for temporal or spatial separation in resource use are limited, shoot and/or root pruning may be necessary to manage competition between trees and crops. This revised version was published online in June 2006 with corrections to the Cover Date.     

Woody legumes as live support systems in yam cultivation

This paper reports on the use of three leguminous perennials (Leucaena leucocephala, Flemingia macrophylla and Gliricidia sepium) as live support systems in yam cultivation. In a planting arrangement in which yam rows alternated with rows of the woody species the tuber yields per ha were 3.4 (leucaena), 5.3 (flemingia) and 10.1 (gliricidia) ton fresh weight. TUKEY's L.S.D. value equalled 2.9 ton. Leucaena leucocephala is unsuitable as live support since the species shows a strong competitive power expressed in terms of leaf productivity and relative density of the root mass in the upper soil stratum, the zone explored by the yam crop. Flemingia macrophylla is unsuitable as support species mainly because of its structural weakness: Its branches do not sufficiently lignify to carry the yam leaf mass. The significantly higher tuber yield of the yam crop grown with Gliricidia sepium is a function of specific properties of the tree species: Low leaf productivity, a relatively weakly developed root system and an open architecture, which leaves sufficient space for a yam crop grown in association.     

不同浓度ABT对杠柳扦插育苗的对比试验

为了更快更好地发挥杠柳植被的优势,采取人工繁育的方式培育优质苗木。根据杠柳的生态学特性和生长特性,采用不同处理措施进行了杠柳硬枝扦插育苗试验。结果表明,用3种不同浓度的植物生长调节剂ABT生根粉,浓度为100×10-6的ABT处理最适合杠柳的扦插繁殖,浓度为50×10-6的ABT处理效果次之,浓度为150×10-6的ABT处理效果最差。     

Towards the management of field bindweed (Convolvulus arvensis) and hedge bindweed (Calystegia sepium) with fungal pathogens and cover crops

The bindweeds Calystegia sepium and Convolvulus arvensis aredifficult to control chemically. Calystegia sepium is often aproblem in maize or in vineyards, while C. arvensis is animportant weed of cereals. The biological control of these weedswith insects or fungal pathogens has been investigated since1970. More than 600 fungi collected in countries throughoutEurope have been isolated in our laboratories. The isolates withthe highest and most stable pathogenicity against bindweed belongto the genus Stagonospora. In a field trial in maize in 1995, oneof these Stagonospora isolates stopped the increase of groundcoverage by the bindweeds. In response to public concern aboutenvironmental problems caused by modern agriculture, new croppingsystems are being developed. Underseeding maize with a livinggreen cover achieves good control of a large spectrum of the weedflora typical of conventional tillage systems. However, C. sepiumand C. arvensis remain as problems. The research reported showsthat C. sepium is partly suppressed by the green cover, butescapes control by climbing the stems of the maize plants.Therefore, the application of spores of Stagonospora sp. in amaize field underseeded with a living green cover may allow alarge or a complete reduction of the herbicide input and promotea more sustainable agriculture     

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.