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We investigated variation in forage production, in sacco dry matter (DM) and nitrogen (N) degradations, and in vitro gas production characteristics of four Albizia (A. lebbeck N 864, A. procera N 865, A. saman N 825) and Paraserianthesfalcataria (N 783) provenances obtained from The Nitrogen Fixing Tree Association. After one year of establishment forage production was assessed by harvesting trees at 0.5 m above ground in the main wet (April-August) minorwet (September-November) and dry (December-March) seasons at Ibadan, southwestern Nigeria. Forage samples from the main-wet and dry seasons were incubated for 6, 12, 48, 72 and 96 h in rumen-fistulated cattle to estimate in sacco DM and N degradation characteristics. In vitro gas production was estimated over 3, 6, 12, 24, 48, 72 and 96 h of incubation. Forage production of A. procera was significantly higher than the other species in all seasons. Cell-wall components were comparatively higher in A. procera than the other species. Potential DM and N degradations of A. lebbeck and A. saman were significantly higher than P. falcataria and A. procera. The results suggest that A. lebbeck and A. saman provenances used in this study have relatively higher feed value than A. procera and P. falcataria.

A study was conducted in the humid-forest, forest-savanna, and Guinea savanna zones of West Africa from 1993 to 1999 to examine the effect of managing crop residues from cereal±legume cropping systems for mulch and fodder for sheep. Increasing the proportion of total crop residues produced from a unit area of land and used as mulch increased maize grain yield, soil organic carbon, nitrogen and available phosphorus. The extra increases obtained when more than half the crop residues were applied as mulch were relatively small, however, suggesting that 25±50% of the crop residues could be removed as feed without any detrimental effect. When any crop residues rejected by sheep were mixed with livestock urine and faeces and returned to the respective ®elds from where the crop residues had been removed, subsequent grain yield and soil organic carbon, nitrogen, and available phosphorus increased. The study demonstrated the possibility of managing crop residues for increased productivity in smallholder mixed crop± livestock systems.introdution In most parts of sub-Saharan Africa, farming systems are predominantly smallscale and have both crop and livestock components. Rapid growth in both human and livestock populations is leading to agricultural intensi®cation, changing landuse patterns and closer integration of the crop and livestock components (Anon., 1992;Jabbar, 1993;Smith et al., 1997). In the smallholder mixed crop-livestock systems, livestock are a source of food, income, manure for crop production, and

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