Effect of Selected Legumes on Biomass Production, Nitrogen Mineralization and Grain Yield of Maize in Sub Humid Parts of Tanzania

Declining soil fertility is among major production constraint facing small holders famers in sub humid areas of Sub Sahara Africa. The convenient of inorganic fertilizer in crop production is vivid, but famers are financial limited to buy and utilize. Residuals of velvets bean (Mucuna pruriens L. ), dolichos (Lablab purpureus L. ) and sunhemp (Crotolaria ochroleuca G. ) are low-input strategies that can be used by the small holders famers to increase soil fertility and crop production in unfertile soils. This study aimed at assessing the effect of these legumes on biomass production and nitrogen mineralization. Also, to evaluate the effects of residues on soil characteristics and maize grain yield. Field and laboratory experiments were used in this study. Inorganic fertilizer UREA was used as a standard treatment. Results showed no significant difference (P=5 %) on biomass production, however velvet bean produced relative higher biomass (15.13 t ha-1) followed by dolichos and sunhemp of 12.67 and 11.75 t ha-1 respectively. Sun hemp had highest N content (2.77 %) followed by velvet bean and dolichos with 2.49 and 2.42 %N, respectively. The percentage mineral N released peaked at 10 weeks for control and sunhamp with 27.56 and 56.82 %N, respectively, while N in inorganic fertilizer peaked at 6 weeks. Velvet bean and dolichos had similar trend of N releasing ability. Urea gave highest grain yield (3.96 t/ha) while famers practices scored the lowest (1.01 t/ha). Maize yield significantly increased by 2.5, 2.6 and 2.7 t/ha when dolichos, velvet bean and sun hemp residuals were used respectively. Use of such residues in crop production should be promoted of restoring soil fertility and increased maize yield in sub humid areas of Tanzania