Grain yield responses in rice to eight tropical green manures

Eight legume species were evaluated as substitutes for fertilizer N for wet season (WS) rice in the Philippines. The above-ground biomass of Sesbania cannabina accumulated mean maximum N (84-199 kg ha −1 ) and indigo accumulated the least N (8-84 kg ha −1 ) in 30-60 days. Mungbean and cowpea, which produced grain and crop residue, are potential dual-purpose grain and green manure species. Regardless of species, mean rice grain yield from green manures was 4.0 t ha −1 in 1984 and 4.6 t ha −1 in 1985, comparable with 4.1 t ha −1 from 50 kg fertilizer N in 1984 and 4.7 t ha −1 from 105 kg fertilizer N ha −1 in 1985. In both years, 60-day Sesbania and Crotalaria accumulated N in excess of the rice crop requirement. Residual effects from green manures on dry season (DS) rice were not significant in 1984 but were significant from Sesbania green manure in 1985