Abstract
Eight legume species were evaluated as substitutes for fertilizer N for wet season (WS) rice in the Philippines. The above-ground biomass of Sesbania cannabia accumulating 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 Sesbainia 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. Soil organic C and total N were also significantly higher after Sesbania and Crotalaria than after other green manures or fertilizer N treatments.
