Eight legume species were evaluated as substitutes for fertilizer N fo
r wet season (WS) rice in the Philippines. The above-ground biomass of
Sesbania cannabina accumulated mean maximum N (84-199 kg ha-1) and in
digo accumulated the least N (8-84 kg ha-1) in 30-60 days. Mungbean an
d cowpea, which produced grain and crop residue, are potential dual-pu
rpose 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 an
d 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 r
equirement. Residual effects from green manures on dry season (DS) ric
e were not significant in 1984 but were significant from Sesbania gree
n manure in 1985. Soil organic C and total N were also significantly h
igher after Sesbania and Crotalaria than after other green manures or
fertilizer N treatments.