Rice Response to Waterlog-Tolerant Green Manures

Nitrogen accumulation was greatest (79 kg N ha −1 ) in 48-d S. cannabina. Accumulation in cowpea was apparently depressed by waterlogging. Rice grain yield response to green manure N was unaffected by location of green manure cultivation (in situ vs. transported from a nearby field). In the second (1984) and third (1985) experiments, Sesbania sp. were flooded during the last 25 d of growth to assure early wet-season waterlogging. Mean N accumulation in flooded S. rostrata (Brem. and Obrem.), which nodulates on its stem, was 90 kg ha −1 in 48 d and 164 kg ha −1 in 60 d. Nitrogen accumulations in nonflooded S. rostrata were 128 kg ha −1 in 48 d and 198 kg ha −1 in 60 d. Accumulation in a Nepalese S. cannabina cultivar averaged 84% of that in S. rostrata