SYMBIOTIC EFFICIENCY OF SESBANIA-ROSTRATA AND S-CANNABINA AS AFFECTEDBY AGRONOMIC PRACTICES

field experiment was conducted to study the Na fixation efficiency of Sesbania rostrata and S. cannabina as affected by agronomic practices in semi-arid subtropical climate. Sowing seeds resulted in smaller num bers of nodules, lower dry weight, lower total biomass, less N uptake, and less N-2 fixation for S. rostrata than S, cannabina, while cut-st em planting improved the symbiotic efficiency. Flooding the soil incre ased the relative humidity of the crop micro-environment by 4-11% and induced early appearance of stem nodules in S, rostrata. Only 67 kg N ha(-1) was fixed by S, rostrata compared to 160 kg N ha(-1) by S. cann abina when normal agronomic practices (sowing and non-flooding) were f ollowed, In contrast, planting stem cuttings and flooding resulted in greater biological N-2 fixation, 307 and 209 kg N ha(-1) by S, rostrat a and S, cannabina, respectively. Therefore, S. rostrata can be succes sfully exploited as a green manure when stem cuttings are planted unde r flooded conditions.