Study on dhaincha ( Sesbania bispinosa ) genotypes for N-fixing capability and rate of mineralization under field and laboratory condition

To ascertain the amount of nitrogen fixed and mineralization rate by green manure dhaincha were studied at Research Farm of Navsari Agricultural University, Navsari. The experiment consists of six dhaincha ( Sesbania bispinosa ) genotypes, NSB-6, NSB-7, NSB-9, NSB-13, CSD-123, and CSD-137, subjected to field incorporation and in vitro decomposition. The experimental treatment also includes sampling intervals for field incorporation 25, 25, 65, 85, 105, and 125 days after sowing and under in vitro decomposition 10, 20, 30, 40, 50, and 60 DAD (Days after decomposition). The differences in amount of soil nitrogen for dhaincha genotypes at different intervals are parallelly compared with mineralization rate of nitrogen under in vitro decomposition. The incorporation of dhaincha significantly increased the amount of soil available N up to 125 DAS (Days after sowing), ammoniacal nitrogen up to 85 DAS, and nitrate nitrogen up to 125 DAS. The straw under in vitro decomposition obtained significantly lower total N, total organic carbon, and cellulose following significant increase of nitrate nitrogen and ammoniacal nitrogen in leachates. First-order kinetics showed that NSB-9 with higher decomposition constant and lower half-life of total N ( k = 0.00823 and DT 50 = 84.20 days) and total organic carbon ( k = 0.01009 and DT 50 = 68.6 days). In conclusion, as a substitution of chemical fertilizers dhaincha incorporated nearly 3 months prior crop production to get maximum available nutrients.