Effect of presubmergence and green manuring (Sesbania aculeata) on nutrition and yield of wetland rice (Oryza sativa L.) on a sodic soil

Summary A field experiment was conducted to evaluate the effect of 0, 1 and 2 weeks' submergence prior to the transplantation of rice (presubmergence), with and without Sesbania aculeata green manure, on the yield and nutrition of rice in a highly sodic soil pH 10.3, exchangeable sodium percentage (ESP) 86.4]. Green manuring significantly enhanced the yield of rice and contributed 112 kg N/ha. One week's presubmergence with incorporated green manure improved the yield of rice significantly over that obtained with no previous flooding, giving a yield on a par with that obtained with 2 weeks' submergence. The beneficial effect of presubmergence without green manure on rice yield was of lesser magnitude and was significant only when it was continued for 2 weeks. Cultivation of rice under submerged conditions improved the sodic soil, and green manuring enhanced the process of reclamation by further decreasing the pH value and the exchangeable Na of soil. Green manuring considerably improved organic C, available N, P, and K status of the soil and enhanced the uptake of N, P, Ca, Mg, S, Fe, Mn, and Zn by the crop. Effects of submergence and green manuring on the availability of Fe, Mn, Zn, and P in soil and their role in the nutrition of rice are discussed.