Effect of concurrent growing of Sesbania aculeata (Willd) on the nitrogen mineralization pattern and soil nutrient status in wet seeded rice

Field experiments were conducted at Agricultural Research Station, Mannuthy to study the effect of stages and methods of incorporation of concurrently grown daincha (Sesbania aculeata) at different nitrogen levels on the nitrogen release pattern and the soil fertility status in wet seeded rice crop. Incorporation of concurrently grown daincha at 30 DAS resulted in higher nutrient contribution, increased nitrogen mineralization, improved the soil nutrient status, increased productivity and profitability. Release of ammoniacal nitrogen was higher at 30 days after incorporation (DAI) from both 20 and 30 days old daincha and then declined up to harvest. The maximum release of NH₄⁺-N from 20 and 30 days old daincha was 157.02 and 176.53 kg ha⁻¹, respectively at 30 DAI. The release of NO₃⁻-N was less compared to NH₄⁺-N. However an increasing trend was noticed in the release of NO₃⁻-N up to harvest. Methods of incorporation had no significant influence on nitrogen mineralization pattern of daincha. Concurrent growing of daincha enormously improved the soil nutrient status and incorporation of 30 days old daincha registered the highest available N (360.5 kg ha⁻¹), P (79.2 kg ha⁻¹) and K (831.8 kg ha⁻¹) status of soil and helped to reduce the use of nitrogen fertilizer by 25 per cent.