Influence of green manuring with Sesbania rostrata and Aeschynomene afraspera or urea on dynamics and uptake of nutrients by wetland rice

Deka Medhi, B.; DeDatta, S.K.

Influence of green manuring with Sesbania rostrata and Aeschynomene afraspera or urea on dynamics and uptake of nutrients by wetland rice

1997

Deka Medhi, B. | DeDatta, S.K.

Nutrient concentrations in the soil and crop uptake from incorporated green manure and urea in flooded rice was studied in field experiments. Release of plant-available nitrogen (NH4(+)-N) from green manure was slightly delayed compared with that from prilled urea (PU) because Sesbania rostrata L. and Aeschynomene afraspera L. released the N gradually after their decomposition, whereas N became available immediately after PU application. Exchangeable NH4(+)-N concentration in soil peaked at 163 mg kg-1 in the transplanted rice (TPR) and 198 mg kg-1 in broadcast-seeded rice (BSR) at 0 and 1 week after PU application. Broadcast-seeded rice depleted NH4(+)-N faster than did TPR because of the crop's vigorous growth in the former during the early stage. Soil solution NH4(+)-N followed a similar trend to that of soil NH4(+)-N. Incorporation of S. rostrata and A. afraspera increased the concentration of P, K(+), Fe(2+) and Mn(2+) in soil solution more than did the application of PU. However, zinc concentration decreased in all treatments. Both PU and green manure increased the N status of the rice plants and enhanced the uptake of P, K, Fe, Mn and Zn by the rice crop. This suggests that application of green manures improves the uptake of these nutrients by the crop. The highest apparent N recovery was obtained with PU followed by green manure.

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