Decomposition pattern of rice straw in poorly drained paddy soil and recovery rate of straw nitrogen by rice plant in no-tillage transplanting cultivation
1999
Saigusa, M. (Tohoku Univ., Sendai (Japan). Faculty of Agriculture) | Hanaki, M. | Ito, T.
A 15N-field experiment was conducted on poorly drained alluvial paddy soil in 1996 and 1997 to investigate the decomposition pattern of rice straw and recovery rate of nitrogen released from it by rice plants in no-tillage transplanting cultivation as compared with tillage cultivation. 1) Decomposition rates of the rice straw from fall to transplanting time in the no-tillage plot tended to be lower than that in the tilled plot, whereas those from transplanting to harvesting time showed a reverse tendency. 2) Nitrogen concentration of the rice straw applied in the fall changed a little or was unchanged till the middle of May both for tilled and no-tillage plots. However, after that, it increased significantly till the middle of August, and this increment was higher in the no-tillage plot. On the other hand, the changes in C/N ratio in the rice straw showed a reverse tendency. 3) The changes of apparent nitrogen remaining in the rice straw were almost the same between no-tillage and tilled plots till the middle of March. However, after that, nitrogen content tended to be increased by the immobilization of mineral nitrogen in the soil, and this increment was higher in the no-tillage plot. 4) Recovery rates of nitrogen released from the rice straw were 3-4% at the maximum tillering stage and 9-10% at harvesting time both in tilled and no-tillage plots
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