耕作方式对还田稻草氮素释放及水稻氮素利用的影响

 【目的】探讨在免耕和常耕条件下,还田稻草氮素释放特性和水稻氮素利用的差异。【方法】2006年和2007年晚稻,在田间将稻草还田,并在不同时期测定稻草中残留的氮素,同时进行桶栽试验,将15N标记稻草还田,成熟期测定水稻积累的总氮素和15N丰度。【结果】稻草中残留的氮素随还田时间延长而下降,但不同时间段下降的速度差异很大。还田后0～40 d,稻草中残留的氮素下降约60%,还田后40～100 d,稻草中残留的氮素下降约10%。两种耕作方式下还田稻草含氮率均呈升高趋势。无论是干稻草还是湿稻草还田,免耕条件下稻草氮素平均释放速率高于常耕。免耕方式下湿稻草的氮素释放速率较高,常耕方式下干稻草氮素释放速率较高。【结论】无论还田稻草状态相同与否,常耕水稻的氮素干物质生产效率和产量较免耕水稻高。免耕有利于还田稻草的氮素释放,但水稻从还田稻草中吸收的氮素和氮素利用效率下降。

Influence of Tillage Patterns on Incorporated Straw Nitrogen Release and Nitrogen Utilization of Rice

【Objective】 The objective of this study was to investigate the difference of nitrogen release from incorporated rice straw and nitrogen utilization of rice under different tillage patterns. 【Method】 Rice straw was incorporated into field under no-tillage and conventional tillage in the late seasons of 2006 and 2007 and nitrogen contents in incorporated straw were measured at different growth stages after incorporation. At the same time, rice straw with 15N feed was incorporated into pot under no-tillage and conventional tillage, nitrogen and 15N uptake by rice plant were measured at maturity. 【Result】 Residual nitrogen amount in incorporated straw decreased and obvious differences were observed at different stages. The nitrogen loss in incorporated straw was about 60% during the 0-40 days and about 10% during the 40-100 days. However, the residual nitrogen content increased in two tillage patterns. Nitrogen in straw was more easily released under no-tillage than conventional tillage if the straw status was not considered. Nitrogen in wet incorporated straw was more easily released under no-tillage while dry straw under conventional tillage. 【Conclusion】 Great nitrogen dry matter production efficiency (NDMPE) and grain yield were observed under conventional tillage. No tillage was beneficial to straw nitrogen release, but nitrogen uptake from incorporated straw by rice plant and nitrogen use efficiency were decreased.