摘要
Although nitrogen （N） loss through runoff and leaching from croplands is suspected to contribute to the deterioration of surrounding water systems, there is no conclusive evidence for paddy soils to prove this hypothesis. In this study, field plot experiments were conducted to investigate N losses through runoff and leaching for two consecutive years with 3 N fertilization rates in rice （Oryza sativa L.）-wheat （Triticum aestivum L.） rotations in the Taihu Lake region, China. A water collection system was designed to collect runoff and leachates for both the rice and wheat seasons. Results showed that dissolved N （DN）, rather than particulate N （PN）, was the main form of N loss by runoff. The NO3^--N concentration in runoff was between 0.1 and 43.7 mg L^-1, whereas the NH4^＋-N concentration ranged from below detection limit to 8.5 mg L^-1. Total N （TN） loads by runoff were 1.0-17.9 and 5.2-38.6 kg ha^-1 during rice and wheat seasons, respectively, and the main loss occurred at the early growing stage of the crops. Nitrogen concentrations in leachates during the rice seasons were below 1.0 mg L^-1 and independent of the N application rate, whereas those during the wheat season increased to 8.2 mg L^-1 and were affected by the fertilizer rate. Annual losses of TN through runoff and leaching were 13.7-48.1 kg ha^-1 from the rice-wheat cropping system, accounting for 5.6%-8.3% of the total applied N. It was concluded that reduction in the N fertilization rate, especially when the crop was small in biomass, could lower the N pollution potential for water systems.
尽管通过流量的氮(N) 损失并且从农田沥滤被怀疑贡献包围水系统的恶化，没有最后的证据让水稻土证明这个假设。在这研究，地小区试验被进行通过流量调查 N 损失并且在大米(Oryza sativa L.) 与 3 N 受精率沥滤二连续的年小麦(Triticum aestivum L.) 在泰胡·莱克区域的旋转，中国。一个水收集系统被设计收集流量并且沥滤为米饭和小麦季节的 ates。结果出现了那溶解 N (DN ) ，而非微粒 N (PN ) ，是由流量的 N 损失的主要表格。NO3 ? 在流量的 -N 集中在 0.1 和 43.7 mg L 之间 ? ，而 NH4+-N 集中从在察觉限制下面到 8.5 mg L ? 。由流量的全部的 N (TN ) 负担是 1.0 17.9 和 5.2 38.6 kg 哈？在米饭和小麦季节期间，分别地并且主要损失在庄稼的早成长的阶段发生了。氮集中在沥滤 ates 在米饭季节期间在 1.0 mg L 下面？并且独立于 N 申请率，而那些在小麦季节期间增加了到 8.2 mg L？并且被化肥率影响。通过流量的 TN 的年度损失并且沥滤从大米小麦的 13.7 48.1 kg ha-1 正在收割系统，财务为 5.6%8.3% 总数使用了 N。它被结束在 N 受精率的那减小，特别当庄稼在生物资源是小的时，能为水系统降低 N 污染潜力。
基金
the National Natural Science Foundation of China (Nos.40571077 and 30390080)
and the Knowledge Innovation Project of the Chinese Academy of Sciences (No.KZCX2-413).
