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为探索巢湖流域稻麦(油)轮作区水稻季减少农田氮素流失的有效耕作措施,降低其对湖区水质的威胁,采用野外定位观测试验并结合室内实验分析,研究了连续两年秸秆还田条件下稻田田面水总氮(TN)、溶解态氮(DN)、溶解态有机氮(DON)、铵态氮(NH4+-N)和硝态氮(NO3--N)浓度的动态变化特征。结果表明,稻田施用尿素后第2天或第4天田面水的TN、DN、DON和NH4+-N浓度达到峰值,然后随着时间的推移迅速降低,至8~10 d后趋于稳定;在整个水稻生育期内,NO3--N浓度普遍较低;尿素施用后8~10 d之内是控制稻田氮素流失的关键时期,秸秆还田降低这一时期TN、DN、NH4+-N浓度的效果显著,而DON浓度差异未达显著水平。DN是稻田田面水氮素存在的主要形态,所占TN比例达63.2%~88.8%,尿素施用后6 d内DN又以NH4+-N为主,NH4+-N所占TN的比例为33.8%~69.9%。DON是稻田田面水氮素的重要组成部分,其生态环境效应不容忽视。秸秆还田还有利于水稻产量的提高,增产幅度分别为12.25%和7.68%,平均为9.96%。在保证水稻产量的前提下,秸秆还田可以作为控制稻田氮素流失的措施在巢湖流域使用。
In order to explore the effective tillage measures to reduce the nitrogen loss of farmland during the rice cropping season in the rice-wheat (oil) rotation area of the Chaohu Lake basin and reduce its threat to the water quality in the lake area, field positioning observation and field experiment were conducted to study the effects of straw returning (TN), Dissolved Nitrogen (DN), Dissolved Organic Nitrogen (DON), Ammonium Nitrogen (NH4 + -N) and Nitrate Nitrogen (NO3 - N) in Paddy Field Surface Water. The results showed that the concentrations of TN, DN, DON and NH4 + -N in surface water reached the peak on the second or fourth day after the application of urea in paddy field, then decreased rapidly with the passage of time and tended to be stable after 8-10 days. During the whole growth period of rice, the concentration of NO3 - N was generally low. During the period of 8 ~ 10 d after urea application, it was the key period to control nitrogen loss in paddy field. Straw returning reduced the concentrations of TN, DN and NH4 + -N in this period The effect is remarkable, but the DON concentration difference has not reached the remarkable level. DN is the main form of water nitrogen in paddy field surface water, accounting for 63.2% ~ 88.8% of TN, DN is NH4 + -N dominated within 6 days after urea application, NH4 + -N accounted for 33.8% 69.9%. DON is an important part of paddy field water nitrogen, its ecological effects can not be ignored. Straw returning is also conducive to the improvement of rice yield, yield increase of 12.25% and 7.68% respectively, with an average of 9.96%. Under the premise of ensuring the rice yield, straw returning can be used as a measure to control nitrogen loss in paddy fields in the Chaohu Lake Basin.