秸秆还田条件下减量施氮对作物产量及土壤碳氮含量的影响

Effects of nitrogen fertilizer reduction on crop yields,soil nitrate nitrogen and carbon contents with straw returning

【目的】探讨关中平原小麦-玉米轮作体系中,秸秆机械化全量还田条件下减量施N对作物产量、土壤碳库及NO-3-N累积的影响,为该地区粮食生产的合理氮肥用量提供理论依据。【方法】2008-06-2012-06在陕西关中平原进行了4年田间定位试验,在作物秸秆全量还田条件下,设置了常规施N(玉米和小麦季施N量分别为188,150kg/hm2)、15%减量施N(玉米和小麦季施N量分别为160,128kg/hm2)、30%减量施N(玉米和小麦季施N量分别为130,105kg/hm2)3个处理,对3个处理的玉米和小麦秸秆、籽粒产量以及植物全氮、土壤硝态氮含量、土壤有机碳及活性有机碳含量进行分析。【结果】与常规施N处理相比,15%减量施N有一定增产效果,作物周年籽粒产量可提高7.2%;且30%减量施N处理并未显著减少小麦和玉米籽粒产量以及小麦秸秆产量。减量施N处理明显降低了土壤NO-3-N累积量,且根据表观氮平衡结果,N肥施用量仍可减少。减量施N处理对土壤有机碳及活性有机碳含量均无显著影响。随着每季作物秸秆还田以及土壤有机碳含量的逐年增加,活性有机碳含量显著增加。【结论】在秸秆还田条件下适量减N,不仅能保证作物不减产,而且还可逐步增加土壤有机碳含量,降低土壤NO-3-N累积量,达到环境效益和经济效益的统一。

[Objective] Effects of nitrogen （N） fertilizer reduction on crop yields,soil carbon pool and NO3-N accumulation with straw returning in winter wheat-summer maize rotation system in Guanzhong Plain were studied to determine the optimal N application rate. [Method] A four-year field experiment was conducted during 2008--2012. There were three N treatments in this experiment： conventional N applica- tion rate （188,and 150 kg/hm2 in maize and wheat growing seasons,respectively）, 15% N reduction （160 and 128 kg/hm2 in maize and wheat growing seasons, respectively）, and 30% N reduction （130 and 105 kg/hm2 in maize and wheat growing seasons, respectively）. Straw and grain yields and total N concentra- tions of maize and wheat, soil NO;--N content, soil organic carbon content, and labile organic carbon content were analyzed. [Result] 15% N reduction increased crop year-around seed yields by 7.2% ,and 30% N re- duction did not decrease either wheat and maize grain yields or straw yields compared to conventional N treatment. Accumulation of NOa-N in soil was significantly decreased with N reduction and N application rate could be further reduced based on apparent N balance. N reduction treatments did not affect soil organ- ic carbon and active organic carbon. The soil organic carbon increased significantly year by year as the re- turning of straw to soil and increase of soil active organic carbon. [Conclusion] Appropriate reduction of N fertilizer with straw returning could increase soil organic carbon and decrease NOa-N accumulation without affecting crop yields.