秸秆还田与氮肥运筹对农田土壤可溶性氮组分的影响

为探究秸秆还田配施氮肥对农田土壤可溶性氮转化特征的影响，研发东北冷凉区土壤氮素供应能力提高的秸秆还田技术，采用田间连续定位试验，对比分析了秸秆还田方式(不还田、粉碎翻压还田、堆腐旋耕还田)与氮肥运筹(N180、210、240kg/hm²；氮肥基施、氮肥后移)作用下农田土壤无机氮(IN)、可溶性有机氮(DON)及可溶性全氮(DTN)的动态变化。结果表明，秸秆还田配施氮肥影响农田土壤可溶性氮组分含量，其作用行为受秸秆还田方式、施氮模式和生育时期的多重制约。秸秆还田配施低量氮肥(N180kg/hm²)土壤IN和DTN均低于无秸秆处理，而配施高量氮肥(N240kg/hm²)时高于无秸秆处理；秸秆还田土壤DON于生育前期(播种-拔节期)较无秸秆处理显著增加，而在生育中后期无规律性变化。随着施氮量增加，秆还田土壤IN和DTN显著增加，而DON仅于春玉米旺盛生长期(拔节期-灌浆期)显著增加。随着生育期推进，除秸秆堆腐旋耕还田土壤DON呈三峰曲线变化外，秸秆还田土壤IN、DON和DTN均呈双峰曲线变化，且峰值越来越低。由此可见，在东北农业产区，N210kg/hm²用量下秸秆粉碎翻压还田配施15％氮肥的秸秆还田技术具有优化氮素管理、提高土壤肥力的潜力。

Effects of straw returning and nitrogen application management on dissolved nitrogen components in farmland soil

In order to understand the effects of straw returning and nitrogen(N)application management on dissolved N transformation characteristics in farmland soil，and to study the straw-returning technology with improving soil N supply capacity for Northeast cold area of China，with a continuous in situ-field experiment，the dynamics of inorganic N(IN)，dissolved organic N(DON)and dissolved total N(DTN)affected by different straw returning methods(no strawreturning，crushed straw-returning ploughing，decomposed straw-returning rotary tillage)and N application management(N 180，210，240 kg/hm²；one-time N application，postponing N application)were investigated. The results showed that，the straw-returning with N application affected soil dissolved N components content，and its behavior was simultaneously affected by straw-returning methods，N application models and growing stages. Compared with no straw returning，the IN and DTN in soil treated with straw returning with low N application rate(N 180 kg/hm²)both decreased，however，increased in soil treated with straw returning with high N application rate(N 240 kg/hm²)；DON in the straw returning treated soil increased significantly during the early growth stages(sowing stage to jointing stage)，and changed with no rule during later growth stages. With the increasing of N application rate，IN and DTN in soil treated with straw returning both increased significantly，however，DON increased significantly only during spring maize exuberant growing period(jointing stage to filling stage).With maize growing，IN，DON and DTN for the straw-returning treated soil all showed a double-peak curve with decreasing peak value，except for the three-peak curve of DON in the decomposed straw-returning rotary tillage soil. Overall，the technology of crushed straw-returning ploughing with 15％ N fertilizer at the rate of N 210 kg/hm² had the potential to improve N management and enhance soil fertility in the agricultural producing areas of Northeast China.