不同还田方式下北方旱作小麦秸秆腐解规律研究

为揭示不同还田方式下北方旱作小麦秸秆腐解规律,以小麦秸秆为试验材料,采用尼龙网袋法,于2014-2015年度在山西临汾保护性耕作长期定位试验区进行试验,设置秸秆还田旋耕(SRT)、秸秆覆盖免耕(SNT)2个处理,分析不同耕作方式下小麦秸秆的纤维素、半纤维素、木质素、有机碳、全氮含量以及秸秆腐解率、有机碳矿化率、全氮释放率的变化。结果显示,经过375 d的田间腐解,SRT秸秆腐解率为50%,SNT秸秆腐解率为31%。SRT秸秆的纤维素、半纤维素、木质素的平均腐解率分别为65%、45%、53%,SNT分别为56%、30%、39%;SRT秸秆有机碳的矿化率为57%,SNT为40%;SRT秸秆全氮素释放率为15%,SNT为36%。研究表明,SRT可加快秸秆腐解与组成成分的分解,SNT有利于秸秆氮素的释放,可减少农田氮投入。SNT秸秆有机碳矿化率低可减少农田碳循环速率,提高麦田固碳能力。本研究结果对我国北方旱作小麦秸秆还田管理具有一定的借鉴参考价值。

Study on the Decomposition Mechanism of Wheat Straw on Rain-fed Croplands in Northern China Under Different Patterns of Straw Returning Practice

In order to study the effects of different patterns of straw returning practice on the decomposition mechanism of wheat straw on rain-fed croplands in northern China, two treatments of straw returning field with rotary tillage (SRT) and straw covering with no-tillage (SNT) were conducted using wheat straw in nylon mesh bag in the long-term positioning test area of conservation tillage in Linfen Shanxi Province from 2014 to 2015. We characterized the change of the decomposing rate, cellulose, hemicellulose, lignin, organic carbon, total nitrogen content, straw organic carbon mineralization rate and total nitrogen release rate of wheat straw under different tillage methods. The results suggest that the decomposing rate of wheat straw was 50% in SRT, 31% in SNT after 375 days of field decomposing. The average decomposing rates of cellulose, hemicellulose and lignin of wheat straw was 65%, 45% and 53% in SRT, and 56%, 30% and 39% in SNT, respectively. The salinization rate of straw organic carbon of wheat straw was 57% in SRT and 40% in SNT. The nitrogen release rate of wheat straw was 15% in SRT, and 36% in SNT. The straw returning field with rotary tillage accelerated the decomposition of straw and components of straw. Straw covering with no-tillage was beneficial to the release of nitrogen from straw resulting in reduced nitrogen fertilizer addition. The low mineralization rate of organic carbon of wheat straw in straw covering with no-tillage can reduce the rate of carbon cycle and thus increase the carbon sequestration capacity in wheat field. This study provides valuable information on the straw returning practice on rain-fed croplands in northern China.