关中平原农田作物秸秆还田对土壤有机碳和作物产量的影响

Effect of Returning of Cropland Straw to Field on Soil Organic Carbon and Grain Yield in Guanzhong Plain

结合关中平原农业生产现状,通过对不同秸秆还田模式组合下土壤有机碳、活性有机碳含量和作物产量变化趋势的研究,揭示秸秆还田效应,为研究区筛选合理的还田模式以及农田土壤培肥和农业可持续发展提供理论依据。结果表明,小麦秸秆还田后经过一季夏玉米生长,能使耕层土壤(0～40 cm)有机碳有所提升;高留茬还田使0～20 cm土层土壤活性有机碳和碳库管理指数呈现降低趋势,而粉碎直接还田使其有所提高,但差异均未达到显著水平。随后对玉米秸秆进行还田,再经过一季小麦生长后,使得耕层土壤有机碳含量有所提高,其中连续两季进行秸秆粉碎直接还田使有机碳含量提高幅度最大,0～20,20～40 cm土层有机碳分别提高1.86,1.69 g/kg;同时显著增加了耕层土壤活性有机碳含量,其中小麦秸秆进行粉碎直接还田增加趋势更为明显,0～20,20～40 cm土层中分别平均提高0.90,0.85 g/kg;且秸秆还田显著增加了碳库管理指数,秸秆粉碎还田条件下增加趋势更明显。在关中平原的雨热条件下,通过田块尺度上秸秆还田能有效改善土壤有机质状况,尤其使有机碳质量明显提升,就短期效果而言秸秆粉碎直接还田对土壤有机碳的调节作用更为明显;针对研究区域容易出现的季节性干旱现象,在小麦秸秆还田时采用高留茬还田能有效提高夏玉米生长期内水分利用率,保证其稳产高产;轮作期内实施小麦高留茬-玉米粉碎直接还田模式组合,是实现该区域水热资源高效利用,农业高效高产的最优耕作模式组合。

Effect of straw returning in field scale on soil organic carbon （SOC） and grain yield was studied to explore more reasonable farming management models, which was helpful to provide a theoretical basis for soil cultivation and sustainable agricultural development in Guanzhong Plain. With the actual situation of agricultural production in test area, the trends of SOC, active organic carbon （AC） content and grain yield in different treatments were examined to clear the effect of straw returning through a comprehensive comparison. After the returning of wheat straw to cropland, the summer maize was grown. The result showed that SOC in topsoil （0 -40 cm） have been improved in straw application, and that soil AC and carbon pool management index （CPMI） of 0 -20 cm soil layer were slightly lowered in high stubble in field, while soil AC and CPMI were increased through smashing the wheat straw into field, which didnt make their mutation change. Subsequently, the result showed that maize stalks were returned to the field in three models, and that, after the wheat growing season, SOC content in the topsoil has increased significantlythrough the straw returning treatment, and that, through smashing straw into field twice the SOC content can increase by 1.86 g/kg in 0 -20 cm soil and 1.69 g/kg in 20 -40 cm soil respectively. And also, the returning of crops stalk to the cropland can increase the AC content in the topsoil strikingly-especially, when wheat straw is smashed into the field, the AC content in the topsoil can increase more strikingly, that is, a average AC content can increase by 0.90 g/kg respectively in 0 - 20 cm and 0.85 g/kg in 20 - 40 cm soil; And straw returning significantly increased CPMI, especially through smashing straw into field treatments. Under the conditions of climate in Guanzhong Plain, soil organic carbon condition could be improved significantly through returning straw to field scale, especially, the SOC quality can be improved. Therefore, in the short run, smashing and returning the straw to the field can change the SOC more obviously. For there easily appear seasonal drought in the study area, it was useful to improve water use efficiency in maize growth period effectively to ensure the stable or higher yield trough high-stubble of wheat straw in field. It was the optimal model combination of high stubble of wheat with maize straw smashed into field in a whole rotation period for productive and efficient agriculture in this region, which can make a full use of water and heat resources in Guanzhong Plain.