旱作地膜覆盖农田土壤有机碳平衡及氮循环特征

近10余年来随着应用面积的迅速增加，地膜覆盖对中国北方旱作农田生产力可持续性的影响受到越来越多的关注。文章对地膜覆盖栽培技术增产效果作了简要评述，重点综述了近年来关于地膜覆盖对农田土壤有机碳平衡和氮循环过程影响的研究进展。地膜覆盖沟垄栽培技术有效减轻了旱作农业区水热条件不足对粮食生产造成的限制，从而对提高耕地生产力发挥了重要作用。对大量文献分析发现，地膜覆盖沟垄栽培技术的增产效果具有明显的地域性，在中国北方半干旱区范围内，水热限制越强烈的地区增产效应越明显。地膜覆盖对农田土壤有机碳平衡和氮循环影响的研究还比较薄弱。目前的研究结果表明，地膜覆盖促进土壤有机碳矿化但同时增加作物根系有机碳输入，初步显示地膜覆盖对土壤有机碳含量的影响可能是中性的。地膜覆盖促进土壤有机氮矿化，提高氮素的有效性，增加作物对氮素的吸收，影响化肥氮的作物利用效率、淋溶和挥发损失，但并不明确是否增加反硝化作用。基于目前研究现状，文章提出了旱作地膜覆盖农田需要加强研究的主要领域：（1）土壤有机质稳定性及其增强机制研究；（2）农田养分管理的系统性研究；（3）在水热条件相对较好的旱作农业区，建议结合秸秆覆盖开展更多研究。

Soil Organic Carbon Balance and Nitrogen Cycling in Plastic Film Mulched Croplands in Rainfed Farming Systems

With the rapid increase in the application area, the effects of plastic film mulch on the sustainability and productivity of rainfed croplands received more and more attention from society. In this review, after briefly summarizing the yield increase effect of plastic film mulch cropping in semiarid rainfed areas, we focused on recent advances in the field of plastic film mulch effects on the soil organic carbon (SOC) balance and nitrogen (N) cycling. Plastic film mulch, especially when combined with a ridge-furrow approach, significantly relieves the limitations of insufficient hydrothermal conditions to crop production, and thus profoundly increases crop yields and cropland productivity. The yield increase effect has a clear regional variation pattern: being greater in more hydrothermally limited areas than in less hydrothermally limited areas. Literature retrieval showed that studies of plastic film mulch effects on SOC balance and N cycling were scarce in croplands. Limited research results showed that plastic mulch stimulates SOC mineralization while increasing crop root-derived carbon input to the soil, and thus the SOC balance can be maintained. Also, limited research results showed that plastic mulch stimulates soil N mineralization thus increases soil N availability and crop N uptake; however, it is not clear if the plastic film mulch increases denitrification. Plastic mulch influences the fertilizer N use efficiency of crops and leaching and ammonia volatilization losses. According to the current research progresses, we proposed three research directions to be further strengthened: (1) Soil organic matter stability and its reinforcement mechanisms in plastic-mulched croplands. (2) Systematically accessing nutrient management strategy and practice. (3) Investigating and introducing straw mulch and no-tillage cropping in areas where the temperature is not a major limitation to production.