秸秆还田对旱作覆膜农田土壤碳库特征的影响及其微生物响应机制研究

In dryland farming regions of northern China, plastic film mulching and high chemical fertilizer input have significant increase the crop yields while accelerating the soil organic carbon mineralization and decomposition, and as resulting in a severe soil carbon loss and farmland degradation occurred. Straw as an organic carbon source, incorporated into soil can be significant increased soil carbon pool and carbon sequestration ability, thus improving soil fertility and quality. Therefore, our current study intends to incorporation crop straw to soil under the conditions of long-term plastic film mulching in rainfed farmland, to study the SOC storage, SOC fractions and stability, SOC cycle microbial characteristics with plastic film mulch combination with straw incorporation; to reveal the mechanism of SOC pool characteristics on soil microbial community to plastic film mulch combination with straw incorporation; combined with maize yield, to evaluate this measurement on the effects of SOC sequestration, fertilizer, and yield increasing in rainfed farmland; and provide a scientific and technical foundation for improvement of the farmland quality and sustainability of crop productivity under rainfed farmland of northern China.

北方旱作区连年地膜覆盖及高量化肥投入在提高作物产量的同时加速了土壤有机碳的矿化和分解，引起农田土壤碳损失，导致耕地土壤质量退化。秸秆作为有机碳源，还田后可明显起到增碳、固碳的作用，从而提升土壤肥力和改善耕地质量。本项目拟在旱作农田长期地膜覆盖条件下进行秸秆还田，探明地膜覆盖下秸秆还田后土壤碳含量、碳组分及其稳定性特征、土壤碳循环微生物特性的变化规律，揭示地膜覆盖下秸秆还田对旱作农田土壤碳库特征及其微生物响应机制，结合春玉米产量变化，阐明覆膜秸秆还田措施对旱作农田土壤固碳培肥增产机理，为旱作农田土壤质量提升和可持续增产提供科学依据和技术支撑。

本课题组完成了国家自然科学基金青年项目《秸秆还田对旱作覆膜农田土壤碳库特征的影响及其微生物响应机制研究》规定的各项研究内容。本项目主要结果如下：（1）覆膜耦合秸秆还田可降低土壤容重，0-20 cm土层平均降低5.42%，从而改善耕层土壤通气环境，使土壤变得疏松有利于作物增产；（2）覆膜与秸秆还田耦合可显著提高了玉米产量（P＜0.05），平均提高5.87%，同时还可增加作物秸秆还田量，平均可显著增加10.81%，从而增加农田土壤秸秆碳投入量，覆膜还田处理较不覆膜还田处理可显著增加22.96%（P＜0.05）；（3）秸秆还田可促进旱作覆膜农田0-100 cm土壤有机碳含量及其储量，同时优化了土层间有机碳的分布，对土壤有机碳的调配决定了有机碳在土层中的分布，促使更多的有机碳储存在0-60 cm玉米根系主要分布区和生理活跃区；（4）旱作农田土壤团聚体组成以微团聚体< 0.25 mm为主，覆盖耦合秸秆还田可显著提高农田土壤0-40 cm土层＞0.25 mm团聚体含量，其中主要增加2-1和1-0.5 mm粒级；各处理粒级有机碳含量均以5-2 mm粒级最高，而<0.25 mm粒级含量最小，其中覆膜秸秆还田可增加0-40 cm土层各粒级有机碳含量， 以1-0.5和0.5-0.25mm两个粒级增幅最大。（5）秸秆还田后可以使土壤营养环境得以改善，微生物数量和种类得到提高，从而提高耕层0-20 cm土壤脲酶、蔗糖酶和磷酸酶活性，尤其是覆膜秸秆还田处理DS，通过覆膜显著改善土壤水温状况，增幅更加显著。总体来看，覆膜耦合秸秆还田可通过影响土壤碳转化的各个因素（如土壤团聚结构、水温、容重、秸秆还田量及秸秆碳投入量）促进土壤有机碳的积累，进而提升旱作农田土壤肥力并增加作物产量。