Abstract. Conservation tillage has attracted increasing attention over recent decades, mainly due to its benefits in improving soil organic matter content and reducing soil erosion. Under intensive conventional tillage systems, some studies have focused on the responses of soil properties in the topsoil to straw retention. However, long-term straw mulching effects on soil physicochemical properties and bacterial communities among different soil depths under a no-till system are still obscure. One twelve-year experiment was conducted that included straw removal (CK) and straw mulching (SM) treatments. Soil samples were collected at 0–5, 5–10, 10–20, and 20–30 cm soil depths. Most soil physicochemical properties and the relative abundances of bacterial phyla were varied with soil depth. Compared with CK, SM increased soil total nitrogen and organic carbon, available phosphorus and potassium, dissolved organic carbon and nitrogen, and water content. SM increased soil bacterial abundance but reduced the Shannon diversity of the bacterial community at 0–5 cm depth. SM increased the relative abundances of Proteobacteria, Bacteroidetes, and Acidobacteria but reduced those of Actinobacteria, Chloroflexi, and Cyanobacteria. SM had different effects on the relative abundances of some C- and N-cycling genera, for instance, increasing Rhodanobacter, Rhizomicrobium, and Terracidiphilus, and reducing Anaeromyxobacter, Mycobacterium, and Syntrophobacter. A principal coordinate analysis indicated that SM largely affected soil bacterial communities at topsoil depth. Soil pH and different nitrogen and organic carbon fractions were the major drivers shaping soil bacterial community. Overall, straw mulch is highly recommended for use under a no-till system because of its benefits to soil fertility and bacterial abundance. However, inorganic nitrogen fertilizer levels may be reduced under straw mulching to maintain or increase soil bacterial Shannon diversity in future studies.

中文翻译：

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免耕制度下长期秸秆覆盖不同土壤深度下土壤理化性质和细菌群落的变化

摘要。近几十年来，保护性耕作引起了越来越多的关注，这主要是由于其在提高土壤有机质含量和减少土壤侵蚀方面的益处。在密集的常规耕作系统下，一些研究集中在表土的土壤特性对稻草滞留的响应上。但是，在免耕制度下，长期秸秆覆盖对不同土壤深度的土壤理化性质和细菌群落的影响仍然不清楚。进行了十二年的实验，其中包括去除秸秆（CK）和覆盖秸秆（SM）。在0–5、5–10、10–20和20–30 cm的土壤深度收集土壤样品。土壤的大多数理化特性和细菌门的相对丰度随土壤深度而变化。与CK相比，SM增加了土壤总氮和有机碳，可用磷和钾，溶解的有机碳和氮以及水含量。SM增加了土壤细菌的丰度，但降低了0-5 cm深度细菌群落的香农多样性。SM增加了变形杆菌，拟杆菌和酸性细菌的相对丰度，但降低了放线菌，绿弯曲菌和蓝细菌的相对丰度。SM对某些C和N循环属的相对丰度有不同的影响，例如，增加Rhodanobacter，Rhizomicrobium和Terracidiphilus，减少Anaeromyxobacter，分枝杆菌和Syntrophobacter。主坐标分析表明，SM对表土深度的土壤细菌群落影响很大。土壤的pH值以及不同的氮和有机碳组分是塑造土壤细菌群落的主要驱动力。总体而言，强烈建议在免耕制度下使用秸秆覆盖物，因为它对土壤肥力和细菌丰富性有好处。但是，在未来的研究中，可以通过秸秆覆盖降低无机氮肥的含量，以维持或增加土壤细菌香农的多样性。