棉秆还田对咸水滴灌棉田土壤酶活性和细菌群落结构多样性的影响

咸水长期灌溉会增加土壤盐分，对土壤理化性质产生不利影响，改变土壤细菌的多样性.秸秆还田可以改善土壤微环境，进而影响土壤酶活性和细菌群落结构多样性.试验设置淡水(FW, 0.35 dS·m^-1)和咸水(SW, 8.04 dS·m^-1)两种灌溉水盐度，在每个灌溉水盐度下秸秆用量分别为0 kg·hm^-2和6 000 kg·hm^-2（分别用FWST和SWST表示）.结果表明，与淡水灌溉相比，咸水灌溉显著增加土壤盐分、容重、全碳和速效磷含量，但是速效钾含量明显下降.在咸水灌溉下，秸秆还田可显著增加土壤全碳、全氮、速效钾和速效磷含量，降低土壤容重.咸水灌溉下土壤蔗糖酶、碱性磷酸酶和过氧化氢酶活性较淡水灌溉分别降低57.24%、 35.15%和3.91%,而脲酶活性增加26.73%,但是秸秆还田显著提高蔗糖酶、碱性磷酸酶和过氧化氢酶活性，降低脲酶活性.咸水灌溉降低酸杆菌门（Acidobacteriota）、放线菌门（Actinobacteriota）、拟杆菌门（Bacteroidota）、疣微菌门（Verruco...

Effects of Cotton Stalk Returning on Soil Enzyme Activity and Bacterial Community Structure Diversity in Cotton Field with Long-term Saline Water Irrigation

Long-term saline water irrigation will increase soil salinity, adversely affect soil physical and chemical properties, and change the diversity of soil bacteria. Straw returning can improve the soil microenvironment and subsequently affect soil enzyme activity and bacterial community structure diversity. This experiment used two types of irrigation water salinity:fresh water (FW, 0.35 dS·m^-1) and saline water (SW, 8.04 dS·m^-1). Under each irrigation water salinity, the amount of cotton straw applied was 0 and 6000 kg·hm^-2 (represented by FWST and SWST, respectively). The results showed that:compared with those under fresh water irrigation, saline water irrigation significantly increased the soil salt, bulk density, total carbon, and available phosphorus but significantly decreased available potassium content. Under saline water irrigation, straw returning significantly increased the soil total carbon, total nitrogen, available potassium, and available phosphorus but reduced soil bulk density. Compared with those under fresh water irrigation, soil sucrase, alkaline phosphatase, and catalase activities under saline water irrigation decreased by 57.24%, 35.15%, and 3.91%, respectively, whereas urease activity increased by 26.73%. However, straw returning significantly increased sucrase, alkaline phosphatase, and catalase activities but decreased urease activity. Saline water irrigation decreased the relative abundance of Acidobacteriota, Actinobacteriota, Bacteroidota, Verrucomicrobiota, and Firmicutes and increased the abundance of Gemmatimonadota and Myxococcota. Under saline water irrigation, straw returning significantly increased the relative abundance of Actinobacteriota, Bacteroidetes, Firmicutes, Crenarchaeota, Sphingomonas, Dongia, and Steroidobacter. NMDS results also showed that saline water irrigation and straw returning changed the bacterial community structure. In conclusion, straw returning can improve soil nutrient content, reduce soil bulk density and salinity, and then change soil enzyme activity and bacterial community structure diversity. The change in soil bacterial community composition was mainly affected by soil salinity and bulk density. Therefore, straw returning can improve soil fertility and help maintain the health of soil ecosystem. This study revealed a relationship between soil enzyme activities and bacterial communities, which provides a theoretical basis and mechanism for applying cotton stalk to regulate the soil enzyme and micro-ecological environment.