Effects of Continuous Return of Bt Corn Straw on Soil Nutrients, Enzyme Activities, and Microbial Communities

The impact of Bacillus thuringiensis (Bt) corn straw returning on the soil ecosystem has attracted significant attention. In this study, taking the homologous conventional corn 5422 as a control, we explored the effects of Bt corn (5422Bt1 and 5422CBCL) straw return after five consecutive cycles on soil nutrients, enzyme activities, and microbial communities. The results showed that in the 5422Bt1 treatment, the levels of available phosphorus (AP), total nitrogen (TN), and sucrose enzyme (SUC) activities significantly increased. In the 5422CBCL treatment, organic matter (OM), alkaline nitrogen (AN), and AP contents, as well as SUC and acid phosphatase (ACP) activities, significantly decreased, while available potassium (AK) and TN contents significantly increased. Through Illumina high-throughput sequencing, it was found that the OTU abundance of soil fungi and bacteria changed after straw returning, and there were no significant differences in alpha diversity (α-diversity) among the three treatments. Redundancy analysis (RDA) indicated that soil nutrients and enzyme activities also affect the soil microbial communities. In summary, Bt corn straw returning affects soil nutrients, enzyme activities, and the structure of microbial communities. Overall, this study revealed the impact of continuous Bt corn straw returning on the soil ecosystem, providing a theoretical basis for subsequent studies.