Impacts of Various Straw-Returning Techniques on the Chemical Characteristics and Bacterial Diversity of Soil

Straw returning enhances soil fertility and increases corn yield, but the impact on soil fertility varies with different incorporation methods. To explore the optimal straw-returning method, this study, based on a long-term field experiment, investigated the following different corn-straw-returning methods: deep plowing and straw returning (B), rotary tillage and straw returning (RT), crushing and mixing straw returning (TM), pulverized cover straw returning (C), high-stubble-retention straw returning (LHS), strip cover (S), and flat no-tillage without straw returning (CK). High-throughput sequencing technology was employed to analyze the soil bacterial community composition and structural changes under different straw-returning methods. The study further explored the relationships between the soil bacterial community and nutrient content. The results indicated that different straw-returning methods altered the composition and structure of the soil bacterial community. The TM treatment significantly increased the richness and diversity of the soil bacterial communities. Shredding and covering (C and TM) effectively improved the soil nutrient content and bacterial community structure. In the C treatment, the abundance of Blastococcus, Nocardioides, and Microvirga increased the most, by 241.02%, 77.79%, and 355.08%, respectively, compared with CK. In the TM treatment, Pseudarthrobacter showed the highest abundance, increasing by 343.30%. The genes involved in soil carbon hydrolysis (pulA), nitrification (hao), organic nitrogen degradation and synthesis (gudB), and the nitrogen limitation response (glnR) significantly decreased by 56.21%, 78.75%, 66.46%, and 67.40%, respectively, in the C treatment. The genes involved in soil carbon hydrolysis (IMA), carbon fixation (pccB-A), methane metabolism (moxF), nitrate reduction in soil (nirD), organic nitrogen degradation and synthesis (gdh, ureAB, ureE), and phosphate absorption (glpT) significantly increased by 93.37%, 92.68%, 95.00%, 23.42%, 35.40%, 114.21%, 59.14%, and 75.86%, respectively, in the C treatment. The nitrate reduction gene (nrfA) significantly increased by 80.27% in the TM treatment. Therefore, we concluded that straw primarily stimulates the activity of bacterial communities and regulates the bacterial community by changing the relative abundance of the soil microorganisms and functional genes, thereby improving the soil nutrient content. This study considered pulverized cover straw returning and crushing and mixing straw returning to be the most reasonable methods.