5. Conclusion
The results of the 5-year continuous straw return experiment revealed that the straw return significantly increased the content of soil carbon and nitrogen pools, particularly active carbon pools, by enhancing the structural diversity of bacterial communities. Straw return also enhanced the ability of microorganisms to utilise carbohydrates, amino acids, and carboxylic acid carbon sources, with amino acid carbon sources more influential in explaining the changes in soil carbon and nitrogen pool contents. Additionally, we observed differences in the fungal community structure and microbial metabolic activity between low (S1/2) and high (S1, S2) amounts of straw returned to the field, indicating that the application of an optimal amount of straw to the field can regulate the soil microbiological environment, affecting the microbial diversity and consequently the content of soil carbon and nitrogen pools, improving the soil quality through biological regulation. Our study provides a theoretical basis for the sustainable development of high-efficiency and high-quality wheat production in drylands.