Difference of Soil Bacterial and Fungal Communities Under Wheat and Maize Straw Incorporation Closely Related to Fractions and Chemical Structure of Soil Organic Carbon

The incorporation of different types of crop straw may lead to distinct forms and chemical structures of soil organic matter (SOM), which are closely associated with soil microorganisms in agricultural ecosystems. However, the relationship between the SOM physical-chemical compositions and soil microbial communities after different types of crop straw incorporation remains largely unknown. In the present study, a long-term (10-year) field experiment, including five treatments of no fertilizer and no straw return (control), mineral fertilizer application alone (F), mineral fertilizer with wheat straw return (WF), mineral fertilizer with maize straw return (MF), mineral fertilizer application combined with wheat and maize straw return (WMF), was conducted to investigate the associations between SOM physical fractions, SOM chemical compositions, and fungal and bacterial communities in using advanced solid-state 13 C nuclear magnetic resonance and high throughput sequencing techniques. We found that long-term wheat straw incorporation increased the carbohydrate Cs of light-fraction organic matter (LFOM) and coarse-particulate organic matter (cPOM) relative to MF treatment, which were significantly correlated to soil bacterial community composition. While long-term maize straw incorporation increased the proportion of cPOM and fine-POM (fPOM) fractions relative to WF treatment, as well as their aromatic components, which were significantly correlated to soil fungal community composition. Together, results from the present study revealed that bacterial and fungal communities have two distinctive response to wheat and/or maize straw incorporation, which were strongly associated with SOM fractions and their chemical structure, especially for POM fractions. Our results provided the critical evidences for understanding the correlation between soil microbial communities and SOM fractions after crop straw incorporation, which will help to develop the optimal strategies for crop straw management