Effects of bio-mulching on wheat soil microbial community and carbon utilization efficiency in southwest China

Bio-mulching is a common agricultural practice in southwest China to improve crop productivity and soil fertility. In this study, a field experiment to investigate the effects of Chinese milk vetch (Astragalus sinicus L.) mulching and soybean straw retention (at the rate of 2250 and 4500 kg ha(-1)) on wheat soil microbial community and carbon utilization efficiency was conducted in southwest China. Results showed that the alpha diversity indices (Chao and Shannon) of bacteria and fungi in milk vetch mulching treatment were significantly increased in the wheat non-rhizosphere soils compared with control soil (without mulching). Within the bacterial com-munity, the relative abundance of Actinobacteria and Chloroflexi was significantly increased by milk vetch mulching over the control, while the relative abundance of Acidobacteria, Firmicutes, Verrucomicrobia, and Gemmatimonadetes were significantly decreased in both wheat rhizosphere and non-rhizosphere soil. Within the fungal community, the relative abundance of Basidiomycota was significantly increased in milk vetch mulching treatment than that of control. By contrast, the differences in microbial diversity and community structure be-tween the soybean straw retention and control were not distinctive. The correlation analysis revealed that wheat soil moisture, soil nitrate content, microbial biomass carbon, dissolved organic carbon and nitrogen content were closely related to the soil microbial community structure under different mulching practices. Results of the Biology ECO-plate revealed that all bio-mulching practices have enhanced the carbon source utilization rate. In addition, the relative abundance of Actinobacteria and Basidiomycota has a positive correlation with the meta-bolism rate of carbon substrates, such as glycyl-L-glutamic acid, I-erythritol, D-xylose, and alpha-cyclodextrin. Overall, our results suggested that bio-mulching, especially milk vetch mulching, has changed greatly the soil microbial community structure and function in the wheat rhizosphere.