Effect of Different Straw Return Modes on Soil Bacterial Community, Enzyme Activities and Organic Carbon Fractions

Core Ideas Straw returned twice each year (WC‐MC and WH‐MC) significantly enhanced SOC and DOC. Return of both wheat and maize chopped straw had highest β‐1,4‐xylosidase, invertase, and enhanced Alphaproteobacteria and Gammaproteobacteria . Retention of high wheat stubble and return of chopped straw had highest β‐1,4‐glucosidase, cellobiohydrolase, and enhanced Acidobacteria and Planctomycetes . Amount and complexity of straw added led to differences in C, enzyme activity, and microbial composition. High wheat stubble and crushed straw improved yields and bacterial richness, but had less C sequestration. Little is known about the responses of organic carbon fractions, enzymes activity, and soil bacterial communities and diversity to different straw return modes in intensive maize‐wheat double‐cropping systems. An 8‐yr field experiment was conducted to evaluate the effects of different straw return modes. Four treatments were compared: (i) return of both wheat and maize chopped straw (WC‐MC); (ii) retention of high wheat stubble and return of chopped maize straw (WH‐MC); (iii) retention of high wheat stubble and no return of maize straw (WH‐MN); and (iv) no return of straw of both wheat and maize (WN‐MN). Soil organic carbon, dissolved organic carbon, and particulate organic carbon content increased significantly in the WC‐MC and WH‐MC. Beta‐1‐4‐xylosidase and invertase were higher in the WC‐MC treatment than in WH‐MC, while the highest β‐1,4‐glucosidase activities were observed in WH‐MC. However, the activity of polyphenol oxidase was low in all three straw return treatments. Alphaproteobacteria and Gammaproteobacteria dominated in WC‐MC, while the Acidobacteria and Planctomycetes phyla dominated WH‐MC. The two high wheat stubble retention modes caused significant increases in bacterial richness. Redundancy analysis showed that C input amount and organic carbon content were the most influential factors determining bacterial community structure. The observed effects were due to straw amount and the complex composition of WH‐MC added during the wheat growing season compared to WC‐MC. In conclusion, the straw return mode that employs high wheat stubble retention and chopped maize straw return is sufficient to maintain organic carbon levels and improve the soil microenvironment