Effects Of Different Rotational Legume Crops And Residue Management Regimes On Soil Microbial Properties And Functions In A Sugarcane Farming System

Background: Legume crop rotation in sugarcane cropping systems can improve soil health and fertility. However, their impacts on soil microbial community composition and function have not been clearly understood to date.Aims: This study aimed to assess responses of soil biochemical properties and composition of microbial communities driving C and N transformations in soils to different legume crop rotations and crop residue management practices.Methods: We investigated the effects of two rotational legume crops (soybean and peanut) and six different crop residue management practices on soil physicochemical and microbial properties as well as biological activities including C and N mineralisation, nitrification capacity and denitrification potential, in a subtropical sugarcane cropping system.Results: Incorporating high-N soybean crop residues into soil significantly increased soil mineral N content in the first month compared to no-till; no significant tillage effects were recorded with low-N peanut residues. Both crop residues increased soil microbial biomass C, C mineralisation capacity and nitrification capacity. However, bacterial and archaeal composition and abundances of 16S rRNA and nitrification genes were not affected. Spraying a nitrification inhibitor (DMPG) onto the crop residues before tillage significantly suppressed soil nitrification capacity.Conclusions: Compared to peanut rotation, soybean rotation could supply significantly more N for the following sugarcane crop due to its much higher crop residue N inputs and faster N mineralisation. Spraying legume residues with DMPG before tillage may provide an effective strategy to inhibit NO3- formation and thus reduce the risk of NO3- losses through leaching or denitrification.