Rhizosphere-induced shift in the composition of bacterial community favors mineralization of crop residue nitrogen

Abstract

Abstract Aims In agricultural systems, residue amendment is an important practice for nutrient management, but it is not well known how the residue-nitrogen (N) mineralization is associated with changes of microbial community composition in the crop rhizosphere. Therefore, this study aimed to examine the role of microbes in crop residue N mineralization.Methods A rhizobox system was deployed to reveal the gradient change of the residue-N mineralization in the root-growth zone, and 2 mm and 4 mm away from the root of soybean. Plants were grown in a Mollisol without or with amendment of 15N-labelled soybean and maize residues. Furthermore, amplicon sequencing was performed to detect the shift of microbial community composition associated with the residue-N mineralization. Results The residue-N was mineralized faster in the rhizosphere than the bulk soil, and from soybean residue than maize residue. The co-occurrence network of N-mineralization associated community altered with the shift in the hubs. Moreover, greater enrichment of taxa against the unit of residue-N mineralization and more hubs in the network in the soybean than maize residue treatment were correspondent with the enriched ammonification genes, likely contributing to the enhanced mineralization of soybean residue-N in the rhizosphere. An increase in dissolved organic C and a decrease in available N concentration in the rhizosphere, relative to the bulk soil, might shift bacterial community favoring the residue-N mineralization. Conclusions The spatial changes in chemical properties across the rhizosphere lead to the recruitment of core microbiome taxa to enhance the mineralization of N derived from crop residues.