Polyaspartic acid facilitated rice production by reshaping soil microbiome

Polyaspartic acid (PASP) is used efficiently to promote yield and nitrogen (N) utilization covering various crops including rice, wherein soil microbiome functions are less understood. The present pot experiment investigated the effects of PASP application on rice growth, N utilization, and the soil bacterial community, and identified underlying associations among them. Results showed that changes in soil N forms due to PASP application contributed to augmentations of biomass and N absorption, leaving significantly increased yields of root (35.76 %), stem (14.62 %), and grain (20.46 %) as well as N use efficiency (13.20 %), respectively. An interesting finding was that PASP application enhanced potassium uptake to support rice growth. The soil bacterial community was reshaped after PASP application, which enhanced species richness and diversity and phylogenetic diversity, and attracted nitrification-related phyla (Chloroflexi and Nitrospirae) reducing N loss and beneficial genera (Novosphingobium, Gaiella, Nocardioides, Hydrogenophaga, Iamia, and Geobacter) involved in the nutrition cycle, pathogen suppression, nutrient assimilation, enzyme production, hormone secretion, etc. Co-occurrence network analysis revealed that PASP application enhanced the complexity, stability, functionality, and collaboration of the bacterial community, and showed a shift of keystone taxa towards those beneficial to rice growth. The structural equation model unveiled the synergistic mechanism of PASP, and highlighted the roles of bacterial species diversity and soil N availability in yield promotion. This study implied that beneficial shift of soil microbiota contributed a lot to the synergistic mechanism of PASP to rice yield.