Soil texture and pH exhibit important effects on biological nitrogen fixation in paddy soil

Abstract

Biological nitrogen fixation (BNF) is an important source of soil nitrogen. However, for dry-wet alternative paddy soil, the combined effects of multiple driving factors, including soil physicochemical properties and the soil microbiome, on BNF are not fully understood. In this study, three types of paddy soil were collected to determine the BNF amount by field-based 15N2 labeling experiments. Soil nitrogen fixing microbiome was analyzed using high-throughput sequencing based on the nifH gene. Random forest analysis, co-occurrence network analysis and hierarchical partitioning were performed to screen the key diazotrophic community and critical soil properties. The results revealed that rice nitrogen acquisition from BNF ranged from 1.62 % to 7.80 %. Three key diazotrophic genera, Rubrivivax, Frankia and Azospirillum, significantly affected BNF. The BNF amount in the 0–1 cm soil layer was significantly higher than that in the 1–15 cm soil layer, which was consistent with the relative abundance of Cyanobacteria. The soil silt content and pH were positively correlated with the BNF amount by mediating the key diazotrophic microbiome. These results indicated that the BNF amount plays an important role in rice nitrogen acquisition and paddy soil nitrogen sources, which might be regulated by soil texture and soil pH.