Response of soil phosphorus fractions and microbial community network to straw returning: Insights from microbial phosphorus limitation

Abstract

Soil microbial metabolism is usually limited by nutrients in agricultural ecosystems; however, the mechanism through which straw return determines microbial nutrient limitations by affecting soil phosphorus (P) fractions and microbial community networks remains unclear. We investigated the effects of no-tillage with straw return (NTS), plow tillage with straw return (PTS), rotary tillage with straw return (RTS), and conventional tillage (CT) without straw return (control) on soil microbial structure, co-occurrence networks, and assembly processes in Northeast China in 2023–2024. All soil microorganisms in the four treatments were subjected to P limitation, and compared with CT, the three straw returning practices significantly alleviated microbial P limitation to a certain extent. Straw returning promoted organic P mineralization and improved P availability by regulating P fractions, as shown by the increased inorganic P content of the NTS, PTS, and RTS treatments of 41.54 %, 6.25 % and 6.80 %, respectively (averaged across rhizosphere and bulk soil, and two years). Random forest and correlation analyses showed that NaHCO₃–Po had a more significant response to P limitation. Straw returning practices did not change the soil bacterial diversity of the rhizosphere and bulk soil but decreased the fungal diversity through microbial high-throughput sequencing. Straw return-sensitive ASVs (rsASVs) was selectively aggregated in different modules, and straw returning induced specific responses in taxa/modules of microbial co–occurrence networks in the rhizosphere and bulk soil. Partial least squares path modeling found that, compared with fungi, changes in the bacterial community structure driven by straw returning crucially alleviated microbial P limitation. Overall, our results highlight the close relationship between microbial community structure and metabolic limitations and provide a theoretical basis for the application of straw returning in agriculture.