Manure application influences microbial stoichiometry and alters microbial life strategies to regulate phosphorus bioavailability in low-P paddy soil

Abstract

Microbial stoichiometry is pivotal in the soil elements cycle within terrestrial ecosystems. However, the impact of microbial stoichiometry on the phosphorus (P) pool transformation in low-P paddy soil, especially with manure addition, remains poorly understood. This study aimed to elucidate the response mechanism of microbial stoichiometry in regulating P pool transformation in two low-P paddy soils during a 60-day flooding-drought incubation. The results demonstrated that pig manure and vermicompost application significantly increased soil Olsen-P by 202–309 %, and microbial biomass P (MBP) by 54.4–79.3 % compared to no fertilization. Additionally, vermicompost treatment increased moderately labile organic P (MLP_o) by 133–257 % and decreased fulvic acidassociated organic P (FAP_o) by 10.5–25.4 % in Acrisol-flooding, Acrisol-drought, and Ultisol-drought, indicating that manure application improved the transformation of FAP_o to MLP_o. The microbial biomass carbon (MBC)/MBP ratio was lowest under Acrisol-flooding and highest under Ultisol-drought, suggesting that microorganisms adjust high ratios for stoichiometric stability and enhanced MBP utilization under deficient resource conditions. Manure treatments increased alkaline phosphatase (ALP) by 5.33–12.9 % under flooding conditions, indicating microorganisms facilitate the mineralization of soil organic P (P_o). Compared to Acrisol-flooding, both ALP and β-1,4-glucosidase (BG) significantly increased by 103 % and 259 %, respectively, under Ultisol-drought, along with a positive correlation between BG and MLP_o, implying that microorganisms enhance soil organic matter mineralization in resource-limited conditions by increasing C-acquiring enzymes and releasing P_o. Additionally, the microbial community composition shifted from r-strategists to K-strategists, primarily by decreasing Proteobacteria and increasing Acidobacteria under resource deficiency and drought. The r-strategists directly mineralize P_o by maintaining a low MBC/MBP and high ALP, while K-strategists indirectly mineralize P_o by maintaining a high MBC/MBP and high BG. The findings suggest that manure application altered the resource status of low-P paddy soils, changed microbial stoichiometry, and influenced soil P availability through adjustments in microbial activity and extracellular enzyme production.