Soil total phosphorus content is a driver of P forms in continuously flooded paddy soils

• Soil total phosphorus (TP) concentration affects soil P pools before and after rice growth. • Redox-sensitive inorganic P (P i ) and organic P (P o ) are the predominant P pools. • In high-P soils, P o forms do not undergo significant changes with rice growth. • Low-P soils contain labile P o species (diesters) that decompose with rice growth. Redox fluctuations in submerged paddy soils strongly influence the transformation and availability of inorganic (P i ) and organic phosphorus (P o ) forms. However, the extent to which these redox-driven processes affect P i and P o pools and speciation, and their contribution to phosphorus (P) availability for rice, remains poorly understood. This study examined P i and P o dynamics in twelve paddy soils with different total P (TP) content, classified as high-P (>800 mg P kg −1 ), medium-P (500–800 mg P kg −1 ), and low-P (<500 mg P kg −1 ). Soils were analysed before and after 60 days of rice growth using sequential P fractionation, liquid-state 31 P nuclear magnetic resonance ( 31 P NMR) spectroscopy, and phosphomonoesterase activity assays to assess P pools (soluble, exchangeable, redox-sensitive, and residual), organic P composition, and enzymatic hydrolysis potential. Redox-sensitive P i and P o were the dominant pools across all soils, accounting for ∼50 % and ∼18 % of total P, respectively. Soluble and exchangeable P pools remained minor. Concentrations of P i and P o were highest in high-P soils and lowest in low-P soils. In high-P soils, orthophosphate monoesters dominated and remained quite stable during plant growth, likely due to selective accumulation of inositol phosphates under repeated Fe redox cycles. In contrast, orthophosphate diesters in medium- and low-P soils represented the most labile component of P o and were rapidly hydrolyzed during rice growth to alleviate P limitation. These findings highlight how TP content modulates the contribution of P i and P o pools to rice nutrition, emphasizing the need to account for P o dynamics when evaluating P availability in paddy systems under fluctuating redox conditions.