Soil properties determine the regional variation in the accumulation of phosphorus inputs in different soil phosphorus pools

Long‐term accumulation of phosphorus (P) in agricultural soils impacts both crop production and the losses to water bodies. Quantifying the accumulation of fertilizer P in soil pools with varying availability is key to designing sustainable P fertilizer strategies. In this study, we aimed to unravel the role of soil properties in determining the fate of fertilizer P inputs and to upscale these insights to predict the regional variation in P accumulation across dissolved, weakly bound, strongly bound, and stable soil P pools in China. These pools were determined by extractions with CaCl 2 (P CACL2 ), NaHCO 3 (P OLSEN ), a mixed solution of oxalic acid and acid ammonium oxalate (P OX ), and H 2 SO 4 –HClO 4 (P TOTAL ). Eight representative soils with highly varying P retention capabilities were fertilized with five P doses (0, 50, 100, 200, and 300 mg P kg −1 ) and incubated for 90 days to quantify how much of the added P ends up in each soil P pool. After 90 days, <3% of the added P ended up in the dissolved P pool, 6%–31% in the weakly bound P pool, 61%–85% in the strongly bound P pool, and 1.7%–32% in the stable P pool. The distribution of P over these pools was highly governed by soil properties, explaining 52% of the fate of added P. Upscaling across China shows strong regional differences in accumulation of added P among soil P pools. The large accumulation and low variation in the P OX content in response to P addition make it a suitable indicator of legacy soil P. This study thus underpins the relevance for introducing P oxalate in regional‐specific P recommendation systems, taking account of differences in soil properties, to enhance the sustainability of P use in agriculture.