Soil Phosphorus Partition and Transformations Under Diverse Land Uses

This study investigates soil phosphorus (P) partitioning and transformations through chemical fractionation and modeling across various land uses to elucidate their impact on P dynamics and the potential for eutrophication. Geo-referenced soils (0–30 cm at various depth intervals) were collected from diverse land uses, including corn, soybean, wheat stubble, modified relay intercropping, corn-soybean with rye under conventional tillage and no-till systems, and sheep pastures, alongside an adjacent forest (control). Processed soils were sequentially extracted to quantify soluble reactive (SRP), exchangeable (EP), Ca and Mg bound (CaMgP), Fe and Al bound (FeAlP), particulate organic (POP), residual (RP), and total P pools. Results showed significant effects of land use and soil depth on extracted P pools. Notably, corn-soybean with rye exhibited a higher SRP accumulation (2.8 mg/kg) compared to the forest. The labile (SRP + EP), moderately labile (FeAlP + CaMgP + POP), and non-labile P (RP) pools accounted for 1 to 2, 23 to 29, and 65 to 76% of total P, respectively. The structural equation model elucidated soil P transformation, indicating the contribution of labile, moderately labile, and non-labile P pools to SRP accumulation in various land uses. Our findings underscore the critical link between land use, soil P dynamics, and eutrophication risk, offering valuable insights for developing agricultural management practices aimed at mitigating edge-of-field P loss and protecting water quality against eutrophication.