Particulate rather than mineral-associated organic matter pool determines soil phosphorus bioavailability in uncultivated Mollisols

Increasing depth drove a consistent decline in the concentration and proportion of labile P (LP) and moderately labile P (MLP) and a rise in proportion of non-labile P (NLP) within both particulate organic matter (POM) and mineral-associated organic matter (MAOM), indicating a shift of the soil P pools toward more stable, less available forms in uncultivated Mollisols. The different fractions of soil organic matter significantly altered the soil phosphorus storage and supply capacity. POM contributed most to P availability with higher concentrations of all P fractions especially LP and MLP. influenced by organic carbon, whereas LP and MLP in MAOM were jointly influenced by organic carbon and iron oxides. These findings could have substantial implications to soil phosphorus management to maintain and improved soil phosphorus storage and availability by increasing the POM pool from organic matter fractions in Mollisols.