Phosphorus (P) is removed from fields in runoff either as dissolved P or as a component of soil particles carried by runoff water. The focus of our work concerns the potential for P to dissolve in water from dairy manure or poultry litter applied to soil. The objectives of our research were to quantify P released from manure-amended soils with different antecedent soil test P levels and to elucidate manure P chemical properties controlling P loss to runoff water. For this research, we used waterextractable P in raw manures and manure-amended soils with water as an indicator of the relative susceptibility of P in these materials in the field to dissolution and removal by runoff water.