Technical Abstract: Soil chemical and physical reactions involving the phosphorus (P) must be understood thoroughly to predict the risk of surface water transporting P from agricultural land to streams and lakes. Addition of P to soils tends to decrease soil’s capacity to bind P, but the addition of organic constituents can increase or decrease binding capacity. In this study, the kinetics of P sorption by topsoil of an Ultisols (Gilpin silt loam) rom West Virginia, USA receiving P from fertilizers were compared to soils amended with turkey litter in both laboratory incubation and field experiments. Addition of 6.6 and 13.2 Mg turkey litter ha-1 increased Bray1 P levels to about the same level as addition of 53 and 115 kg P ha-1, respectively. Soil’s binding capacity for P decreased to a greater extent when P was added as fertilizer compared to turkey litter: for example, P binding maximum was 360 mg P kg-1 soil (dry weight) when soil was amended with 6.6 Mg turkey litter ha-1 as compared to 260 mg P kg-1 soil (dry weight) when amended with 53 kg P ha-1. This study demonstrates by direct comparison that the decrease in P binding capacity with increasing soil P is less when P is added as turkey litter compared to P fertilizer.