The fate of phosphorus and molybdenum after biosolids, swine manure and triple superphosphate were applied to a soil

The possible effects of the application of swine manure and biosolids to high phosphorus (P) test soils has been widely debated due to the potential increase in P pollution. The application of these materials to soils might result in changes in water, soil, and crop quality. Increasing P in an already high soil P test (STP) soil may result in changing P dynamics in agro-ecosystems and enhancing P movement away from sorption sites. The purpose of this study was to determine the effect of swine manure (SM), biosolid (BS) and triple superphosphate (TSP) applications on the soil P content in a Webster soil. An incubation study and a field study were conducted where BS, SM and TSP were applied at three rates to a high STP soil. Soybeans and corn were planted in the field experiment. Soil, plant, and grain samples were analyzed for P and Mo. The application of BS, SM, and TSP to a high STP soil resulted in an increase of soil P. This increase of soil P resulted in different response to plant Mo accumulation. A high soil P did not cause an increase of either grain or whole plant Mo uptake in corn. However, increasing P application rate increased P and Mo concentration in soybean whole plant and grain. The results of this study suggest that the fate of P and Mo after 2 years of application of BS and SM is an accumulation in the soil plant system. Accumulations of P in already high STP soils may lead to potential movement of P off-site. This P movement out of sorption sites may contribute to the already high P surplus in the ecosystem. Accumulations of Mo in the soil and subsequently in soybean may increase the potential for molybdenosis in livestock that use soybean as main source of protein.