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

Abstract

The effect of applying phosphorus (P) on high P test soils (STP) is a concern due to possible changes in water, soil, and crop quality. Increasing P in the soil may change relationships with other nutrients such as molybdenum (Mo). The purpose of this study was to determine the effects of the application of triple superphosphate (TSP), swine manure (SM), and biosolids (BS) on soil P forms and extractable Mo. An incubation study was conducted in a chamber with controlled temperature and light. The treatments consisted of mixing 10 g of soil from 4 different depths with TSP, SM, and BS at a low and a high rate. A sequential fractionation for inorganic and organic P forms was performed. Soil extractable Mo was determined as well. There were differences in extractable Mo after treatments were applied, and the BS application always produced the highest values. Soil P was higher in the BS treatment than in the SM and TSP treatments in all P fractions. Increasing P rate increased soil extractable P and Mo in soils. Extractable Mo within the treatments was not affected by soil properties with soil depth. The application of BS, SM, and TSP to high STP soil resulted in differences in extractable P fractions in the soil. The proportion of soil P fractions were: NaOH-Po > HCI-P > NaHC03-Pi > H2S04-P. ^ Hernandez, J. D. Research Assistant. Dept. Agronomy, Iowa State University, Ames IA 50010 Killorn, R. Professor. Dept. Agronomy, Iowa State University, Ames IA, 50010