Effects of organic manure on solubility and mobility of different phosphate fertilizers in two paddy soils

Abstract

The solubility and mobility of three phosphate fertilizers [superphosphate (SP), Ca-Mg phosphate (Ca-Mg-P) and diammonium phosphate (DAP)] with or without combination of farmyard manure (FYM) and/or farmyard manure juice (FYMJ) in two paddy soils (Ultisol and Entisol) from the Zhejiang Province of China were determined. Incubation experiments were conducted under controlled greenhouse conditions in the Institute of Agricultural Chemistry, Bonn University, Germany. The results showed that water soluble P and Olsen P in both the application band and the adjacent zones (10 and 20 mm from the application band) was highest with DAP, and lowest with Ca-Mg-P. Both FYM and FYMJ increased water soluble P (100–300%) and Olsen P (80–300%) for the application band in both soils. Moreover, the combination of FYM significantly increased water soluble P and Olsen P for the adjacent zones (20 mm for the Ultisol and 10 mm for the Entisol), but such effects were not significant in combination with FYMJ. Consequently, the main effect of FYM is due to organic substances from decomposition rather than organic compounds in the FYMJ. Also, the combination of FYMJ with SP and DAP significantly increased the pH value in the application band. The pH in the adjacent zone (10 mm) was slightly increased by the combination of FYM with each of three P fertilizers. The solubility and mobility of phosphate in soils differed greatly among phosphate fertilizers. The combinations of organic manure with mineral phosphate fertilizers increased solubility and mobility of phosphate in both paddy soils, especially in the Ultisol.