Phosphate adsorption characteristics of two soils responding differently to P fertilization

Authors

• Markku Yli-Halla Kemira Oy, Espoo Research Centre, Luoteisrinne 2, SF-02270 ESPOO, Finland

DOI: https://doi.org/10.23986/afsci.72409

Abstract

The soil samples of the present study originated from two field experiments in which five rates of P (annually 0, 13 or 16, 26 or 32, 47 or 56, 60 or 72 kg P/ha) had been applied for 11 or 12 years. The fields were silty clay soils (Cryochrepts) not differing markedly in pH, contents of clay, organic C, or poorly crystalline Al and Fe oxides. Before the field experiment, the quantities of P extracted with an ammonium acetate solution (pH 4.65) were approximately 6 mg/dm3 in both fields. However, the fields differed considerably in the response of the crop to P fertilization. Phosphorus adsorption by the soil samples was studied by shaking the samples in solutions of different P concentrations (0 —0.5 mg/l). Soil I, showing greater response to P fertilization in the field, adsorbed P considerably more effectively than did soil II. Also the quantities of reversibly adsorbed P were smaller in the subsamples of soil I as compared to those of soil II receiving the same fertilization. Fertilizer P applied during the field experiments had been adsorbed and converted to forms unavailable to plants to a larger extent in soil I, resulting in greater response to P fertilization in this soil. The difference in response to applied P or in residual effect of P fertilization could not be predicted from soil characteristics other than P sorption.