Abstract
To predict P sorption and leaching behavior in calcareous soils, we examined the adsorption and movement of applied P in columns of two calcareous soils. Phosphorus and various other ions were monitored in the leachate of the soil column by passing a 100 mg P l−1 solution through the soil column. Concentrations of P, K+, Ca2+, Mg2+, Na+, HCO− 3, Cl−, EC and pH were determined in the leachates. Movement of K+ and P ions was retarded due to K+ ion-exchange and P adsorption and precipitation, respectively. Phosphorus leaching was affected by supersaturation with respect to P-Ca minerals, but undersaturated with respect to Mg-P minerals. Phosphorus retention based on batch and miscible displacement experiments revealed profound discrepancies that can be attributed to the short residence time of P in the miscible displacement. Breakthrough curves of P and K+ were analyzed by a CXTFIT program. The equilibrium model provides good results to the transport process of P and K+. Results indicated that the mobility of P in these calcareous soils reflects that a high downward movement of water-soluble P in soils may occur and much attention should be paid to leaching of P and potential contamination of P to surface and ground waters.
Acknowledgements
The authors are especially grateful to Professor Sjoerd van der Zee for critical review, perceptive comments and editing on the manuscript on primary draft of the paper.