Transport and fixation of phosphate in acid, homogeneous soils III. Experimental case study of acid, sandy soil columns heavily treated with pig slurry

A computer simulation model of the migration of orthophosphate in soils was applied to undisturbed soil columns treated with amounts of pig slurry up to the equivalent of 1000 t of wet slurry per ha. The kinetic parameters and adsorption data necessary in filling in the model were obtained from long-term batch phosphate fixation experiments. Computer simulation predicted a somewhat greater mobility of phosphate than was found in soil columns. The causes of this discrepancy are discussed. The necessity of taking into account the mineralisation of organic phosphorus is shown. The direct contribution of organic P in pig slurry to P-mobility in the soil was found to be negligible.