A SIMPLE ANALYTICAL TRANSFER-FUNCTION APPROACH TO MODELING THE LEACHING OF REACTIVE SOLUTES THROUGH FIELD SOIL

Results from a previous study, in which two different forms of sulphur fertilizer were applied to a grazed pasture, were re-examined to show that the movement of sulphate to subsurface drains over three consecu tive drainage seasons could be satisfactorily predicted using a simpli fied analytical form of the transfer function model (TFM). Two simple parametric forms: the exponential Burns and lognormal functions, were used for the probability density function for solute travel, and more realistic assumptions about the biologically mediated source-sink term s were incorporated. Sensitivity analysis showed that the model's pred iction was very sensitive to the retardation coefficient for sulphate relative to the non-adsorbed solute chloride and the volume of soil wa ter that is effective in solute transport. The procedures can be easil y adapted for management purposes.