A simple analytical transfer function approach to modelling the leaching of reactive solutes through field soil

Summary 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 consecutive drainage seasons could be satisfactorily predicted using a simplified 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 terms were incorporated. Sensitivity analysis showed that the model's prediction was very sensitive to the retardation coefficient for sulphate relative to the non‐adsorbed solute chloride and the volume of soil water that is effective in solute transport. The procedures can be easily adapted for management purposes.