Predicting the Leaching of Sulphur Fertilizer on Yellow-Brown Pumice Soils

Leaching of sulphate can have a major influence on pasture yield and fertiliser efficiency on the yellow-brown pumice soils of New Zealand. This study aimed to measure and predict sulphur (S) leaching on these soils. The Rose model (an approximate analytical method based on the convective-dispersive equation) accurately simulated S leaching data from intact cores when a retardation factor was included to allow for sulphate adsorption, The model was then used to predict the leaching of sulphate or elemental S fertilisers applied in spring or autumn. Predicted amounts leached below 260 mm depth after 12 months were 91, 71, 38 and 61 % of fertiliser applied for autumn sulphate, spring sulphate, autumn elemental and spring elemental S fertilizers respectively. These results were consistent with plant S uptake in a field trial. Autumn applications of elemental S seem to offer the most effective means of supplying plant requirements with minimum wastage.