Quantification of Oxidation of Elemental Sulphur in Pastoral Soils of New Zealand

A cubic model to describe elemental sulphur (S) oxidation as proposed by Watkinson (1989) was tested under field conditions. Trials were conducted throughout New Zealand to examine the effects of climate, particle size and frequency of application on the rate of S oxidation. Elemental S (75-1S0 mm size) was added to duplicate plots at a rate of 30 kg/ha. Soil samples (0-38 mm) were collected regularly for determining the amounts of added elemental S remaining in the soil. The results showed that the oxidation of elemental S could be adequately described by the cubic model, Por most sites it explained more than 80% of the variability in residual S levels. The oxidation of elemental S was faster by a factor of approximately 2.S on soils from warmer climatic zones compared with colder climate soils. The previous application of elemental S had no effect on the rate of oxidation of subsequent application of elemental S.