SEASONAL FLUCTUATIONS IN MINERAL SULPHUR UNDER SUBTERRANEAN CLOVER PASTURE IN SOUTHERN NEW SOUTH WALES

Seasonal changes in sulphate sulphur were studied in a soil under subterranean clover pasture. Fluctuations in sulphate content were found to be similar to those in nitrate. Both sulphate and nitrate accumulated in the surface soil during summer, immediately after senescence of the pasture. High concentrations were maintained throughout the summer-autumn period and these decreased to low values in winter and spring. The higher values in summer probably resulted from mineralization of soil organic matter under favourable moisture and temperature conditions, and lack of plant uptake. Minor fluctuations were associated with partial leaching by rainwater. The low values in winter and spring were probably brought about by leaching and plant uptake, together with low rates of mineralization at low soil temperatures. © 1968, Australian Journal of Soil Research.