Effect of applied sulphur on the uptake by wheat of selenium applied as selenite

This study examined the effect of sulphur (S) on the transformation of selenium (Se) fractions and Se species in soil and on the uptake by wheat of Se applied as selenite. Pot and hydroponic experiments were conducted at the wheat seedling stage. The Se concentrations in shoots and roots of wheat and soil were analyzed by HG-AFS-8220. Selenium content in the soil was divided into different fractions and species. The application of 150 mga (TM) kg(-1) S reduced Se concentrations in wheat shoots and roots significantly, declining 47 % and 45 %, respectively. Sulphur treatment changed soil pH (maximum decrease of 0.52 units) and organic matter content (maximum increase of 0.96 ga (TM) kg(-1)) significantly, thereby reduced the soluble Se concentration, increased the iron (Fe)/manganese (Mn) oxide-bound Se concentration. Sulphur treatment also reduced the concentration of Se6+ in the exchangeable fraction. The application of S fertiliser promoted soluble Se transformation to Fe-Mn oxide-bound Se, organic matter-bound Se and residual Se by lowering soil pH and increasing organic matter content, and inhibited the transformation of Se4+ to Se6+ in the exchangeable fraction, hence reducing wheat uptake of Se in high-Se areas.