Effect of particle size on the oxidation of elemental sulphur, thiobacilli numbers, soil sulphate, and its availability to pasture

Abstract The effect of particle size of elemental sulphur (ES) on thiobacilli numbers, oxidation of ES to sulphate, uptake of sulphur (S) by plants, and dry matter (DM) yield was measured for 340 days in a field experiment in a cool temperate environment at Invermay Agricultural Centre. Particle size ranges of 0.01 – 0.038, 0.01 – 0.15, 0.038 – 0.075, 0.075 – 0.15, 0.15 – 0.25, 0.25 – 0.5, 0.5 – 1.0, and 1.0 – 2.0 mm diam. were applied once at a rate of 50 kg S/ha in a randomised block experiment. The residual ES in the soil was measured by a high performance liquid chromatography procedure. After 340 days, about 80 – 90% of the applied ES from the treatments with particle size ranges 0.15 mm (coarse ES treatments) was oxidised because of their smaller surface area. Also, there was more soil sulphate and there were larger numbers of thiobacilli in the fine ES than coarse ES treatme...