Sulfur Sources for Flooded and Non Flooded Rice and Pastures

Abstract

It has long been known that sulfur is an essential element for plant growth, however it has received little attention compared to the three main elements, nitrogen, phosphorus and potassium. Sulfur deficiency in crop production has been reported in many parts of the world and has resulted in a decline in both the quality and quantity of crops. Little information is available on the behaviour of different sources of S in flooded and non-flooded rice and in pasture, hence this study. Using an S-deficient granitic Aquic Haplustalf soil, two nested experiments planted to rice were conducted in a heated glasshouse of the Department of Agronomy and Soil Science, University of New England. The experimental components were S rate and S source, two water regimes (flooded and non-flooded) and two consecutive crops. in the S rate study, gypsum was applied at rates equivalent to 0, 5, 10 and 20 kg S ha-¹ . Yield, S uptake and fertiliser S recovery were determined at active tillering (AT), 59 days after transplanting (dat), maximum tillering (MT, 89 dat) and maturity (M, 144 dat). The effectiveness of six commercial S-containing fertilisers, gypsum (G), elemental sulfur (E) of particle size < 0.01 mm, urea-S melt (US), sulfur-coated urea (SCU), elemental S coated triple superphosphate (HF) and S bentonite (S5), and three experimental elemental S coated triple superphosphates (TSP) which were developed at the University of New England, were investigated in comparison to a zero S control (C). In the experimental coatings, three different adhesives were used to bind elemental S to the TSP : polyvinyl alcohol (PVA), calcium ligno sulfonate (LS) and slack wax (SW). In the S source experiment, all fertilisers were applied at 10 kg S ha-¹ . in both experiments S was applied to the first crop only. The release of S from the fertilisers was also investigated at different growth stages (AT, MT and M). The use of 35S labelled soil allowed the study of fertiliser transformation and movement through the soil and plant system.