A GLASSHOUSE EVALUATION OF SULFUR FERTILIZER SOURCES FOR CROPS AND PASTURES .1. FLOODED AND NON-FLOODED RICE

The increasing use of high analysis fertilizers such as TSP, DAP and urea has contributed to an increased incidence in sulfur deficiency in rice-growing areas of the world. Two pot experiments (flooded and non-flooded soil) were conducted with IR-43 rice to evaluate S availability from a range of P-S, N-S and S sources. The reverse dilution S-35 technique was used to estimate fertilizer S uptake by the crops following fertilizer application and a second crop grown on residual S. The fertilizers evaluated were gypsum (G), elemental S (E), urea-S melt (US), sulfur-coated urea (SCU), S-coated TSP (HF), S-bentonite (SB) and three S-coated TSP products in which the adhesives were UNE1, UNE2 and UNE3. Highest grain yields in crop 1 were obtained with G, UNE1 and UNE3 under flooded conditions, and G, UNE1, UNE3, SCU and E under non-flooded conditions. Fertiliser S uptake was highest from G under flooded conditions and uptake was higher with UNE1 and UNE3 than E. Under non-flooded conditions, fertilizer S uptake was highest with G and UNE1 followed by UNE3 and E. Yield and fertilizer S uptake in the second crop were generally inversely related to those in crop 1. The results have shown differences between TSP-S products due to the method of bonding of the S coat to the TSP.