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 u rea 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 availabilit y from a range of P-S, N-S and S sources. The reverse dilution S-35 te chnique was used to estimate fertilizer S uptake by the crops followin g fertilizer application and a second crop grown on residual S. The fe rtilizers evaluated were gypsum (G), elemental S (E), urea-S melt (US) , sulfur-coated urea (SCU), S-coated TSP (HF), S-bentonite (SB) and th ree S-coated TSP products in which the adhesives were UNE1, UNE2 and U NE3. Highest grain yields in crop 1 were obtained with G, UNE1 and UNE 3 under flooded conditions, and G, UNE1, UNE3, SCU and E under non-flo oded 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 fo llowed 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.