EFFECT OF BLENDING UREA WITH PYRITE OR COATING UREA WITH POLYMER ON AMMONIA VOLATILIZATION LOSS FROM SURFACE-APPLIED PRILLED UREA

Laboratory studies on a sandy clay loam (Typic Ustochrept) alkaline soil showed that NH3 volatilization loss from surface-applied prilled urea during an 8-day incubation under aerobic conditions was 27.5% of applied N (400 kg N ha(-1)) and was reduced to 8.9% when the urea was blended physically with pyrite in a 1:2 ratio; under anaerobic conditions the values for urea and pyrite-urea were 19.3 and 16.9%, respectively. Other treatments tested were urea-gypsum, neemcake-coated urea and polymer-coated urea. A 6% polymer coating showed the least NH3 volatilization under anaerobic conditions and was next best to pyrite-urea under aerobic conditions. A 3% polymer coating was slightly inferior to the 6% coating. Urea-gypsum and neemcake-coated urea did not differ very much from urea alone under anaerobic conditions, but under aerobic conditions neemcake-urea showed a significantly lower total NH3 loss compared to prilled urea alone and urea-gypsum.