Evaluation of Ammonia Volatilization from Some Modified Urea Fertilizers

Effect of different additives like coal tar (CT), neem cake (NC) and mustard cake (MC) and organic nutrient sources like greenmanure (GM) and farmyard manure (FYM) on urea hydrolysis, NH_4⁺-N content, ammonia volatilization loss and soil pH was evaluated in an Alfisol, a Vertisol and an Inceptisol. Coating of urea with MC retarded urea hydrolysis and consequently reduced ammonia volatilization loss, whereas coating of NC accelerated the ammonia loss from urea. Application of GM with urea effectively reduced pH of soil and reduced ammonia loss from urea in Vertisol and Inceptisol but not in Alfisol. Maximum ammonia volatilization loss occurred between two to four days after fertilizer application in Vertisol and Alfisol, and between four to six days in the case of Inceptisol. Cation exchange capacity of soil appeared to influence in reducing ammonia loss than native soil pH.