Department of Plant Sciences

Effects of incorporating urea with wheat or corn straw at different soil moisture levels on ammonia volatilization were measured in a field experiment using a sponge-tripping method with KCl extraction. Over a 10-day period following incubation NH3 volatilization peaked on day 3 for urea alone, while highest emission rates were observed on day 2 for urea plus wheat or corn straw. Total NH3 losses decreased in the order: urea > urea + maize straw > urea + wheat straw. Emissions of NH3 were more sensitive to soil moisture after straw addition and correlation analysis showed that NH3 volatilization was also significantly affected by pH of the surface soil. To reduce ammonia losses at the farm level application of urea fertilizer should consider the straw type and soil properties.