A model of ammonia volatilization from applied urea. II. Experimental testing

Experimental methods for the measurement of the transfer coefficient for ammonia volatilization from the soil surface to the atmosphere, the gaseous diffusion impedance factor in soil, and other parameters required by the predictive model are described. Following surface application of urea to soil columns, the measured concentration profiles of urea, ammoniacal-nitrogen and soil pH, and the losses of ammonia by volatilization, were compared with the model predictions. The very good agreement between the measured and the predicted results suggested that all important processes have been accounted for in the model.