SUMMARYA sensitivity analysis of the model described in Part I showed that the proportion of N lost as ammonia from surface applied urea is very sensitive to the initial pH of the soil, its pH buffer capacity, the rate of urea application, and the soil urease activity. Under the conditions tested, the diffusion of bicarbonate ion to the soil surface, to neutralize the acid generated when NH4+is volatilized as NH3, appeared to be the main process controlling the rate of ammonia volatilization.The amount of ammonia volatilized was not very sensitive to the value of the transfer coefficient between the soil surface and the atmosphere, nor to the soil moisture status if this was around field capacity. Adsorption of ammoniacal‐nitrogen was less important than the soil pH buffer capacity in influencing the ammonia volatilization.Further applications and extensions of the model are discusse