The volatilization of ammonia from cattle urine applied to soils as influenced by soil properties

The amounts of ammonia volatilized, following the application of cattle urine to 22 soils, were measured in the laboratory during an incubation period of 10 days. The urine contained 12.0 g N dm^-3 and was applied to small columns of soil at a rate equivalent to 26.5 g N m^-2. The soils were from fields of both grassland and arable cultivation and varied widely in properties. Ammonia volatilization ranged from 6.8 to 41.3% of the total urinary N, with a mean value of 26.4%. The soil property most closely related to the extent of volatilization was cation exchange capacity (CEC), and this was so whether all 22 soils were considered together or whether the 14 grassland and 8 arable soils were considered separately. In general, the higher the CEC the less the amount of ammonia volatilized. However, for a given value of CEC, volatilization tended to be greater from a grassland than from an arable soil. The pH of a soil/urine mixture measured after 24 hours was also quite closely correlated with the amount of ammonia volatilized, but the initial pH and titratable acidity of the soil were poorly correlated with ammonia volatilization. ei]H Marschner ei]H Lambers