AMMONIA VOLATILIZATION FROM SURFACE-APPLIED UREA: EFFECT OF HYDROGEN ION BUFFERING CAPACITY.

The influence of soil pH and soil cation exchange capacity on ammonia volatilization from surface applied ammoniacal nitrogen has been reported in previous studies. Since the hydrolysis of urea-containing N fertilizers causes an increase in alkalinity, a soil's inherent H** plus buffering capacity (defined as the soil's total acidity, comprised of exchangeable acidity plus non-exchangeable, titratable acidity), should exert a dominant influence on the maximum soil pH at the site of urea fertilizer application. The objective of this study was to demonstrate the importance of a soil's H** plus buffering capacity in affecting NH//3 volatilization from surface-applied urea. It is concluded from this work that H** plus buffering capacity of a soil is a better indicator of NH//3 loss potential than a soil's initial pH.