Agricultural Perturbations of the Nitrogen Cycle and Related Impact on Atmospheric N_2O and Ozone

The available data are employed to identify the fate of agricultural nitrogen in the environment. Best estimates predict denitrification of nearly 50% of fertilizer nitrogen in less than 10 years after application. We also discuss in detail the expected demand curve for agricultural N. If population growth continues at projected levels, between 100 and 200 M tons/yr of agricultural N will be needed by the year 2000. We estimate that as a result, atmospheric N_2O could be more than doubled by 2050, and that perturbations of O_3 at that time could range from 10 to more than 20%. Major uncertainties remain however, and we emphasize the importance of further experimental research into the nitrogen cycle.