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
