Nitrogen cycle factors contributing to N2O production and associated ozone perturbations are examined. It is pointed out that fertilizer nitrogen losses are non-linear and increase with application rate. Losses are apportioned between rapid denitrification (~1 year) and slower transfer processes of 102 to 103 years between nitrogen reservoirs. It is concluded that different estimates of N2O production result from selecting nitrogen models with different denitrification and transfer efficiencies. A significant ozone perturbation cannot be ruled out because of uncertainties in the relative efficiency of agricultural denitrification. |