Global N2O balance and nitrogen fertilizer

N2O is generated mainly by the processes of denitrification in the terrestrial and oceanic ecosystems. The increase in the concentration of this greenhouse gas in the troposphere is a result of changes in the global nitrogen cycle. A model for N2O balance, based on the global nitrogen cycle, is proposed here. The amount of nitrogen fertilizer fixed by industry has increased and is currently almost one third of that fixed naturally. This increase has quantitatively modified the global nitrogen cycle. Presently, the concentration of N2O in the troposphere is about 310 ppb (volume). Assuming the amount of industrial fertilizer use increases to 126 Tg y(-1), it is predicted that it will reach about 415 ppb by the end of the next century.