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Nitrous oxide (N 2 O) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of N 2 O, predicting soil response to changes in climate or land use is central to understanding and managing N 2 O. Here we find that N 2 O flux can be predicted by models incorporating soil nitrate concentration (NO 3−), water content and temperature using a global field survey of N 2 O emissions and potential driving factors across a wide range of organic soils. N 2 O emissions increase with NO 3− and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of N 2 O emission from all organic soils. Above 5 mg NO 3−-N kg− 1, either draining wet soils or irrigating well-drained soils increases N 2 O emission by orders of magnitude. As soil temperature together with NO 3− explains 69% of N 2 O emission, tropical wetlands should be a …