[1] Arable soils are a large source of nitrous oxide (N 2 O) emissions, making up half of the biogenic emissions worldwide. Estimating their source strength requires methods capable of capturing the spatial and temporal variability of N 2 O emissions, along with the effects of crop management. Here we applied a process-based model, Crop Environmental REsources Synthesis (CERES), with geo-referenced input data on soils, weather, and land use to map N 2 O emissions from wheat-cropped soils in three agriculturally intensive regions in France. Emissions were mostly controlled by soil type and local climate conditions, and only to a minor extent by the doses of fertilizer nitrogen applied. As a result, the direct emission factors calculated at the regional level were much smaller (ranging from 0.0007 to 0.0033 kg N 2 O-N kg À1 N) than the value of 0.0125 kg N 2 O-N kg À1 N currently recommended in the IPCC Tier 1 methodology. Regional emissions were far more sensitive to the soil microbial characteristics governing denitrification and its fraction evolved as N 2 O, soil bulk density, and soil initial inorganic N content. Mitigation measures should therefore target a reduction in the amount of soil inorganic N upon sowing of winter crops, and a decrease of the soil N 2 O production potential itself. From a general perspective, taking into account the spatial variability of soils and climate thereby appears necessary to improve the accuracy of national inventories, and to tailor mitigation strategies to regional characteristics.