Nitrous oxide (N₂O) emissions were measured and compared on 2 typical crop rotations of a grain farm and a dairy farm with feed cropping, over 5 years (from 2012 to 2016) in southwestern France. The annual N₂O emissions of the 5 typical rotational crops of the region (summer crops: irrigated maize and sunflower; winter crops: winter wheat, rapeseed and barley) varied from 0.95 ± 0.88 to 7.96 ± 1.73 kgN ha⁻¹, with the highest values observed on the dairy farm plot and for summer crops. N₂O emissions were analysed on a daily, monthly, seasonal and annual basis, and correlated with their main direct or indirect drivers, i. e. water and nitrogen (mineral or organic) supply amount, rotational crops, vegetation covering and tillage. We observed a marked seasonal pattern of N₂O emission peaks. On average, more than 50% of N₂O emissions occurred during spring for summer crops, and more than 40% occurred in winter for winter crops. We have identified agricultural practices that increase N₂O emissions. In particular, our results show that when the soil is left bare or with limited crop development, spring mineralization of organic N residues (from previous crop or winter cover crop) results in N losses, partly as emissions of N₂O, which are detrimental to agronomic performance (low NUE).

We also conducted an agronomic assessment of annual N₂O emissions versus nitrogen surplus and nitrogen use efficiency (NUE), which lead us to discuss agricultural practices that may mitigate N₂O emissions while optimizing agronomic and economic performance of crops. Indeed, we point out that N surplus and N fate may be controlled through the right timing of sowing, cover crop, irrigation and fertilization.

一氧化二氮 (N ₂ O) 排放量在法国西南部 5 年（2012 年至 2016 年）的 5 年（2012 年至 2016 年）期间对粮食农场和奶牛场的 2 个典型轮作进行测量和比较。该地区 5 种典型轮作作物（夏季作物：灌溉玉米和向日葵；冬季作物：冬小麦、油菜籽和大麦）的N _{2 O 年排放量从 0.95 ± 0.88 到 7.96 ± 1.73 kgN ha} ^-1不等，其中在奶牛场和夏季作物上观察到的最高值。氮₂每天、每月、季节性和每年都会分析 O 排放，并与它们的主要直接或间接驱动因素相关联，即水和氮（矿物或有机）供应量、轮作作物、植被覆盖和耕作。我们观察到 N ₂ O 排放峰值的明显季节性模式。平均而言，50% 以上的 N ₂ O 排放发生在夏季作物的春季，40% 以上的冬季作物发生在冬季。我们已经确定了增加 N ₂ O 排放的农业实践。特别是，我们的研究结果表明，当土壤裸露或作物生长受限时，有机氮残留物（来自先前作物或冬季覆盖作物）的春季矿化会导致 N 损失，部分原因是 N _2的排放O，对农艺性能有害（低 NUE）。

我们还对年度 N ₂ O 排放与氮过剩和氮利用效率 (NUE) 进行了农艺评估，这使我们讨论了可以在优化农作物的农艺和经济性能的同时减轻 N _{2 O 排放的农业实践。}事实上，我们指出，氮的过剩和氮的归宿可以通过播种、覆盖作物、灌溉和施肥的正确时机来控制。