An increasing area of oilseed rape cultivation in Europe is used to produce biodiesel. However, a large amount of straw residue is often left in the field in autumn. Straw mineralization provides both carbon (C) and nitrogen (N) sources for emission of soil nitrous oxide (N₂O), which is an important greenhouse gas with a high warming potential. Some studies have focused on soil N₂O emissions immediately post‐harvest; however, straw mineralization could possibly last over winter. Most field studies in winter have focused on freeze‐thaw cycles. It is still not clear how straw mineralization affects soil N₂O emissions in unfrozen wintertime conditions. We carried out a field experiment in northern Germany in winter 2014, adding straw and glucose as a source of C with three rates of N fertilizer (0, 30, and 60 kg N ha⁻¹). During the 26 days of observation, cumulative N₂O emission in treatments without C addition was negative at all N fertilizer levels. Straw addition produced –3.2, 11.2, and 5.0 mg N₂O‐N m⁻² at 0, 30, and 60 kg N ha⁻¹, respectively. Addition of glucose surprisingly caused –1.5, 74.6, and 165 mg N₂O–N m⁻² at 0, 30, and 60 kg N ha⁻¹, respectively. This study demonstrates that oilseed rape straw does not cause high N₂O emissions in wintertime when no extreme precipitation or freeze‐thaw cycles are involved, and soil organic C content is low. However, N₂O emission could be intensively stimulated, when both easily available organic C and nitrate are not limited and the soil temperature between 0 and 10°C. These results provide useful information on potential changes to N₂O emissions that may occur due to the increased use of oilseed rape for biodiesel combined with less severe winters in the northern hemisphere driven by global warming.

中文翻译：

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秸秆改良剂在非冻结的冬季条件下不会引起大量的N2O排放：德国北部的一项研究

欧洲越来越多的油菜种植面积用于生产生物柴油。但是，秋天常常在田间残留大量秸秆残留物。秸秆矿化为土壤一氧化二氮（N ₂ O）的排放提供了碳（C）和氮（N）来源，土壤一氧化二氮是一种具有高升温潜能的重要温室气体。一些研究都集中在土壤氮素₂立即收获后O排放; 但是，秸秆矿化可能会持续整个冬天。冬季大多数实地研究都集中在冻融循环上。秸秆矿化如何影响土壤N ₂尚不清楚冬季未冻结时的O排放。我们于2014年冬季在德国北部进行了田间试验，添加了秸秆和葡萄糖作为碳源，并添加了三种氮肥比例（0、30和60 kg N ha ^-1）。在观察的26天中，在所有氮肥水平下，不添加C的处理中累积N ₂ O排放均为负。秸秆添加分别在0、30和60 kg N ha ^-1时产生–3.2、11.2和5.0 mg N ₂ O-N m ^-2。意外地，在0、30和60 kg N ha ^-1处添加葡萄糖会分别导致–1.5、74.6和165 mg N ₂ O–N m ^-2。这项研究表明，油菜籽秸秆不会引起高氮在没有极端降水或冻融循环且土壤有机碳含量低的冬季，O排放量为₂。但是，当不限制容易获得的有机碳和硝酸盐且土壤温度在0至10°C之间时，可以强烈刺激N ₂ O的排放。这些结果提供了有用的信息，说明由于油菜籽在生物柴油中的使用增加，加上北半球由于全球变暖导致的严酷冬季，N ₂ O排放量可能发生变化。