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.
Soil Use and Management – Wiley
Published: Oct 1, 2020
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