Grassland renovation by cultivation and reseeding has been shown to increase short‐term emissions of N₂O, but there is uncertainty about long‐term effects, despite the potential impacts of reseeding on sward composition and soil functions. A field experiment was therefore carried out to determine how N₂O emissions from previously renovated grasslands varied in the intermediate to long‐term, compared with an undisturbed permanent grassland (PG). Plots on the PG site were renovated, either two (G2) or five (G5) years prior to the two experimental years. In each sward age and experimental year, annual N₂O‐measurements were conducted on a weekly basis and compared with the undisturbed PG. Plots were either unfertilized or were fertilized with slurry (240 kg N ha⁻¹ year⁻¹). On average, annual N₂O emissions were 0.39 kg N/ha for the unfertilized swards, and 0.91 kg N/ha for slurry‐fertilized swards. Sward age had no effect on N₂O emissions. With increasing sward age the proportion of legumes in the sward was reduced, but a minimum biological nitrogen fixation (BNF) of 88 kg N/ha was maintained even in the fertilized PG. Both sward age and BNF were of limited importance for the annual N₂O emissions compared with the effects of soil carbon content and nitrogen surplus levels. However, measured N₂O emissions were low in all sward age treatments, with a low risk of additional N₂O emissions when BNF is taken into account in fertilizer planning.

中文翻译：

---

草草三叶草中一氧化二氮的排放受草龄和生物固氮的影响

通过耕种和播种进行草地翻新已显示出会增加N ₂ O的短期排放，但是尽管播种会对草料组成和土壤功能产生潜在影响，但对长期影响尚不确定。因此，进行了一次野外试验，以确定与未扰动的永久性草地（PG）相比，先前翻新过的草地的N ₂ O排放在中长期内如何变化。在两个实验年之前的两年（G2）或五年（G5），对PG站点上的地块进行了翻新。在每个草龄和实验年，每周都要进行年度N ₂ O测量，并将其与不受干扰的PG进行比较。地块未施肥或用泥浆施肥（240 kg N公顷^-1 年^-1）。平均而言，未施肥的草皮每年的N ₂ O排放量为0.39 kg N / ha，而施肥的草皮则为0.91 kg N / ha。草地年龄对N ₂ O排放没有影响。随着草龄的增加，豆科植物中豆类的比例减少，但是即使在受精的PG中，仍能保持88 kg N / ha的最低生物固氮率。与土壤碳含量和氮过剩水平的影响相比，草龄和BNF对年度N ₂ O排放的重要性均有限。但是，在所有龄期处理中，测得的N ₂ O排放量均较低，且额外N _2的风险较低。在肥料规划中考虑BNF时的O排放。