Measurement of N2O emissions over the whole year is necessary for estimating reliable emission factors

Ziyin Shang* (Corresponding Author), Mohamed Abdalla, Matthias Kuhnert, Fabrizio Albanito, Feng Zhou, Longlong Xia, Pete Smith

*Corresponding author for this work

Research output: Contribution to journalLiterature reviewpeer-review

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Nitrous oxide emission factors (N2O-EF, percentage of N2O–N emissions arising from applied fertilizer N) for cropland emission inventories can vary with agricultural management, soil properties and climate conditions. Establishing a regionally-specific EF usually requires the measurement of a whole year of N2O emissions, whereas most studies measure N2O emissions only during the crop growing season, neglecting emissions during non-growing periods. However, the difference in N2O-EF (ΔEF) estimated using measurements over a whole year (EFwy) and those based on measurement only during the crop-growing season (EFgs) has received little attention. Here, we selected 21 studies including both the whole-year and growing-season N2O emissions under control and fertilizer treatments, to obtain 123 ΔEFs from various agroecosystems globally. Using these data, we conducted a meta-analysis of the ΔEFs by bootstrapping resampling to assess the magnitude of differences in response to management-related and environmental factors. The results revealed that, as expected, the EFwy was significantly greater than the EFgs for most crop types. Vegetables showed the largest ΔEF (0.19%) among all crops (0.07%), followed by paddy rice (0.11%). A higher ΔEF was also identified in areas with rainfall ≥600 mm yr−1, soil with organic carbon ≥1.3% and acidic soils. Moreover, fertilizer type, residue management, irrigation regime and duration of the non-growing season were other crucial factors controlling the magnitude of the ΔEFs. We also found that neglecting emissions from the non-growing season may underestimate the N2O-EF by 30% for paddy fields, almost three times that for non-vegetable upland crops. This study highlights the importance of the inclusion of the non-growing season in the measurements of N2O fluxes, the compilation of national inventories and the design of mitigation strategies.
Original languageEnglish
Article number113864
Number of pages8
JournalEnvironmental Pollution
Early online date20 Dec 2019
Publication statusPublished - Apr 2020

Bibliographical note

We thank Dali Nayak, Thomas Cornulier and Arindam Datta for data collection and helpful discussions during the development of this analysis. This work was supported by the National Natural Science Foundation of China (41671464). P.S. and M.A. acknowledge support from the UK-China Virtual Joint Centre, N-Circle (grant number BB/N013484/1). Z.S. appreciates the financial support from the China Scholarship Council (201706010406) to support her study in the UK


  • nitrous oxide
  • greenhouse gas
  • fallow
  • residual fertilizer N
  • nitrogen use efficiency
  • Residual fertilizer N
  • Nitrogen use efficiency
  • Greenhouse gas
  • Nitrous oxide
  • Fallow


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