Direct nitrous oxide emissions in Mediterranean climate cropping systems: emission factors based on a meta-analysis of available measurement data

Maria L. Cayuela, Eduardo Aguilera, Alberto Sanz-Cobena, Dean C Adams, Diego Abalos, Louise Barton, Rebecca Ryals, Whendee L. Silver, Marta A. Alfaro, Valentini A. Pappa, Peter Smith, Josette Garnier, Giles Billen, Lex Bouwman, Alberte Bondeau, Luis Lassaletta

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Many recent reviews and meta-analyses of N2O emissions do not include data from Mediterranean studies. In this paper we present a meta-analysis of the N2O emissions from Mediterranean cropping systems, and propose a more robust and reliable regional emission factor (EF) for N2O, distinguishing the effects of water management, crop type, and fertilizer management. The average overall EF for Mediterranean agriculture (EFMed) was 0.5%, which is substantially lower than the IPCC default value of 1%. Soil properties had no significant effect on EFs for N2O. Increasing the N fertilizer rate led to higher EFs; when N was applied at rates greater than 400 kg N ha–1, the EF did not significantly differ from the 1% default value (EF: 0.82%). Liquid slurries led to emissions that did not significantly differ from 1%; the other fertilizer types were lower but did not significantly differ from each other. Rain-fed crops in Mediterranean regions have lower EFs (EF: 0.27%) than irrigated crops (EF: 0.63%). Drip irrigation systems (EF: 0.51%) had 44% lower EF than sprinkler irrigation methods (EF: 0.91%). Extensive crops, such as winter cereals (wheat, oat and barley), had lower EFs (EF: 0.26%) than intensive crops such as maize (EF: 0.83%). For flooded rice, anaerobic conditions likely led to complete denitrification and low EFs (EF: 0.19%). Our results indicate that N2O emissions from Mediterranean agriculture are overestimated in current national greenhouse gas inventories and that, with the new EF determined from this study, the effect of mitigation strategies such as drip irrigation or the use of nitrification inhibitors, even if highly significant, may be smaller in absolute terms.
Original languageEnglish
Pages (from-to)25-35
Number of pages11
JournalAgriculture Ecosystems & Environment
Early online date6 Oct 2016
Publication statusPublished - 1 Feb 2017

Bibliographical note

The authors are grateful to M. Scholes, D. Plaza-Bonilla, S. Menendez, P. Merino, S.C. Maris, H. Heller, D. Savvas, C. K. Kontopoulou, who were contacted and kindly supplied any missing information necessary for the meta-analysis. Special thanks to J.P.C. Eekhout for preparing Fig. 1 and F. Estellés for providing the basic data for the calculation of the fertilization in Spain. Also thanks to two anonymous reviewers for their helpful comments. M. L. Cayuela was supported by a ‘Ramon y Cajal’ research contract from the Spanish Ministry of Economy and Competitiveness. Thanks to Fundación Séneca, Agencia Regional de Ciencia y Tecnología de la Región de Murcia for support (grant number 19281/PI/14). Australian studies included in the meta-analysis were funded by the Australian Government, the Grains Research and Development Corporation, and the Department of Agriculture and Food WA.


  • N2O
  • greenhouse gases
  • field studies
  • mitigation
  • systematic review


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