Nitrous oxide emission factors across Mediterranean regions: a meta-analysis of available data from field studies

Maria L. Cayuela1*, Eduardo Aguilera2, Alberto Sanz-Cobena3, Dean C. Adams4,5, Diego Abalos6, Louise Barton7, Rebecca Ryals8, Whendee L. Silver9, Marta A. Alfaro10, Valentini A. Pappa11,12, Pete Smith13, Josette Garnier14, Gilles Billen14, Lex Bouwman15,16, Alberte Bondeau17, Luis Lassaletta15

1Departamento de Conservación de Suelos y Aguas y Manejo de Residuos Orgánicos. CEBAS-CSIC. Campus Universitario de Espinardo. 30100 Murcia. Spain.

2 Universidad Pablo de Olavide, Ctra. de Utrera, km. 1, 41013, Sevilla, Spain

3 ETSI Agronomos, Technical University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain

4 Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames IA, USA, 50010

5 Department of Statistics, Iowa State University, Ames IA, USA, 50010                                                                   

6 Department of Soil Quality, Wageningen University, PO Box 47, Droevendaalsesteeg 4, Wageningen 6700AA, The Netherlands

7 Soil Biology and Molecular Ecology Group, School of Geography and Environmental Sciences, UWA Institute of Agriculture, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia

8 Department of Natural Resources and Environmental Sciences, University of Hawaii, Manoa, Honolulu HI, 96822, USA

9 Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94707, USA

10Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación Remehue, Casilla 24-O, Osorno, Chile

11 Agricultural University of Athens, Department of Crop Science, Iera Odos 75, 11855 Athens, Greece

12 Texas A&M University, 302H Williams Administration Bldg, College Station, TX 77843-3372, USA

13 Institute of Biological and Environmental Sciences, University of Aberdeen, 23 St Machar Drive, Aberdeen, AB24 3UU, UK

14 CNRS/UPMC, UMR Metis, 4 Place Jussieu, 75005 Paris, France

15 PBL Netherlands Environmental Assessment Agency, Bilthoven, PO Box 303, 3720 AH Bilthoven, The Netherlands

16 Department of Earth Sciences – Faculty of Geosciences, Utrecht University, PO Box 80021, 3508 TA Utrecht, The Netherlands

17 Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale (IMBE) Aix Marseille Université, CNRS, IRD, Avignon Université. Aix-en-Provence, France.


Studies on soil N2O emissions from Mediterranean climate regions are less abundant than in other temperate areas and they are often not included in recent reviews and meta-analyses. In this paper we aimed at collecting and synthesizing all available current data from field studies on N2O emissions across Mediterranean climate regions. We calculated through meta-analytical methods the averaged emission factor (EF, the percentage of fertilizer N applied that is transformed and emitted as N2O) for Mediterranean cropping systems, which was found to be significantly lower (0.5%) than the IPCC default value (1%). We found that soil properties had no significant effect on N2O emissions, but the irrigation system and the type and rate of applied N fertilizer influenced EFs. Rain-fed crops in Mediterranean regions had, in average, lower emissions (EF: 0.27%) than irrigated crops (EF: 0.63%). Drip irrigation systems showed 44% lower emission factors than sprinkler irrigation methods. Regarding the different N fertilizers, liquid slurries showed the highest EF, slightly lower, but not significantly different to 1%, whereas the remainder of the fertilizer types were significantly lower than 1%. Increasing the rate of nitrogen fertilizer led to higher EFs. The use of nitrification and ammonification inhibitors significantly reduced emissions (EF: 0.14%) and therefore seems a good strategy to mitigate direct N2O emissions under Mediterranean conditions.