A comparison of farm-scale models to estimate greenhouse gas emissions from dairy farms in Europe

Nicholas Hutchings


Farm-scale models quantify the cycling of nitrogen (N) and carbon (C) so are powerful tools for assessing the impact of management-related decisions on greenhouse gas (GHG) emissions, especially on dairy cattle farms, where the internal cycling is particularly important. Farm models range in focus (economic, environmental) and the detail with which they represent C and N cycling. We compared four models from this range in terms of on-farm production and emissions of GHGs, using standardized scenarios. The models compared were SFarMod, DairyWise, FarmAC and HolosNor. The scenarios compared were based on two soil types (sandy clay versus heavy clay), two roughage systems (grass only versus grass and maize), and two climate types (Eindhoven versus Santander). Standard farm characteristics were; area (50 ha), milk yield (7000 kg/head/year), fertiliser (275 kg N and 150 kg N/ha/year for grass and maize, respectively). Potential yields for grass 10t dry matter (DM)/ha/year in both areas, maize 14 t DM/ha/ year in Eindhoven and 18t DM/ha/ year in Santander. The import of animal feed and the export/import manure and forages was minimized. Similar total farm direct GHG emissions for all models disguised a variation between models in the contribution of the different on-farm sources. There were large differences between models in the predictions of indirect GHG emission from nitrate leaching. Results could be explained by differences between models in the assumptions made and detail with which underlying processes were represented. We conclude that the choice of an appropriate farm model is highly dependent upon the role it should play and the context within which it will operate, so the current diversity of farm models will continue into the future.

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Authors: Nicholas Hutchings1 Daniel Sandars2, Şeyda Özkan3 Michel de Haan4

Affiliations: 1Dept. of Agroecology, Aarhus University, Blichers Allé 20, PO Box 50, 8830 Tjele, Denmark; 2Institute for Environment, Health, Risk and Futures, School of Energy, Environment and Agrifood (SEEA), Cranfield University, Cranfield, Bedfordshire, MK43 0AL, United Kingdom; 3Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Ås, Norway; 4Wageningen UR Livestock Research, PO Box 338, 6700 AH Wageningen, Netherlands

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