Validation of DNDC for 22 long-term N2O field emission measurements |
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| Institution: | 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, 712100, China;2. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi, 712100, China;1. Università degli Studi di Firenze, Department of Agri-Food Production and Environmental Sciences, 50144 Florence, Italy;2. Università degli Studi di Milano, Department of Agricultural and Environmental Sciences, Milan, Italy;3. INRA, AgroParisTech, UMR1402 EcoSys, 78850 Thiverval-Grignon, France;4. NREL, Colorado State University, Fort Collins, CO 80523, USA;5. Desertification Research Centre, Department of Agricultural Sciences, University of Sassari, 07100 Sassari, Italy;6. INRA, 63039 Paris, France;7. CREA-RPS, Research Centre for the Soil-Plant System, Via della Navicella 2–4, 00184 Roma, Italy;8. Institute of Biological and Environmental Sciences, University of Aberdeen, St Machar Drive, AB24 3UU Aberdeen, UK;9. Queensland University of Technology, Brisbane, Australia;10. INRA, UR 1158 AgroImpact, site de Laon, F-02000 Barenton-Bugny, France;11. INRA, FARE Lab, 51100 Reims, France;12. New Zealand Institute for Plant and Food Research, 7608 Lincoln, New Zealand;13. Agriculture and Agri-Food Canada, Ottawa, Ontario K1A 0C6, Canada;14. INRA, UREP, 63039 Clermont-Ferrand, France;15. IBIMET-CNR, Via Caproni 8, 50145 Firenze, Italy;p. Texas A&M AgriLife Research, Blackland Research & Extension Center, Temple, (TX), USA |
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| Abstract: | Twenty-two long-term measurements of direct N2O emissions from soils in an intensive agricultural area were used for the validation of the process-based DNDC model (version 8.3P). Model simulations were evaluated for temporal patterns of N2O, NH4+, NO3? and water-filled pore space (WFPS) and total N2O emissions. Several soil and crop input parameter adjustments to the model were evaluated but only the recalculation of the WFPS at wilting point and at field capacity, using pedotransfer functions, resulted in a clear improvement of the simulated variables (WFPS in all cases, N2O in some cases). Therefore, only this adjustment was made to DNDC 8.3P. This change, however, resulted for some cases (both cropland and grassland) in retardation of nitrate leaching and to a lesser extent of NH4+ to the deeper soil layers. The goodness of fit of the simulated temporal pattern of N2O varied considerably between sites. The total simulated N2O emissions from cropland showed a good agreement with the measurements, although there was a systematic overestimation of 7.4 kg N2O-N ha?1. Grassland soils, in contrast, gave a low agreement between total simulated and measured N2O losses. On the basis of all measured data a regional emission factor of 3.16 with a 95% confidence interval of ?0.89 to 7.21 could be calculated. DNDC simulations resulted in an emission factor of 6.49 with a 95% confidence interval of 4.04–8.93. The overall outcome of the N2O emission measurements and DNDC simulations were compared with several empirical regression models, which may be applicable for a temperate climate system. All of the tested regression models showed reliable results up to a N2O emission of 10 kg N2O-N ha?1. Higher emissions, however, were systematically underestimated. Though DNDC both under- and overestimated specific sites, the general agreement, over the whole range between measurements and simulations of total N2O losses (simulations=0.82×meas.+6.2), was better than for the different regression models. |
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