A study of the N2O emission from grassland with the FASSET farm model D. Chatskikh1, J. E. Olesen1, J. Berntsen1, K. Regina2 and S. Yamulki3 Archived at http://orgprints.org/4130 1 Department of Agroecology, Danish Institute of Agricultural Sciences, Foulum, Tjele, Denmark. 2 Environmental Research, Agrifood Research Finland (MTT), Jokioinen, Finland. 3 North Wyke Research Station, Institute of Grassland and Environmental Research, Okehampton, Devon, UK. Introduction Local adaptations of the IPCC methodology (http://www.ipcc.ch) are applied in different countries. They include a combination of theoretical, experimental and simulation methods for evaluating the activity and factors indicated N2O emission. The N2O emission from agricultural soil is considered an important source both for environmental impact and non-industrial losses of nitrogen (Petersen, Olesen, 2002). In this study a multifactorial approach, based on dynamic modelling, is used at a farm/field level to estimate N2O emission from grassland. For this purpose an algorithm for modeling of gaseous N2O emission was developed and analyzed. In the algorithm, based on the conceptual process-oriented model HIP (Davidson et al., 2000), both nitrification and denitrification are included as important sources for the N 2O emission (Bremner, 1997). Soil- microbiological processes are described with first-order kinetics. The algorithm was implemented within the Danish farm model FASSET (Berntsen et al., 2003) to study of N 2O emission from grassland under different treatments. Results and discussion For the FASSET evaluation, experimental data of the N 2O emission fluxes from the 3 sites within EU were used: Taw Green (South-West UK, 50.64°N and 03.84°W), Jokioinen (South Finland, 60.82°N and 23.50°E) and Jægersborg (East Denmark, 56.50°N and 9.58°E). Sites differ in meteorological conditions, soil clay content and grassland management. The analysis of sensitivity shows that the algorithm implemented in the FASSET was stable and could predict the N2O emission. There was obtained a good agreement between experimental and calculated values (R2=0.58) of the N2O emission within the period (see Table). Predicted N2O emission is in accordance with the known IPCC emission factors (Petersen, Olesen, 2002). Table. Results of computational experiments (N2O emission is in kgN-N2O·ha-1). Site Reference Period of N2O emission Experimental values Calculated values Jægersborg Christensen, 1983 April-August 1981 0.61 1.11 April-August 1981 2.01 2.88 April-August 1981 3.34 3.39 Jokioinen Regina, unpubl. May-December 2000 0.46 0.50 January -December 2001 0.96 0.47 January -August 2002 1.33 0.50 July-December 2000 0.49 0.59 January-December 2001 1.51 0.92 January - August 2002 0.82 0.82 Taw Green Yamulki, unpubl. February-November 2002 5.97 4.55 February-November 2002 2.42 2.73 Special attention in the study was paid on spatial and temporal heterogeneity questions of the N2O emission, and on soil-ecological factors which influence the N2:N2O partition. It was shown that in spite of difficulties in prediction of some spring fluxes at the Danish site, the impact of such processes as freezing-thawing and chemodenitrification on the annual emission was negligible. References Berntsen, J., Petersen, B. M., Jacobsen, B. H., Olesen, J. E., and Hutchings, N. J. 2003. Evaluating nitrogen taxation scenarios using the dynamic whole farm simulation model FASSET. Agricultural Systems 76: 817-839. Bremner, J. M. 1997. Sources of nitrous oxide in soils. Nutrient Cycling in Agroecosystems 49: 7-16. Christensen, S. 1983. Nitrous oxide emission from a soil under permanent grass: seasonal and diurnal fluctuations as influenced by manuring and fertilization. Soil Biol. Biochem. Vol.15 5: 531-536. Davidson, E. A., Keller, M., Erickson, H. E., Verchot, L. V., and Veldkamp, E. 2000. Testing a conceptual model of soil emissions of nitrous and nitric oxides. BioScience Vol.50 8: 667-680. Petersen, S.O., and Olesen, J. E. 2002. Greenhouse gas inventories for agriculture in the nordic countries. DIAS report Plant Production no. 81.
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