4130 by lanyuehua

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									                                        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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