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2. Materials & Methods Two years of measured (seasonal) datasets for N2O emissions were used to evaluate the ECOSSE model (Estimating Carbon in Organic Soils - Sequestration and Emissions). This is a multi-pool dynamic simulation model (Smith et al., 2010) based on the concepts of the RothC and SUNDIAL models. It has a number of advantages compared to other models, including limited meteorological and soil data requirements (e.g. soil water, plant inputs, nutrient applications, timing of managements). It can simulate the impacts of land-use, management and climate change on C and N emissions and stocks (Khalil et al., 2011) for both mineral and organic soils at a range of scales.
The experiment was carried out at a conventionally tilled (22 cm) arable site (spring barley - a major cereal crop) located in Oak Park, Carlow (52°86' N - 6°54' W). Details of the experiment are given by Abdalla et al. (2009). The soil was a sandy loam with a pH of 7.4 and a mean organic C and N content at 15 cm of 19.4 and 1.9 g kg-1 soil, respectively. During the crop growth period (2004 and 2005), three different N fertilizer rates (0, 70-79 and 140-159 kg N ha-1) were applied as calcium ammonium nitrate. The control was unfertilized from 2003 but the whole field had received 140-160 kg N ha-1 before 2003. Full daily weather records and details of cropping and land management practices were included. The ECOSSE model was run to predict N2O flux response to N fertilizer levels and the model performance was evaluated statistically.
3. Results & Discussion The modelled responses of N2O fluxes were found to be consistent with the two-year measured values (Fig. 1). The bias in the total difference between measured and the corresponding modelled N2O fluxes were large due to the impact of a single unexpected measurement. In the control, the correlation coefficient (r) was poor (0.02) and root mean square error (RMSE) was high (43.6 g N ha-1 d-1), indicating poor performance of the model in describing N2O emissions. In the fertilized fields, significant (p0.01) correlation between modelled and measured N2O flux was observed, with r of 0.54-0.60 and RMSE of 18.6-20.8 g N ha-1 d-1. The RMSE values suggest that this model
Figure 1. Measured and simulated N2O fluxes as influenced by N fertilizer rates applied (arrows) to spring barley.
Irrespective of N fertilizer rates, the ECOSSE model somewhat overestimated seasonal total N2O fluxes compared to the measured values, similar to the simulations of the unfertilized control using DNDC (Abdalla et al., 2009). The measured seasonal N2O losses were 0.41 and 0.50% of the N applied at rates of 70-79 and 140-159 kg ha-1, respectively. The corresponding losses were 34 and 22% lower than reported by Abdalla et al. (2009), which is probably due to the differences in integration method. The integration of simulated values for each date when measurements were taken provided seasonal N2O losses of 0.69 and 1.11% of the applied N, suggesting an increase by 70-123% of the measured values. This could be due to missed emissions associated with the sporadic timing of measurements (2-15 day intervals), implying that intensive measurements following fertilizer application and rainfall are required to more fully evaluate model performance.
The corresponding simulated N2O emission factors obtained by summing the modelled daily fluxes over the year were 0.49 and 0.62%, which more closely matches the measured seasonal values.
4. Conclusion The ECOSSE model predicts N2O emission factors with accuracy similar to the predictions of the more data-demanding DNDC model. Improvements to ECOSSE to reduce overestimated emissions, particularly at lower N rates, are required. Results suggest that the ECOSSE model can reliably be used to estimate N2O emissions from arable fields. However, further analyses are needed to fully determine the uncertainty in the estimates across all land-use and soil types under Irish conditions.
References Abdalla, M., Wattenbach, M., Smith, P., Ambus, P., Jones, M. and Williams, M. 2009. Application of the DNDC model to predict emissions of N2O from Irish agriculture. Geoderma 151, 327-337.
Khalil, M.I., Smith, J.U., Abdalla, M., O’Brien, P., Smith, P. and Müller, C. 2011. Predicting coupled emissions of N2O, CO2 and CH4 from arable fields in Ireland using the ECOSSE model. In: Proceedings of the American Geophysical Union Fall Meeting, 05-09 December 2011, San Francisco, CA, USA. B51H-0502.
McGettigan, M., Duffy, P., Hyde, B., Hanley, E., O’Brien, P., Ponzi J. and Black, K. 2010. National Inventory Report 2010: Greenhouse Gas Emissions 1990-2008. Reported to the United Nations Framework Convention on Climate Change. Environmental Protection Agency, Ireland. 364 pp.
Smith, J., Gottschalk, P., Bellarby, J. et al. 2010. Estimating changes in national soil carbon stocks using ECOSSE – a new model that includes upland organic soils. Part I. Model description and uncertainty in national scale simulations of Scotland. Climate Research 45, 179-192.
Nitrogen Workshop 2012
Reducing N inputs and surpluses in baking wheat production by modifying the valuation system – an assessment of feasibility and potential in Germany Techen, A.-K., Osterburg, B.
Institute of Rural Studies, Johann Heinrich von Thünen-Institut (vTI), Federal Research Institute for Rural Areas, Forestry and Fisheries, Bundesallee 50, 38116 Braunschweig, Germany
1. Background & Objectives The prices that farmers receive for their wheat depend on the baking quality. The baking quality is not easy to measure. Thus an indicator is used that can be assessed very quickly, namely the crude protein (XP) content. In Germany, the XP content of bread wheat is =12 % while for baking wheat it is =13 %.
Due to this system of quality assessment, farmers have an incentive to have high XP contents which can be achieved by additional N fertilizer input in the late stage of plant growth.
Research findings show that high baking qualities of wheat can be reached with lower XP contents (e.g. Obenauf, 2009; Seling, 2010), using new wheat varieties. However, this has not led to a change of pricing and thus not of management and N input either.
The aim of this paper is to show the potential of a new quality assessment allowing for decreased N input and N surplus in wheat production, using the example of Germany. It investigates what the obstacles are for putting this new approach into practice, and how they could be overcome.
2. Materials & Methods Information on the baking quality of different varieties at certain XP contents has been drawn from the literature, complemented by expert interviews. The emission reduction potential on a per ha basis was calculated by information on plant uptake and fertilization practices acknowledging field trials, fertilization recommendations and assumptions from experts. The resulting assumptions on reduction potentials range from 20 kg N ha-1 reduced input and 40 % surplus at the one far end to 40 kg N ha-1 reduced input and 60 % surplus at the other end. A simplification was made by assuming that all bread and baking wheat is fertilized with mineral fertilizer. The reduction potential for Germany was calculated based on statistical information on production of different wheat classes (Seling et al. 2007-2010). Further, the potential of saving greenhouse gas (GHG) emissions was calculated as the reduction based on reduced application of mineral N fertiliser according to IPCC 19961 and the GHG emissions arising from production of 1 kg of mineral N fertiliser and transport to the farm. Further information on the feasibility of a new approach for wheat quality assessment was gained by conducting a literature review and expert interviews.
3. Results & Discussion The emission reduction potentials are displayed in Table 1. The amounts of mineral fertilizer N which could be saved in Germany range between 46,630 and 93,270 t N. This corresponds to around 3 to 6 % of purchased mineral fertilizer N. Accordingly, the reduction of direct GHG emissions from N fertilization (284 kt to 569 kt CO2-eq.) corresponds to those 3 to 6 % of direct emissions from all mineral fertilizers applied in Germany. The impact of N losses to the environment, mainly as nitrate to water bodies and ammonia to the atmosphere could be reduced by 18,650 to 55,960 t N altogether. This is up to 3.3 % of total N surplus in Germany.
Emission factors: 5 kg CO2-eq./kg N for direct emissions, 3.9 kg CO2-eq./kg N for indirect emissions and 7.5 kg
CO2-eq. /kg N for emissions from mean N fertiliser production (database:
Nitrogen Workshop 2012
The reduction of these amounts of fertilizer N would lead to a corresponding decrease of production costs, namely around 42 to 83 million € year-1 in Germany based on average fertilizer prices in the years 2006/07 to 2008/09. Additionally, it would reduce the farmers’ risk: the N applied in May or June to increase XP content cannot always be taken up by the plants. Especially with increased summer droughts this is a problem that leads to cost inefficacy and N-emissions. Interviewed farmers’ representatives thus said they would appreciate a change of the wheat quality assessment. However, the direct measurement of baking quality is costly and not quick enough for quality management in the trade system. The wheat variety is a feasible indicator to complement the XP indicator. For this, at least for German conditions, there is no fast enough variety determination method available or even in sight. This is why an elaborated logistical and institutional system to track wheat varieties in the supply chain would have to be developed in order to allow for an innovative N-reduced wheat production system. The trade representatives are very sceptical concerning such a conversion due to the involved investment and transaction costs. From an economic and environmental point of view the aggregated costs of conversion are likely to be lower than the aggregated costs of not changing the system. A change, however, would require negotiations and agreements between different actors of the supply chain. All actors would have to acknowledge that the benefits and costs have to be shared along the value chain. For example, farmers may need to commit themselves to a certification system based on voluntary disclosure of delivered wheat varieties connected to sanctioning procedures for false statements revealed with spot checks. After all, currently, there are not enough incentives for the actors to seriously consider a change. Government intervention or consumer demand could create incentives to enable these innovations in quality wheat production.
4. Conclusion In bread and baking wheat production, a relevant amount of fertilizer N is applied to the soils in the late growth stage. This results in high N-surpluses, which could be avoid by using new wheat varieties of high baking qualities, hence leading to reduced N losses to the environment and more cost-efficient fertilization. However, the implementation of a new wheat quality assessment would require an investment in negotiation and conversion of the trade system for which incentives have to be created.
References Obenauf U. 2009. Qualität neu bewerten!, DLG-Mitteilungen 6/2009, 22-24.
Seling S. and Lindhauer M.G. 2007. Die Qualität der deutschen Weizenernte. Teil 1: Quantitatives und qualitatives Ergebnis in Bund und Ländern, Mühle + Mischfutter 143, 692-704.
Seling S. 2010. Bedeutung des Proteingehaltes von Backweizen aus Sicht der Wissenschaft, Getreidetechnologie 64, 103-110.
Seling S. and Lindhauer M.G. 2008. Die Qualität der deutschen Weizenernte 2008. Teil 1: Quantitatives und qualitatives Ergebnis in Bund und Ländern, Mühle + Mischfutter 145, 683-695.
Seling S., Schwake-Anduschus C. and Lindhauer M.G. 2009. Die Qualität der deutschen Weizenernte 2009. Teil 1: Quantitatives und qualitatives Ergebnis in Bund und Ländern, Mühle + Mischfutter 146, 672-681.
Seling S., Schwake-Anduschus C. and Lindhauer M.G. 2010. Die Qualität der deutschen Weizenernte 2010. Teil 1: Quantitatives und qualitatives Ergebnis in Bund und Ländern. Mühle + Mischfutter 147, 626-636.
Nitrogen Workshop 2012 Relationship between management, economics and environmental quality on Dutch arable farms Daatselaar, C.H.G.a, Prins, H.a, Reijs, J.W.a a Agricultural Economics Research Institute (LEI), part of Wageningen UR, The Hague, the Netherlands.
1. Background & Objectives The growth of crops on arable farms is inevitably associated with losses of nitrogen (N) to the environment. These losses can compromise the quality of air, groundwater and surface water.
Actual losses of nitrogen in the field are determined by many factors in which the management decisions of the farmer play a decisive role, as demonstrated by Daatselaar et al. (2010) on dairy farms. For a sustainable arable farming sector, the economic performance of the farms is crucial.
Therefore, it is important to know whether farmers can reduce N-soil surpluses on and nitrate concentration under their farms with the least possible negative effects on income. If changes to farm management practices result in a decrease in nitrate concentration, without hampering the economic performance, then farmers will be more willing to adapt their management. The objective of this paper is to estimate the relationship on Dutch arable farms between farm management, nitrogen soil surplus and nitrate concentration in groundwater or drain water.