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Abstract Evaluations of soil organic carbon (SOC) stocks are often based on assigning a carbon density to each one of a number of ecosystems or soil classes considered, using data from soil profiles within these categories. A better approach, in which the use of classification methods by which extrapolation of SOC data to larger areas is avoided, can only be used if enough data are available at a sufficiently small scale. Over 190 000 SOC measurements (0–24 cm) have been made in the Flemish cropland (the Northern part of Belgium) in the 1989–2000 period. These SOC data were grouped into 3-year periods and as means plus standard deviation per (part of) community (polygons). This large dataset was used to calculate SOC stocks and their evolution with time, without data extrapolation. Using a detailed soil map, larger spatial groups of polygons were created based on soil texture and spatial location. Linear regression analysis showed that in the entire study area, SOC stocks had decreased or at best had remained stable. In total, a yearly decrease of 354 kton OC yr-1 was calculated, which corresponds with a net CO2 emission of 1238 kton CO2 yr-1 . Specific regions with a high carbon sequestration potential were identified, based on SOC losses during the 1989–2000 period and the mean 1999 SOC content, compared to the average SOC content of soils in Flanders with a similar soil texture. When restoring the SOC stocks to their 1990 level, we estimated the carbon sequestration potential of the Flemish cropland soils to be some 300 kton CO2 yr-1 at best, which corresponds to a 40-year restoration period. In conclusion, we can say that in regions where agricultural production is very intense, carbon sequestration in the cropland may make only a very modest contribution to a country's effort to reduce greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

In the frame of the European TOPPS project (Train the Operator to prevent Pollution from Point Sources), 200 on farm audits and 300 tele interviews were performed in the Yser catchment area. The objective was to determine the critical points for point source pollution within the spraying process and to inform advisors, intermediaries and farmers on practical measures and achievable solutions to reduce the contamination of the surface water by Plant Protection Products (PPP) due to point source pollution. For the on farm auditing, the Aquasite tool (Arvalis-France) was used. This audit was performed on 100 farms in the Flemish Yser catchment and on 100 farms at the French side. This audit reveals the weak points in infrastructure and technology on the farm in relation to the spraying process. Next, 150 tele interviews were held in the respective catchment areas. These interviews assess the awareness and behaviour of the farmers on point source pollution. The strength of these studies is in giving a view on the real situation on the farms with respect to spraying. The critical points and risks for point source pollution were similar for both regions. Especially the filling and mixing of the sprayer, internal and external cleaning of the sprayer and the management of the waste fraction need specific training, demonstration and advice. However, there is a large difference in the risk perception of point source pollution between farmers on both sides of the border. The transgressing approach of the Yser catchment allows to make a comparison between both regions and allows to assess in which way the legislation had part in explaining the differences between the regions as the agriculture in both regions is similar. Also, the results stress the importance of trainings and sensibilisation at a regional scale.