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.

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This paper reviews the recent development of the scientific, legislative, economic and environmental aspects of plant organic farming. The impact of organic farming on biodiversity and soil fertility is discussed in comparison with conventional systems. A significant barrier for wide application and future development of organic farming is the existing diversity of national and international policy instruments in this sector. Special attention is paid to up-to-date research techniques that could help solve a number of the problems typically faced in plant organic farming. It is argued that organic farming is still not productive enough to be considered fully sustainable. This underlines the necessity of strong support for more effective implementation of scientific research innovations and improvement of the networking between all stakeholdersorganic producers, scientists and corresponding policy makers at the national and international level.

-Different European Biomass Expansion Factors (BEFs) were compared for the inventory-based quantification of total aboveground and belowground biomass in forests. Therefore a qualitative analysis is performed on the biomass results obtained through the BEF approach and those from experimentally established allometric relations based on destructively sampled and fully excavated trees. Total organic carbon (OC) stock in aboveground and belowground living biomass of Flemish forests amounts to 12 Mt on average, with a significantly larger OC stock per hectare in deciduous forests compared to coniferous or mixed forest types. Total forest biomass seems to be fairly well approximated by a multiplication of the standing stock with either one of the applied BEFs. However an indication of the volume and age class for which the BEFs are established and a refined diameter-volume-biomass relation for oak trees in Europe, are required to gain more accurate results.

Total soil organic-carbon (SOC) stocks for grassland soils in Flanders (N Belgium) were determined for the Kyoto Protocol reference year 1990 and 2000 in order to investigate whether these soils have been CO 2 sinks or sources during that period. The stocks were calculated by means of detailed SOC datasets, which were available at the community scale for the whole of Flanders. The total SOC stocks for Flemish grassland soils (1 m depth) were estimated at 38 Mt SOC in 1990 and 34 Mt SOC in 2000. The loss of SOC resulted from a decrease in the SOC content of grassland soils (71%) and could also partly (29%) be explained by a decline in grassland area. Significant decreases in %SOC for the 0-6 cm depth layer were found for the 1990s for the coarser-textured soils with SOC losses ranging between -0.3% and -0.5% over the 10 y period. Specific management practices that disturb the SOC balance such as conversion to temporary grassland and a reduction of animal-manure application are hypothesized to have contributed to the observed loss of SOC stocks. We furthermore conducted an analysis of uncertainty of the 1990 and 2000 grassland SOC-stocks calculation using Monte Carlo analysis. Probability-distribution functions were determined for each of the inputs of the SOC-stock calculation, enabling us to assess the uncertainty on the 1990 and 2000 SOC stocks. The frequency distributions of these simulated stocks both closely approached lognormal distributions, and their 95%-confidence intervals ranged between 150% and 50% of the calculated mean SOC stock. The standard error on the measured decrease in SOC stocks in Flemish grassland soils during the 1990s was calculated to be 7-8 Tg SOC, which is equivalent to twice this decrease. This clearly shows that large-scale changes in SOC stocks are uncertainty-ridden, even when they are based on detailed datasets.