Modelling the impact of declining soil organic carbon on soil compaction: Application to a cultivated Eutric Cambisol with massive straw exportation for energy production in Northern France

• A decrease in soil carbon content decreases the soil porosity, the soil water content and the precompression pressure.
• We evaluated the consequences of massive straw exportation for the risk of soil compaction by calculating the occurrence of soil deformation in topsoil for a decrease in SOC from 23.4 to 0.47 g kg−1.
• The day number without compaction increases considerably with straw exportation when considering sugar beet sowing in North of France and typical climatic conditions.

Loss of organic matter has been recognized as being a major threat to soils in Europe with important consequences for the physical functioning of soils. We present the result of a numerical analysis of the integrated effects of changes in soil porosity and soil water status, along with decreased soil organic carbon (SOC) and the subsequent changes in the risk of compaction. This study concerns the impact of straw exportation on the risk of soil compaction. We evaluated the risk of compaction of a cultivated Eutric Cambisol in Northern France having a dominant silt loam soil texture, by simulating vehicle wheeling during sugar beet cropping for contrasting soil organic carbon contents (4.7, 11.1 and 23.4 g kg−1). To do this, we coupled two models: (1) a crop model (STICS) to calculate the changes in the water content of the 0–30 cm depth layer; and (2) a compaction model (COMPSOIL) to calculate soil stresses as a function of vehicle characteristics. Our study suggests that a decrease in SOC reduces the risk of topsoil deformation due to a decrease in soil water content, which tends to augment soil precompression stress. The method requires improvement in the future because it is very sensitive to input parameters for soil physical properties. Nevertheless it provides the first method for evaluating the impact of SOC decline on soil compaction. Its genericity permits it further applications to various soil management practices that decrease SOC.