The impacts of land use policy on the soil erosion risk: a case study in central Belgium

Set-aside programs of the European government have a double impact on the regional soil erosion risk in agricultural regions: (1) there is less area susceptible to soil erosion and (2) fields with a high erosion rate are preferably taken out of production resulting in a decrease of the average erosion risk. In order to quantify this double effect an inquiry among farmers in central Belgium was set up to find out which fields are preferably taken out of production. A statistical analysis pointed out that fields with a weak slope gradient, a loamy topsoil and good soil drainage have a low probability of being taken out of production. The results of the questionnaire were used to construct a transition probability map representing for each field the probability that it will be taken out of production. These transition probabilities were used to simulate the decrease in regional erosion risk for different scenarios. The outcome of these simulations suggests that there is a negative power relation between the set-aside percentage and the regional soil erosion risk.