Effects of double drilling of small grains on soil erosion by concentrated flow and crop yield

Soil erosion on agricultural land and its detrimental environmental and economical effects has aroused increased interest among both the research and policy-making communities. The call for erosion control measures adapted to local farming practices is high, especially in Europe where farmers are reluctant to adopt soil conservation techniques. This study investigates a new technique for controlling concentrated flow erosion rates in the loess belt of central Belgium: i.e. double drilling of cereals in zones of concentrated flow. Cross-sectional areas of erosion channels as well as crop yield parameters in single- and double-drilled zones were compared. The technique is based on the combined effect of the increased density of plant shoots and roots for reducing soil loss. Results indicate that double drilling can reduce soil loss through concentrated flow by 25% on average and by up to 40% under optimal conditions. No net change in wheat grain yield was observed, and farmers who participated in the experiments were satisfied with the results and the easy application of the technique. Globally, benefits were larger than costs. However, the effectiveness of the technique in reducing soil loss by concentrated flow erosion seems to be topographically restricted. For positions in the landscape with a contributing drainage area larger than ca. 0.75 ha, the effectiveness of double drilling can be doubted. Double drilling should therefore be regarded as one possibility amongst others to reduce concentrated flow erosion rates in farmers’ fields.