Oilseed rape sown in summer only forms a dense canopy in the following spring. In autumn and winter, the stands can become infested with weeds, and in vulnerable areas, soil erosion can occur. Undersowing helps to increase soil cover in autumn and thus suppress the emergence and growth of weeds. In oilseed rape, frost-sensitive legumes are best suited for undersowing. They fix nitrogen and thus contribute to the large nitrogen requirement of oilseed rape plant through mineralisation. After dieback in winter they form a thin layer of mulch on the field.