Post-harvest effect of cover crops on creeping thistle Circium arvense

Cover crops move nitrogen (N) to the top soil. This enhances the N uptake of the succeeding barley crop, especially at early growth stages, and limits the access of the thistle to the N from the subsoil. The autumn tillage for perennial weed control, in contrast, provides a N distribution favorable for the uptake by thistles rather than barley crop. The evidence of post-harvest effect of cover crops on the N status of C. arvense gives a better understanding of their roles in weed control.