The implication of stubble tillage for weed population dynamics in organic farming

Summary In practical farming, early and shallow stubble tillage is carried out post‐harvest to stimulate germination of freshly ripened crop and weed seeds, to kill the resulting seedlings and hence to reduce the input into the soil seedbank. Additionally, it aims at reducing perennial weeds by mechanical damage. In this paper, field experiments and laboratory studies are presented which show that stubble tillage can reduce perennial weeds. However, it had a variable effect on annual weeds. After 5 years of experimentation, no effect of stubble tillage was seen on the aboveground vegetation. In contrast, the soil seedbank of the control was roughly doubled where the stubble had been left uncultivated until autumn ploughing. These results indicate that practical experience which assumes that stubble tillage reduces annual weed populations may be correct, despite the fact that in other published studies stubble tillage exerted no control on annual weeds or had a variable effect. This will have practical application in organic arable production systems.