Mechanical and cultural strategies to control Cirsium arvense

Infestation with Cirsium arvense in organic cropping is an increasing problem in many parts of Europe. Non-chemical management strategies against C. arvense based on cultivation tactics and/or different cutting regimes have acquired very little attention for years. This study presents results from four experiments, undertaken under organic growing conditions, on the effects of repeated mowing or hoeing during the first part of the growing season used in combination with competition from a suppressive crop (grass white-clover mixture and red clover). The strategies were mainly aimed at diminishing the regenerative capacity of C. arvense and effects were thus measured in the subsequent year in spring barley. In general, number of passes of mowing and hoeing linearly reduced the amount of aboveground C. arvense biomass in the subsequent year. Increased competition induced by the competitive crops further reduced C. arvense biomass. Differences in barley yield were explained by the amount of C. arvense biomass in the two experiments, while strong confounding effects from Elymus repens infestations occurred in the other two experiments. Our results suggest that the strategies studied are likely to increase crop yield and that an acceptable level of C. arvense control can be achieved within one growing season only