Effect of annually repeated weed harrowing against Chenopodium album (L.) in organically grown spring cereals

Spring-tine harrowing is a common physical weed control practice employed in organic cereal cropping. The effectsof harrowing treatments on weeds and crop yield were studied in a field experiment of organically grown springcereals during 2018–2020. The objective was to demonstrate the feasibility of weed harrowing to enhance overallweed management in organic cropping in Finland. Single post-emergence weed harrowing, with or without covercrop drilling, at the 2–4 crop leaf stage was compared with a combined pre- and post-emergence weed harrowing.Treatments were repeated in the same plots for three years and weed occurrence was assessed prior to harrowing,two weeks later and at harvest time. Chenopodium album was the predominant weed species in all years.Although harrowing effectively reduced the weed abundance, which was best with the double treatment, the yieldresponse in terms of quantity and quality was negligible. Even so, weed harrowing in cereal years is recommendedto suppress weed proliferation in crop rotation.