Evaluation of mechanical weed control in legume crops

Two three-year field experiments with soya bean (Glycine max (L.) Merr.) and faba bean (Vicia faba L., var. minor Beck.) were carried out in central Italy in order to evaluate the effects of different mechanical methods (spring-tine harrowing, hoeing, hoeing-ridging, split-hoeing, finger-weeding) on weed control and crop yield. Split-hoeing + finger-weeding was the best mechanical weed control option, both in soya bean and faba bean, showing an excellent control of both inter- and intra-row weeds with efficacy values ranging from 73% to 97%. Split-hoeing and hoeing gave a good inter-row weed control, showing an effective action against both broadleaves and grasses also in relatively advanced developmental stages, although they did not effectively control weeds along the row. Harrowing and finger-weeding gave the worst weed control due to low efficacy against grasses and weeds bigger than 12-14 BBCH-scale. Yield crop showed not significant differences among the untreated control and all the other treatments, confirming the high competitive ability of legume crops. All the treatments gave crops yield values around the overall mean of trials with contained inter-annual variation, showing as the mechanical weed control can be a sustainable method to manage weeds in this legume crops without considerable losses in yield. Furthermore, the adoption of legume crops thanks to their good competitive ability against weeds and other important characteristics, offers the potential of enhancing the productivity and sustainability of the cropping system, especially in the organic farming.