Weed control strategies for grain legumes

There has been increasing interest in sustainable weed management in low-input farming systems. In an integrated approach, the development of cropping systems such as appropriate spatial arrangement and efficient tillage will help crops themselves to compete with weeds. With this aim, we investigated the strategic use of plant lodging combined with mechanical weed treatment to improve crop competitiveness and reduce the use of herbicides. We studied weed infestation and grain yield of three grain legumes, field bean, chickpea and field pea, grown according to different plant lodgings (narrow, wide and twin rows) and weed suppression methods: untreated, chemical and mechanical control. In the two years of the trial, two different weed infestation levels were observed due to different meteorological conditions. Our results show that the different crops showed different competitive behaviours, especially in weedy conditions. Indeed, in the bean plots, weed infestation was decreased from 70% in wide rows to 30% in narrow rows. Mechanical treatment produced weed levels similar to those in narrow rows (27%). Mechanical treatment gave grain yields of 2.3 t ha-1, that are comparable with chemically treated plots (2.7 t ha-1). For chickpea, mechanical treatment combined with wide rows proved effective in fighting weeds at a similar level to chemical treatment. Moreover, the yield using mechanical treatment, of 1.6 t ha-1, was only slightly lower than the yield using chemical treatment (2.3 t ha -1). For field peas, mechanical and cropping weed control can limit herbicides, but they are unable to control weed infestation on their own.