Managing species dominance in cereal-legume intercrop systems

Weeds threaten crop productivity, while herbicide reliance raises environmental and health concerns. Intercropping offers an alternative for sustainable weed suppression, particularly when component crops differ in competitive ability. However, such differences can also lead to competitive dominance by the stronger crop species, reducing the yield of its companion. To design intercrops for enhanced weed suppression without compromising yield, it is important to understand how species selection and spatial arrangements influence competitive dynamics. We conducted four field experiments (2022–2024) evaluating how species combination, mixing ratio, and spatial design influence dominance in cereal–legume intercrops under herbicide-treated and weed-infested conditions. Cereals showed greater light capture and weed suppression compared to legumes, which generally aligned with cereal dominance in intercrops. Intercrop design can moderate cereal dominance, but with varying trade-offs. Reducing triticale proportion from 50% to 25% achieved balanced yield contributions from both species while maintaining weed suppression and overall productivity. Contrastingly, wider row spacing (37.5 cm vs 12.5 cm) reduced triticale dominance but at the cost of both yield advantages and weed suppression. Weed presence further moderated competitive dynamics: under weed-infested conditions, triticale’s dominance over faba bean decreased compared to weed-free (herbicide-treated) conditions, and faba bean performed better relative to its sole crop, indicating indirect facilitation through cereal–weed competition. On a land-area basis, faba bean in weed-infested alternate row intercrops with 50 or 75% faba bean matched weed-free sole crop productivity. These findings demonstrate that appropriately designed cereal-legume intercrops can suppress weeds effectively while maintaining productivity of both component crops. • Cereal-legume intercrop light interception resembles that of sole crop cereal. • High intercrop weed suppressiveness generally coincides with competitive dominance. • Reduced cereal proportion boosts legume yield without reducing weed suppression. • Weeds in intercrop indirectly facilitate faba bean by competing with cereals. • Thoughtful intercrop design can balance weed suppression with legume productivity.