The impact of weeds on performance of cereal-legume intercropping systems

Context Weeds threaten crop productivity, but current reliance on herbicides poses risks to ecosystems and human health, necessitating sustainable alternatives such as intercropping. Cereal-legume intercrops enhance weed suppression, but the effect of weed pressure on component crops remains unclear. Objectives We investigated cereal-legume intercrops and sole crops in weed-free and weed-infested circumstances. Methods Four field experiments were conducted over three years (2022–2024). Main treatment factors included species selection, species mixing ratios, planting pattern, and herbicide application. We evaluated interactions between intercropping and presence and absence of weeds on biomass, yield, and light interception. Results Cereals dominated the intercrops, achieving yields comparable to or exceeding their proportional contributions relative to sole crops. In the absence of weeds, intercropped legumes yielded proportionally less than sole crops. However, legumes in weed-infested intercrops yielded proportionally similar to both herbicide-treated sole crops and intercrops. Cereals experienced weed-induced yield losses in both sole crops and intercrops, while legumes showed yield losses in sole crops but slight gains in intercrops, indicating that cereal-weed competition facilitated legume growth. Light interception by cereal sole crops was higher in weed-free than in weed-infested areas, whereas the opposite was observed for legume sole crops. Conclusion Our findings showed that under weed-infested conditions, cereal-legume intercrops have the potential to achieve higher component and total yields compared to their sole stands, offering a win-win scenario. We highlight indirect facilitation, cereal-weed competition that benefits legumes, as a to date poorly considered mechanism for overyielding in intercrops.