Optimizing grain legume intercropping with buckwheat to improve weed management and reduce yield loss

Increasing grain legume cultivation is key to Europe's protein autonomy and agroecological transition goals. Weeds represent a major issue for grain legumes, commonly managed mechanically in organic farming, although intercropping (IC) is emerging as an agronomic alternative. Alternate row IC can replace mechanical weeding but often reduces legume yields, while mixed row IC in addition to mechanical weeding may provide more effective results. This study examined soybean, chickpea, and lentil intercropped with buckwheat, comparing additive alternate and mixed row IC for weed suppression and crop performance and different IC ratios (2:1, 4:1). Buckwheat (Fagopyrum esculentum Moench.) is a pseudocereal known for its weed suppressive abilities but is seldom considered in intercropping studies. Three randomized trials took place in 2023–2024 in the plains of northeastern Italy. Crop and weed aboveground biomass and crop grain yield were measured, and the land equivalent ratio and weed performance ratio were calculated. Intercropping at the 4:1 ratio with buckwheat in mixed IC (where MIX25 is within row intercropping with buckwheat at 25% of its pure stand seed rate) was the only case where legume yield was maintained across species. The MIX25 also provided satisfactory weed suppression. Combining agronomical and mechanical weed control methods could facilitate the spread of agroecological practices in arable crops by reducing redesign risks while increasing agro-biodiversity. This study is among the few to propose buckwheat as a suitable companion crop for three grain legumes in a Mediterranean rainfed environment, showing promising results for weed control and legume performance.