Evaluation of mechanical and combined chemical with mechanical weeding in maize (Zea mays L.), soybean (Glycine max (L.) Merr. and winter wheat (Triticum aestivum L.)

Joint field experiments were established in Southwestern Germany to investigate the potential of herbicide savings on-farm sites with high densities of problematic weed species. From 2020 until 2024, 21 field studies were conducted in maize, soybean and winter wheat, all realised as randomised complete block designs with four replications. Mechanical weeding and two combined chemical with mechanical weeding methods were compared to conventional broadcast pre- and post-emergence herbicide spraying and an untreated control. Weed density, herbicide savings, greenhouse gas emissions and crop yield were determined for all treatments. On average, 142 weeds/m2 were counted in the untreated plots. The most frequent weed species were Chenopodium album, Echinochloa crus-galli, Solanum nigrum, Stellaria media, and Veronica persica. Combined chemical with mechanical weed control in soybean and winter wheat was more effective than chemical and mechanical weed control alone. In maize, the combination of hoeing and herbicide application achieved equal weed control efficacy (WCE) as chemical weeding alone. Hoeing removed less intra-row weeds than inter-row weeds. Hoeing and harrowing had low WCE against Chenopodium album and perennial weed species. Combined treatments reduced herbicide use by 24-60% in relation to conventional herbicide treatments. Mechanical and combined weed control achieved equal yield as the conventional herbicide treatment. This study underlines the potential for herbicide savings by integrating mechanical weed control methods.