Effect of row distance on plant architecture, weed suppression and yield of silage maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) in a pesticide-free cultivation system in Southern Germany

Conventional farming prioritizes monocultures and synthetic chemicals to secure high yields. However, there are a growing number of initiatives worldwide to reduce or eliminate the use of pesticides. One option for pesticide-free weed management is the adjustment of sowing pattern (row distance, plant arrangement, sowing density). This study investigated the effects of an equal distance sowing versus a normal distance sowing (EDS and NDS¹) at constant sowing density on plant morphology, growth and yield of silage maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) as well as the weed occurrence. Therefore, a 3-year (2020–2022) pesticide-free, field experiment was conducted at the Heidfeldhof Research Station, University of Hohenheim, Germany. In silage maize, neither plant architecture nor biomass yield showed significant differences between EDS with 0.375 m and NDS with 0.75 m row distance. In contrast, soybean developed a bushier plant architecture with more branches and shorter petioles in EDS with 0.15 m compared to plants in NDS with 0.50 m row distance, demonstrating phenotypic plasticity. A higher number of pods per plant (EDS: 28.05; NDS: 22.73) and seed yield (EDS: 406.58 g m⁻²; NDS: 389.34 g m⁻²) indicated the potential for increased yields applying EDS. Crop competitiveness against weeds was higher in EDS than in NDS, especially early in the growing season. The results highlight the importance of EDS as a valuable tool for pesticide-free, non-organic cropping systems through positive effects on crop yield and efficient weed control.