Effect of planting geometry on wheat yield and wild radish ( <i>Raphanus raphanistrum</i> ) suppression

Abstract Wild radish ( Raphanus raphanistrum L.) is a highly competitive annual broadleaf weed that significantly constrains wheat ( Triticum aestivum L.) production, particularly under increasing herbicide resistance and limited chemical control options. Optimizing sowing geometry offers a practical, non-chemical approach to enhance crop competitiveness and suppress weed growth. A field study was conducted during 2022 and 2023 to evaluate the impact of different sowing geometries on R. raphanistrum suppression and wheat productivity. The experiment was arranged in a randomized complete block design with seven treatments, including broadcast sowing; line sowing at 11, 22, and 33 cm; ridge sowing (30 cm); bed sowing (60 cm); and cross sowing (22 cm). Sowing geometry significantly influenced R. raphanistrum density and biomass at all growth stages (15–45 days after sowing). Narrow spacing (11 cm) consistently resulted in the lowest weed density and biomass, while the wider 33 cm spacing resulted in the highest weed pressure. Crop growth and yield responses were consistent across years, with 11 cm line sowing producing the highest number of productive tillers (393.7 m -2 ), grains per spike (42.9), biological yield (15.4 t ha -1 ) and grain yield (6.0 t ha -1 ) averaged across two years. This treatment was closely followed by cross sowing (22 cm). In contrast, wider spacing (33 cm) reduced grain yield by approximately 25–30% due to increased weed competition and reduced crop competitiveness. Correlation and principal component analyses revealed a strong negative association between late-season weed biomass and wheat productivity, emphasizing the importance of sustained weed suppression during critical growth stages. Overall, narrow row spacing, particularly 11 cm line sowing, enhanced crop competitiveness, effectively suppressed R. raphanistrum , and maximized wheat yield, demonstrating its potential as an eco-friendly strategy for integrated weed management.