Competitive Ability and Biomass Partitioning of Raphanus raphanistrum in Winter Oilseed Rape Fields

Abstract

Competitive ability and biomass partitioning patterns of Raphanus raphanistrum were investigated in winter oilseed rape (Brassica napus L.) fields to understand its impact on crop performance and resource utilization under field conditions. Field experiments were conducted under natural infestation gradients, and weed density, crop growth traits, and biomass allocation between above- and below-ground components were quantified across the growing season. Results indicated that R. raphanistrum exhibited strong competitive potential, significantly reducing oilseed rape plant height, leaf area, and biomass accumulation at increasing weed densities. Early emergence and rapid seedling establishment enabled the weed to effectively capture light, nutrients, and soil moisture during critical crop growth stages, intensifying interspecific competition. Biomass partitioning analysis revealed a higher allocation to root structures under competitive stress, suggesting adaptive plasticity to enhance resource acquisition in resource-limited environments. Above-ground biomass was also substantially increased in high-density treatments, contributing to greater shading effects and suppression of crop canopy development. Regression analysis demonstrated a strong negative relationship between weed density and crop yield, highlighting the economic significance of early-season interference. Phenological overlap between weed and crop further exacerbated competitive interactions, particularly during the vegetative growth phase of oilseed rape. The study underscores the importance of timely weed management interventions to minimize yield losses caused by R. raphanistrum. These findings provide valuable insights into weed–crop interaction dynamics and support the development of integrated weed management strategies, including optimized herbicide timing and cultural practices, to improve productivity in winter oilseed rape systems under competitive weed pressure.