Competitive Effects of Ridolfia segetum Density on Biomass Accumulation and Seed Yield of Coriander

Abstract

Competition from weed species is a major constraint in coriander cultivation, particularly in low-input and rainfed agricultural systems where early crop establishment is critical for yield formation. Field experiments were conducted to evaluate the competitive effects of varying densities of Ridolfia segetum on biomass accumulation, growth attributes, and seed yield of coriander (Coriandrum sativum). Different weed density levels were established to simulate crop–weed interference throughout the growing season. Increasing density of R. segetum significantly reduced coriander germination success, plant height, branching, leaf area development, and total aboveground biomass due to intense competition for light, nutrients, and soil moisture. Early emergence of the weed exerted the strongest suppressive effect on crop growth, indicating the importance of initial establishment timing in determining competitive outcomes. Yield components, including umbel number, seed number per umbel, thousand-seed weight, and overall seed yield, declined progressively with increasing weed density. Higher coriander plant density partially mitigated weed effects by enhancing canopy closure and reducing resource availability for weed growth, although complete suppression was not achieved under high infestation levels. Environmental conditions influenced the intensity of crop–weed interactions, with adequate moisture and moderate temperatures favoring rapid weed growth and increased crop suppression. The results demonstrate the strong competitive ability of R. segetum in coriander agroecosystems and its potential to significantly reduce crop productivity if not effectively managed. Integrated weed management strategies, including optimized sowing density, timely mechanical control, and improved field sanitation, are essential to minimize yield losses.