Critical Period for Weed Removal in Soybean and Its Relationship to Canopy Closure and Weed Species Composition

Abstract

Critical period for weed removal in soybean and its relationship to canopy closure and weed species composition were investigated to determine the timing and duration of weed interference that most significantly affects crop yield. Field experiments were conducted under varying weed infestation levels and removal timings, and soybean growth parameters, weed density, biomass, and yield attributes were recorded. Results indicated that early-season weed competition had the greatest impact on soybean productivity, with yield losses significantly reduced when weeds were removed before the critical interference window. The critical period for weed removal was closely associated with the timing of soybean canopy closure, where rapid canopy development reduced light availability to emerging weeds and suppressed later weed emergence. Weed species composition played a key role in determining competitive pressure, with fast-growing broadleaf weeds exerting stronger early competition compared to slower-emerging species. Delayed weed removal beyond the critical period resulted in irreversible yield losses due to early-season resource competition for light, nutrients, and moisture. The study also observed that effective canopy closure reduced late-season weed biomass but was insufficient to compensate for early competition effects. These findings emphasize the importance of timely weed management interventions synchronized with crop growth stages. The results support integrated weed management strategies that prioritize early-season control and promote rapid canopy development to minimize weed interference in soybean production systems.