Competitive Index and Economic Threshold of Avena ludoviciana in Durum Wheat Under Supplemental Irrigation

Abstract

Weed interference from Avena ludoviciana poses a significant challenge to durum wheat productivity, particularly under irrigated and resource-intensive production systems. The present study evaluated the competitive ability of A. ludoviciana and determined its economic threshold level in durum wheat under supplemental irrigation conditions. Field experiments were conducted using a replacement series design and graded weed density treatments to assess crop–weed interaction, yield reduction, and competitive indices. Results indicated a significant decline in wheat growth parameters, including tiller number, biomass accumulation, and grain yield, with increasing weed density. The competitive index analysis revealed strong aggressiveness of A. ludoviciana, which exhibited superior resource acquisition compared to wheat during early growth stages. Yield loss models demonstrated a negative exponential relationship between weed density and wheat grain yield, with substantial reductions observed even at low infestation levels. The economic threshold was estimated by integrating yield loss data with weed control costs and market wheat prices, indicating that early-season weed presence beyond a minimal density significantly reduces economic returns under supplemental irrigation. Supplemental irrigation enhanced overall crop growth but simultaneously favored weed competitiveness, intensifying crop–weed competition for nutrients, light, and space. These findings emphasize that irrigation management alone is insufficient to suppress A. ludoviciana interference and must be integrated with timely weed control strategies. The study highlights the necessity of adopting integrated weed management approaches combining pre-emergence herbicides, competitive cultivars, and optimized irrigation scheduling. Overall, A. ludoviciana demonstrates high competitive ability in durum wheat systems, and its management should be prioritized at early infestation stages to prevent irreversible yield and economic losses under irrigated agroecosystems.