Ecological Management of Wild Oat (Avena fatua L.) in Winter Wheat: Modeling Yield Loss and Determination of Economic Thresholds under Varying Crop Densities

Abstract

Wild oat (Avena fatua L.) is widely recognized as one of the most detrimental grassy weeds in winter wheat production systems globally. While chemical control remains the dominant strategy, the reliance on herbicides without considering Economic Injury Levels (EIL) has led to environmental concerns and the evolution of herbicide resistance. This study was conducted to quantify the competitive effects of wild oat on winter wheat yield and to determine the Economic Threshold (ET) under different crop density scenarios. A factorial experiment based on a randomized complete block design was utilized, featuring three wheat densities (300, 400, and 500 plants m-2) and four wild oat densities (0, 30, 50, and 70 plants m-2). Grain yield data were fitted to Cousens' rectangular hyperbolic model to estimate competition parameters (I and A). The results indicated that wheat density significantly altered the crop-weed competitive balance. The parameter I (percentage yield loss per unit weed density as density approaches zero) was significantly lower in high-density wheat stands, indicating suppressed weed competitiveness. However, severe intra-specific competition was observed at 500 plants m-2, reducing the potential yield even in weed-free conditions. Economic analysis revealed that the ET of wild oat increased with increasing crop density, suggesting that farmers adopting higher seeding rates can tolerate higher weed populations before chemical intervention becomes economically justifiable. These findings support the integration of seeding rate adjustment as a fundamental component of Integrated Weed Management (IWM) to optimize profitability and reduce herbicide loads.