Competitive Effects and Economic Threshold of Bifora testiculata in Durum Wheat Under Semi-Arid Conditions

Abstract

Competitive interactions between Bifora testiculata and durum wheat (Triticum durum Desf.) were evaluated under semi-arid field conditions to quantify yield impacts and determine the economic threshold for effective weed management decision-making. Field experiments were established with graded weed densities under natural infestation and augmented emergence plots, and crop performance parameters including plant height, tiller density, biomass accumulation, and grain yield were recorded throughout the growing season. Results demonstrated a significant decline in wheat growth and productivity with increasing B. testiculata density, primarily due to competition for limited soil moisture and nutrients characteristic of semi-arid environments. Early-season interference had the greatest impact on yield reduction, indicating a critical period of competition during crop establishment. Regression analysis revealed a strong inverse relationship between weed density and wheat grain yield, enabling estimation of yield loss coefficients and economic injury levels. The calculated economic threshold indicated that even low-density infestations can cause economically significant losses when left unmanaged under moisture-limited conditions. Phenological overlap between weed and crop intensified competitive pressure, resulting in reduced spike formation, lower grain weight, and decreased harvest index. The study highlights that delayed weed control significantly exacerbates yield penalties, particularly under drought-prone conditions where resource availability is highly constrained. Integration of timely weed management strategies, including early post-emergence control and cultural suppression practices, is essential to minimize economic losses.