EVALUATING TOLERANCE OF WILD OAT (AVENA FATUA) TO CONTROLLED WATER DEFICIT REGIMES

Abstract

Wild oat (Avena fatua L.) is a competitive annual weed that thrives in temperate and semi-arid agroecosystems, where water availability often limits crop productivity. This study aimed to evaluate the growth, physiological, and reproductive responses of A. fatua under controlled water deficit conditions to identify potential moisture thresholds for weed suppression. A pot experiment was conducted using four irrigation regimes based on field capacity (FC): 100%, 80%, 60%, and 40%. Key traits including plant height, tiller number, shoot and root dry biomass, relative water content (RWC), chlorophyll fluorescence (Fv/Fm), stomatal conductance (gs), and reproductive attributes were measured. Results indicated a consistent decline in all parameters with increasing water stress. RWC and Fv/Fm dropped significantly under 60% and 40% FC, indicating impaired physiological functioning. Seed yield per plant was reduced by over 50% at 40% FC compared to full irrigation. These outcomes suggest that A. fatua is moderately drought-sensitive, with 60% FC representing a physiological tipping point. Despite some adaptive responses such as increased root allocation and reduced stomatal conductance, severe water stress constrained reproductive success. These findings suggest that regulated deficit irrigation could suppress A. fatua competitiveness and reproduction without chemical inputs, offering a sustainable weed management strategy. Further field validation is needed to assess long-term weed seedbank depletion under variable rainfall and irrigation schedules..