Effects of Sowing Date, Water Deficit, and Potassium and Sodium Silicate on Yield and Quality Traits of Faba Bean (Vicia faba L.)

Faba bean production in Iraq is becoming much harder due to climate change. Arid environments in the region suffer from a combination of low rainfall, outdated irrigation networks, and extreme heatwaves, all of which directly suppress final crop productivity. As a protein-rich legume of high nutritional and economic value, faba bean requires effective agronomic strategies to maintain yield and quality under stress conditions. This study evaluated, under field conditions during the 2023–2024 growing season in Iraq, the interactive effects of three sowing dates (September, October and November), two deficit irrigation regimes (80% and 60% of the full irrigation control), and foliar application of two silicate compounds (potassium silicate and sodium silicate) on branching ability, yield, and quality traits of faba bean. A Nested with split plot design and three replications was used; treatment means were compared using analysis of variance ANOVA followed by the L.S.D. test at P < 0.05. Results showed that the interaction of September sowing, 80% irrigation, and sodium silicate significantly enhanced branching (14.10 branch plant–1) and proline (135.83 mg 100g–1) compare to control. Conversely, potassium silicate under the same treatment maximized seed yield (51.83 t ha–1), flower set rate (23.11%), relative water content (RWC 83.19%), and folic acid (186.80 mg 100g–1). These findings demonstrate that silicon's ion, especially the potassium, functionally compensate for heat and water stress induced losses by stabilizing branching and reproductive development. This work provides a strategy to enhance faba bean tolerance to combined abiotic stresses under semi-arid conditions.