The Effect of Foliar Spraying with Different Concentrations of Algamix Seaweed Extracts on Growth, Yield, and Seed Strength of Hordeum vulgare L. Barley Varieties

This study examined the effects of seaweed extract on growth, yield, and seed vigor in four Iraqi barley cultivars through field and laboratory experiments. Field trials were conducted west of Nineveh during the 2024–2025 and 2025–2026 seasons; laboratory tests took place at the University of Mosul. Field treatments comprised cultivars Al-Jazeera, Furat-9, Rihan, and Hader 462, sprayed with Algamix at 3 or 5 mL L⁻¹, or water (control). The field experiment used a randomized complete block design with three replications; laboratory tests used a completely randomized design with three replications. Cultivars differed significantly in all traits. Rihan achieved the highest field values across both seasons for flag leaf area, total tillers, spikes, 1,000-grain weight, and grain yield. Its yields were 4.42 and 4.61 t ha⁻¹, respectively. Algamix at 5 mL L⁻¹ outperformed the lower dose and control, increasing flag leaf area, spike number, grain weight, and yield; yields reached 4.17 and 4.52 t ha⁻¹. The strongest cultivar-treatment combination was Rihan with 5 mL L⁻¹, producing yields of 4.64 and 4.82 t ha⁻¹, alongside the highest values for yield components. In laboratory testing, seeds from Rihan had the highest germination speed index (27.56 and 29.53) and germination percentage (95.01 and 95.45%), and the shortest mean germination times (5.30 and 5.05 days). Seeds from plants receiving 5 mL L⁻¹ also showed superior vigor, with germination speed indices of 28.62 and 30.89, germination percentages of 94.91 and 94.98%, and shortest germination times of 5.21 and 4.92 days. Overall, Rihan and the higher Algamix rate improved field performance and seed quality.