Effect of Seaweed Extract on Morpho-physiological Response and Seed Yield ofSoybean under Drought Stress

Soybean crop is often exposed to water shortage during the dry growing season in Bangladesh. BARI Seaweed-1 extract was used as biostimulant to address drought stress on soybean. BARI Soybean-6 was grown in field during 2024-25 under well-watered as control (80-90% field capacity, FC) and water stress (50-60% FC) with foliar application (five levels: 0, 2.5, 5.0, 7.5, and 10 mL L−1 of water) of seaweed extract at second trifoliate leaf to R6 stage (pod containing a full green seed) with seven days interval. Seaweed extract showed significant effect on soybean growth characters and seed yield. Relative water content and chlorophyll fluorescence were also varied due to different levels of seaweed extract. Proline accumulation and reactive chemical compounds like hydrogen peroxide (H2O2) and malondialdehyde contents were observed maximum in water stress plant and the contents were decreased with increasing levels of seaweed extract. Antioxidant enzymes activities like glutathione S-transferase, peroxidase, catalase and ascorbate peroxidase were observed maximum in water stress along with seaweed extract @ 10 mL L−1 of water. The lowest seed yield (774 kg ha−1) was observed in water stress without seaweed extract treatment which was 48.9% lower as compared to well-watered treatment. However, water stress along with seaweed extract @ 7.5 and 10 mL L−1 of water treatments produced 86.13% (1304 kg ha−1) and 87.52% (1325 kg ha−1) seed yield as compared to well watered treatment, respectively. Foliar application of BARI Seaweed-1 extract @ 7.5 and 10 mL L−1 resulted in substantial seed yield recovery in soybean under water-limited conditions, suggesting that seaweed extract is a promising biostimulant for sustainable soybean production in drought -prone areas. Bangladesh Agron. J. 2026, 29(1): 11–19