Exogenous Calcium Mediates Improved Salt Stress Tolerance in Soybean

Abstract

Aims: To evaluate the effect of exogenous calcium (Ca²⁺) on salinity-induced stress in soybean (Glycine max) and to determine its role in improving growth, physiological, and biochemical parameters contributing to salt tolerance. Study Design: A factorial pot experiment arranged in a completely randomized design (CRD) with three replications was conducted. Place and Duration of Study: Crop Physiology Division, Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh, and Subarnachar, Noakhali, during the 2023–2024 growing season. Methodology: Four soybean genotypes (Sem-05, Sem-08, Sem-11, and Binasoybean-6) were exposed to salinity stress (8 dS m⁻¹ NaCl) with foliar application of calcium sulfate (CaSO₄·2H₂O) at concentrations of 5, 10, and 15 mM. Growth, yield attributes, chlorophyll, proline, soluble sugar, malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) contents were measured. Data were analyzed statistically using ANOVA, and treatment means were compared with the LSD test at a 5% level of significance. Results: Calcium application significantly mitigated the adverse effects of salinity across all genotypes. The 10 mM Ca treatment showed the most beneficial effects, increasing shoot and root biomass, chlorophyll content, and osmolyte accumulation while reducing MDA and H₂O₂ levels. Sem-11 and Binasoybean-6 exhibited superior tolerance, recording the highest yield (6.61 and 5.90 kg ha⁻¹, respectively) and lowest was in Sem-08 (1.51 kg ha⁻¹) under salinity with calcium application. Calcium supplementation improved Na⁺/K⁺ homeostasis and enhanced antioxidant enzyme activity, leading to reduced oxidative damage and improved physiological stability. Conclusion: Exogenous calcium application, particularly at 10 mM concentration, effectively enhances salt tolerance in soybean by stabilizing membranes, maintaining ion balance, and strengthening antioxidant defenses. This approach offers a cost-effective, non-genetic strategy to improve soybean productivity in saline-prone environments.