Sorbitol-Stabilized Silicon Formulation Improve Root Traits and Antioxidant Response in Drought-Stressed Soybean

Silicon (Si) plays a pivotal role in modulating plant physiological responses, particu-larly by influencing non-enzymatic antioxidant systems and amino acid metabolism. The objective of this study is to evaluate soybean performance in response to soil and foliar Si applications under both well-watered and drought conditions, aiming to en-hance Si accumulation in plant tissues and potentially amplify the crop’s physiological responses under water deficit stress. This is particularly relevant given that the mech-anisms underlying Si fertilization and its role in soybean stress tolerance remain insuf-ficiently explored. A greenhouse experiment was conducted using a 3×2 factorial de-sign. The factors were: i) three foliar Si treatments: a control (no Si), potassium silicate (SiK; 128 g L⁻¹ Si, 126.5 g L⁻¹ K₂O, pH 12.0), and sorbitol-stabilized potassium silicate (SiKe; 107 g L⁻¹ Si, 28.4 g L⁻¹ K₂O, 100 mL L⁻¹ sorbitol, pH 11.8); and ii) two soil water levels: water-restricted and well-watered, 40% and 80% of field capacity, respectively. The drought condition simulated tropical dry spells. Si was applied to the soil via irri-gation and to the leaves via foliar sprays prior to water restriction. All Si solutions were adjusted to pH 7.0 with 1M HCl immediately before use. Potassium (K) levels were balanced across all treatments using soil and foliar applications of KCl. Biometric and physiological attributes were measured. Sorbitol-stabilized silicon increased Si accumulation in soybean tissues and enhanced plant resilience under both well-watered and drought conditions by improving key physiological traits, such as elevated daidzein and ascorbic acid levels, along with reduced amino acid concentra-tions, as well as biometric parameters, including leaf area, root development, and number of pods per plant. These findings reinforce the role of Si as a beneficial element in promoting stress tolerance and advancing sustainable agricultural practices.