Exogenous Silicon and Salicylic Acid Applications Enhance Growth, Yield, and Physiological Traits of Cotton Plants under Drought Stress

Drought stress has become a highly detrimental environmental factor that poses significant threats to sustainable cotton (Gossypium hirsutum L.) production necessitating the implementation of appropriate measures to mitigate the adverse impacts of drought stress in the cotton production system. Silicon (Si) and salicylic acid (SA) applications can benefit cotton yield under environmental stress conditions, including drought. The objective of this study was to evaluate how the individual and combined applications of Si and SA influence growth, yield, and physiological responses of cotton plants subjected to drought stress. A polyhouse experiment, arranged in a completely randomized design with four replications, comprising six Si and SA treatments (control, 60 kg ha^–1 Si applied as a soil drench, 1 mM Si applied as a seed priming material, 1 mM SA applied as a foliar spray, 60 kg ha^–1 Si applied as a soil drench + 1 mM SA applied as a foliar spray, and seed priming with 1 mM Si + foliar spray of 1 mM SA) along with three soil moisture levels (100% field capacity [FC], 75% FC, and 50% FC) was conducted. A decrease in soil moisture level from 100 to 50% FC reduced growth (plant height by 18–26%, shoot dry matter by 46–53%, and root dry matter by 27–43%), seed cotton yield (45–55%), irrigation water productivity (41–54%), and physiological response (leaf relative water content by 11–17%, membrane stability index by 44–55%, and up to 102% increase in electrolyte leakage) of cotton plants across Si and SA doses. Among Si and SA doses, a combined application of seed priming with 1 mM Si + foliar spray of 1 mM SA outperformed all other doses and caused an increase of 14–20% in plant height, 78–99% in root dry matter, 24–76% in seed cotton yield, 22–60% in irrigation water productivity, 9–14% in ginning outturn, and 40–94% in membrane stability index across different soil moisture levels. A combined application of Si at 1 mM as a seed priming material and SA at 1 mM as a foliar spray is recommended for cotton cultivation in drought-affected areas.