Effects of silicon fertilizer on growth, yield, and fiber quality traits of cotton (Gossypium hirsutum L.)

Abstract Background Cotton is a leading cash crop worldwide, yet its productivity is severely subject to diverse biotic and abiotic stresses. Silicon (Si) effectively enhances crop yields and quality by improving their stress tolerance. However, little is known about how Si additions improve cotton yield and fiber quality by enhancing its physiological stress tolerance. Thus, this field study was launched to explore the effects of different Si foliar spraying concentrations on agronomic traits, leaf physiological indicators, yields, and fiber quality, to identify the optimal concentration. Results Si foliar spraying significantly increased plant height, stem diameter, number of fruit branches, and number of main stem leaves, with the greatest increases under Si 2 concentration (7.15%−23.95%). Meanwhile, total and reproductive dry matter were observed to be significantly increased by Si foliar spraying, especially under Si 2 and Si 3 concentrations in 2024 (8.10%−21.65%). Si foliar spraying obviously improved the seasonal mean SPAD value in 2024. Additionally, it was found that Si foliar spraying (i.e., Si 2 and Si 3 concentrations) sharply reduced the marker of oxidative stress injury (i.e., malondialdehyde) while boosting osmotic regulatory substances (i.e., proline) and antioxidant enzyme activities (i.e., superoxide dismutase, peroxidase, catalase, and glutathione reductase). Although Si foliar spraying significantly increased boll weight, especially under Si 2 and Si 3 concentrations (13.79%−17.29% in 2024), there were slight increasing trends for seed cotton and lint yields in both years. Furthermore, Si foliar spraying markedly improved fiber strength, especially at Si 1 and Si 3 concentrations, in 2025. Conclusions Our results implied that Si foliar spraying decreased the markers of oxidative stress and injury, elevated the contents of osmotic regulatory substances and antioxidant enzyme activities in cotton leaves, and thereby improved cotton fiber quality, despite no significant effects on yields. In the future, more in-depth studies on Si additions in the cotton field are needed to obtain higher fiber quality.