The effects of biochar on improving the tolerance to salinity stress and some growth traits in cotton

Background and objectives: Today, soil and water salinization are among the most important limiting factors for agricultural production. Salt stress, a major environmental stress, adversely affects plant growth and development by causing the accumulation of excessive salt content in the soil. Like other abiotic stresses, salt stress negatively impacts plant growth and reproduction in various ways. Consequently, research on agronomic and physiological approaches is vital for improving salinity tolerance in crops. Management practices such as using biochar are essential in mitigating the adverse effects of salinity stress. Therefore, the present study was conducted to investigate the effect of biochar on certain growth traits of cotton plants under salt stress conditions.
Materials and methods: The experiment was conducted at the Minab Higher Education Center (University of Hormozgan), Iran, in 2023. According to the Köppen–Geiger climate classification, Minab features a hot desert climate (BWh). This experiment employed a factorial design based on a completely randomized layout with three replications. Treatments included three levels of biochar (0%, 1%, and 2%) and four salinity levels (control, 4, 8, and 12 dS/m). Six cotton seeds were sown on January 20, 2023, in pots (30 cm in height and 20 cm in diameter) containing a soil and biochar mixture. The salinity levels were prepared by dissolving sodium chloride (NaCl) in water. Parameters measured included plant height, collar diameter, number of leaves, number of bolls, fiber weight, wet and dry weight of the plant, root length, and volume.
 
Results: The results showed that increasing levels of biochar significantly enhanced plant height, boll number, fiber weight, wet and dry weight, root length, and volume compared to the control. The study indicated that plant growth (plant height, number of bolls, fiber weight, dry and wet weight, root length, and volume) decreased significantly at the highest salinity level (12 dS/m) compared to the control. The interaction effect of biochar and salinity revealed that the highest number of bolls (9.6 bolls) and fiber weight (27.84 g) were obtained with the 2% biochar treatment and salinity control. In contrast, the highest plant dry weight was observed in the salinity control treatment across all biochar levels.
 
Conclusion: The application of biochar increased the values of growth traits, while salinity decreased these traits. Furthermore, under salinity conditions, the highest number of favorable traits was observed in the biochar treatments. Therefore, biochar effectively increased the salinity tolerance of cotton. It can be concluded that biochar can be used as a soil amendment to improve growth and reduce the adverse effects of salinity on cotton, potentially increasing cotton production in saline conditions.