Effects of potassium application timing and humic acid on cotton yield and fiber quality traits

This study was conducted during the 2024 cotton growing season at the GAP Agricultural Research Institute, Serince Cemile Adıyaman station, to determine the effects of different potassium application periods and humic acid applications on yield and fiber quality characteristics of cotton. The experiment was established in a factorial arrangement (2 humic acid × 8 potassium application periods) based on a randomized complete block design with three replications. Seed cotton yield, ginning outturn, fiber fineness, fiber length, and fiber strength were evaluated. According to the results, potassium application periods had a statistically significant effect on seed cotton yield and fiber strength (p<0.01). The highest yield was obtained from applications covering multiple phenological stages (Squaring + Flowering + Boll Development), while applications during squaring and squaring+bol formation (S+B) were prominent in terms of fiber strength. The effect of humic acid application on the investigated traits was statistically non-significant. No significant differences were observed among treatments for ginning outturn, fiber fineness, and fiber length. In conclusion, potassium fertilization applied at appropriate phenological stages plays a decisive role in improving seed cotton yield and fiber strength. In contrast, fiber length and fineness exhibited a more stable pattern and were less responsive to fertilization practices. Although humic acid application alone was not effective, it may act as a supportive factor when used in combination with potassium applications.