Response to Reduced Doses of Mepiquat Chloride on Yield and Quality Characteristics of Cotton (Gossypium hirsutum L.) in the Mediterranean Region of Türkiye

Objective: A field study was undertaken to examine the effect of reduced Mepiquat chloride (MC) dosage applied at different times to enhance the yield and quality attributes of cotton at the Eastern Mediterranean Agricultural Research Institute, Adana, Türkiye, during the 2022 cropping season. Material and Methods: A split-split plot experiment following a randomized complete block design (RCBD) with three replications was employed.Varieties (Sezener and Selin) were assigned to the main plots, application times (before and after flowering) to the sub-plots, and MC concentrations (0, 40, 40+40 and 80 cc/da) to the sub-sub-plots. Results: Results shown that Sezener outperformed Selin across metrics: higher fiber yield (490.6 vs 447.5 kg/ha), reflectance (69.8 vs 63.5), and yellowness (11.9 vs 10.8). Under Sezener, the 80 cc/da dosage at 60 days after sowing maximized yield (530.2 kg/ha). Selin showed poorest yield (360.3 kg/ha) and highest trash (2.60%), while Sezener had lowest (0.57%). Mepiquat chloride doses effected quality parameters differently for both varieties. The effect changed within application time. It has been determined that the application of Mepiquat chloride has different effects on the quality parameters in two varieties, and the effect varied according to the time of application. As a matter of fact, in the yellowness parameter, unlike other quality parameters, Selin variety had the lowest, while Sezener had the highest value. Conclusion: Although most effects were not statistically significant, certain variety-application time interactions revealed practical differences that may inform future studies. Therefore, to maximize monetary returns, further research is needed to enhance yield and quality parameters in the Mediterranean region of Türkiye. In addition, more comprehensive studies should be carried out to understand the change in the effect of Mepiquat chloride application on the basis of varieties.