Exogenous application of mepiquat chloride and crop geometry alters cotton growth and yield traits of compact cotton cultivars (Gossypium hirsutum L.)

Mepiquat chloride is widely used as a growth regulator in cotton fields to increase crop yield. The present study investigated the effects of growth regulator (mepiquat chloride) and row spacings on compact cotton's growth and yield attributes. An experiment was conducted during summer and winter seasons of 2023-2024 at Cotton Research Station, Veppanthattai and the field trial was designed as a split-split plot with three main plots (Varieties - CO 17, VPT 2, Suraksha), four sub-plots (crop geometry - 90 x 15 cm, 70 x 15 cm, 90 x 10 cm, 70 × 10 cm), and two sub-sub plots (growth regulators - mepiquat chloride @150 ppm, mepiquat chloride + cyclanilide @400 ppm), each replicated three times. Results concluded that the Suraksha variety showed superior performance with greater plant height, higher biomass, more sympodial branches, higher bolls/m2 and higher seed cotton yield than CO 17 and VPT 2. Wider spacing of 90 cm resulted in greater plant height, more sympodial branches and more bolls/m2 to a significantly rise in dry matter production due to the higher number of plants per unit area. Combining mepiquat chloride with cyclanilide at 400 ppm during square initiation and boll development stages significantly increased sympodial branches and bolls/m2, improving seed cotton yield.In contrast, applying mepiquat chloride alone led to more significant biomass accumulation, increased plant height and longer internodal distances. It was suggested that the Suraksha variety be sown at a spacing of 90 x 15 cm and treated with a combination of mepiquat chloride and cyclanilide. This resulted in a plant architecture well-suited for mechanical harvesting.