Abstract <p>Cotton is one of the most important fiber and cash crops, which plays a dominant role in the industrial and agricultural economics of the world. Most cotton cultivars produce excessive foliage even at crop maturity due to their indeterminate growth habit, which delays boll opening and results in unsynchronized maturation. Due to this, the multiple pickings in cotton require more labour and is also time-consuming process. These problems can be overcome by the practice of mechanical picking in cotton cultivation. For mechanical picking, it is necessary to defoliate the leaves artificially through application of chemicals which will also synchronize the boll opening, finally yield. To address this, we evaluate the various chemicals on morpho-physiological traits, the nutrio- hormonal changes for efficiency in defoliation, boll opening percentage, and synchronization of the entire yield in cotton. The results show that chemical defoliation makes a significant contribution in the improvement in leaf abscission, decreases green leaf retention, and hastens boll opening, allowing for a more even harvest. Among the chemicals, the application of thidiazuron + diuron exhibited the greatest defoliation percentage (96%) and boll opening rate (84%), resulting in enhanced the synchronized boll opening of harvesting efficiency and fiber quality. Overall, this research offers important information for cotton producers seeking to maximize the defoliant application for efficient mechanized harvesting.</p>