**8. Conclusion**

The world population will increase up to 9 billion in the year 2050. The biotic and ambitious factors are the main cause of the reduction of yield as well as quality. Therefore, it is necessary to reduce the massive application of fertilizers; however, overuse of N fertilization and K deficiency become a source of poor yield and quality. Recently, more attention has been focused on the effects of morpho-physiological traits that ultimately determine yield. Although all stages of cotton development are affected by drought stress, however, the reproductive phase of flowering and boll development is generally accepted as the most sensitive stages. Therefore, it is necessary to develop nutrient-efficient cultivars to fulfill the yield gap in many regions. According to our knowledge, little information is available for the characterization of cotton cultivars for potassium uptake under drought stress. The knowledge of drought tolerance of K-efficient cotton cultivars during drought stress is crucial for maintaining yield production in regions where water supply is limited or annual rainfall is less.
