Drought stress is considered to be major environmental factors limiting crop growth and yield. Drought stress induces many morphological and biochemical changes and responses that influence various cellular and whole plant processes that affect growth and chemical contents. Crop performance in terms of growth, development and biomass accumulation depends on the crop's ability to withstand, acclimate, or recover from the stress. The results of this study confirmed earlier findings and added new clear field evidence of cassava response to different water regimes through supplemental irrigation. From this study, it can be recommended that in areas where water is very scarce, cassava can be tolerance drought stress with T25. So we can say that for cassava, it has a critical threshold for tolerant the drought stress on cassava.