The conditions and norms of application of the new UzDEF and PoliDEF defoliants depending on irrigation regimes and timing of cotton “Zarafshon” in moderate loamy soils with shallow-gray, groundwater depths of 7-8 meters in Samarkand region. According to the data obtained, there is a direct impact on the efficiency of defoliants used in the experimental field as a result of the different effects of irrigation procedures and timing periods on plant growth and development.