Two field experiments were conducted in El-Gemmeiza Agric. Res. Station, Agric. Res. Cent., El-Gharbiya Governorate, Egypt for two successive seasons (2013 and 2014) to study the influence of irrigation systems and spraying of potassium silicate on growth, productivity and quality of cotton Giza 86 cultivar. A split-plot design was used with four replicates. The main plots included five irrigation systems (normal irrigation every two weeks all season as a control- system 1, normal irrigation every two weeks until end of June then irrigation every 21 day to end of season- system 2, normal irrigation every two weeks until end of July then irrigation every 21 day to end of season- system 3, normal irrigation every two weeks until end of June then irrigation every 28 day to end of season- system 4 and normal irrigation every two weeks until end of July then irrigation every 28 day to end of season- system 5.  The sub plots involved three treatments of spraying with potassium silicate (control without potassium silicate, spraying of potassium silicate two times at the start of flowering and every 15 days later and spraying of potassium silicate three times at squaring stage, at the start of flowering and 15 days later). Obtained results revealed that normal irrigation every two weeks all season (system 1) significantly increased height of plant, No. of fruiting branches per plant, No. of open bolls per plant, seed index, boll weight, yield of seed cotton per fed, fiber length, fiber strength and fiber fineness. Treatments of potassium silicate had significant effect on final plant height, number of fruiting branches, number of open bolls/plant, seed index, boll weight, seed cotton yield (kentar/fed), fiber length, fiber strength and fiber fineness in both seasons and lint % in one season. The highest values resulted from spraying with potassium silicate (2.5 cm3 /L) three times. The interaction between irrigation systems and spraying with potassium silicate gave a significant effect on final plant height, No. of fruiting branches /plant, boll weight, No. of open bolls/plant, seed cotton yield(kentar/fed), fiber length, fiber strength and fiber fineness, where the highest values of these traits were obtained from normal irrigation every two weeks all season (system 1) and foliar application of 2.5 cm3 /L potassium silicate three times. Finally, it could be concluded the normal irrigation every two weeks all season and foliar application of potassium silicate (2.5 cm3/L) three times at squaring stage, at the flowering initiation and 15 days later to obtain better growth, high yield and yield components and quality of fiber of Egyptian cotton (Giza 86 cultivar), under the conditions of El-Gharbiya Governorate.