The field experiment was carried out during the two growing seasons of 2013-2014 and 2014-2015, at the farm of Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Egypt, to investigate the effect of irrigation after the depletion of different available soil water levels, soil conditioner, foliar application of glycine betaine and potassium silicate on vegetative growth and chemical composition of garlic (Allium sativum L.), cv. Sids-40 under water stress conditions. The experimental treatments were arranged in a split split plot design, with three replicates Irrigation levels were conducted after the depletion of 60%, 75% and 90% of available soil water in the main plots. Irrigation treatments were started six weeks from planting, soil conditioner at the rates of 2 m3/Fed and control were distributed in the sub-plots. Foliar applications of glycine betaine was used at 2 mM/Land potassium silicate was used at 0.5 g /L, after 50, 65, 80, 95, 110, 125 and 140 days respectively, from planting compared with control were devoted in the sub-sub plots. The results indicated thatthe irrigation after depletion of 60 % available soil water with applying soil conditioner and glycine betaine or potassium silicate increased the Plant lengthof garlic after 150 days from planting. Bulb diameterand nitrogen contentshowed significant increase as a result of irrigation after depletion of 60 % available soil water with applying soil conditioner in addition to the foliar application ofglycine betaine.Prolin content was significantly increased as a result of irrigation after depletion of 90 % available soil water without applying soil conditioner with the foliar application of distilled water (control).Whereas, the lowest value of Prolin content appeared with irrigation after depletion of 60 % available soil water with applying soil conditioner and foliar application of glycine betaine.Total soluble solids (TSS) andtotal Sugarsincreased significantly as a result of irrigation after depletion of 90 % available soil water without applying soil conditioner with the foliar application of glycine betaine.It was therefore concluded that vegetative growth and chemical analyses of garlic responded positively to irrigation, applying soil conditioner and foliar application of 2 mM/L glycine betaine or 0.5 g/L potassium silicate