Improving maize productivity can be succeeded by choosing the best methods of application of some growth promoter substances i.e. gibberellic acid (GA₃), oxalic acid and yeast extract as a new technique in enhancing maize growth and productivity. So, two trails were conducted at El-Hajarsh Village, Center of Kafr Saqr, Sharkia Governorate, Egypt, in 2013 and 2014 growing seasons to determine the effect of application methods and treating with various growth promoter substances and their interaction on productivity of maize hybrid single cross 10 (SC 10). A strip-plot design with four replications was used. Three application methods i.e. soaking, foliar application and soaking + foliar application were organized in the vertical plots. While, growth promoter substances i.e. without (control treatment), water, gibberellic acid "GA₃" (100 ppm), oxalic acid "OA" (400 ppm) and yeast extract "YE" (100 ml/L) were distributed on the horizontal plots. The results showed that seed soaking for about 18 hours plus foliar application twice later than 25 and 45 days since sowing of maize with YE (100 ml/200 liter water/fed) in order to obtained high growth, yield and its components under the environmental conditions of Sharkia Governorate, Egypt.