A series of lab and field experiments were carried out to evaluate the possibility of using some substances as adjuvants added to the foliar fertilizer tank to improve fertilizer application and use efficiency. Each of the suggested substances was prepared in 10 concentrations treatments, ranging between 0.05 and 2g/L. The effect of each concentration on static surface tension and static contact angle in liquid/air/glass and solid plant leaves/air interface were used to evaluate and find out the optimum concentration of each substance to be used as adjuvant. An Adjmix-D1 was prepared using 0.6g/L Triethanolamine and 0.6g/L liquid soap as surfactants, 0.6g/L glycerin as a humectant, 0.6 g/L Arabic gum as a sticker and 0.6g/L urea as a penetrator. The obtained results showed that fruit yield as well as N, K, Fe, Zn and Mn contents in white eggplants and cucumber leaves are positively increased by the applications of improved foliar fertilizers (IFF). This increase can be arranged in the following descending order: Adjmix-D1 > Adjmix-D2 > Liquid soap > Rixi film > Triethanolamine. It could be concluded that the Adjmix-D1 can be used as an effective adjuvant for improving foliar fertilizer application efficiency.