The use of yeast as a bio-fertilizer in agriculture has taken a considerable attention because of their bioactivity and safety for human and the environment. The current study aimed to evaluate the effect of potassium fertilization and two yeast strains on maize productivity grown on salt affected soil in Dakahlia Governorate to find out their beneficial effect as biofertilizer. Two years field experiment were conducted to investigate the effect of potassium application levels (0, 30. 40 and 50 kg K/fed.) combined with or without Saccharomyces cerevisiae or Rhodotorula mucilaginosa on the maize yields, potassium use efficiency, NPK uptake and soil fertility after harvest. In addition, total microbial and yeast counts as well as dehydrogenase activity after 50 and 80 days from planting were studied. The results showed that application of potassium with yeast significantly increased maize grain and stalks yield, 1000-grain weight and weight of ear/plant. The application of potassium enhanced K % in maize stalk and grain and decreased Na %, as well as markedly raised the maize salt tolerance via increasing the K/Na ratio, especially with the highest rate of potassium fertilization. Potassium use efficiency and potassium uptake were markedly increased with the application of potassium combined with yeast. The highest K- utilization rate 84.93 % was recorded with the treatment consists of 30 kg K/fed + Rhodotorula mucilaginosa. Potassium fertilization positively affects the nitrogen and phosphorus uptake in both studied seasons. Soil salinity and fertility were slightly increased with the application of potassium fertilizers. The highest values of total microbial and yeast counts as well as the dehydrogenase activity were observed with the low levels of K fertilizer associated with Rhodotorula mucilaginosa. So it could be recommended to apply the low levels of potassium together with the yeast strains as a biofertilizer to overcome the salt stress of maize plants.