A field experiment was conducted at EL- Ismaielia Agric. Res. Station (ARC), EL- Ismaielia Governorate, in the winter season of 2007 / 2008, to study the effect of inoculation with either Azotobacter chroococcum  (nitrogen fixers and plant growth promoters) or Bacillus circulans (Silicate potassium) dissolving bacteria on the availability of potassium from both potassium sulfate (48 % K₂O) and feldspar (10.5% K₂O) as a natural source of potassium to potato plants, as well as, to investigate their effect on potato yield and its characters and soil available N, P and K contents after potato harvesting and soil biological activities. Results indicated that inoculation with                B. circulans and Azotobacter chroococcum in the presence of different potassium sources increased all examined potato tuber yield, tuber content of carbohydrate and soluble sugar, soil biological activity and soil available N, P and K compared to the sole use of K- sources. The dual inoculation with B. circulans and Azotobacter chroococcum in combination with both K-sources at both tested levels surpassed all the tested treatments and gave the highest potato tuber yield with priority of K- sulfate source than K- feldspar source. However, the use of potassium (K-rock) minerals in combination with biofertilizers can be agronomically more useful and ecofriendly more feasible than that of the soluble sulphate- K.