A field experiments was carried out at the Experimental Farm of the Faculty of Agriculture, Moshtohor, Benha university, Qalubiya governorate, Egypt during the two successive seasons of 2010 and 2011 to investigate K fertilization ,using feldspar-K and sulphate-K and biofertiliztion with a mixture of N-free fixing bacteria, P-dissolving bacteria and silicate dissolving bacteria on growth of potato (Solanum tuberosum L cv. Sponta). The experimental design was a randomized complete block, factorial, in 3 replicates. Factors of the experiment and their treatments were as follows: (A)K-addition, five treatments :(A1) 100% dose sulphate-K(SK) ,(A2) 75% dose as SK + 25% dose as feldspar-K(FK) ,(A3) 50% SK + 50% FK,(A4) 25% SK + 75% FK and (A5) 100% dose of FK, the full dose of K 300 kg K/ha;(B)Biofertilization, two treatments :(B0) no addition of biofertilizer and (B1) addition of biofertilizer. Nitrogen and phosphorus were added to all treatments at a rate of 350 kg N/ ha and 75 kg P/ ha. Plants were sprayed with Fe, Zn, and Mn-EDTA. Treatment A3 gave the highest yield (tubers and shoots), macro nutrient uptake (N, P and K) in both tubers and shoots, tuber size, starch content, leaf area, and total chlorophyll. Increasing the dose of feldspar-K increased nitrate content in tuber. Biofertiliztion increased yield (tubers and shoots), macro nutrient uptake (N, P and K) in both tubers and shoots, tuber size, starch content, leaf area, and total chlorophyll. It decreased slightly nitrate content in tubers.