Two field experiment were carried out during two successive summer seasons of 2018 and 2019 at Private Farm, Belbies District, Sharkia Governorate, Egypt, to study the effect of level and source of potassium (K-sulphate, potassium silicate and K-feldspar with silicate dissolving bacteria) on growth, productivity and tuber quality of potato (Solanum tuberosum L.) cv. Spunta grown in sandy clay soil. Fertilizing potato plants grown in sandy clay soil with 48 kg K2O as potassium sulphate (KS) with potassium silicate (Ksil) gave the tallest plants, whereas 36 kg K2O as KS + 36 kg K2O as feldspar (KF) with silicate dissolving bacteria (SDB) + Ksil gave the highest values of number of main stems, number of lateral branches, leaf area, fresh and dry weight of shoots and number of leaves / plant. Moreover, fertilizing with 72 kg K2O (36 kg K2O as KS + 36 kg K2O as KF) with inoculation with SDB + foliar spray with Ksil increased tuber yield / plant, yield of grade 1, marketable yield and total yield / fad. Potato plants which fertilized with 48 kg K2O as KS + 48 kg K2O as KF with SDB + Ksil gave the highest values of tuber dry matter (%) and starch content.