Potassium plays a pivotal role in improving potato quality and yield. Field experiment was conducted during fall seasons of 2018/2019 and 2019/2020 at the experimental facilities of Minia University, Egypt, in order to study effects of different organic and inorganic sources of potassium (Potassium Sulfate - Potassium Humate - Potassium Nitrate - Potassium Silicate) on growth and yield performance of potato cultivars of (Lady Balfour and Cara).  After 75 days from planting, maximum plant height and number of branches was obtained with cultivar Lady Balfour fertilized with potassium humate. Use of potassium humate with Lady Balfour gave superlative results in terms of length of branches, number of stems and weight of branches, while the leaf area was increased in the Lady Balfour with potassium silicate treatment. The greatest amount of tubers/plant in both seasons were achieved by Cara fertilized with potassium silicate, while the weight of tubers/plant was recorded by Lady Balfour with potassium humate treatment in the second season. The greatest tuber yields for both seasons were achieved by Cara with potassium silicate and Lady Balfour with potassium humate. Tuber's texture, TSS and contents of chlorophyll a, b and carotene were higher with Cara cultivar fertilized potassium humate and potassium silicate.  The results of experiment showed that the highest contents of nitrogen, phosphorous and potassium in potatoes leaves obtained by humic acid with both cultivars.  Positive impacts of potassium humate followed by potassium silicate over other examined potassium sources on potato growth and quality were confirmed.