Potassium (K) is an essential element vital for plant growth, as it actively regulates water balance within their cells. This research focused on studying the effects of alternative forms of potassium on growth and yield of potato plants. Rosetta potato variety was cultivated under surface drip irrigation systems at the experimental farm of the Soils and Water Department, Faculty of Agriculture, Assiut University, Egypt, during the winter seasons of 2020/2021 and 2021/2022. Three different sources of potassium, i.e. K-humate, K-sulfate, and Vinasse (Vinasse is organic by-product of the sugarcane industry) were used. The three fertilizers were tested under four water levels of surface drip irrigation (I₁ =100, I₂ = 88, I₃ = 74, and I₄ = 61% of evapotranspiration (ETc). Split-plot design was used in the experiment.
The Results showed that the highest mean values of potato tubers yield, were recorded from the first irrigation treatment) I₁) compared to the other water levels treatments (I₂, I₃, I₄). Fertilization with organic materials such as vinasse and K-humate gave a higher yield rate than potassium sulphate. However, fertilization with vinasse gave the highest yield and quality parameters including tuber size, number of tubers, dry weight, amount of starch, and amount of potassium in tubers. Also soil fertility was better with vinasse application than potassium sulfate.