Increasing potassium fertilizer rate up to 80 kg K₂O/fed significantly induced growth and carbohydrates concentration and ion percentage in potato shoots as compared to control in both seasons. The highest values was obtained due to application of 40 kg K₂O/fed in the first and second seasons as compared with untreated plants. Addition of effective microorganisms and exogenous application of biostimulants, in particular, seaweed extract significantly increased shoot growth, carbohydrates concentration and ion percentage as compared to control in both seasons. As for the interactions, application of biostimulants, in particular, seaweed extract, significantly increased shoot growth, carbohydrates concentration and ion percentage in potato shoots grown under all potassium fertilizer rates with or without an addition of effective microorganisms. The highest value was obtained under the treatment of 40 kg K₂O/fed with addition of effective microorganisms and spraying plants with 500 mg/l seaweed extract as compared with control plant in the first and second growing seasons.