Increasing potassium fertilizer rate up to 80 kg K₂O/fed significantly increased yield and improved its quality as well as increased the net income and investment rate. The highest values were obtained due to application of 40 kg K₂O/fed in the first and second seasons as compared with untreated plants. Exogenous application of biostimulants, in particular, seaweed extract significantly increased yield and improved its quality as well as increased the net income and investment rate as compared to control in both seasons. Addition of effective microorganisms to the soil significantly increased yield and improved its quality as well as increased the net income and investment rate. As for the interactions, application of biostimulants, in particular, seaweed extract, significantly increased yield and improved its quality as well as increased the net income and investment rate 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 an addition of effective microorganisms and spraying plants with 500 mg/l seaweed extract as compared to control plant during the first and second growing seasons.