The aim of the present study was to determine a correlation between the applied increasing potassium doses and the most important parameters of the plant. Growth and development of Pioneer- PR64H42 sunflower (Helianthus annuus L.) hybrid were studied in a pot experiment under greenhouse conditions in the University of Pannonia, Georgikon Faculty. The main subject of the experiment was to quantify the influence of potassium and water supply on the growth, development and nutrient uptake. Effects of four increasing rates of K were studied (K0,1,1.5,2,3) in a Ramann’s brown forest soil (FAO taxonomy: Eutric cambisol) having medium levels of nutrients at 2 levels of water supply (70 and 35 % WHC). From the results of the experiment it was evident that effects of treatments were significant compared to the control. The double rate of K had a positive effect on most of the parameters studied. It can be concluded that under deficient soil moisture conditions, with adequate potassium rates and proper agrotechnics, favourable development can be achieved, therefore yield losses can be avoided.