Vegetables are important dietary components and constitute a group of the lowest calorie raw produce with a high nutritional value. The aim of the present study was to determine the nutritional and energy potential of the leaves of rocket (Eruca sativa Mill.) as affected by different regimes of plant nitrogen and potassium nutrition. Plants were grown in a greenhouse in a peat substrate, using varying amounts of nitrogen and potassium: 0.3 and 0.6 N as calcium nitrate (Ca(NO₃)₂) as well as 0.3 K, 0.6 K, and 0.9 K in the form of potassium sulphate (K₂SO₄ ) and potassium chloride (KCl), with a constant level of the other macro- and micronutrients. Fresh leaf yield and the content of soluble sugars, fat, ash and dietary fibre were determined, as well as the caloric value of the plant material studied was estimated. It was shown that the nutritional value of rocket leaves could be increased by using an appropriate system of plant mineral nutrition. The use of KCl significantly increased the nutritional value of rocket leaves, as determined by the presence of fat and dietary fibre. The application of K₂SO₄ proved to be more beneficial due to the concentration of carbohydrates and available carbohydrates. An increase in the rate of nitrogen caused an increase in biomass and fat content, but also contributed to a decrease in the concentration of glucose and fructose. The higher rates of potassium had an effect on increasing the content of fat, ash and glucose. The energy value of rocket leaves was not modified by mineral fertilization applied.

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