The influence of fertilization with composted mixtures of waste activated sludges with CaO or ash from brown coal on the content of calcium, magnesium, potassium and sodium in the tested plants was studied. The tested plants harvested from objects fertilized with CaO contained a higher amount of calcium and lower of magnesium than plants fertilized only with waste activated sludge or with the mixture of waste activated sludge with addition of brown coal ash. The content of potassium and sodium in the tested plants was not directly dependent on the kind of materials added to waste activated sludge.