The influence of fertilization with composted mixtures of waste activated sludge with CaO or ash from brown coal on yield and effectiveness of 1 g of nitrogen was studied. The yield of the tested plants and the effectiveness of 1 g of nitrogen were higher on objects fertilized with the mixture of waste activated sludge with brown coal ash than with CaO. The composted mixtures were applied in August and therefore the effevtiveness of fertilization was higher in the 2nd than 1st year of pot experiment.