Large amounts of sludge which occur during processing sewage water could be used more efficiently if we would devide their use in the food production from non-food production. Regulation of sludge use in agricultural production in Croatia (Article 8., NN 38/2008.) the prescribed quantity of 1,66 t DM yearly sludge by farmland, no matter the type of agricultural production. Number of prescribed 1,66 t DM could be much larger in use for non-food production, such as fertilization energy crops. In energy crops we assing those crops which are bread with a purpose of biomass production which we converte in energy or we use in industrial purposes. In one of the most represented perennial energy crop we have Miscanthus x giganteus (miscanthus) the goal of this paper was to determine the production of its biomass ratio application in four different sludge amounts (control, 1,66 t/ha, 3,32 t/ha, 6,64 t/ha) as a main factor and the harvest deadline as the main subfactor (autumn and spring). The results of the work showed that there were no significant differences in yields DM and the content DM in between fertilization treatments within individual harvest dates (P > 0.05), but the differences have already been determined between harvest dates (P<0.01). In relation to the autumn harvest period, there was a significant drop in yields in the spring term of DM miscanthus biomass in all fertilization treatments (P<0.01) from 46,24 % at OM6,64 to 48,45 % in OM1,66. In contrast, there has been increase in content DM in all fertilization treatments (P<0.01) and for more then 100 % (106,8 % at OM6,64 and 112,5 % at OM3,32) due to the natural drying of the miscanthus plantations from november to march/april.