The amount of fertilizer depends on the fertility of the natural soil, the degree of growth you want and the type of grass you are growing.
First, Bluegrass requires 2-3 kg of actual nitrogen, 1-1.5 kg of actual phosphorous, and the same of potassium per 100 square metres per year. Fertilizer applications are determined by the amount of nitrogen they contain, because it is the most difficult of the three to handle, we recommend using fertilizer from a reputable manufacturer. As this will provide a well balanced feeding for your lawn and the fertilizer will release slowly.
Secondly, about half of the annual amount of fertilizer should be applied in the spring, and the remaining half in the early summer and fall. Always water the fertilizer to prevent burning.