The goal of this study is to evaluate the possibilities to use the city sludge as a fertilizer in agriculture, especially upon alfalfa crop, with a very complex and precise methodology, in the conditions of assuring environment protection and human health integrity. The aim of this study is to determine physico-chemical properties of soil after applying city sludge from water treatment station Tetarom III, Cluj - Napoca. Neutralizing city sludge with the help of soil, considered a biological treatment station for water is one of the most important perspectives to protect the environment together with an increase of agricultural production. In the new socio economical structures of Romania, the natural fertilizer is to be found less and less due to the decrease of the animal number, and also due to the way of their breeding, and the replacement of natural fertilizer with sludge from the used water treatment, it is an alternative to use due to the sure advantages of the fertilized sludge appliance.