Total production, and leaf concentration of protein, phosphorous, potassium, calcium, magnesium, copper and zinc were examined in a two-year trial in a rangeland sown with Trifolium subterraneum, Lolium rigidum and Ornithopus compressus, in Mértola (Alentejo). The experiment design was 4 random blocks with seven modalities: no fertilization, mineral fertilization each year, three levels of sludge application (4, 8 and 12 t per ha) the first year and two levels of sludge application (4 and 8 t per ha) the first year supplemented with mineral fertilization each year. Production of dry matter increased with the application of sludge. In the first crop cycle, leaf phosphorous concentration increased by applying the higher rates of sludge. Pasture copper and zinc concentrations never reached the toxicity limit for small ruminants. These studies will continue and more practical recommendations will be made concerning the value of sludge as a fertilizer, avoiding soil pollution and damage to the animals.