The effect of four sulphur levels (0, 20, 40, 80 kg/ha), applied at planting as Na2SO4, en the dry matter (DM.) production of the mixture was studied in a complete randomized blocks design, with four replicates. The planting was in autumn 1981, in unes at 20 cm, with 12 kg/ha of red-dover cv. Quiñequeli and 20kg/ha of italian ryegrass cv. Tetrone. A basic fertilization with 65.5 kg/ha of P,41.5 kg/ha of K and 32 kg/ha of N was applied in les, under the seed. Two cuttings were done eachseason and D.M. and botanical composition determined. Total D.M. production varied between 2.7 and 3.5 ten/ha the first season and 7.2 and 7.8, the second. Total yield was significantly larger only at the highest su[phur rates on the second cutting of the first year. However, red-dover production increased significantly (P < 0.01) in a lineal fashion between 0 and 80 kg/ha of sulphur, in bothseasons. Ryegrassyielddid not show differences the first year and decreased significantly (P < 0.01) Ihe second year, with the increment of sulphur rate.