The effect of using a cover crop of spring oats under three managements and two levels of Nitro- Chalk in the seeding year on Italian rye-grass and broad red clover in the first harvest year were investigated and the following results obtained.

1. Undersowing increased the total yield of dry matter in the Italian rye-grass/broad red clover mixture in the first harvest year. Using a cover crop with the April sowing only increased the yield of herbage when frequent grazing was practised in the seeding year. The percentage of broad red clover and the yield and percentage of crude protein in the clover were higher in spring when a cover crop was used. In the hay cut the percentages of clover and of protein were higher in the Italian rye-grass/broad red clover mixture sown without a cover crop and the yield of crude protein was not affected by undersowing.

2. Early sowing in April resulted in a higher total yield of dry matter and Italian rye-grass in the first harvest year. The growth of broad red clover and the yield of crude protein were also increased in the spring grazing but not in the hay cut. The August sowing resulted in higher winter casualties of the Italian rye-grass and broad red clover, but gave a greater density of plants in the following spring than the swards sown in April.