The influence of undersowing on the establishment of broad red clover and Italian rye-grass was investigated under three managements and two levels of nitrogen applied in spring. The following conclusions are drawn:

1. The cereal cover crop reduced the aggressiveness of Italian rye-grass towards red clover.

2. The cereal cover crop produced a high initial yield of dry matter and crude protein. In midseason, when keep from maiden seeds is important, the highest yield was obtained in the absence of the cereal cover crop.

3. The danger of failure in the take of undersown herbage seeds is increased when soil moisture is very low.

4. Total dry-matter yield in the seeding year was increased by using a cover crop, but starch-equivalent yield was not greatly affected. Crude-protein production was increased when the cover crop was cut for silage or frequently grazed, but not when a grain crop was harvested.

5. Undersowing Italian rye-grass and clover gave a higher yield of dry matter, starch equivalent and crude protein than sowing the herbage after the cereal was harvested.

6. The cover crop depressed weed growth, and ‘Nitro-Chalk’ increased it, except where Italian rye-grass was undersown.

7. The application of ‘Nitro-Chalk’ increased the yield of dry matter, particularly early in the seeding year. ‘Nitro-Chalk’ encouraged the growth of Italian rye-grass and oats but depressed the clover. This reduction in legume yield was least when defoliation was frequent. The influence of nitrogen on plant growth was especially noticeable when soil moisture was low and a cover crop used.