1. Data on the crude-protein content and crudeprotein production of five grass species (each sown with white clover) over the period 1954–56, at six levels of compound fertilizer application, are reported. Perennial rye-grass (S. 101), meadow fescue (S. 215), timothy (S. 48), cocksfoot (S. 26) and bent (N.Z. Browntop) were sown in 1953 at appropriate seed rates, each with 2 lb./acre S. 100 white clover. The fertilizer treatments were 0, 1, 3, 5, 7 and 9 cwt./ acre of a compound of composition 10% N, 4%P2O5, 9·5% K2O applied in the early spring of each of the years 1954–56. The swards were cut three times a year in 1954 and 1956, but only two cuts were possible in 1955.

2. Bent mixtures had a higher crude-protein content than any other mixture in all years and (with one exception) at every cut within years. Differences between other mixtures were smaller and often erratic, though timothy invariably had the lowest crude-protein content at the second cut and cocksfoot at the third. Application of the fertilizer raised the crude-protein level of the herbage at the first cut, but depressed it in subsequent cuts.

3. The bent mixture gave the highest yield of crude-protein per acre followed by the timothy mixture, while the lowest yield was produced by the perennial rye-grass mixture. The bent mixture differed from all others in its distribution of crudeprotein production over the season, producing less at the first cuts and more at the second and third cuts. This reflects its pattern of production of dry-matter. Response to spring application of fertilizer in terms of crude-protein yield declined rapidly from cut to cut. Over the whole period of the experiment 1 cwt./acre/ annum of fertilizer containing 10% N gave a response of about 0·5 cwt. crude-protein/annum.