CLOVER NITROGEN AND SWARD PRODUCTIVITY

Under mowing conditions in the absence of the animal, ultra‐simple swards based either on ryegrass or cocksfoot gave large increases in yield of dry matter and nitrogen from the inclusion of white clover in the seeds mixture. Raising the clover seed rate from 1 to 3 lb./acre gave a further response in yield. As the swards aged, the continuing effect of increased clover seed rate was dependent on applied nitrogen. The rate of transference of nitrogen from clover to the soil depended upon the species of the associated grass, the clover seed rate, the age of the sward and the degree of reduction of the clover in the sward. Suppression of clover led to an increase in soil nitrogen, particularly with high seed rates of clover. Dry matter response to applied nitrogen (69 lb./acre/annum) was greater in cocksfoot than in ryegrass. Fertilizer nitrogen had little effect on the yield of nitrogen from the sward except where the high seed rate of clover had been used.