Factors influencing the role of clover in grass-clover leys fertilized with nitrogen at different rates III. The effects of the variety of companion grass and of the variety of clover on the botanical composition of the sward

1. In an experiment designed to study some of the factors influencing the role of clover in grassclover swards fertilized with nitrogen at different rates, botanical studies of the sward were made each spring and autumn. The methods used, and the results obtained in the autumn studies, are described in this paper. 2. Full details of the experimental treatments and design, and the yield results have been reported previously. 3. The botanical composition of the sward depended to a far greater extent on the variety of grass than it did on the variety of clover included in the seeds mixture. This was true also of the yields from the different swards. 4. Some relationships are suggested between the yield and nitrogen response results and the variations in the botanical composition of the sward attributable to the variety of grass included in the seeds mixture. 5. Kersey white clover appeared to be more persistent than S. 184 and S. 100 where fertilizer nitrogen was applied to the sward, although no differences in persistency were noted in the absence of applied nitrogen. 6. A statistical study of the botanical data obtained indicated that the intensity of sampling employed gave the optimum balance between variance and time expenditure, since only a slight reduction in variance would have been obtained if double the number of samples had been taken.