EFFECT OF INTERVAL BETWEEN HARVESTS AND SPRING-APPLIED FERTILIZER-N ON THE GROWTH OF WHITE CLOVER IN A MIXED SWARD

A perennial ryegrass (Lolium perenne)-white clover (Trifolium repens) sward, that had been grazed for over 2 years, was cut at 1-, 2-, 3- or 6-week intervals from 18 April to 28 November 1986. The effects of tw o rates of N application in spring, O and 66 kg N ha(-1), were compare d. Clover growth was studied in three six-week periods that began on 1 8 April, 18 July and 17 October respectively. Increasing the interval between cuts increased the yield of herbage without reducing the propo rtion of clover in the harvested herbage, but the combination of appli ed N and the six-week interval was harmful to clover production. Incre asing the interval between cuts tended to increase the proportion of r esources allocated to stolons rather than to leaves, and to increase t he weight of new dry matter (DM) per growing point rather than per m(2 ). In the third period of the study, when the ten youngest internodes per stolen were examined separately, all ten ages of internode were fo und to have been affected by the cutting management. This was indicate d by the positive effect of the length of the interval between cuts on the weights of N, P and K per internode. The concentrations of N, P a nd K were highest in the youngest internodes. The application of N red uced the proportion of new DM allocated to stolen rather than to leaf and it reduced the number of clover growing points per m(2).