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 ( Trifollum 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 two rates of N application in spring, 0 and 66kg Nha⁻¹, were compared. Clover growth was studied in three six-week periods that began on 18 April, 18 July and 17 October respectively. Increasing the interval between cuts increased the yield of herbage without reducing the proportion of clover in the harvested herbage, but the combination of applied N and the six-week interval was harmful to clover production. Increasing the interval between cuts tended to increase the proportion of resources allocated to stolons rather than to leaves, and to increase the weight of new dry matter (DM) per growing point rather than per m². In the third period of the study, when the ten youngest internodes per stolon were examined separately, all ten ages of internode were found to have been affected by the cutting management. This was indicated by the positive effect of the length of the interval between cuts on the weights of N, P and K per intemode. The concentrations of N, P and K were highest in the youngest intemodes. The application of N reduced the proportion of new DM allocated to stolen rather than to leaf and it reduced the number of clover growing points per m².