Effects of white clover and fertilizer nitrogen on clover and grass leaf dimensions, percentage cover and numbers of leaves and tillers

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Abstract
Summary: Effects of seven levels of N application and three seeds mixtures were studied on two sites for 4 years. One seeds mixture comprised perennial ryegrass (Lolium perenne L.) and two comprised perennial ryegrass with white olover (Trifolium repens L.). One site (Trefloyne) was 24 m above sea level on deep soil and the other (Pwllpeiran) was 328 m above sea level on relatively shallow soil. The plots were cut seven times per year.The application of N to swards without clover considerably increased the number of ryegrass tillers as well as increasing ryegrass leaf blade length and width and sheath length. At Trefloyne the presence of clover greatly reduced the number of ryegrass tillers, had a greater positive effect on grass sheath length, relative to its effect on blade length and width, than that obtained by applying fertilizer N to a sward without clover, and tended to reduce grass leaf length during the winter. At Pwllpeiran the clover was less competitive, but it still tended to have a greater effect on sheath length and a less positive effect on numbers of tillers, relative to its effect on blade length and width, than that obtained by applying fertilizer N to a sward without clover. The application of N to grassolover swards increased the size of grass leaves and the number of tillers, but did not increase clover leaflet size. The number of olover leaves in the sward was greatly reduced by fertilizer N at Pwllpeiran, but was not affected by fertilizer N at Trefloyne. Blanca white clover had larger leaves than Aberystwyth S.100, but S.100 appeared to compensate for this by producing rather more leaves. In respect of number of leaves, leaf dimensions and rate of leaf emergence, clover appeared more sensitive than ryegrass to the differences between the sites. The leaf dimensions of the clover varied more from one time of year to another, but not from one year to another, than those of the ryegrass. The number of leaves per unit area of ground varied more in clover than in grass from year to year and from one time of year to another. The rate of emergence of leaves was faster in clover (per marked stolon tip) than in grass (per tiller).