The effects of variety, cutting interval and nitrogen application on the morphology and development of stolons and leaves of white clover

Abstract

Six varieties of white clover, each grown with perennial ryegrass, four intervals between cuts and two levels of applied nitrogen in all combinations, were compared in a field experiment during the first 27 months after sowing. Information about yields, crop fractions, heights and ryegrass tillers has been presented in an earlier paper (Wilman and Asiegbu, 1982). The present paper is concerned with the more detailed studies of white clover, which help to explain the yield results and contribute to the understanding of the response of this species to management when grown in competition with grass.Increasing the interval between harvests increased the length of clover stolon per unit area of ground and increased stolon diameter, petiole length, weight per leaf and number of leaves harvested as a proportion of the number present in the sward while only slightly reducing the rate of leaf emergence, helping to explain the positive effect of increasing the interval on clover yield noted in the earlier paper. During regrowth, successive leaves had longer petioles and the length of individual petioles increased beyond the stage at which the leaflets were fully opened. Weight per leaf in clover increased considerably from April to June and declined to below the April value by October. It was shown that weight per leaf can be greatly increased by increasing the interval between harvests without reducing the number of leaves harvested per unit area per year. The stolon length measurements provided some support for the view that medium large-leaved varieties of white clover can with advantage be defoliated rather less frequently than small-leaved varieties. Stolon length was less adversely affected by applied N in the medium large-than in the smallleaved varieties. The small-leaved varieties had thinner stolons than the medium large-leaved varieties but about twice the stolon length when no N was applied, and a relatively high proportion of leaves which escaped defoliation. The application of N reduced stolon diameter, increased petiole length and had little or no effect on weight per clover leaf.

Seasonal variation in the distribution of white clover (Trifolium repensL.) stolons among 3 horizontal strata in 2 grazed swards

“…Observations made during this study confirm and extend those of Wilman & Asiegbu (1982) in that stolon death progressing towards the tip often stopped at the point of rooting of a node in both buried and surface stolons. Also, death of buried stolons was sometimes seen to cease at the point where a vertical growing branch stolon was initiated.…”

Comparison of herbage yield of European and Mediterranean ecotypes of white clover

“…Although the strong correlation between total leaf production and unit stolon weight does not prove a causal relationship, this is possible and needs to be researched. Few investigations have measured cultivar differences in stolon thickness or weight but the results of Wilman & Asiegbu (1982) and Harris Rhodes & Mee (1983) show clearly the larger diameter and weight per unit length, respectively, of stolons grown by largeleaved white clovers. However, stolons are generally below grazing or cutting height and, apart from perhaps supporting the growth of large leaves, do not themselves contribute to herbage yield unless grazing is particularly severe.…”

Morphological variation among white clover (Trifolium repensL.) populations collected from a range of moist hill country habitats

“…It is well understood that increasing frequency ofdefoliation, as occurs under set-stocking, reduces leaf size and petiole length (Wilman & Asiegbu 1982). Lambert et al (1986) also observed that leaf size of white clover in rotationally grazed cattle swards were larger than those in swards either setstocked or rotationally grazed by sheep.…”