SEASONAL AND SHEEP GRAZING MANAGEMENT EFFECTS ON BRANCHING STRUCTURE AND DRY WEIGHT OF WHITE CLOVER PLANTS IN MIXED SWARDS

Abstract

Swards that had been either set stocked (SS) or rotationally grazed (RG) for five years were sampled monthly over two years by removing turves. The uncut white clover plants were then washed out, classified by branching structure (lst, 2nd, 3rd, 4th order) and then dissected into stolon and leaf before drying and weighing Under both managements stolon dry weight per plant and branching structure of the population each indicated a strong seasonal shift from larger plant size during summer, autumn and winter (February, 109 mg stolon DW/plant, 7% of population 1st branching order) to a preponderance of smaller plants in spring (October, 41 mg stolon DW/plant, 30% of population 1st branching order). Grazing management affected stolon DW per plant (means. RG 106 mg. SS 53 mg) but had little effect on branching structure. However, in spring, under RG management proportions of 1st branching order plants in the population were higher for a longer period than under SS management. The simpler structure of plants in spring is thought to increase the vulnerability of the white clover population to adverse conditions at this time. While RG management allowed white clover to better utilize favourable growth conditions, it also increased the susceptibility of the population to large declines during stress periods; SS management reduced the potential for growth, but enhanced stability during stress periods. Hence where environmental conditions are unpredictable SS rather than RG management will favour retention of white clover in the sward. The seasonal and grazing management effects reported are likely to occur across a wide range of environments. Keywords: Trifolium repens, individual plants, plant size, seasonal variation, branching.