Fluctuations in white clover content of sheep grazed swards

Three treatments of a long-term grazing experiment namely: CaPKN, CaPK and no nutrients (nil inputs), were chosen to illustrate the role of white clover (Trifolium repens) in swards of widely differing nutrient status. The balance of two indicator grass species (Lolium perenne and Agrostis capillaris) was also used to describe the swards in terms of low or high input status. Both CaPKN and nil input treatments produced swards consistently dominated by a single grass species and low clover stolon abundance. Lolium perenne dominated the CaPKN treatment whilst Agrostis capillaris was heavily dominant in the nil input treatment. The CaPK treatment produced a much higher presence of clover within the swards but two major declines were identified over the eight-year period 1991-1998. These declines affected the grass species balance indicating that the CaPK treatment cycled between high and low input status. However, the changes in grass species balance were more gradual than the violent fluctuation in clover stolon abundance and caused longer-term cycles of animal production.