Effect of different grazing management systems on the herbage mass and pasture height of a Nardus stricta grassland in western Scotland, United Kingdom

The aims of this study were to examine the effect of three grazing treatments (year-round stocking rates of 0.8 ewes ha(-1), 0.5 ewes ha(-1) and 0.5 ewes ha(-1) plus grazing cattle in summer), imposed for 4 years, on the herbage mass and surface height of a Nardus stricta-dominated grassland in western Scotland and to obtain estimates of annual productivity of this grassland. Nardus stricta-dominated grassland comprised proportionately 0.20 of the grazing area. Stocking rate of sheep had no significant effect on the herbage mass of the grassland in the first 2 years of the experiment, although mean summer pasture heights were significantly higher under the lower stocking rate of sheep. The pasture on the treatment with cattle grazing in summer had a significantly lower herbage mass and lower surface height than the two sheep-only grazing treatments. Year-to-year variation in the herbage mass and surface height of herbage in summer was greater than the effect of treatments. Despite changes in surface height, the structural diversity of the grasslands was not increased by the treatments. The annual production of vascular plant material ranged from 417 g DM m(-2) in 1994 to 628 g DM m(-2) in 1996.