Sheep grazing in a young Sitka spruce plantation.
Sheep were grazed at a high stocking rate for a few days 3 times each summer in a Sitka spruce plantation in Co. Antrim from 1970 to 1974 (7th to 11th years after tree planting); the ground cover was typical of rough hill pasture on peat, with Calluna vulgaris the main dominant, and with Molinia caerulea, Deschampsia flexuosa and Yorkshire fog on the more fertile areas. In 1971, the area was given a broadcast application of 150 kg N + 100 kg P + 150 kg K/ha. Herbage DM yield decreased from 3.15 t/ha in 1970 to 1.07 t in 1974 in the unfertilized plots and from 3.37 t/ha in 1971 to 1.47 t in 1974 in the plots given NPK; the tree canopy was almost closed in 1974. Herbage CF content was 28-31% in all plots. Grazing reduced tree growth, probably by damage to the roots by poaching, as browsing damage was negligible.