EFFECT OF CONTROLLING BRACKEN [PTERIDIUM-AQUILINUM (L) KUHN] ON PASTURE PRODUCTION

The outcome of spraying two bracken‐infested hill sites in July with asulam at the commercial rate of 4·5 kg a.i. per ha was a 98% reduction in frond numbers which persisted for the following 3 years. Broad‐leaved grasses, Agrostis tenuis, Agrostis canina and Poa pratensis, were susceptible to asulam and were severely reduced at both sites while fine‐leaved grasses, Festuca ovina and Deschampsia flexuosa, were resistant. Over a period of 3 years after spray application the original bare ground under the bracken canopy and that produced by the effects of asulam was recolonized by the recovery of the broad‐leaved grasses and an increase in the cover of herbs. The latter also increased on the unsprayed control areas. A favourable aspect and an abundance of the productive broad‐leaved grasses appeared to be the main factors which determined the amount of increase in herbage yield observed following spray treatment. One such area gave a herbage DM yield of 3039 kg ha‐1 during the growing season which was 47% greater than the control while an area with a less favourable aspect and dominated by the less productive fine‐leaved grasses gave a herbage yield of 2069 kg ha‐1 which was only 18% greater than the control. Copyright © 1979, Wiley Blackwell. All rights reserved