The effects of asulam, frond cutting and ground mineral phosphate on the yields of swards dominated by bracken [Pteridium aquilinum (L.) Kuhn

Abstract

AbstractTwo methods were adopted of measuring sward output, following the prevention of bracken frond growth, with differing results. Accumulated growth estimation, corresponding to production under a system of open‐range grazing, showed that asulam used for frond control had no effect on herbage yield in the year of application and large increases were observed in succeeding years compared with untreated control plots. In measuring production by sward regrowth after cutting, corresponding to intensive pasture utilization systems, asulam reduced yields in the year of treatment and increases were not observed until 2 years later. The inhibition of growth could be overcome by applying ground mineral phosphate at rates of 300 or 500 kg ha‐1 before spraying but the 500 kg ha‐1 rate showed no advantage over 300 kg ha‐1. Applications of ground mineral phosphate after spraying had no effect on sward output.It is concluded that indigenous pasture plants in bracken‐infested areas of western Scotland cease growth by mid July unless subjected to major earlier defoliation or severe soil moisture deficits and the removal of the frond canopy does not change this pattern significantly. Obtaining the full benefit of bracken clearance depends on making use of the resulting production of extra herbage and limiting as far as possible frond regrowth in treated areas.