GRAZING MANAGEMENT OF OVERSOWN TUSSOCK COUNTRY .2. EFFECTS ON BOTANICAL COMPOSITION

The botanical composition of an oversown tussock pasture on a steep (30-degrees), southeast hillside (760-930 m altitude, 500 mm annual rainfall) was measured each spring for six consecutive seasons under nine grazing management treatments. Continuous stocking, alternating (two paddock), and rotational (six paddock) grazing with merino wether hoggets were each compared at low, medium, and high stocking rates (1.9, 3.0, and 4.1 SU/ha per year respectively). After 6 years, the cover of standing vegetation, assessed by point analysis, was similar for all treatments (79%) although there was less detached litter and more bareground at the high than the low stocking rate. Tussock cover declined in all treatments during the first 2 years, and even after 6 years there was no significant treatment effect. There was less Dactylis glomerata and more Rumex acetosella at the medium and high than the low stocking rate after 6 years. D. glomerata cover was greater with rotational and alternating grazing than it was with continuous stocking. Lolium perenne cover became greater at the high than the medium or low stocking rate. An abnormally cold winter caused an overall 60% loss in L. perenne. Trifolium repens increased in wet years and decreased in dry years, but was not affected by treatment. At the low stocking rate standing vegetation, particularly T. repens and Poa colensoi, was reduced by the incidence of porina (Wiseana spp.). The suitability of the commonly used New Zealand pasture cultivars, bred principally for intensive lowland farming, in an efficiently managed oversown tussock environment is questioned. Practical application is discussed with emphasis on management options to maintain desired species.