Performance and persistence of six perennial grasses under different intensities of drought and defoliation

Abstract

An experiment was conducted under a rain-out shelter at CSIRO's Pastoral Research Laboratory near Armidale, New South Wales, Australia to assess the production and persistence of perennial grasses under different intensities of drought and defoliation stresses. The trial consisted of six perennial grass species; four introduced (tall fescue, cocksfoot, perennial ryegrass and phalaris) and two native (weeping grass and wallaby grass). Two defoliation intensities and three moisture regimes (two droughts and a 'non-stress' control) were applied. The treatments were applied for two six-monthly experimental seasons, Spring-Summer (SS) and Summer-Autumn (SA). Measurements taken included basal area, dry matter yields, green foliage index, nutritive value, carbohydrate reserves, soil water and root distribution. The aims of this thesis were to quantify the separate and interactive effects of defoliation intensity, drought severity and season of perennial grasses on the measures listed above, and to investigate plant traits which may be important if the persistence of these grasses. With a better understanding of persistence and how pasture grass species respond to drought and defoliation stresses, better management recommendations can be developed.