Seasonal changes in the growth, dry matter distribution and herbage quality of three native grasses in northern Queensland

Abstract

The growth of unfertilized native pasture was studied at two sites (Lansdown near Townsville and Redlands near Charters Towers) over a 30-month period. Seasonal changes in the dry matter distribution between green leaf, green stem, dry leaf, dry stem and inflorescence, and the nitrogen and phosphorus concentrations and in vitro digestibility of these components were measured in Chrysopogon fallax, Heteropogon contortus and Themeda australis. Maximum herbage yields ranged from 4000-6000 kg/ha at Lansdown and 1500-2000 kg/ha at Redlands with perennial grasses contributing over 90% of the herbage. There were large differences between the species in the pattern of dry matter distribution, with C. fallax having a higher proportion of leaf during most of the sampling period. The nitrogen and phosphorus concentrations and digestibility levels in the various plant components were usually similar in the three grasses but all showed large seasonal variations at both sites. Green leaf was the most nutritious component but even this was of too low a quality to support animal growth during part of the year.