Selection of perennial grasses as a component of legume-based pastures on light-textured soils in the dry tropics of Queensland

Abstract

Adaptation indices for introduced perennial grasses were derived for a site in the seasonally dry tropics of North Queensland to determine the suitability of grasses as a component of sown legume pastures. Grasses are required to replace native species that are intolerant of the heavy grazing pressure imposed on these legume-based pastures. Agronomic, production, morphological, and reproductive data on 143 accessions of 20 perennial grass genera were compared from 1983 to 1987. The grasses were grown in rows in a grazed Seca and Verano stylo pasture. The seed production potential of 40 Digitaria accessions grown in swards under irrigation was also assessed. The stoloniferous species Bothriochloa pertusa, Digitaria milanjiana, D. taatalensis, B. insculpta, and Urochloa mosamhicensis had the highest adaptation indices under continuous grazing. Digitaria accessions with the ability to produce appreciable viable seed were identified. Andropogon gayanus, a tussock species, had the highest yield and most spread in the first 2 years in the absence of wet season grazing. The potential of B. pertusa and D. milanjiana for stabilising legume pastures has been identified, and the need for wet season grazing management of tussock species has been shown. The range of genetic material in D. milanjiana requires further environmental evaluation.