The black spear grass (Heteropogon contortus) problem of the sheep country in central-western Queensland

Abstract

Results of a study of back spear grass in a semi-arid area of Queensland are reported.
The grass occurs mainly on open eucalypt forest country on which the dominant climax grass is Themeda australis.
Increase and recession have been associated with rainfall, increase occurring during a series of years with above-average rainfall and recession during a period with below-average rainfall.
The increase noted since 1949 is attributed largely to favourable seasonal conditions, reduced grazing pressure, and the degraded condition of the pastures. A widespread changeover from sheep to cattle has aided the increase by removing the necessity for heavy grazing to control seeding.
Burning of pastures is not essential to the spread of black spear grass in the central-west.
Under heavy grazing, black spear grass is replaced by less palatable grasses and the recession may proceed further through species of Bassia to bare ground.
Exotic grasses found suitable for the climatic conditions of the region are not sufficiently aggressive to compete with black spear grass except in limited areas.