Information
Pasture yield and composition changes in a Central Queensland black speargrass (Heteropogan contortus) pasture in relation to grazing management options
Level 1 General description
Purpose:
Orr et al. (2001): To determine the effects of grazing management practices on pasture and animal production in a native black speargrass (Heteropogon contortus) pasture.
Sallaway & Waters (1994): Soil surface hydrological characteristic, under varying stocking rates and pasture compositions, were determined to investigate the effect of runoff and soil movement, influenced by grazing pressure, on landscapes with black speargrass (Heteropogon contortus).
Methods (brief)
Orr et al. (2001): The effects of stocking rate, legume over-sowing and animal diet supplements / burning were measured by monitoring yield and pasture composition at the pasture community scale on a grazing property.
Sallaway & Waters (1994):The study was undertaken on an existing grazing experiment, on a commercial grazing property at Galloway Plains, west of Gladstone, Queensland. Treatments were three stocking rates, two land classes and two patch types.
Rectilinear plots with a slope of 5% were installed within each of the three stocking rates. Plot lengths ranged between 120 – 180 m with the larger plots being 20 m wide. Small plots were 60-80 m2 and larger landscape plots covered 0.4 ha. The plots were fitted with instruments to measure runoff and sediment movement. A disk permeameter and rainfall simulator were used to determine soil surface hydrological characteristics.
Key findings (brief)
Orr et al. (2001):
- At the pasture community scale, the highest stocking rate of 1 steer/2 ha reduced pasture yield but had little impact on pasture composition.
- The frequency of H. contortus showed no clear differences due to stocking rate although there was a slight overall trend for it to decline with time.
- Burning has reduced the occurrence of H. contortus compared with that in unburnt native pasture and this may be due to the stocking rates being too high following the fire.
Sallaway & Waters (1994):
- Grazing pressure had a noticeable effect on runoff, with greater runoff recorded from the heavily stocked plots (0.9 steers/ha) than the 0.6 steers/ha or 0.0 steers/ha plots.
- Changes in the soil hydrological characteristics is a major component in producing increased runoff at a high stocking rate.
- Total runoff and peak runoff rates were reduced if black speargrass was maintained.
Location
Galloway Plains, Calliope (24°10′S, 150°57′E), Central Queensland
Related studies
Grazing experiment at Glenwood, west of Mundubbera