Feathertop grass and fire

by David Phelps, Queensland Department of Primary Industries

From Savanna Burning—Understanding and Using Fire in Northern Australia , Tropical Savannas CRC, Darwin 2001

Why is feathertop a problem?

Feathertop wiregrass is a problem plant throughout the Mitchell grasslands for both wool and beef producers. The dart-like seeds penetrate the staples of wool, and prevent it from being combed out. This contamination costs the wool industry up to $10 million every year. Forage value of feathertop is also low, degrading the value of cattle pastures. Feathertop can dominate otherwise productive Mitchell grass pastures.

The effects of fire

In Queensland feathertop wiregrass can be controlled with burning followed by two to three months of dry weather. Just as a drought will kill this relatively shallow-rooted native grass, the combined stresses of burning and a lack of moisture leads to a 50–75% kill and a reduction in the size of plants.The optimum time for controlled burning is July or August as this maximises the chances of dry conditions following the burn. A clean burn is needed from a moderately hot fire, followed by a two to three-month dry spell (to kill the feathertop), with light grazing over an average summer for pasture recovery. The conditions at the time of burning also need to be dry: if there is moisture within the top 30 cm of soil, the feathertop will be able to respond following the burn. Kill rates with moist soil (or rain within six weeks) can be as low as 10–30%.

The use of improved long-range weather forecasting may provide the key to strategic burning. Controlled burning in late July or early August when the Southern Oscillation Index is in a rising phase would enhance the probability of receiving sufficient summer rains for pasture production, but provide the additional post-burn dry weather stress to keep feathertop under control.