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Desert bluegrass can be a massive help for Queensland graziers

By Future Beef
Updated May 6 2022 - 3:00am, first published April 30 2022 - 8:00pm
Desert bluegrass basal cover is improving with spelling compared to continuous grazing under a moderate stocking rate (8 ha/AE).

Desert bluegrass (Bothrichloa ewartiana) has again proven to be a cornerstone of beef production for northern Australian rangelands.

Its resilience has been convincingly shown during the ongoing drought where weaker species died. While large numbers of desert bluegrass plants also died, many survived.

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These surviving plants maintained a good basal cover (area of living material at ground level) through the drought and are now starting to increase in response to slightly better seasons and wet season spelling. This will form the foundation for future pasture recovery.

Desert bluegrass is like an old battle-hardened warhorse that's always there in the worst times - if it is looked after.

Better understanding

An ongoing research project within the Wambiana Grazing Trial near Charters Towers is testing different wet season spelling strategies under moderate (eight hectares/adult equivalent) and heavy (4ha/AE) stocking rates. The study has been running since 2012, with the last eight years one of the driest periods on record.

With the severe drought, only about 40 per cent of the mature desert bluegrass plants survived under a moderate stocking rate. While some seedling recruitments occurred in most years, only those that germinated in the last three years have survived - about one every 10 square metres. Under heavy stocking, desert bluegrass was almost eliminated with only 5pc of tussocks surviving through the drought. There has also been negligible seedling survival, with only about one every 50m2 surviving under heavy stocking.

Conditions have improved slightly in the last two years, but it is currently very dry. Despite this, a very encouraging increase in desert bluegrass basal cover has occurred with spelling under moderate stocking rates. Basal cover gives a good indication of the health and vigour of perennial grasses. In contrast, despite spelling, there has been no recovery in desert bluegrass under heavy stocking.

The other grasses studied included wiregrasses (Aristida spp), golden beard grass (Chrysopogon fallax) and hairy panic (Panicum effusum). Of these, wiregrass and hairy panic were almost eliminated by the drought with only very limited recovery since then. However, golden beard has been able to survive under moderate stocking and to a certain extent under heavy stocking.

Summary

The responses of the above grasses can be explained partly by their growth strategies. Golden beard is very long-lived (30 years) with underground stems enabling it to survive drought and heavy grazing. Although it's a strong perennial, golden beard never produces anywhere near as much forage as desert bluegrass. Desert bluegrass is also long-lived but its growing points on the base and stems make it susceptible to heavy grazing. It has maintained its basal cover under moderate stocking due to a better survival of original plants and greater recruitment.

Hairy panic and wiregrasses are short-lived perennials very susceptible to drought. However, their big seedbanks allow quick recovery in good years. Desert bluegrass is a cornerstone grass due to its high productivity and ability to survive and provide ground cover during a drought. It is the foundation not only for recovery when better seasons return, but indeed for the whole production system.

Recommendations

  • Improve land condition with regular wet season spelling and moderate stocking rates.
  • Match stocking rates to pasture available and land condition.
  • In dry years the area of country spelled and the length of spelling must be managed to avoid applying excessive grazing pressure on the grazed country.
  • Set stocking rates so there is 800 to 1000kg dry matter per hectare at the end of the dry season.

Paul Jones, senior pasture agronomist, DAF Emerald, 0428 103 923.

This article was produced by FutureBeef-a collaboration between Meat & Livestock Australia and the Queensland, Northern Territory and Western Australian agriculture departments.

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