Managing gamba grass: Discussions from the Douglas Daly Field Day

Discussing gamba management at the Douglas Daly Field Day

Containing gamba grass to where is has already established may be achieved with effective grazing combined with quarantining, wash-downs, and the maintenance of buffer zones where outbreaks are controlled before plants seed.

Intensive grazing was discussed as a containment strategy at the Douglas Daly Field Day. Trials by Jeff Blake at Camp Creek Station suggest that intensive grazing is preferable to set stocking in terms of utilisation, weight gain, and weed and erosion control. Click here to read more.

Sam McBean said he trialled intensive grazing with up to 12 head / ha in 50ha paddocks but found that utilisation was insufficient and control ineffective. I phoned Jeff Blake afterwards and he thought that greater than 20 head / ha may be necessary. He recommended a rotation with a maximum of two weeks grazing followed by 6 weeks rest during the wet season, but being careful not to overstock.

Sam and Spud Thomas both said that where jarra grass was present, cattle preferred it over gamba and grazed it out, opening more space for gamba to fill. Sam noted that the opposite occurred in tully grass paddocks where gamba was preferred and grazed out.

Sam got his best results burning and ploughing a paddock in November, spraying, ploughing again and then seeding with jarra grass (image below). This treatment cost more than $500/ha and would only be feasible if a hay crop could be produced and sold.

 

Boom spraying was less effective probably due to the difficulty of getting full plant coverage. Roundup Attack was applied with 250L of water per hectare, but this appears too low. Burning prior to spraying may also increase coverage.

Spot spraying was considered too labour intensive.

Tony Harrower told me afterwards that he had used a mix of metsulfuron and 2,4-D to kill wattle on fencelines and that the treatment also killed gamba grass but no other grasses. He thought getting the mix right was critical and needed trialling.

Chris and Phil Howie also discussed the use of Spinnaker in cavalcade paddocks. Spinnaker inhibited gamba growth and it was easily knocked out the following year with roundup. Chris thought Spinnaker would work best on gamba as a pre-emergent. This is useful given Arthur Cameron’s comment that gamba has dormant tillers that may emerge after early wet season spraying. Perhaps Spinnaker could be used to mitigate this risk where suitable.

 
A national code of practice for the containment of gamba to genuine grazing systems is being developed and stakeholders can request a copy for comment here. Industry engagement is critical in this process. Research is also being discussed, so feel free to comment (you can do so anonymously) so we can generate more ideas.