Innovative Use of Gibberellic Acid (GA)
| Project start date: | 30 May 2014 |
| Project end date: | 30 June 2017 |
| Project status: | Completed |
| Livestock species: | Sheep, Lamb |
| Relevant regions: | Victoria |
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Summary
Gibberellic Acid (GA) is made naturally in plant roots and stimulates shoot and cell elongation, promoting plant growth during spring. The application of manufactured GA in winter aims to stimulate plant growth and therefore increase winter feed availability.
This Producer Demonstration Site (PDS) was designed to evaluate the extra winter feed growth produced using GA in comparison to Nil and nitrogen treatments in phalaris based pastures in the Upper Wimmera/Central region of Victoria.
Results indicate the greatest benefit of GA would be opportunistic rather than strategic in lower rainfall regions on phalaris pastures due to vastly different yearly growth patterns as a result of variable autumn breaks and subsequent pasture availability on farm. This affects the ability to meet the optimal pasture requirements for GA application to produce more winter feed, including the recommended period of destocking.
Objectives
The objectives of this PDS were to:
• assess the additional winter feed gains that can be made in the region by using GA and the cost/benefit of its use
• develop best practice guidelines for the use of GA in the region, to increase the uptake of the technique and increase winter feed availability in a cost-effective way
• have half of PPS member farms using GA to increase winter feed production by the end of the project.
Progress
The three-year demonstration resulted in 133 kg DM/ha increase in pasture grown after GA application averaged over the sites, a net benefit of $2.97/ha based on the long-term average feed barley prices and $12.91/ha based on October 2018 prices. With a GA treatment cost of $22.43/ha, this would be a worthy feed option compared to grain feeding at October 2018 grain prices of $35.19/ha. A sensitivity analysis concluded that to break even on GA treatment cost, an extra 117kg DM/ha would need to be produced based on long-term average feed barley prices, or an extra 84kg DM/ha based on October 2018 prices, to justify the GA application.
The individual phalaris plants responded to the GA treatments and increased the amount of pasture dry matter (DM) grown, but the responses at most sites were not as substantial as was anticipated. The density of phalaris, even in a good phalaris/sub clover pasture, appears to be a limiting factor in the response to the GA applications in the demonstration.
