Tasmanian dairy farmers and industry will soon have the opportunity to hear firsthand results from one of Australia's most comprehensive investigations into reducing synthetic nitrogen fertiliser in pasture-based dairy systems.
Researchers from the Tasmanian Institute of Agriculture (TIA) are taking the findings of the Dairy HIGH2 farmlet trial on the road and will host a series of regional events across Tasmania during June and July.
TIA Livestock Production Centre Leader, Associate Professor James Hills, said encouraging results emerged from the farmlet trial after data was collected over three full lactation seasons from 2023 until 2026.
"The findings demonstrate that dairy farms can substantially reduce synthetic nitrogen inputs while maintaining high levels of pasture growth and milk production," Associate Professor Hills said.
"Over the three-year trial, the irrigated farmlets receiving low to moderate nitrogen fertiliser inputs exceeded industry benchmarks by around 1,000 kilograms of milk solids (milk fat and protein) per hectare.
Pasture production was also high throughout the trial, and all farmlets produced between 19 and 22 tonnes of dry matter per hectare which is almost double the industry average."
Associate Professor Hills said a key reason for these high levels of production was the contribution of legumes such as white clover, which can naturally supply nitrogen to pastures through biological fixation and increase feed intake.
"In the first year of the trial, white clover supplied more than 200 kilograms of nitrogen per hectare across all farmlets. This is equivalent to the average amount of synthetic nitrogen applied on Tasmanian dairy farms," he said.
The Dairy HIGH2 farmlet trial is funded by Dairy Australia and was conducted at TIA's Dairy Research Facility at Elliott. Four irrigated farmlets, or mini farms, were established to test different production systems under commercial farming conditions – an approach not happing anywhere else in Australia.
The farmlets differed in both the amount of synthetic nitrogen fertiliser applied and the pasture species grown, with nitrogen applications ranging from 300 kilograms per hectare to zero synthetic nitrogen inputs.
Associate Professor Hills said productive pastures are the foundation of profitable dairy farming in Tasmania.
"The Tasmanian dairy industry has intensified significantly over recent years supported by major investment in irrigation. This growth has increased the industry's reliance on synthetic nitrogen fertiliser, which is costly, vulnerable to price shocks and can contribute to environmental concerns," he said.
"Farmers and industry are increasingly interested in ways to reduce nitrogen fertiliser use without compromising pasture growth or milk production and there has been strong interest in this trial since its beginning. We've been sharing preliminary data and observations each month and are looking forward to sharing the final findings and discussing how they could be applied on farm."
As part of the regional roadshow, events will take place at host farms at Bracknell, Scottsdale and Edith Creek from 30 June until 3 July. The tour will conclude with a farm walk at TIA's Dairy Research Facility at Elliott on 7 July, providing farmers and industry the opportunity to see the trial site firsthand.
"At the regional roadshow events we'll delve into the trial results and discuss clover management, strategic nitrogen use and alternatives, fertiliser supply outlook and planning, and opportunities to get involved in upcoming focus farms," Associate Professor Hills said.
"The event at TIA's Dairy Research Facility is an opportunity to inspect all four farmlets, including paddocks that have received no synthetic nitrogen fertiliser for the past three years."
These events provide a valuable opportunity for discussion around future nitrogen management strategies for Tasmanian dairy farms.
