Dairy HIGH 2

Project details

Status: Completed

Project background

Productive pastures are the foundation of profitable dairy farming in Tasmania. Over the past decade, the dairy industry has expanded significantly through the development of irrigated land, allowing farmers to grow more pasture and support higher milk production.

However, this intensification has also increased reliance on synthetic nitrogen fertiliser, which can be costly and subject to price shocks, and can contribute to environmental concerns. As a result, farmers and industry are increasingly interested in finding ways to reduce nitrogen fertiliser use without compromising pasture growth or milk production.

One promising approach is to make greater use of legumes such as white clover. Legumes can naturally supply nitrogen to pastures through biological nitrogen fixation, reducing the need for fertiliser. They can also improve feed quality, increase pasture intake by cows, and support milk production.

More diverse pasture mixes that include additional legumes and forage herbs have also been suggested as a way to improve pasture resilience and productivity.

Research questions

• How much can synthetic nitrogen fertiliser be reduced while maintaining pasture production?

• What changes to pasture composition may be needed to support productive dairy systems with lower nitrogen inputs?

Project activities

Researchers established four irrigated farmlet systems (mini farms) at the TIA Dairy Research Facility in Elliott, north-west Tasmania. The farmlets were managed over three consecutive lactation seasons from 2023 – 2026 to test research theories under real farm conditions. The farmlets differed in the amount of synthetic nitrogen fertiliser applied and the types of pasture species grown.

• Farmlet 1: 80% perennial ryegrass and 20% white clover, with 300kg of nitrogen per hectare

• Farmlet 2: 80% perennial ryegrass and 20% white clover, with 150kg of nitrogen per hectare

• Farmlet 3: 40% perennial ryegrass, 30% white clover, 30% plantain, with 150kg of nitrogen per hectare

• Farmlet 4: 40% mixed grasses, 30% mixed legumes, 30% mixed herbs, with little to no nitrogen application

Project outcomes

White clover contributed substantial amounts of biologically fixed nitrogen across all farmlets, supplying more than 250kg of nitrogen per hectare during the first year of the study.

Pasture production remained high across all farmlets. In the first year, all farmlets produced around 21 tonnes of dry matter per hectare, which is double the industry average. In the second year, the farmlet receiving half the nitrogen fertiliser (F2) produced almost the same amount of pasture as the farmlet receiving the conventional amount of nitrogen fertiliser (F1).

Milk production was also impressive. Over the three-year study, the farmlets receiving low to moderate nitrogen fertiliser inputs exceeded industry benchmarks by more than 1,000kg milk solids (milk fat and protein) per hectare, demonstrating an opportunity to lift milk productivity.

Importantly, this higher productivity was achieved while reducing total nitrogen inputs, with farmlets 2 and 3 receiving approximately 25 per cent below industry averages.

There may also be an increased milk production benefit to high clover pastures, but this requires further research and will form the basis of the next phase of work in the Closing the Clover Gap project.

Farmlet Reports

Factsheets