Riverine Plains, funded by the Grains Research and Development Corporation, is exploring strategies to reduce the wheat cropping industry’s reliance on synthetic fertilisers.
Photo by
Rachel Lenehan Photography
Researchers at Riverine Plains are investigating whether vetch can be used as a companion crop in wheat systems to improve nitrogen availability and reduce fertiliser reliance.
Hold tight - we’re checking permissions before loading more content
The Australian Bureau of Statistics reported Australia produced about 34 million tonnes of wheat last financial year, valued at $10.1 billion.
Riverine Plains estimates those yields required about 1.2 million tonnes of soil-fixed nitrogen, with 45 per cent supplied by synthetic fertilisers.
Australia currently imports most of its nitrogen fertiliser from overseas, including from the Middle East, leaving the cropping industry exposed to global supply disruptions.
The Riverine Plains study, funded through the Grains Research and Development Corporation, will explore the use of vetch as a companion crop to provide a nitrogen boost for wheat, offering a potential alternative to traditional fertiliser inputs.
Sabita Duwal is a Riverine Plains project manager, overseeing the companion cropping research project.
Photo by
Rachel Lenehan Photography
Riverine Plains project manager Sabita Duwal said the key challenge was balancing the nitrogen-fixing benefits of vetch with its competition against wheat, particularly for moisture in dry seasons.
While vetch can contribute nitrogen to the system, this benefit is closely tied to biomass production, meaning tough seasons can limit its effectiveness.
“In dry years, both wheat and vetch are competing for the same limited resources,” she said.
“That reduces biomass, which in turn reduces how much nitrogen the vetch can fix.”
This competition becomes especially critical during flowering and grain fill, where water stress can directly reduce wheat yield.
The project has identified termination timing as the most important management tool.
Ending the vetch earlier reduces competition and protects yield, but comes at the cost of lower nitrogen fixation.
“In a dry finish, maintaining wheat yield usually becomes the priority,” Miss Duwal said.
“Early termination may be safer because it reduces water demand from the vetch and minimises the negative impact on yield.”
Early results suggest terminating vetch at wheat growth stages 21-23, when the plant begins to form small side-shoots called ‘tillers’, provides the best balance under many conditions.
Sabita Duwal said the project would provide practical recommendations for farmers aiming to reduce their reliance on synthetic nitrogen fertilisers.
Photo by
Rachel Lenehan Photography
This approach is now being tested at paddock scale, including at sites near Corowa.
Rather than a one-size-fits-all system, the research is highlighting the need for flexible decision-making based on seasonal conditions.
“The system can still work in dry seasons, but it becomes much more conservative,” Miss Duwal said.
“Success depends heavily on matching termination timing to seasonal conditions rather than following a fixed approach.”
While legumes offer a pathway to reduce fertiliser costs, Miss Duwal said they were not a complete substitute.
“The amount of nitrogen fixed depends on biomass and timing, which both depend on seasonal conditions,” she said.
“It can offset fertiliser inputs, but won’t completely replace synthetic nitrogen.”
Ultimately, the project aims to provide practical recommendations to growers, helping to maximise their yields.
9°C