Case study - Nitrous oxide emissions - no longer such a mystery (South)

​Case study – Department of Agriculture, Fisheries and Forestry, Australia’s Farming Future Climate Change Research Program (CCRP)

Nitrous Oxide Research Program (NORP)

Nitrous oxide emissions — no longer such a mystery

Results from a national research program not only quantified Australia’s nitrous oxide (N2O) emissions, but also helping farmers develop new ways to manage the gas.

Professor Grace who headed the Australian Government’s Nitrous Oxide Research Program (NORP) said the majority of N2O emissions come from human activities, with much of this resulting from agriculture.

“Nitrous oxide gas is emitted naturally from the microbial processes in the soil,” he said.

While traditional greenhouse gas emissions research focused on carbon dioxide, Professor Grace said data regarding N2O soil emissions from Australian soils was limited. “Nitrous oxide is effectively around 300 times more potent than CO2 when it comes to impact on global warming. That is why the NORP is so important,” Professor Grace said.

“The NORP brought together researchers who measured and modelled N2O emissions for dryland and irrigated farming —particularly grains, cotton, sugarcane and dairy — from sites right across the country,” said Professor Grace. “Nitrous oxide is also a good indicator of overall nitrogen use efficiency, so the research outcomes are a win-win in terms of reducing emissions and increasing profitability.

“From that we then developed a range of tools and advice for farmers, consulting agronomists, extension officers and policy makers to manage, and hopefully reduce, these potent emissions as well as improving nitrogen use efficiency.”

Funded through the Australian Government Department of Agriculture, Fisheries and Forestry under its Australia’s Farming Future Climate Change Research Program, the NORP partners included the Department of Primary Industries Victoria, the Grains Research and Development Corporation, Dairy Australia, New South Wales Department of Primary Industries, the Queensland University of Technology, the Queensland Department of Science, Information Technology, Innovation and the Arts , University of Melbourne and the University of Western Australia.

Professor Grace said N2O research was undertaken at six core field sites including Mackay and Kingsthorpe in Queensland, Tamworth in New South Wales, Hamilton and Terang in Victoria and at Wongan Hills in Western Australia.

“Research conducted in different dryland and irrigated farming sites — particularly grains, cotton, sugarcane and dairy — allowed us to gain a clearer picture of the major emissions sources,” he said.

“We then used that information to tailor specific management techniques for each individual industry, land-use type and climatic condition.”

Professor Grace said there are a range of management techniques that farmers can adopt to reduce N2O emissions from agricultural soils.

“For example, farmers may be able to change the timing, type and amount of nitrogenous fertiliser that they apply to their soil,” he said.

“They may also be able to use chemicals to inhibit nitrous oxide production, such as dicyandiamide, use legumes as a replacement for nitrogen fertilisers, plant cover crops that soak up excess nitrogen and adopt irrigation practices.”

Dr Richard Eckard, Associate Professor and Director, Primary Industries Climate Challenges Centre at the University of Melbourne said nitrous oxide emissions are heavily dependent on soil temperature and moisture and the source of nitrogen in the soil. These factors also determine the ability of the farming system to produce significantly large amounts of biomass (either as pasture or residues) that are retained either above or below the surface.

He said research found that emissions fluctuate in different agricultural settings and while dryland cereal production systems are historically low emitters of N2O, it was a different story for sugar cane and dairy systems.

“It ranged from less than 0.06 kg N/ha/year in the coarse textured dryland cropping soils of the Western Australian wheat belt to up to 1 kg N/ha/day from fertile soils of south-eastern Victoria under dairy production,” Associate Professor Eckard said.

“The latter received significant inputs of urine based nitrogen in contrast to more controlled fertiliser nitrogen inputs in cropping systems.”

At Terang in Victoria, NORP researchers found that applying the chemical dicyandiamide (DCD) to pasture almost halved the rate of nitrous oxide emissions in high rainfall dairy systems.

Kevin Kelly, Senior Research Scientist with DPI Victoria, said while dairy farmers are aware they have a nitrous oxide emission issue, it isn’t high on their agenda.

“About 15-25 per cent of greenhouse gas emissions in the dairy industry come in the form of nitrous oxide,” Mr Kelly said.

“And given that the dairy industry has a higher stocking intensity on an area basis than most other industries, if something was found to reduce emissions profitably, it could be the first industry to implement it.”

Mr Kelly said while DCD has been around for the past 50 years, it has only been in the past decade that scientists have been looking at its potential value in reducing N2O emissions.

“A series of experiments conducted at the DemoDairy facility at Terang in southwest Victoria showed that applying DCD to the pasture’s surface can result in reductions of between 35 and 45 per cent,” Mr Kelly said.

Mr Kelly said the experiments also looked at whether applying DCD could have a beneficial effect on pasture production.

He said if farmers could increase pasture production by applying DCD then they could reduce the need to apply nitrogen fertilisers or supplementary feed to their stock, thereby saving themselves money.

But so far, he said they’ve only seen minor increases in pasture production.

“On urine patches we’ve seen a 10 to 18 per cent increase in pasture production at some sites, but when you take it to a larger scale and distribute across the paddock, the production increase is likely to be negligible,” Mr Kelly said.

“Preliminary economic analysis suggests that applying DCD simply to reduce nitrous oxide emissions alone will not cover the cost of application.”

Mr Kelly said although DCD proved to reduce N2O emissions, there are several drawbacks to the chemical including the fact that it wasn’t very soluble and required high levels of water to be sprayed out.
 
Mr Kelly said DCD was also sensitive to soil temperatures and needed relatively cool temperatures to have an extended efficacy.

“We tried it in the irrigation regions in summer and found it to last only 30 to 40 days. Whereas in the cooler regions it might last up to 90 days,” he said.

“While DCD has some potential in hotter and drier dairying regions, the real benefit would be in the higher rainfall, lower temperature, regions in Victoria and Tasmania.”