Nitrogen (N) fertilisers supply a significant proportion of the N required in food production globally, so are essential to food security and supporting the growing global population.
The appropriate use of N fertiliser can significantly improve the yield and quality of crops and pastures, contributing to the profitability and sustainability of the Australian agricultural sector.
However, the emissions of nitrous oxide (N2O) resulting from the use of N fertilisers is likely to come under increasing public scrutiny given the desire to reduce greenhouse gases (GHG) across all aspects of the economy.
“Taking steps to reduce the emissions profile associated with the end use of N fertiliser by encouraging the use of nitrification inhibitors, will be one small step the fertiliser industry can take to reduce overall emissions relating to our industry,” said Stephen Annells, executive manager of Fertilizer Australia.
Peter Grace, professor of global change at Queensland University of Technology said N2O is a potent greenhouse gas, contributing over 4% of Australia’s national greenhouse gas emissions in terms of its global warming potential.
He said Australia’s agriculture sector is the primary emitter of N2O, producing approximately 60% of total annual emissions.
“Within the Agriculture sector, soils produce 95% of the N2O, mainly from the direct emissions associated with application of N fertilisers, crop residues, dung and urine which approximates to eight million tonnes of carbon dioxide equivalents,” Professor Grace said.
The current National Greenhouse Gas Inventory estimates two million tonnes of carbon dioxide equivalent (CO2e) emissions are directly emitted per year from the application of N fertiliser to soil in Australia.
Fertilisers also contribute to an additional two million tonnes CO2e of indirect N2O emissions via nitrogen leaching and atmospheric deposition. Since one tonne of N2O has an equivalent warming effect to 273 tonnes of CO2, this conversion value is then used to ensure all greenhouse gases can be brought together into a single currency for standardising emissions.
“Depending upon a number of soil factors, as the amount of N applied as fertiliser increases, N2O emissions also tend to increase,” Mr Annells said.
Currently, the cost of urea coated with a nitrification inhibitor is around 14% more expensive per unit of N applied, compared to conventional urea. “While highly effective at reducing nitrous oxide emissions from urea application, the actual N saved is typically less than 10kg N per hectare per year, Professor Grace said.
“In many situations this saving is not agronomically significant for farmers, and not surprisingly, most of the research suggests no significant productivity benefit.
“Given the public benefit of reduced N2O from treated N fertiliser application, Mr Annells said Fertilizer Australia is exploring public policy measures which will reduce the cost of treated N fertiliser for farmers and make it easy for growers to claim a reduction in the emissions profile of their farming operation.
A range of policy mechanisms and approaches are currently being explored with relevant stakeholders.
“If a suitable policy mechanism can be identified and agreed, it may have a range of benefits,” Mr Annells said.
“For instance, N2O emissions reduction from treated N fertiliser are immediate.
“This is very different to capturing carbon in the soil or vegetation, which takes many years to achieve. The risk to growers in reducing N2O emissions through the use of treated N fertiliser would be very low, compared to sequestering carbon in soil or vegetation where the risks for farmers are much greater.
“In the coming months and years, Fertilizer Australia will be progressing these matters with the aim to be ‘one step ahead’ of the general public expectation on this issue,” Mr Annells said.
