Ag's nitrous oxide output under review

Soil scientist at NSW DPI’s Tamworth Agricultural Institute, Dr Graeme Schwenke, will lead a research project aiming to measure nitrous oxide emissions from soils under common cropping rotations in north-west NSW.

The project, which will receive $400,000 in funding from the Grains Research and Development Corporation, is part of a national network of projects including irrigated cotton, grain growing, sugarcane, and dryland grain production.

Use of fertiliser nitrogen in the agricultural sector accounts for 32 per cent of total nitrous oxide (N2O) gas emissions into the atmosphere each year.

Since each N2O molecule is around 300 times as potent a greenhouse gas as a carbon dioxide molecule, this equates to 5.2 million tonnes of carbon dioxide equivalent each year.

Of the one million tonnes of fertiliser nitrogen used annually in this sector, approximately 70pc is applied to cereals.

"One option for mitigating emissions in cereal production systems of the North West Slopes and Plains is partial substitution of fertiliser nitrogen with biologically fixed legume nitrogen," Dr Schwenke said.

"Legume derived nitrogen is available to plants in a more slow release form that should be less liable to gas losses to the atmosphere than fertiliser nitrogen."

The greater use of legume derived nitrogen also saves on the significant greenhouse gas emissions associated with nitrogen fertiliser manufacture, transport and application to the soil.

Emissions calculations for NSW and Australia use high default values from overseas when accounting for legume-derived nitrogen.

"One of our project’s aims is to develop real-world multiplier factors to replace the International Panel on Climate Change default values used in calculating greenhouse gas emissions from fertiliser and legume use," Dr Schwenke said.

A concurrent PhD research program with the University of New England will be conducted to examine in greater detail the conditions promoting loss of N2O gas from soil and the pathways of gas loss through the soil.