Nitrogen use in the spotlight as grain industry pushes to reduce greenhouse gas emissions

Nitrogen use in the spotlight as grain industry pushes to reduce greenhouse gas emissions

With several governments around the world pursuing limits on nitrogen fertilizer use in agriculture, how would farmers adapt if the Australian government took a similar approach?

Birchip Cropping Group senior research manager James Murray said the obvious way to reduce emissions from nitrogen fertilizer was to use less of it.

“I naturally guess the go-to option is to grow more legumes in the rotation, because when we grow legumes we don’t need to apply nitrogen to meet production,” he said.

“But it’s not as simple as that, because there are greenhouse gas emissions such as nitrous oxide associated with the breakdown of legume stubbles.”

In broadacre cropping, fertilizer production and use accounted for 58 per cent of the Australian wheat crop’s greenhouse gas footprint in the past five years, according to the Department of Agriculture.

Of that, 31 per cent occurred on-farm, a large part of which came through the volatilization of nitrogen fertilizer, where nitrous oxide is released into the atmosphere.

Nitrous oxide is a greenhouse gas that is almost 300 times more potent than carbon dioxide.

James Murray says regardless of motivating factors, more efficient fertilizer use will benefit both the environment and the hip pocket.(Rural ABC: Angus Verley)

Apart from growing more nitrogen-fixing legumes to reduce fertilizer use, Mr Murray says there are products available to slow the volatilisation process, which occurs when nitrogen is applied to a crop and there is insufficient rainfall following application to break it down.

“There are a couple of products on the market — one is a urease inhibitor, which reduces that volatilization risk by slowing that release when you apply if you don’t get follow-up rainfall relatively quickly,” he said.

“The other one is a polymer coating, which slows the release of nitrogen quite significantly.

“But the challenge with them is they’re not necessarily cost-effective to utilize, with the urease inhibitor retailing for about $50 a tonne on top of your urea cost, so it opens up a question about how cost effective that is in farming system.”

Mr Murray said whether or not farmers used a urease inhibitor, there was significant value in getting nitrogen application right and minimizing volatilisation.

“We talk a bit about the four Rs — so the right rate, the right product, the right source and the right timing, which at the end of the day will have significant benefits for production, and if we’re reducing our greenhouse gas footprint at the same time, that’s a bonus,” he said.

Countries including New Zealand, Canada and the Netherlands are enforcing limits on fertilizer application to reduce emissions, which Mr Murray says is a consideration for farmers here.

“There are considerations around market access and potential future mandates on how things are utilized,” he said.

“I think there’s a great opportunity for the Australian grains industry to be ahead of the game on this stuff, whether it’s for market access or potential mandate considerations.

“In terms of improving the way we use our inputs, the biggest benefit is to the bottom line in terms of improving crop production.”

A pair of hands cradling innumerable small balls light-coloured of fertiliser.
Urea can release nitrous oxide into the atmosphere.(ABC Wimmera: Andrew Kelso)

What are the alternatives?

Some farmers are trialling alternatives to synthetic fertilizer under the broad umbrella of “regenerative agriculture”.