Added benefits in greenhouse cure

By Alec Nicol

The greenhouse gas focus in Australia is increasingly turning to agriculture – as part of the problem and as part of the answer.

The Cooperative Research Centre for Greenhouse Accounting (CRCGA) has identified the grain, cotton and dairy industries as contributing between 18 and 20 percent of Australia’s greenhouse gas emissions. This compares to the US where agriculture contributes about seven percent.

However, the CRCGA’s chief executive, Dr Chris Mitchell, says the circumstances leading to this scenario in Australia have created the situation where farmers could benefit significantly in the course of redressing the problem.

“The major contributor is nitrogen fertiliser, so our aim is to improve the efficiency of nitrogen use, reaping a reward for the environment and cost-savings for the producer,” he says.

Dr Mitchell says that while many people equate greenhouse gas with carbon dioxide, nitrous oxide and methane (from livestock) are much more potent in the atmosphere.

The use of nitrogen fertiliser exploded in the early 1990s when the AWB introduced payment for protein. Australia’s use of nitrogen fertiliser doubled – but up to 3.5 percent is lost to the atmosphere as nitrous oxide (N20), a gas 310 times more damaging than CO2.

The CRCGA hopes to encourage improved management practices that would reduce nitrogen fertiliser applications by the equivalent of 260,000 tonnes of urea a year, which would save growers about $100 million.

The issue for researchers is to achieve this without a drop in either production or quality, and there are big holes in their knowledge base. The figures being used to calculate greenhouse gas emissions are based on northern hemisphere data.

CSIRO researcher Clive Kirkby says temperature, moisture, soil type and the soil biota are all interacting to produce these gases and Australian conditions are very different.

Mr Kirkby is running a series of trials to measure the amount of greenhouse gas emissions generated by standard farming systems. The trials use specially designed perspex boxes that collect and measure the small amounts of gas emitted from the ground and the crop.

“Whatever changes we eventually introduce, they will need to be whole-system changes,” he says. “That means we must know what’s happening at every phase of the farming system.”

Mr Kirkby’s experiments are attempting to track gas emissions in a corn crop from land preparation through to corn chips in plastic bags.

He is also comparing emissions from country where stubble has been burned, where it has been incorporated, and from high and standard nitrogen fertiliser applications.

The CRCGA is counting on the ‘carrot’ of reduced costs to encourage growers to adopt recommendations that come from the research. However, he warns there is also a stick: “We need to be prepared for carbon trading and anticipate that greenhouse gas mitigation will play a part in future trade deals,” he says.