KEY POINTS:
Farmers could almost meet their share of New Zealand's target under the Kyoto climate change treaty by doing something it makes financial sense to do anyway, says an economist.
The gas-cutting solution is the central claim of a report by economist Simon Terry for the Sustainability Council.
It is called A Convenient Untruth, a reference to the common claim that agriculture can do little to reduce its greenhouse gas emissions, so the taxpayer has to pick up the bill.
Farm emissions of nitrous oxide - a greenhouse gas much more potent that carbon dioxide - account for about a sixth of national emissions, twice as much as produced by all the gas and coal burned in power stations.
Terry said New Zealand was forecast to exceed its Kyoto emissions target for the 2008 to 2012 period by 29 per cent in gross terms, or 10 per cent when the offset for the carbon sequestered by post-1990 forests was taken into account.
Agricultural gases, which are about two-thirds methane and one-third nitrous oxide, are just under half New Zealand's emissions.
Terry says using nitrification inhibitors and other techniques to reduce nitrous oxide emissions could eliminate 18.5 million tonnes of carbon dioxide-equivalent over that period, or almost half of the national total excess.
Nitrification inhibitors are chemicals which prevent soil nitrogen turning into nitrous oxide, or into nitrates which leach into waterways polluting them. Instead the nitrogen remains available for pasture growth.
Terry said fertiliser manufacturer Ravensdown was sure its its nitrification inhibitor, called eco-n, was a cheaper option than urea fertiliser for increasing pasture growth.
"Recent results from trials of a nitrification inhibitor in four major New Zealand soil types show an average 70 per cent reduction in emissions from pasture land," the report says.
Terry said such results undermined the assumption underpinning a 2003 memorandum of understanding between the Government, Fonterra and other agricultural bodies, under which the Government undertook to bear the cost of farming's non-CO2 emissions under the Kyoto Protocol, which runs until the end of 2012.
The Government accepted farming had no way of cutting these emissions.
Ravensdown's product has been available since 2004, and the Ballance fertiliser company has a similar one.
The Ravensdown company had said it was used on 25 per cent of dairy pasture in Canterbury and North Otago this year, but the national figure was about 5 per cent.
Its use would spread if dairy farmers were exposed, through Fonterra, to the cost of their emissions and could claim back an offset from using inhibitors to reduce them, Terry said.
"Emulsion reductions available from the dairy industry are large and and can be achieved quickly," he said.
Fonterra's general manager for sustainable milk growth, Mark Leslie said trials were encouraging, but were based on a limited number of soil types, leaving questions about whether they could be extrapolated nationally.
Federated Farmers president Charlie Pedersen said he used nitrification inhibitors on his Manawatu property.
"But I don't think they have been well promoted. And I don't think many farmers are aware they are a potential climate change tool."
CLEAN AIR
* Substantial cuts in emissions of nitrous oxide, a potent greenhouse gas, are possible if dairy farmers use nitrification inhibitors instead of urea fertiliser, says a report to the Sustainability Council.
* That undermines agriculture's case for exemption from Government moves to put a price on emissions, it says.
* But Fonterra says it is early days for the gas-reducing technology.
