Nitrogen fertiliser
Reducing the use of nitrogen-based fertiliser is a measurable way of reducing the amount of nitrogen entering the soil that's available to be transformed into nitrous oxide.
How it works
Nitrous oxide is produced by naturally occurring soil microbes. The microbes convert urea or animal urine into different forms of nitrogen, such as ammonium and nitrate, but also nitrous oxide. Very simply, the less nitrogen applied or returned to the soil either by fertiliser or dung/urine, the less nitrous oxide is produced.
Another action to consider is the use of fertiliser containing urease inhibitors. Urease inhibitors reduce losses of ammonia (through volatilisation) from urea use and maximise nitrogen available for plant uptake. This results in small reductions in nitrous oxide emissions. It also means that less nitrogen needs to be used, which in turn leads to less nitrous oxide being emitted.
How will this affect my GHG number?
Emissions from nitrogen fertiliser use make up about 3.7% of New Zealand's carbon dioxide equivalent agricultural emissions. Research for the Biological Emissions Reference Group found that if all nitrogen fertilisers in New Zealand were coated with a urease inhibitor, the national reduction in carbon dioxide equivalent emissions would be 0.2%. Therefore, reducing nitrogen fertiliser use won't have a big impact nationally. It can, however, substantially influence the emissions from cropping and horticultural enterprises.
Reducing nitrogen fertiliser use will also have co-benefits for reducing nitrogen leaching. High nitrogen fertiliser use on pastures can also mean a high concentration of nitrogen in the diet of grazing animals, resulting in increased nitrogen in urine, which influences nitrous oxide emissions and nitrogen leaching losses.
Many farmers and growers have already done all they can to reduce nitrogen fertiliser use, often with the help of nutrient budgeting tools like OVERSEER and/or implementing good management practices through Farm Environment Plans. If you haven't already, you should also find out what your on-farm greenhouse gas emissions are.
Risks
Plants need nitrogen to grow and sub-optimal nitrogen supply will affect plant productivity, resulting in reduced crop and pasture yields. On pastoral farms, if reduced pasture production means more off-farm feeds need to be purchased, profitability could go down while the net reduction in emissions may be negligible.
More information
For more on the sources and science of nitrous oxide, see:
- The Reduce nitrous oxide goal page
- Farmer case studies featuring George Moss, Jay Clarke, Phill Everest, Rick Burke and Craige Mackenzie
- The NZAGRC website
Case studies
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Robin Oakley, Canterbury
Fifth generation farmer, Robin Oakley, has been growing vegetables in Canterbury since he was a kid and now supplies supermarkets around the country. His family is committed to sustainable farming and is starting to think about what that means for the climate.
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Dion Gordon, Canterbury
In 2019, Canterbury dairy farmer Dion Gordon experienced something of a nightmare. The Rangitata River burst its banks, flowed onto his farm and took a huge swathe of topsoil out to sea. Dion had no choice but to drop stock numbers - but what happened next was a surprise.
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Hugh Ritchie, Hawke's Bay
An emphasis on efficiency improvements and soil health are helping keep greenhouse gas emissions down on Hugh Ritchie's complex arable, livestock and horticulture operation in Hawke's Bay.
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Jay Clarke, Horowhenua
At Woodhaven Gardens near Levin, Jay Clarke and his family have been figuring out how to reduce their vegetable farm's impact on the climate.
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George and Sharon Moss, Waikato
George and Sharon Moss have been dairy farming in Tokoroa for nearly 40 years. Their impact on the climate wasn't a consideration back then, but it's at the forefront of how they farm now.
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Craige Mackenzie, Canterbury
Mid-Canterbury arable and dairy farmer Craige Mackenzie's philosophy is right input, right quantity, right place, right time—which makes sense for his business and for the land, waterways and climate.
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Phill and Jos Everest, Canterbury
A balanced approach to dairy farming on the heavy soils of coastal mid-Canterbury is essential in Phill and Jos Everest's efforts to reduce Flemington Farm's agricultural greenhouse gas emissions.
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Rick Burke and Jan Loney, Bay of Plenty
Rick and Jan have been working hard to improve their sheep and beef farm's impact on freshwater and biodiversity, and are now turning their attention to the climate.
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The Abbiss family, Manawatū
A passion for innovation has been a common thread through four generations of farmers on the Abbiss' property near Halcombe. Now they're turning their attention to how they might reduce their impact on the climate.
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Orete No. 2 and Other Blocks Incorporation, Eastern Bay of Plenty
Farming has long been a way of life for Orete – a Māori Incorporation with 1,500 owners on the tip of the remote East Cape. Te Taiao is at the heart of all they do, including finding ways to keep their agricultural greenhouse gas emissions down.