29 November 2019
Options for farmers have now broadened when it comes to managing their greenhouse gas (GHG) footprint on-farm.
The recent inclusion of urease-coated urea fertilisers as an option in the nutrient budgeting tool OverseerFM means
farmers will now be able to demonstrate the benefits of its use in reducing farm emissions.
Urease-inhibited urea fertiliser, such as Ravensdown’s N-Protect, has dual benefits. It decreases volatilisation losses,
therefore increasing agronomic efficiency by retaining more nitrogen (N) in the root zone. The inhibitor slows down the
action of the naturally occurring urease enzymes in soil, which in turn slows down the conversion of urea to ammonium
ions and the consequent rise in soil pH around the dissolving granule. The rise in pH converts ammonium ions into
ammonia gas (ammonia volatilisation). The secondary benefit is that less ammonia gas is lost to the atmosphere. A
portion of the gas returns to the soil, some of which can be converted into the potent greenhouse gas nitrous oxide.
Farmers will eventually be responsible for their GHG emissions at a farm level, so the recent inclusion of urease
inhibitors in OverseerFM means those who are using it will be a step closer to demonstrating the benefits of reducing
their emission footprint.
While the greenhouse gas saving is small on a single application of urea basis, it’s the multiplier effect of how much
urea is used in total per year in New Zealand. If all the urea that was used was inhibited, it would have the following
effect on the total nitrous oxide evolution from New Zealand soils and pasture systems:
Reduce indirect N fertiliser losses of N2O by 6-7%
Reduce total agricultural N2O emissions by 1%
Save around $970,000 in national GHG liabilities, assuming 500,000 tonnes of urea is sold annually (coated with 250 ppm
NBPT at application and a carbon price of $20 per tonne).