How to reduce the risk of ammonia gas loss with N-Protect.
Did you know that every time you apply urea fertiliser to your pastures there’s a risk that some of the nitrogen (N) in the fertiliser can be lost to the air? This process is called volatilisation.
When you apply urea to your pasture, an enzyme called ‘urease’, produced by at least 20 different types of soil bacteria, splits the urea molecule in two (hydrolysis). As further chemical changes occur during this hydrolysis, ammonium ions are produced and the pH of the solution around the fertiliser granule can be as high as pH 9. This causes some of the ammonium ions to be converted into ammonia gas which can be lost into the air.
How bad is the risk?
During the months of spring through to autumn, research shows the average ammonia loss can be 18%, with an average 8% loss over the winter months. In the extreme, losses of 33% have been measured in hot, dry conditions with little pasture cover. Volatilisation risk is greatest when the following conditions occur:- High rates of N in a single application (ie, 50-100+kg N/ha)
- Lack of rain/irrigation - 10mm required within eight hours of application
- No or minimal plant cover/bare soil
- High wind
- High temperature
No one can tell you what the volatilisation loss will be on the day of application. Research has also shown that you need at least 10mm of rainfall or irrigation within eight hours of a urea application to minimise volatilisation losses. Having moist soil is not good enough and can, in fact, make volatilisation worse.
N-Protect: The smart choice
To reduce the risk of ammonia gas loss, the urea in N-Protect has been coated with a urease inhibitor. This slows down the activity of the enzyme and reduces any rise in pH levels around the dissolving granule.Trials on N-Protect application to pastures in New Zealand have shown that on average the use of N-Protect reduces volatilisation losses by as much as 50%. Given that the average ammonia loss is 18%, this would reduce this level down to 9%.
Greenhouse gases
Some of the ammonia gas goes back down onto soil when rain falls. Some of this ammonia is at risk of being converted into nitrous oxide (N₂O) by soil bacteria. Nitrous oxide is a potent greenhouse gas and using N-Protect will help reduce this. Lincoln University Professors calculated that if all urea applied annually in New Zealand was urease inhibited, it would achieve the following:- Reduce indirect N fertiliser losses of N₂O by 6-7%
- Reduce total agricultural N₂O emissions by 1%
- Save about $970,000 in national greenhouse gas liabilities (assuming 500,000MT of urea sold annually is coated with 250ppm NBPT at application and a carbon price of $20 a tonne).
