Carbon Farming & Nitrous Oxide Management

Dr Helen Suter of the University of Melbourne talks about nitrous oxide management.

Nitrous Oxide Becoming a Concern

Nitrous oxide is a greenhouse gas that comes from various sources. So, it can come from naturally produced or through anthropogenic activities. It’s a gas that’s of concern because it has a global warming potential that’s around 300 times that of CO2. For nitrous oxide emissions agriculture accounts for about 75% of the total N2O emissions for Australia, and around 33% comes from management of agricultural soils, which includes the use of synthetic fertilizers.

If we started with an application of, say, urea, which is a commonly used fertilizer, that first becomes hydrolyzed to ammonia and ammonium and then the processes that lead to production of N2O nitrification, which is the oxidation of ammonium to nitrate and then denitrification, which is the reduction of nitrate through to nitrous oxide and then N20 gas as well, so both processes can lead to emissions of N20.

Reducing N2O Nitrification

It’s one of the gasses that’s seen that can be reduced relatively easily. Things as simple as reducing nitrogen application rates. To reduce losses we need to reduce inputs and make the system much more efficient. If you think that nitrogen efficiency may be around 50-60% of applied nitrogen. We’re trying to reduce what is lost or not taken up by the plant and through that process you can then reduce the end rates and maintain productivity.

One of those ways is with these nitrification inhibitor products that can be applied to fertilizers. So, what those products do is when, after you have ammonium, they prevent the oxidation of that to nitrate. So it slows down the release of ammonium, so there is more ammonium available in the soil for the plant to take up, and less nitrate available for leeching losses or for denitrification to occur.

In our studies that we’ve done, we do a lot of lab work where we look at soil, the impact of the inhibitors on different soils and we find that in many instances we do get a reduction into our emissions and it can range from essentially zero in some soils to up to ninety-five percent reduction in the level of N2O that’s emitted with the use of one of these inhibitor products.

In systems where you had high emissions, the cost almost is going to justify itself. You can then buy less fertilizer at a premium cost but reduce your emissions of nitrous oxide. So, the production that you’ll get could be could be higher in those systems.