Nitrous Oxide – a greenhouse gas of concern

WaiBER Post Graduate researcher Jordan Goodrich. Photo: Catherine Fry.

“New Zealand is unique in that its national greenhouse emissions are dominated by nitrous oxide and methane, rather than carbon dioxide,” says post doctorate researcher, Jordan Goodrich.

In New Zealand to further his studies, American-born Jordan is part of the Waikato Biogeochemistry and Ecohydrology Research team – WaiBER – at the University of Waikato, researching the ever increasing nitrous oxide concentration in the atmosphere.

“Nitrous oxide (N2O) is a greenhouse gas of concern, as it is 300 times more efficient at trapping heat than carbon dioxide (CO2).”

Agriculture, especially dairy farming, is a big source of N2O emissions. The nitrogen cycle in cows involves its release in urine, which enters the ground in concentrated patches.

This localised nitrogen application is too much for the surrounding plants to process, and the excess is either processed by soil microbes releasing N2O, or leached from the soil into waterways.

Previous research into N2O emissions has been limited to small plot trials.

Jordan’s research involves measuring emissions at a paddock scale, over multi-year periods, on a commercial farm in Waharoa, near Matamata.

“The farmers farm as they wish and we set up monitoring equipment along the fence line, gathering data constantly from year to year.”

Using the eddy covariance technique, with sensors set about two metres above the land, the concentration of N2O (and also CO2 and methane) is measured to calculate the emissions of a paddock.

“We’ve partitioned the data by wind direction to cover two adjoining paddocks, allowing us to compare these paddocks.”

Current research is to determine whether planting plantain in with the usual rye and clover mix reduces the emissions from that paddock. While environmental factors such as humidity, rainfall and wind vary from year to year, small plot trials have shown good evidence that plantain does slow down the nitrogen cycle.

“Plantain helps dilute the cows’ urine so that it has less nitrogen.

“We have one and a half year’s data as a baseline and have now re-grassed including plantain.”

The initial process of spraying off the paddock, followed by direct drill planting causes a pulse emission of N2O.

“In order to be sure we can make up for that initial pulse, the paddock will be monitored for a two-year period which allows for the new planting to settle.

“We also look at all the factors in the real life, rotationally grazed paddocks, that could affect our research.”

This project is funded by the New Zealand Agricultural Greenhouse Gas Research Centre.


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