Nitrification inhibitors in intensively grazed pasture systems

Nitrification inhibitors in intensively grazed pasture systems

Background

The project built on the earlier PICCC inhibitors project, which showed 35-45% reductions in direct emissions from urine patches through the application of a nitrification inhibitor, with the effects lasting for up to 90 days post application.

The objectives of this project were to evaluate:

  • the potential of nitrification inhibitors to reduce direct emissions from urine and dung deposition when surface applied to pasture
  • the mitigation potential of inhibitor-coated inorganic fertiliser applied to pastures in dairy systems.

Project outline

The project addressed both productivity and emissions mitigation implications of inhibitor use, aiming to provide dairy farmers with practices and Carbon Farming Initiative offset methodologies that reduce nitrous oxide loss from dairy production systems.

Researchers assessed the impact of inhibitors on nitrous oxide losses, pasture production and nitrogen use efficiency, and also examine nitrogen movement to depth in the soil profile.

Results

The research, conducted in south-west Victoria, showed that nitrification inhibitors can effectively reduce nitrous oxide emissions resulting from the deposition of urine and dung, and the application of inorganic nitrogen fertiliser and dairy sludge to grazed dairy pastures. Inhibitors were particularly effective under wet conditions, when high soil moisture levels typically lead to greater rates of nitrification. However, there were no increases in pasture production associated with the use of inhibitors. Given the cost associated with using inhibitors, the results suggest that in the absence of a high carbon price or other incentives, their use on such pastures is not likely to be economic.

There was evidence, however, that the emissions attributed to agriculture may be lower than previously thought. The research supports a reduction in the nitrous oxide emission factor for nitrogen fertiliser use on rain-fed pastures and the nitrous oxide emission factor for dung deposition on pasture. The difference means that the Australian National Greenhouse Gas Inventory may be significantly overestimating emissions from the dairy sector.

Outcomes

The research expanded on PICCC’s other nitrous oxide work, investigating the direct application of inhibitors to dairy dung and urine. As with the other studies, the findings suggest that in the current price and policy environment, inhibitor use on pasture is not economic for the dairy industry.

The emissions data collected have been used to develop new national inventory emission factors for nitrous oxide for fertiliser, dung and urine from dairy farms.

Related resources

Titlesort ascending Excerpt
Nitrous oxide publications A bibliographic survey of research publications produced by PICCC's nitrous oxide projects.