About 27% of the nitrous oxide emitted from agricultural soils stems from direct emissions from animal production — principally via urine and manure excreted onto pasture and rangelands. Research in New Zealand has shown that the nitrification inhibitor dicyandiamide (DCD) can reduce nitrous oxide emissions when surface-applied to pastures. To assess the potential of DCD as a mitigation tool, a team of PICCC researchers looked at the impact of strategic DCD applications in animal production systems in south eastern Australia.
Researchers used automatic chambers to intensively study nitrous oxide losses from urine patches in south west Victoria, using a range of application timings of both urine and an inhibitor.
The three experiments conducted at DemoDAIRY at Terang in south west Victoria examined nitrous oxide losses from urine patches. The same treatments were applied across a range of climate and soil conditions at the six field sites, where the impact on pasture production was been measured. These satellite sites were monitored for soil mineral nitrogen fractions and dry matter production.
The aim of the project was to improve understanding of emissions from urinary returns under Australian conditions, and the mitigation potential of inhibitors.
In the DemoDAIRY experiments, there were significant reductions in nitrous oxide emissions:
Experiments assessing the impact of DCD on pasture production had the same treatments applied except that ‘synthetic’ cow urine was used. Results showed statistically significant responses to DCD at some sites at the whole-of-urine-patch level, however when scaled up to paddock level they were negligible.
A field experiment examining the effect of inhibitor on fertiliser nitrous oxide emissions showed that urea coated with 3,4-dimethyl pyrazole phosphate (DMPP) or sprayed with DCD led to a 40% reduction in emissions compared with the use of urea alone. Again, there was no yield advantage from the use of inhibitors.
The lack of pasture response to inhibitor use in this study suggests increases in dry matter production are not likely to provide an incentive for industry to surface apply DCD. As such, although the use of nitrification inhibitors to reduce nitrous oxide emissions has potential for development of a methodology under the Carbon Farming Initiative, preliminary estimates of the cost of application are much larger than likely returns at the current carbon price.
This project was part of the national Nitrous Oxide Research Program, funded by the Australian Government Department of Agriculture, Fisheries and Forestry under its Australia’s Farming Future Climate Change Research Program.
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| Nitrous oxide publications | A bibliographic survey of research publications produced by PICCC's nitrous oxide projects. |