Trials show benefits of Nitrification Inhibitors across NZ

Trials show benefits of Nitrification Inhibitors across New Zealand

A three-year research programme into the effectiveness of the nitrification inhibitor Dicyandiamide (DCD) has confirmed it is a tool to reduce environmental impacts of pastoral farming.

The Nitrous Oxide Mitigation Research (NOMR) trials commenced in autumn 2009. They were conducted in the Waikato (AgResearch Tokanui Research Farm), Manawatu (Massey University), Canterbury (Lincoln University) and South Otago (Telford Farm) dairy regions.

At each location there was a grazing trial to measure the effect of DCD treatment on pasture dry matter (DM) response, small plot trials to measure effects of DCD on nitrous oxide emissions, and DCD movement in soil beneath cattle urine patches, and also, in years two and three, measurement of the effects of DCD application on nitrate leaching.

Previous research has shown that animal urine patches are the main sources of nitrous oxide emissions and nitrate leaching under grazed pastures, and that application of DCD can reduce these losses.

The trials were funded by Fonterra, Dairy NZ, the Ministry of Agriculture and Forestry and the Fertiliser Manufacturers Research Association (FMRA), and managed through the Pastoral Greenhouse Gas Research Consortium (PGgRc).

Early results were presented recently at a Massey University Fertiliser and Lime Research Centre (FLRC) workshop by Project manager Dr Allan Gillingham and showed that DCD application:

• Inhibited nitrous oxide (N2O) emission from urine patches at all sites in all years with an overall average of 50% reduction;
• Decreased N leaching from urine patches by around 40% and in grazed pasture by 21%; and
• DCD application increased winter-spring dry matter production by an average of 3% (range 0-17%); and the response was statistically significant in four of the12 site years.

PGgRc manager Mark Aspin, commenting on the results, notes: “The NOMR trial results are consistent with other research showing reductions in N2O emissions and nitrate leaching where DCD has been used, and fit within the range of those observations. The grazed pasture results are on average at the lower end of the range of results reported in other studies.”

The comprehensive NOMR trial series will result in multiple benefits flowing to farmers as the full analysis is completed, he says.

“Already the data has contributed towards reducing the nitrous oxide emission factor used in the national GHG inventory, by enabling the separation of the contribution of dung and urine. This was a result from work done in a sub-trial in year one of the project. This means a lower calculated national GHG emissions liability from agriculture.”

The trial results will be analysed, published and incorporated into industry courses and tools like the Overseer nutrient management tool.

“The trial has reinforced the opportunity that nitrification inhibitors like DCD offer pastoral farming. But it is important to understand how this will work in local areas, and to achieve best practice in their application we recommend farmers should use informed advice by trained representatives, including the use of Overseer to optimise their use.”

ENDS

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