Nitrification inhibitors

Nitrification inhibitors are substances that slow or stop the conversion of soil ammonium to nitrate. There are several compounds that can be used in this manner, including dicyandiamide (DCD), the active ingredient in Ballance's nitrification inhibitor, DCn.

Nitrification inhibitors are of value in farm systems as they can help reduce unwanted environmental impacts of nitrogen. These impacts include the effects of nitrate leaching (which can contribute to the deterioration of waterways) and nitrous oxide emissions (which raise the level of greenhouse gases in the atmosphere). Using a nitrification inhibitor may also result in increased pasture production.

In order for the most benefit to be gained from the use of nitrification inhibitors, they need to be applied before soil ammonium (derived from the urea in stock urine or fertiliser) is converted to nitrate, and also before the first drainage event of the season is due.

Results from trial work indicate that on well-drained soils, DCn should be applied in April/May and July/August. The April/May application covers the high-risk leaching period over winter; a July/August application further retains the autumn nitrogen in the system and also ensures coverage through spring.

On wetter soils with artificial drainage systems and where stock are wintered off, most nitrate leaching will occur during early winter drainage, so best results are acheived from two applications of DCn around March and May