Approach

In a nationwide network of coordinated field experiments, we are testing and evaluating measures to reduce ammonia emissions from the application of synthetic nitrogen fertilizers at ten different sites. The focus is on the nitrogen fertilizers urea, calcium ammonium nitrate, ammonium nitrate-urea solution and ammonium sulfate-urea.

We are investigating the following options as mitigation measures:

• Choice of nitrogen form
• Usage of stabilized fertilizers (with urease and nitrification inhibitors)
• Application time
• Fertilizer injection

At all sites, we quantify ammonia emission and fertilizer efficiency and record factors that influence losses, such as site and crop characteristics, weather, and field management. Our investigations focus on winter wheat, the most important field crop in Germany in terms of area.

We use the results to build models of ammonia emission and nitrogen dynamics. The aim is to use measured values and models to estimate emissions and the effect of mitigation measures in Germany on a site-specific basis.