For a reliable recommendation for the use of nitrification inhibitors as a climate protection measure, some uncertainties still have to be clarified. This concerns the correct quantification of their effects, especially under German cultivation conditions, and the occurrence of possible side effects when they are used. In detail, the following questions are addressed in the NitriKlim project:

• Effect of inhibitors on annual N₂O emissions from different sites, i.e. beyond their short-term effect on the immediate period after fertilization
• Effects of long-term use of the inhibitors on agricultural soils on the nitrification and the effect of newly applied nitrification inhibitors
• Quantification of the reduction in nitrate leaching and associated indirect N₂O emissions by nitrification inhibitors under different site conditions
• Effects on yield, quality and fertilization management through the use of nitrification inhibitors in cereal and vegetable production, including an economic assessment
• Recording of possible negative environmental effects through influences on the microbial life in the soil, through possible release of active substances as well as through ammonia and methane emissions

Finally, a comprehensive assessment of the use of nitrification inhibitors as a climate protection measure will be carried out.