Nitrification inhibitors are proposed as a robust and scalable GHG reduction measure for crop production. However, whether this is an efficient, practical and environmentally sound measure to reduce fertiliser-induced N₂O emissions under conditions of Central Europe is controversially discussed by science, policy and practice. On the one hand, there is the potential to significantly reduce both direct and indirect N₂O emissions by inhibiting nitrate formation and thus improve the efficiency of nitrogen fertilisation. On the other hand, scientifically robust and site-differentiated results are lacking that reliably assess NI effects taking several points in consideration: i) the site-differentiated annual N₂O emissions and nitrate leaching, ii) the ecological long-term efficacy of the inhibitors and their influence on other environmentally and climate-impacting emissions (e.g. ammonia emissions), and (iii) the overall evaluation as a climate protection measure, taking into account climate protection effects, ecological risks, and economic and crop production effects.

The aim of the interdisciplinary joint project is the site-differentiated evaluation of the use of nitrification inhibitors in combination with nitrogen fertilisers as a climate protection measure. The collaborative project comprises both a Germany-wide network of seven coordinated field sites and laboratory experiments at four research institutes, analysing the effects of nitrification inhibitors on soil nitrogen dynamics, direct N₂O emission, nitrate leaching as well as nitrogen efficiency and yield level and quality. Furthermore, integrated studies on effects of nitrification inhibitors on the soil microbiome involved in the biogeochemical transformation of soil nitrogen (target and non-target organisms), translocation of inhibitors, interaction with other environmental and climate-impacting emissions (ammonia, methane) as well as the economic assessment of nitrification inhibitors as a climate protection measure are included. Additional focal points are the modelling and regionalisation of the effects of nitrification inhibitors, the quantification of their possible climate protection effects in Germany's greenhouse gas emissions inventory, their comprehensive assessment as a potential climate protection measure and the transfer of knowledge into practice.