Regionalized ammonia emission abatement by urease inhibitor treatment of urea for agro-environmental conditions of Western Central Europe

Urea is the most widely used synthetic fertilizer worldwide, covering 16% of fertilizer consumption in Germany in 2022. It has a notable propensity to release nitrogen (N) in the form of ammonia (NH₃) when applied to soil, contributing to environmental pollution, and indirectly increasing nitrous oxide (N₂O) emissions. This loss of NH₃ from urea also represents a loss of N for crop production. Consequently, urease inhibitors (UIs) are increasingly applied in agricultural practice to mitigate N losses, and to ensure compliance with regulations recently introduced in some European countries. This development should be reflected in reported emissions at national level. Representative emission and abatement factors are, therefore, required for a precise calculation of NH₃ losses from urea application. While some meta-studies suggest abatement factors on a global scale, their applicability across countries is questionable, due to variable environmental and crop conditions, especially within Europe.

We conducted an analysis of the current international literature to derive a new emission factor for NH₃ losses after application of urea with UIs for Western Central Europe, that is suitable for integration into the German emission inventory and inventories of other countries with similar cropping conditions. Based on a linear mixed-effects model, we found an abatement factor of 60 %. In contrast to theoretical expectations, environmental factors, such as temperature, soil pH, soil CEC and land use had no significant influence on this abatement effect. Our findings emphasize the need for further comprehensive data sets to refine emission calculations at the national level, reflecting effects of regional weather and cropping conditions on the NH₃ abatement by use of UIs.