On-farm effects of urease and nitrification inhibitors on resource use, soil C and climate impact

Efficient nitrogen (N) use in crops is vital for promoting sustainable and profitable agriculture and has significant implications for greenhouse gas (GHG) mitigation. While urease (UI) and nitrification inhibitors (NI) are known to influence N transformations, soil N availability, and N utilization efficiency (NUE) in ammonium sulfate urea (AS-HS), their impacts on the carbon (C) and water cycles are less well understood. To address this knowledge gap while reflecting realistic agronomic conditions, we conducted an on-farm strip trial in northeastern Germany, focusing on examining potential interactions among nitrogen (N), carbon (C), and water cycling. The trial compared non-fertilized plots with AS-HS, AS-HS+UI, and AS-HS+UI+NI treatments across a maize–wheat–barley rotation. Compared to AS-HS, the application of UI and UI+NI generally reduced cumulative N2O emissions up to 72% and NH3 emissions up to 91%, while it improved the N recovery efficiency (NRE) and the agronomical N use efficiency (ANUE). In addition, the use of inhibitors shifted the net ecosystem C balance (NECB) from source to sink. Although evapotranspiration (ET) increased slightly, the agronomical water use efficiency (aWUE) remained similar or even improved due to a higher biomass production. The same was observed for the net GHG emission which were similar for AS-HS and AS-HS+UI and slightly improved for AS-HS+UI+NI. These effects of UI and UI+NI on not only the N but also C and water cycles underscores the complex interactions among N, C, and water dynamics in agroecosystems, highlighting both the environmental impact and potential benefits of using UI and NI inhibitors.Graphical abstract