Dual versus single inhibitors: Which strategy best mitigates nitrogen losses in coarse‐textured soils? A laboratory evaluation

Abstract Enhanced efficiency fertilizers, including urease inhibitors (UIs), nitrification inhibitors (NIs), and dual inhibitors (DIs [UI + NI]), are widely used to reduce nitrogen (N) losses and improve crop nitrogen use efficiency (NUE). However, their relative effectiveness across multiple nitrogen loss pathways remains unclear. This study aimed to address that gap through a 31‐day soil column experiment and a 25‐day soil incubation study using loamy sand soil. Here we assessed the impact of single and DIs on nitrate (NO 3 ‐N) and ammonium (NH 4 ‐N) leaching, ammonia (NH 3 ) volatilization, nitrous oxide (N 2 O) emissions, and residual soil nitrogen. Treatments included UAN alone and UAN with established (Agrotain, Instinct NXTGEN, and Nitrolock) and novel (VLS‐UI, VLS‐NI, and VLS‐UI + NI) inhibitors. The NIs reduced potential NO 3 − ‐N leaching by up to 20% compared to UAN and outperformed DIs by 10%. In contrast, UIs and DIs did not reduce NO 3 − ‐N leaching. UI treatments increased NH 4 ⁺‐N leaching, while NIs and DIs had no significant effect. DIs were most effective in reducing NH 3 volatilization (82%–89% reduction), surpassing UIs and NIs (68%–75%). N 2 O emissions did not differ significantly among treatments. NIs significantly reduced nitrification potential, with VLS‐NI showing the greatest reduction (22%). Soil pH decline correlated with increased NO 3 − ‐N leaching and nitrification. Total mineral N leaching accounted for 31% of applied N, and gaseous losses (NH 3 + N 2 O) accounted for up to 9%. Overall, NIs were more effective in reducing NO 3 − ‐N leaching and nitrification, while DIs were best for controlling NH 3 volatilization. These findings highlight the importance of selecting nitrogen stabilizers based on dominant loss pathways and site‐specific conditions to optimize NUE and reduce environmental impacts.