Urea Inhibitors Reduce Volatile Sulfur Emissions from Grassland

Urea-based fertilisers are widely used in agriculture, and their environmental impacts have prompted policy efforts to reduce associated nitrogen losses. However, their application and mitigation strategies have rarely been considered in the context of other biogeochemical cycles. This study examines how urea inhibitors, applied as a mitigation strategy to reduce nitrogen losses, affect sulfur gas emissions from temperate grassland soil–plant systems. Using a proton transfer reaction mass spectrometer (PTR-MS), emissions were monitored from twelve automated chambers under three treatments (control, urea only, urea with inhibitor). Urea application increased emissions of methanethiol (MeSH), dimethyl disulfide (DMDS), and dimethyl sulfide (DMS), particularly under solid fertiliser and higher initial soil moisture conditions. Emissions from the urea with inhibitor treatment were consistently lower, with the strongest suppression observed for MeSH. These findings highlight the potential for nitrogen mitigation strategies to alter sulfur cycling in an agricultural environment.