Urease inhibitor and biochar independently affected N₂O emissions from Camellia oleifera soils

Nitrous oxide (N2O) is a long-lived greenhouse gas that impacts climate change. Agricultural soils with intensive nitrogen (N) application are the main source of N2O emissions. Reducing N2O emissions from N-fertilised soils is, therefore, important for climate change mitigation. The application of urease inhibitor and/or biochar provides the potential for mitigating N2O emissions. However, the interactive effect of urease inhibitor and biochar on N2O emissions remains limited. In this study, an incubation experiment was performed to investigate the gradients of urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) ( 0, 0.08, 0.16, and 0.24%) and biochar additions (0, 2.5, and 5%) on N2O emissions from urea-fertilised Camellia oleifera soils. Results showed that urease inhibitor decreased, but biochar increased cumulative N2O emissions. No significant interactive effects were observed between urease inhibitor and biochar on the cumulative N2O emissions, but cumulative N2O emissions were decreased by NBPT under a 2.5% biochar addition rate. Soil N2O emission rates were negatively correlated with net ammonification and N mineralisation rates and positively correlated with net nitrification rates. This study indicates that NBPT, with the characteristic of delaying urea hydrolysis, can be better than biochar in mitigating N2O emissions from urea-fertilised soils of C. oleifera plantations.