Greenhouse gas emissions from agricultural soils contribute substantially to global atmospheric composition. Nitrous oxide (N2O) is one important greenhouse gas induces global warming. Nitrification inhibitors (NI) or biochar can be effective soil N2O emission mitigation strategies for agricultural soils. However, due to differences in crop physiological traits or agricultural management, the effectiveness of mitigation strategies varies among agricultural systems. Camellia oleifera is a woody oil plant widely grown and requires intensive N input, which will potentially increase N2O emissions. Thereby, mitigation of N2O emissions from C. oleifera field soil is vital for sustainable C. oleifera development. Besides NI, incorporation of C. oleifera fruit shell-derived biochar into its soil will benefit waste management and simultaneous mitigation of N2O emissions but this has not been investigated. Here, we conducted two studies to examine effects of biochar addition and NI (dicyandiamide, DCD) application on N2O emissions from C. oleifera field soil with different N (urea or NH4NO3) and incubation temperatures. Biochar effects on nitrification rates varied among N treatments. Biochar applied in combination with DCD further reduced nitrification rates (for urea treatment, decreased from 1.1 to 0.3 mg kg-1 day-1). Biochar addition consistently increased soil N2O emissions (for urea treatment, increased from 0.03 to 0.08 ng g-1 h-1) and their temperature sensitivity. DCD application reduced soil N2O emissions with greater reductions with urea application. In future cultivation of intensively managed C. oleifera gardens, NI should be applied to mitigate N2O emissions if biochar is added, especially when urea is used.
Keywords: Biochar application; Camellia oleifera; Nitrification; Nitrification inhibitors; Nitrogen mineralization; Nitrous oxide; Warming.