Biochar's Impact on Soil N Dynamics and Nitrous Oxide Emissions in a Deficit Irrigation Maize System.

To curb increasing greenhouse gas (GHG; CO₂, N₂O and CH₄) emissions from the agricultural sector, particularly nitrous oxide (N₂O), producers must seek practices that maximize improve nitrogen (N) use efficiency and decrease N loss to the environment. Biochar soil amendments demonstrate the ability to mobilize N and decrease soil N₂O production in laboratory incubations, but exhibit mixed results in the field. Biochar impacts on soil redox may play an important role in biochar’s ability to mitigate N₂O efflux by controlling nitrification and denitrification rates in soils. We tested this hypothesis using a woody biochar in a fertilized maize cropping system with deficit irrigation treatments (full irrigation, temporally limited irrigation and 50% deficit irrigation). This study used a comprehensive GHG sampling protocol to capture both temporal and spatial variability in GHG emissions by combining dynamic cavity ring down spectroscopy measurements using automatic chambers with traditional gas chromatography measurements using static chambers. Results of this field study indicate no significant impact of biochar on soil mineral N availability, grain N uptake or cumulative N₂O emissions. Biochar plots did show a 16.6% decrease in cumulative N₂O across irrigation regimes, consistent with other field trails exploring the impact of biochar on N₂O emissions, but there was large spatial variability.