Effectiveness of the nitrification inhibitor dicyandiamide and biochar to reduce nitrous oxide emissions

Animal urine from grazing animals is responsible for the majority of New Zealand’s nitrous oxide (N₂O) emissions. A field lysimeter study was conducted to determine the ability of the combination of the nitrification inhibitor dicyandiamide (DCD) and biochar to mitigate N₂O emissions from a winter grazing forage crop soil. The results showed that over a 4 month period, applying cow urine at a rate of 700 kg N ha⁻¹ increased N₂O emissions from 0.7 kg N₂O-N ha⁻¹ to 14.7 kg N₂O-N ha⁻¹. The application of DCD at 20 kg ha⁻¹ reduced total N₂O emissions by 65%. The application of biochar at 5 t ha⁻¹ had no significant effect on N₂O emissions. The combination of DCD with biochar did not lead to greater N₂O reductions than DCD alone. These results indicated that DCD was highly effective whereas biochar was ineffective in reducing N₂O emissions in the winter forage soil