Reducing Nitrous Oxide Emissions Associated With Fertiliser Using Nitrogen Enriched Biochar

ABSTRACT

There is a need for agricultural practices that decrease nitrous oxide emissions while sustaining yields for food production. In the current paper, we investigate the possibility of reducing emissions by co‐applying or enriching biochar with mineral nitrogen and using it as a fertiliser. By measuring the nitrous oxide fluxes from soil incubation experiments with biochar and mineral N fertiliser at 60%, 70% and 80% water‐filled pore space (WFPS), we examined the effect of biochar on fertilisation associated nitrous oxide emissions at different soil moisture levels. Furthermore, we examined the effects of different biochar feedstocks and mineral N application methods, either as mineral N enriched biochar (biochar soaked in mineral N solution and dried) or as co‐applied biochar and mineral N fertiliser. Nitrous oxide emissions were negligible at 60% WFPS, whereas at 80% WFPS mean accumulated N ₂ O emissions over 34 days of 12.1 μg N ₂ O‐N g soil ⁻¹ for the mineral N treatment and 9.1 μg N ₂ O‐N g soil ⁻¹ for the co‐applied biochar and mineral N treatment were found, but the difference was not statistically significant. When applying biochar from four different feedstocks, accumulated nitrous oxide emissions were not significantly different between them, but the mean accumulated soil nitrous oxide emissions across all mineral N enriched biochars did show a significant reduction compared to the mineral N positive control. These results indicate a potential for using mineral N enriched biochar for reducing mineral N fertiliser associated N ₂ O emissions.