Assessing Microbial Contributions to N2O Impacts Following Biochar Additions

Abstract

Varying degrees of soil nitrous oxide (N2O) mitigation have been observed following biochar applications. Laboratory incubation experiments were conducted using soils from agriculture, forest, prairie, and a sterilized sand to examine the relative contributions of bacteria and fungi to this N2O alteration. Selective chemical inhibitors were used to distinguish the relative contributions of fungal and bacterial groups to N2O production/suppression in each soil type following a fast-pyrolysis macadamia nut shell biochar (10% w/w) addition. Overall, suppressed production of N2O was initially observed between the agricultural and prairie soils following biochar addition and stimulation of N2O production was observed in the biochar amended forest soil. However, if the N2O production that was observed in the biochar control (sterile sand and biochar = 4.2 ± 0.7 ng-N g−1 day−1) was subtracted from all treatments, N2O production following biochar addition was consistently lower in all soils following biochar additions. In terms of the microbial contributions, there were no significant differences in N2O production between the microbial inhibitor treatments, despite CO2 production rate differences. Therefore, the response in the N2O production to biochar could not be directly attributed to a particular microbial group (fungi or bacteria). These results suggest the presence of abiotic production or consumption routes for nitrogen species in biochar amended soils.

Keywords

• biochar
• nitrous oxides
• soil fungi
• iron