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Assessing Microbial Contributions to N2O Impacts Following Biochar Additions

Xiurong Lin, Kurt A. Spokas, Rodney T. Venterea, Renduo Zhang, John M. Baker, Gary W. Feyereisen
Agronomy 2014 v.4 no.4 pp. 478-496
agricultural soils, biochar, carbon dioxide, carbon dioxide production, chemical inhibitors, denitrification, forest soils, forests, gas emissions, hulls, macadamia nuts, nitrates, nitrification, nitrites, nitrogen, nitrous oxide, prairie soils, sand, soil amendments, soil bacteria, soil fungi
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.