Pyrolysis temperature has greater effects on carbon and nitrogen biogeochemistry than biochar feedstock when applied to a sandy forest soil

Abstract

Most studies evaluating effects of biochar on soil properties and plant responses have focused on agricultural soils, with limited focus on forested settings. There is increasing interest in applying biochar in forests because of the perceived benefits to soils and productivity, and because biochar could be produced from large quantities of residual woody biomass that is typically unmerchantable due to its size or quality. To test if findings from agricultural soils are applicable to forest soils, we applied biochars created from black ash or balsam fir woody feedstock pyrolyzed at 350 °C or 450 °C to a nutrient-poor forest soil in a laboratory incubation. To assess the influence of biochar on carbon (C) and nitrogen (N) cycling, we measured fluxes of carbon dioxide (CO₂) and nitrous oxide (N₂O), leaching of dissolved inorganic and total N and organic C (DOC), and post-incubation C and N soil chemistry. We found mixed effects, but a generally clear response to pyrolysis temperature. The lower temperature (350 °C) biochar generally increased CO₂ fluxes and had greater N and DOC leaching while the higher temperature (450 °C) biochar appeared to retain N and had little impact on CO₂ fluxes. The black ash feedstock had greater C leaching than balsam fir, but responses were similar across other metrics suggesting that these woody feedstocks produce biochar with similar properties.

Citation

Toczydlowski, Alan J.Z.; Slesak, Robert A.; Venterea, Rodney T.; Spokas, Kurt A. 2023. Pyrolysis temperature has greater effects on carbon and nitrogen biogeochemistry than biochar feedstock when applied to a sandy forest soil. Forest Ecology and Management. 534(5): 120881. https://doi.org/10.1016/j.foreco.2023.120881.