ARS | Publication request: The Influence of Biochar on Soil Processes

Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2010
Publication Date: N/A

Technical Abstract: Biochar may be a good soil amendment with the potential to sequester Carbon (C) for long periods of time. In addition, biochar added to soils could increase water infiltration and retention, increase cation exchange capacity and perhaps soil aggregation. However the effects of biochar on soil biological processes are virtually unknown. It has been reported in the literature that the addition of charcoal to forest humus caused a loss of native soil organic matter (SOM) (Science 320:629, 2008). If this is the case there could be a tremendous negative effect trading inert C for SOM-C. Our objective was to compare biochar and activated charcoal to determine their effect on biological activity of soil, and to estimate the loss of native SOM-C from these soils. We used two approaches in this study, first we incubated soil with biochar or activated charcoal to monitor CO2 evolution and nitrogen mineralization. In the second approach we used a similar set up but we trapped the CO2 in a NaOH solution precipitated the CO2 with a StCl2 solution. Titration of the remaining solution quantified total CO2. The precipitate was dried, ground and prepared for 13C analysis by IRMS. In the first study the biochar seemed to increase N mineralization in sandy soils and decrease N mineralization in silt loam soils but not to a significant degree. Activated charcoal increased the reduction in N mineralization. Biochar decreased nitrate production probably due to adsorption of NH4+ substrate. The analysis of d13C of the CO2 evolved showed that most of the CO2 in the first few days of incubation came from the biochar not soil organic matter. Since the extra CO2 loss from biochar amended soils over the control came from the biochar it is doubtful that biochar will increase soil organic matter loss.