Microbial Activity, Abundance and Community Composition of an Ohio Agricultural Soil Treated with Biochar.

Biochar, the thermochemical conversion of biomass in an oxygen-limited environment (pyrolysis), has gained interest as a soil amendment to improve soil quality, and as means to mitigate climate change.  The latter is attributed to biochar’s resistance to microbial degradation, thus limiting the amount of carbon (C) being released as carbon dioxide (CO₂) into the atmosphere. The effects of biochar on chemical and physical soil properties have been investigated.  However, much less is known about its effect on soil microbial activity and community composition.  The objective of this study was to determine the effect of different biochars on microbial community composition, abundance and enzyme activity in an Ohio agricultural soil.  A short-term incubation was conducted on a Bennington silt loam soil with amendments of corn and hardwood biochars.  The latter were produced from corn plant residues, and repurposed hardwood at 450 °C and analyzed for C, and nitrogen (N) content.  Biochar was added on a C content basis, without exceeding 2.5 % w/w. Samples were incubated at 22 °C using a randomized design, and were destructively sampled in triplicate at days 15, 30, 45, or 60.  Microbial community abundance and composition were evaluated by phospholipid fatty acid (PLFA) analysis.  Microbial activity was assessed by measuring the potential enzyme activities of β-glucosidase and fluorescein diacetate hydrolysis (FDA).  There were no significant differences in microbial community composition, microbial abundance or FDA activity between control and biochar treatments.  However, the potential activity of β-glucosidase decreased in samples amended with biochar.