Biochar Effects On Soil Microbial Communities and Resistance of Enzymes to Stress.

Biochar, a product of the pyrolysis of organic material, has received wide attention as a means to improve soil fertility and crop productivity, absorb pollutants in soil, and sequester carbon to mitigate climate change. Little information exists on the short- and longer-term effects of biochar on soil microbial communities and enzyme activities, relative to other organic amendments such as manure. In this field study, a fast pyrolysis biochar (CQuest) derived from oak and hickory hardwood was applied to replicate field plots in fall 2008, at a rate of 22.4 Mg ha^-1 dry wt. Other plots received dairy manure (42 Mg ha^-1 dry wt), a combination of biochar and manure, or no amendment (control). Plots were annually cropped to maize.  Surface soils (0-10 cm) were sampled directly under maize plants in late June 2009 and early August 2012, one and four years after treatment application, and assayed for microbial community fatty acid profiles and extracellular enzyme activities. In addition, arbuscular mycorrhizal (AM) fungal colonization was assayed in corn roots in 2012. At the rate applied, biochar had no or only slight effects on microbial communities, enzyme activities and AM root colonization relative to manure. Biochar slightly altered microbial community structure in 2009 but not 2012 and had no effects on six different enzymes at the rate applied. A laboratory incubation study is underway to determine if higher rates of biochar will stabilize soil enzymes and increase enzyme resistance to heat stress.