Biochar has been shown to increase microbial activity, alter microbial community structure, and increase soil fertility in arid and semi-arid soils, but at relatively high rates that may be impractical for large-scale field studies. This contrasts with organic amendments such as manure, which can be abundant and inexpensive if locally available, and thus can be applied to fields at greater rates than biochar. In a field study comparing biochar and manure, a fast pyrolysis hardwood biochar (10 tons per acre), dairy manure (19 tons per acre), a combination of biochar and manure at the aforementioned rates, or no amendment (control) was applied to an Aridisol (n=3) in fall 2008. Plots were annually cropped to corn. Surface soils (0-12 inches) were sampled directly under corn plants in late June 2009 and early August 2012, and assayed for microbial community fatty acid methyl ester profiles and six extracellular enzyme activities involved in soil carbon, nitrogen, and phosphorus cycling. Arbuscular mycorrhizal fungal colonization was assayed in corn roots in 2012. Biochar had no effect on microbial biomass, community structure, extracellular enzyme activities, or arbuscular mycorrhizal fungi root colonization of corn. In the short-term, manure amendment increased microbial biomass, altered microbial community structure, and significantly reduced the soil concentration of the arbuscular mycorrhizal fungal fatty acid methyl ester biomarker 16:1'5c. Manure also reduced the percent root colonization of corn by arbuscular mycorrhizal fungi in the longer-term. Depending on the rate applied, biochar may not cause significant shifts in the microbial community status and therefore not affect soil nutrient cycling activities and nutrient availability.