Analysis of Nitrogen Cycling Genes in Biochar-Amended Soils.

For agricultural soils, tillage practices result in a decrease in organic residue. This degradation also results in acidic soil conditions, as well as soils which have low cation exchange capacities (CEC). Overall, these characteristics lead to overall lower soil fertility. To counteract these conditions, it has been proposed to amend these damaged soils with biochar. The application of biochar has been demonstrated to increase soil organic carbon, as well as provide improved soil CEC and pH levels. One question that remains however is, given the addition of this recalcitrant carbon source, the impact that biochar has on the microbial populations of the amended soils. To this aim we performed a six month analysis of an agricultural soil amended with 1, 2, and 10 percent (w/w) of switchgrass-derived biochar. We used qPCR to measure the levels of the 16S rDNA gene as well as four nitrogen cycling genes (nifH, amoA, nirS, and nosZ); subsequently examining the effect that biochar-amendment had on the abundances of all five qPCR targets. Our results demonstrated that biochar-amendment led to an increase in all genes over non-treated soils, a result that generally trended throughout the entire six month study leading us to conclude that, at least for switchgrass-derived biochar, amending soils with biochar will not prove detrimental to the microbial communities of agricultural soils.