The effect of young biochar on soil respiration

The low temperature pyrolysis of organic material produces biochar, a charcoal like substance. Biochar is being promoted as a soil amendment to enhance soil quality, it is also seen as a mechanism of long-term sequestration of carbon. Our experiments tested the hypothesis that biochar is inert in soil. However, we measured an increase in CO 2 production from soils after biochar amendment which increased with increasing rates of biochar. The ∂ 13C signature of the CO 2 evolved in the first several days of the incubation was the same as the ∂ 13C signature of the biochar, confirming that biochar contributed to the CO 2 flux. This effect diminished by day 6 of the incubation suggesting that most of the biochar C is slowly decomposing. Thus, aside from this short-term mineralization increasing soil C with young biochar may indeed be a long-term C storage mechanism.