Quantitative analysis of biochar in field soil

Biochar is used with increasing frequency as a soil amendment because of its potentially beneficial effects on soil carbon sequestration, crop yield, nutrient leaching and greenhouse gas emissions. Simple methods for the analysis of biochar in soil, however, are currently unavailable. Therefore, we have adapted the “loss on ignition” method for this purpose. The technique requires knowledge of the proportions of both biochar and biochar-free soil that are lost on ignition. One can use values determined prior to the amendment of the soil with biochar, assuming that the values do not change after biochar is incorporated in the soil. We tested these assumptions. Over the course of 15 months, the assumptions proved to be valid under our test conditions. The technique accurately determined a wide range of biochar concentrations in field soil.