Historical soil amendment with charcoal increases sequestration of non‐charcoal carbon: a comparison among methods of black carbon quantification

Summary

We have shown previously that soil with historical (> 150 years) applications of charcoal had larger recent ( C4 ‐maize derived) carbon content than adjacent soil; however, we could not determine whether there was an effect on older, C3 ‐plant‐derived, soil organic carbon ( SOC ). Therefore, we assessed the effect of historical additions of charcoal on the sequestration of recent and older SOC with a combination of δ 13 C analysis and different quantification techniques for black carbon ( BC ): dichromate oxidation ( Cr 2 O 7 ), chemo‐thermal oxidation ( CTO ‐285) and differential scanning calorimetry ( DSC ). Topsoils cropped with maize ( Zea mays ) under former charcoal production sites ( N = 12) were identified in the field as black spots and had a larger (3.5%, P < 0.05) percenta