A novel approach, using 13C natural abundance, for measuring decomposition of biochars in soil

There is growing interest in the use of artificially-produced biochar (black carbon) as a soil amendment, with potential to increase soil carbon (C), reduce greenhouse gas emissions, improve soil properties, and enhance agricultural productivity. However, promoting the use of biochar for increasing soil C sequestration will depend on demonstrating its ability to persist in soil. The biochar produced during incomplete combustion of biomass at temperatures > 200°C, and under limited oxygen supply (pyrolysis), is considered highly resistant to biological degradation due to its increased chemical recalcitrance (aromaticity) compared with the parent feedstock. Despite some exceptions, C in natural biochar has been shown to posses turnover time of a few 100 to >1000 years in soil. However, little research has been undertaken to: (i) document turnover rate of artificially-produced (in thermal reactors) biochars applied to soil, (ii) measure and account for any priming effect of biochar addition on turnover of 'native' soil C, and (iii) elucidate stabilisation mechanisms of biochar C in soil.