Biochar built soil carbon over a decade by stabilizing rhizodeposits

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Weng, Z, Van Zwieten, L, Singh, BP, Tavakkoli, E, Joseph, S, Mcdonald, LM, Rose, TJ, Rose, MT, Kimber, SWL, Morris, S, Cozzolino, D, Araujo, JR, Archanjo, BS & Cowie, A 2017, 'Biochar built soil carbon over a decade by stabilizing rhizodeposits', Nature Climate Change, vol. 7, pp. 371-376.

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Biochar can increase the stable C content of soil. However, studies on the longer-term role of plant–soil–biochar interactions and the consequent changes to native soil organic carbon (SOC) are lacking. Periodic 13CO2 pulse labelling of ryegrass was used to monitor belowground C allocation, SOC priming, and stabilization of root-derived C for a 15-month period—commencing 8.2 years after biochar (Eucalyptus saligna, 550 °C) was amended into a subtropical ferralsol. We found that field-aged biochar enhanced the belowground recovery of new root-derived C (13C) by 20%, and facilitated negative rhizosphere priming (it slowed SOC mineralization by 5.5%, that is, 46 g CO2-C m−2 yr−1). Retention of root-derived 13C in the stable organo-mineral fraction (<53 >μm) was also increased (6%, P < 0.05). Through synchrotron-based spectroscopic analysis of bulk soil, field-aged biochar and microaggregates (

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