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Microspectroscopic visualization of how biochar lifts the soil organic carbon ceiling

journal contribution
posted on 2024-11-17, 15:25 authored by Zhe (Han) Weng, Lukas van Zwieten, Ehsan Tavakkoli, Michael T Rose, Bhupinder Pal Singh, Stephen Joseph, Lynne M MacDonald, Stephen Kimber, Stephen Morris, Terry J Rose, Braulio S Archanjo, Caixian Tang, Ashley E Franks, Hui Diao, Steffen Schweizer, Mark J Tobin, Annaleise R Klein, Jitraporn Vongsvivut, Shery LY Chang, Peter M Kopittke, Annette Cowie
The soil carbon (C) saturation concept suggests an upper limit to the storage of soil organic carbon (SOC). It is set by the mechanisms that protect soil organic matter from mineralization. Biochar has the capacity to protect new C, including rhizodeposits and microbial necromass. However, the decadal-scale mechanisms by which biochar influences the molecular diversity, spatial heterogeneity, and temporal changes in SOC persistence, remain unresolved. Here we show that the soil C storage ceiling of a Ferralsol under subtropical pasture was raised by a second application of Eucalyptus saligna biochar 8.2 years after the first application—the first application raised the soil C storage ceiling by 9.3 Mg new C ha−1 and the second application raised this by another 2.3 Mg new C ha−1. Linking direct visual evidence from one-, two-, and three-dimensional analyses with SOC quantification, we found high spatial heterogeneity of C functional groups that resulted in the retention of rhizodeposits and microbial necromass in microaggregates (53–250 µm) and the mineral fraction (<53 µm). Microbial C-use efficiency was concomitantly increased by lowering specific enzyme activities, contributing to the decreased mineralization of native SOC by 18%. We suggest that the SOC ceiling can be lifted using biochar in (sub)tropical grasslands globally.

Funding

Australian Nuclear Science and Technology Organisation (15754)

History

Journal title

Nature Communications

Volume

13

Issue

1

Language

English

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