The accumulation of rhizodeposits in organo-mineral fractions promoted biochar-induced negative priming of native soil organic carbon in Ferralsol

Zhe (Han) Weng, Lukas Van Zwieten, Bhupinder Pal Singh, Ehsan Tavakkoli, Stephen Kimber, Stephen Morris, Lynne M. Macdonald, Annette Cowie

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Organo-mineral interactions control the stabilisation of soil organic matter (SOM) in mineral soils. Biochar can enhance these interactions via a range of mechanisms including Al-dominant cation bridging in acidic soils, ligand exchange, H-bonding, and π- π-bonding with polycyclic aromatics. But, field-based evidence of their magnitude is lacking. Here we assessed the role of organo-mineral interactions on the observed biochar-induced negative priming of native soil organic carbon (SOC) in a Ferralsol under annual ryegrass. Using repeated pulse labelling, the magnitude of production and fate of recently photosynthesised 13C was traced amongst: soil plus root respiration, root biomass, soil aggregates and aggregate-associated C fractions. Biochar (Eucalyptus saligna, 450 °C) amendment (30 Mg ha−1) increased total belowground 13C recovery by 10% compared to the unamended control over the 12 month sampling period. We detected the greatest quantity of rhizodeposit in the mineral-protected SOM within macroaggregates (250–2000 μm). Through synchrotron-based spectroscopic analysis of bulk soils, we provide evidence of a mechanism for biochar-induced negative priming which is the accumulation of rhizodeposits in organo-mineral (i.e. aggregate-protected and silt/clay-bound) fractions.
Original languageEnglish
Pages (from-to)91-96
Number of pages6
JournalSoil Biology and Biochemistry
Volume118
Early online dateDec 2017
DOIs
Publication statusPublished - Mar 2018

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