Journal
SOIL BIOLOGY & BIOCHEMISTRY
Volume 118, Issue -, Pages 91-96Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2017.12.008
Keywords
Negative priming; Plant-biochar-soil interactions; C-13 partitioning; Synchrotron; Soft X-ray; NEXAFS
Categories
Funding
- Department of Agriculture, Fisheries and Forestry (DAFF) National Biochar Initiative II (NBI II)
- Australian Synchrotron, Victoria, Australia [AS151_SXR_9599]
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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 pi-pi-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 C-13 was traced amongst: soil plus root respiration, root biomass, soil aggregates and aggregate-associated C fractions. Biochar (Eucalyptus saligna, 450 degrees C) amendment (30 Mg ha(-1)) increased total belowground C-13 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 mu m). 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.
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