A preliminary investigation into the reliability of soil carbon analytical techniques
Barwe, AJ; Ayanda, Fatai; Owen, Alun; Crew, Adrian
Authors
AJ Barwe
Fatai Ayanda
Alun Owen
Dr Adrian Crew Adrian.Crew@uwe.ac.uk
Senior Lecturer in Environmental Microbiology
Abstract
The estimation of soil carbon is essential to land management recommendations and policy realisation and climate change abatement. The measurement of soil carbon relies on new and established techniques that are of uncertain reliability but nevertheless provide the basis for carbon-related farming subsidies. We conducted a series of simple experiments to examine the recovery rates of spiked materials of two major standard techniques: loss-on-ignition (LOI) and combustion catalytic oxidation with NDIR detection via a TOC Analyser. Carbon was removed from samples of standard loamy clay soil, vermiculite and horticultural sand, which were subsequently spiked with naturally occurring organic compounds with different structural properties; glucose, stearic acid, glycine, humic acid and cellulose. These compounds were added to the solid substrates at concentrations of 1-6% carbon (w/w). The recoveries of these compounds demonstrated that both techniques revealed significant errors in estimating the percentage carbon (%C) of the spiked material. LOI generally overestimated %C from glycine and glucose added to all materials and from all added compounds added to vermiculite. The extent of the overestimation was inconsistent and between 125% and 1400%. TOC overestimated %C in more specific circumstances: humic acid in loamy clay soil and sand, glucose in sand, and stearic acid in loamy clay soil and vermiculite. However, the extent of the overestimation by TOC was more limited than LOI at a maximum of 250% at low concentrations and generally within 150%. The TOC tended to underestimate compounds in the vermiculite except stearic acid, contrary to the results from LOI, which also underestimated %C from the more complex organic compounds in the loamy-clay soil and sand. The results demonstrate the urgent need to evaluate the methods used for soil carbon analysis for reliability and accuracy to inform effective land management and carbon estimations.
Presentation Conference Type
Poster
Conference Name
BSSS Annual Conference: Sustainable Soils for People and Planet
Ensure sustainable consumption and production patterns
Take urgent action to combat climate change and its impacts
Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss
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A preliminary investigation into the reliability of soil carbon analytical techniques
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