WHAT THE EVIDENCE SAYS
A 42-day experiment added seven 13C-labelled litters spanning contrasting C:N ratios to low- and high-fertility soils at 23°C and 33°C. High-quality litter with C:N below 25 produced positive priming of existing soil carbon, whereas lower-quality litter above 25 produced negative priming. Priming magnitude was generally larger in high-fertility soil, while temperature had a comparatively minor effect; total carbon balance remained positive over the experiment.
WHY IT MATTERS / OUR READ
‘Add organic matter’ is not a single carbon treatment. Substrate quality and nutrient context change whether new inputs stimulate microbes to mineralize older soil carbon or suppress that loss, which matters when translating amendment practices into carbon claims.
CAVEATS / UNCERTAINTY
This was a 42-day laboratory incubation, not a field management trial. Priming responses can change over longer periods and under intact roots, moisture variability and real litter mixtures; a positive short-term carbon balance does not establish long-term sequestration.
SOURCE
Carbon Balance and Management — primary study
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