Figure S1. Soil respiration rate in different studies as a function of time, in treatments where no PyOM was added, i.e. in controls. The size of the points is proportional to the weight of each case calculated using Eqn (1).

Figure S2. Distribution of the time points recorded in the database.

Figure S3. Priming effect as a function of the PyOM C content. The data base was divided into six time quantiles to highlight the different influence of the PyOM C content over time. The influence of PyOM C content is particularly strong in the first 15 days (first time quantile).

Figure S4. Distribution of PyOM-C added to the soil in the different experiment (left axis). The line represents the impact of cumulative PE calculated over 1 year (0.3 mg g−1 soil, Fig. 2) on PyOM C abatement capacity, expressed as percentage of PyoM C added to the soil (right axis).

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