Crop Productivity Meta-analysis
Citation: Jeffery S, Verheijen FGA, van der Velde M, Bastos AC (2011). A quantitative review of the effects of biochar application to soils on crop productivity using meta-analysis. Agriculture, Ecosystems & Environment 144(1): 175–187. https://doi.org/10.1016/j.agee.2011.08.015
What it is: The first widely cited meta-analysis of biochar effects on crop productivity (yield or above-ground biomass). Its subgroup results are where the vault’s liming and water-holding explanations come from.
Key figures
| Figure | Value | Where | Check |
|---|---|---|---|
| Grand mean productivity effect | +10% (small but statistically significant) | Abstract (Europe PMC record) | ✓ abstract |
| Range of subgroup means | −28% to +39% | Abstract | ✓ abstract |
| Soil pH subgroups | Acidic +14%, neutral +13% | Abstract | ✓ abstract |
| Texture subgroups | Coarse +10%, medium +13% | Abstract | ✓ abstract |
| Application rate | Largest positive effect at 100 t ha⁻¹ (+39%) | Abstract | ✓ abstract |
| Feedstock | Poultry litter +28% (strongest significant positive); biosolids −28% (only significant negative) | Abstract | ✓ abstract |
| Study length | Available studies limited to 1–2 years | Abstract | ✓ abstract |
| Typical research rates of ~5–50+ t ha⁻¹ | Used in vault rate tables | — | not re-checked (full text not accessible) |
Use with care
- The authors read the pH and texture subgroups as pointing to liming, better water holding, and nutrient availability. That’s an interpretation of subgroup means, not a tested mechanism.
- The 100 t ha⁻¹ result is a research extreme, not a farm rate.
- Every underlying study ran only 1–2 years, so this says nothing about long-term yield effects.
Related: compares tropical vs temperate yields · Crop Yield Effects · Key Sources