Summary
This field study examined long-term biochar persistence and effects on soil fertility by sampling 17 pre-industrial charcoal kiln sites in Wallonia, Belgium, where hardwood biochar has resided in soil for over 150 years. Biochar markedly elevated soil C:N and C:P ratios and increased exchangeable divalent cations (Ca²⁺, Mg²⁺), whilst displaying high cation exchange capacity (414 cmol_c kg⁻¹ for charcoal-C versus 213 for uncharred organic carbon). The authors conclude that biochar's high persistence in soil warrants careful consideration of long-term soil fertility implications, though effects on phosphorus availability were minimal.
UK applicability
The findings are relevant to UK temperate soils and biochar application strategies, particularly regarding soil properties in regions with similar climatic and pedological conditions. The study's long-term observational approach provides evidence on biochar persistence applicable to UK arable and mixed farming systems considering biochar amendments.
Key measures
Charcoal-C content (g kg⁻¹, by differential scanning calorimetry); soil organic carbon (SOC); total nitrogen; C:N and C:P ratios; pH; cation exchange capacity (CEC, cmol_c kg⁻¹); exchangeable K⁺, Ca²⁺, Mg²⁺; nitrates; available, inorganic and total phosphorus; copper availability
Outcomes reported
The study characterised soil properties at pre-industrial charcoal kiln sites (containing 1.8–33.1 g kg⁻¹ charcoal-C) compared with adjacent reference soils, measuring organic carbon, nutrient ratios, cation exchange capacity, and nutrient availability. Key findings included marked increases in organic C:N and C:P ratios, higher exchangeable Ca²⁺ and Mg²⁺ content, and reduced copper availability in charcoal-enriched soils.
Topic tags
Dig deeper with Pulse AI.
Pulse AI has read the whole catalogue. Ask about this record, its theme, or how the findings apply to UK farming and policy — every answer cites the underlying studies.