Summary
This field experiment examined how biochar (20 Mg ha⁻¹) and lime (2 Mg ha⁻¹) applications affect soil greenhouse gas emissions and gas transport properties in a maize-cropped system. Biochar substantially reduced cumulative N₂O emissions whilst decreasing CO₂ emissions less than lime; the mechanism appears linked to improved soil aeration, as N₂O emission peaks corresponded to periods of reduced soil gas diffusivity. The findings suggest that soil gas diffusion capacity (Dp/D0) may be a key explanatory variable for understanding N₂O mitigation by biochar amendments.
UK applicability
These findings from a temperate field experiment may be broadly relevant to UK arable systems, particularly maize cultivation, though soil type, climate, and management practices differ regionally. The identification of soil gas diffusivity as a mechanistic driver of N₂O emissions could inform UK farm practices and policy around biochar use for greenhouse gas mitigation, subject to further validation in diverse UK soil conditions.
Key measures
Cumulative N₂O and CO₂ emissions (automated chamber measurements); relative soil gas diffusion coefficient (Dp/D0) at varying matric potentials; in situ soil water content; number of days with Dp/D0 < 0.02
Outcomes reported
The study measured cumulative N₂O and CO₂ emissions from soil treated with biochar or lime, and related these to changes in soil gas diffusion coefficients (Dp/D0) measured in situ and in the laboratory. Biochar significantly reduced N₂O emissions compared to control and lime treatments, with N₂O peaks associated with decreases in soil gas diffusivity below a critical threshold of 0.02.
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