How does biochar influence soil nitrification and nitrification-induced N₂O emissions?

Area of Science:

• Soil Science
• Environmental Science
• Biogeochemistry

Background:

• Nitrification is a key process in soil nitrogen cycling and a significant source of nitrous oxide (N2O) emissions.
• Biochar amendment is proposed to mitigate N2O emissions by influencing soil nitrogen transformations.
• A comprehensive understanding of biochar's quantitative effects on soil nitrification and N2O production is lacking.

Approach:

• A meta-analysis was performed using data from 95 peer-reviewed studies.
• The study quantified the impact of biochar on soil nitrification rates and N2O emissions.
• Investigated the influence of biochar on ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) populations.

Key Points:

• Biochar significantly increased soil nitrification rates by 56% and ammonia-oxidizing bacteria (AOB) abundance by 37%.
• Overall, biochar had no significant effect on nitrification-induced N2O emissions, suggesting a reduced N2O emission fraction.
• Impacts were heterogeneous, with greater effects on nitrification and AOB in poorly pH-buffered, acidic, low-organic carbon, or poor-textured soils.

Conclusions:

• Biochar amendment enhances soil nitrification, primarily by influencing AOB communities.
• The liming and structural effects of biochar are crucial in mediating its impact on soil properties and processes.
• Understanding soil-specific responses to biochar is essential for optimizing its application to regulate soil N cycling and minimize N2O emissions.