Separated pathways for biochar to affect soil N₂O emission under different moisture contents

Area of Science:

• Soil Science
• Environmental Science
• Biogeochemistry

Background:

• Drylands are significant sources of global nitrous oxide (N₂O) emissions.
• Biochar, a soil amendment, has the potential to mitigate N₂O production.
• Soil moisture variability in drylands necessitates understanding biochar's impact under varying conditions.

Purpose of the Study:

• To investigate the effect of two distinct biochars (B300 and B500) on soil N₂O emissions across a range of soil moisture contents.
• To elucidate the mechanisms by which biochar influences N₂O production and reduction pathways.
• To assess the potential of biochar for suppressing N₂O emissions in dryland environments.

Main Methods:

• Column experiments were conducted using two biochars (B300, B500) and five soil moisture levels (18-30% w/w).
• Measurements included soil N₂O emissions, dissolved organic carbon content, and the abundance ratio of key microbial genes (nosZ/nirS) involved in N₂O cycling.

Main Results:

• B300 increased N₂O emissions at lower moisture (18-24%) by enhancing dissolved organic carbon and microbial N₂O production.
• At higher moisture (27-30%), B300 decreased N₂O emissions by promoting N₂O reduction, indicated by an increased nosZ/nirS ratio.
• B500 showed minimal impact on N₂O emissions at lower moisture but reduced emissions at higher moisture by increasing the nosZ/nirS ratio.

Conclusions:

• Biochar's effect on soil N₂O emissions is highly dependent on soil moisture content.
• The influence of biochar on N₂O cycling is mediated by changes in soil organic matter and microbial community structure (nosZ/nirS ratio).
• Specific biochar types and soil moisture conditions can be leveraged to optimize N₂O emission mitigation strategies in drylands.