Rice Residue-Based Biochar Mitigates N2O Emission from Acid Red Soil

Biochar application is considered an effective approach to mitigating nitrous oxide (N2O) emissions from agricultural soils. However, the mechanisms of biochar to mitigate N2O emissions from acidic red soils are still unclear. Therefore, the present study aims to underpin mechanisms associated with rice residue-based biochar in mitigating N2O emissions from acid soils. Soil treated with different rates of biochar control, from 1%, 2%, and 3%, and different soil properties, including soil pH, microbial biomass carbon (MBC), NH4+-N, NO3−-N, genes abundance (nosZ, nirK, AOA, and AOB), and enzymatic activities ((nitrate reductase (NR) and urease (UR)) were studied. The application of 3% biochar increased the soil pH (5.21–6.48), MBC (565–685 mg/kg), NO3−-N contents (24.23–44.5 mg/kg), genes abundance (nosZ, nirK, AOA, and AOB) and UR activity. The highest N2O emission (43.60 μg kg−1) was recorded and compared with the application of 1% (26.3 μg kg−1), 2% (18.33 μg kg−1), and 3% biochar (8.13 μg kg−1). Applying 3% biochar effectively reduced the N2O emission due to increased soil pH, MBC, NO3−-N contents, genes abundance (nosZ, nirK, AOA, and AOB), and weakened NH4+-N and NR activities. Therefore, increasing soil pH, genes abundance, and weakened nitrification following the addition of rice residue-based biochar can effectively reduce the N2O emissions from acidic red soils.