AUTHOR=Qi Jian-Qing , Yuan Hai-Yan , Zhuang Qi-Lu , Zama Eric-Fru , Tian Xiao-Fei , Tao Bao-Xian , Zhang Bao-Hua 

TITLE=Effect of different types of biochar on soil properties and functional microbial communities in rhizosphere and bulk soils and their relationship with CH4 and N2O emissions

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1292959

DOI=10.3389/fmicb.2023.1292959

ISSN=1664-302X

ABSTRACT=<p>Biochar as an agricultural soil amendment plays vital roles in mediating methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) emissions in soils. The link between different types of biochar, bulk soil, and rhizosphere microbial communities in relation to CH<sub>4</sub> and N<sub>2</sub>O emissions is being investigated in this study. The rice pot experiment was conducted using biochar at two temperatures (300°C and 500°C) in combination with three biochar levels (0, 2, 10% w/w). Soil properties and the abundance of genes associated with CH<sub>4</sub> and N<sub>2</sub>O emissions from both rhizosphere and bulk soils were investigated. The study also aimed to examine the structure of microbial communities (<italic>pmoA</italic>, <italic>nosZ</italic>) in rhizosphere and bulk soils whereas CH<sub>4</sub> and N<sub>2</sub>O emissions were monitored while growing rice. Results showed that biochar at 300°C and 10% incorporation significantly increased the CH<sub>4</sub> emissions by up to 59% rise compared to the control group. Random Forest analysis revealed that the ratio of <italic>mcrA/pmoA</italic> along with the abundance of <italic>mcrA</italic> from both rhizosphere and bulk soils, the abundance of <italic>AOA</italic>, TN, DOC, and the community composition of <italic>pmoA</italic>-harboring microorganisms from both bulk and rhizosphere soils were important predictors of CH<sub>4</sub> emissions. Therefore, the ratio of <italic>mcrA/pmoA</italic> in rhizosphere soil and the abundance of <italic>AOA</italic> in bulk soil were the main factors influencing CH<sub>4</sub> emissions. Variation Partitioning Analysis (VPA) results indicated that the effects of these factors on bulk soil were 9% of CH<sub>4</sub> emissions variations in different treatments, which contributed more than rhizosphere soils’ factors. Moreover, random forest analysis results indicated that the abundance of <italic>AOB</italic> in bulk soil was the most important predictor influencing N<sub>2</sub>O emissions. The VPA result revealed that the factors in rhizosphere soil could explain more than 28% of the variations in N<sub>2</sub>O emissions. Our study highlights that rhizosphere soil has a more significant effect than bulk soil on N<sub>2</sub>O production. Our findings further the understanding of the link between bulk and rhizosphere attributes, and their impact on CH<sub>4</sub> and N<sub>2</sub>O emissions in paddy soils. In summary, we recommend the application of biochar at 500°C and 2% incorporation rate for agricultural production in the area.</p>