Methane and Nitrous Oxide Flux after Biochar Application in Subtropical Acidic Paddy Soils under Tobacco-Rice Rotation

Abstract

Biochar amendment is a good means of mitigating methane (CH4) and nitrous oxide (N2O) emissions. However, the effects of biochar amendment on N2O and CH4 reduction in soil under rotation with different soil moisture contents is not well understood. To understand CH4 and N2O flux from soil with biochar amendment under water-unsaturated and water-saturated conditions, a field experiment was conducted in a tobacco-rice rotation field in subtropical China to investigate N2O and CH4 emissions following soil amendment with tobacco straw biochar at rates of 0, 10, 40 and 80 t·ha−1 (B0, B10, B40 and B80, respectively). N2O and CH4 emissions were monitored by a closed-chamber method in the water-unsaturated tobacco (UT) and water-saturated rice (SR) seasons during the 2015 planting season. The soil pH increased from 5.4 in the control to 6.1 in the soil amended with biochar at 80 t·ha−1 in the UT season. During both the UT and SR seasons, with biochar amendment at 40 and 80 t·ha−1, the soil bulk density (BD) decreased, while the soil organic matter (SOM) and available potassium (Av. K) contents increased. N2O flux was significantly greater in UT than in SR in the controls but decreased with the application of biochar during both the UT and SR seasons. The cumulative CH4 emission decreased with the rate of biochar application and the methanotroph pmoA gene copy number in soils and increased with the methanogenic archaea 16Sr DNA gene copy number in soils during the rice-cropping season. These results indicated that biochar amendment could decrease methanogenic archaea and increase of methanotroph pmoA gene, which are the mechanistic origin for CH4 reduction.

Review of Large-Scale Biochar Field-Trials for Soil Amendment and the Observed Influences on Crop Yield Variations

“…Biochar application (20 t ha −1 ) in this study did not have any effect on SOC or soil pH, whereas it increased the soil DOC, Total N, NH 4 + -N significantly and reduced NO 3 − -N concentrations compared to non-amended soil (Yang et al, 2019). Another study reported that the biochar addition reduced the abundance of methanogenic archaea resulting in lower CH 4 emission (Huang et al, 2019). Beyond its application in the agricultural context, biochar has also gained interest in the waste management industry as a media to enhance control of landfill gas emissions.…”

Hydrochar did not reduce rice paddy NH3 volatilization compared to pyrochar in a soil column experiment

“…Pyrolysis biochar (PC, pyrochar) has been intensive studied in carbon sequestration, soil improvement and greenhouse gas mitigation 6,7 . However, PC always has a high pH value, usually ranged from 8-10, depends on different conditions 8 .…”

In‐situ biochar production associated with paddies: Direct involvement of farmers in greenhouse gases reduction policies besides increasing nutrients availability and rice production

“…Regard to the previous studies, methanogenic anaerobic bacteria are the main cause of CH 4 production in soils (Bridgham et al, 2013; Cai et al, 2018), and methanotrophic aerobic bacteria are able to consume the produced CH 4 and convert it to O 2 and CO 2 in the presence of oxygen. The decrease in CH 4 emissions following biochar addition should be associated with a decrease in the ratio of methanogens to methanotrophs, because of increasing soil porosity (Figure 2), better aeration, and increasing oxygen availability induced by biochar functional groups (Huang, Wang, et al, 2019) which support a wide range of aerobic methanotrophs.…”

“…The C : N ratio is also an important parameter of biochar that can be used to interpret the effects of biochar on preventing N 2 O emission from soils (Huang, Wang, et al, 2019). The produced biochar from crop residues (such as rice husk or straw) with a C : N ratio > 40 immobilizes nitrogen (Asadi et al, 2021; Y. F. Cui et al, 2017; Singh Mavi et al, 2018).…”