[Effects of Biochar Application Rates on Greenhouse Gas Emissions in the Purple Paddy Soil].

In order to explore the effects of different amounts of biochar applied in purple paddy soil on greenhouse gas (GHG) emissions, potted experiments using a static opaque chamber and gas chromatography method were used to study the regulations and influences of biochar on soil greenhouse gas emission using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10 t ·hm biochar+NPK (LBC), 20 t ·hm biochar+NPK (MBC), and 40 t ·hm biochar+NPK (HBC). ① Soil CH emission flux reduced significantly with all biochar application treatments; the emission flux followed the order, from large to small, of NPK > CK > LBC > MBC > HBC. The CH emission flux of each treatment showed a single peak curve, and the peak value was mainly concentrated in the late growth stage of the paddy cropland. During the entire observation period, the emission flux of CH was between -0.05 mg ·(m ·h) and 47.34 mg ·(m ·h). The CO emission flux of each treatment was complicated and ranged from 32.95 mg ·(m ·h) to 1350.88 mg ·(m ·h). The CO emission flux of the LBC and MBC treatments showed bimodal curves, and the CO emission flux of other treatments showed single peak curves. In addition, all biochar treatments delayed the peak time of the CO emission flux. The NO emission flux of each treatment ranged from -309.39 to 895.48 μg ·(m ·h), and the NO emission flux of the LBC treatment showed a bimodal curve, while other treatments showed single peak curves. ② Compared with the CK treatment, biochar treatment can significantly reduce the cumulative emissions of CH and promote the cumulative emissions of CO and NO. The average amount of CH cumulative emissions followed the order CK > LBC > MBC > HBC, while the average amount of CO cumulative emissions followed LBC > MBC > HBC > CK, and the average amount of NO cumulative emissions followed HBC > MBC≈LBC > CK. Compared with conventional fertilization treatment, different application rates of biochar addition significantly reduced CH and CO emissions. As more biochar was added, CH and CO cumulative emissions were lower. Although the regulation of NO cumulative emissions on biochar addition was not obvious, the application of nitrogen fertilizer could promote the emission flux of NO to some extent. ③ Over the time scale of 100 years, the integrated global warming potentials (GWP) of CH and NO emission under different biochar treatment were decreased significantly, indicating that biochar combined with chemical fertilizer is an effective GHG emission reduction measure.