氨氧化过程中稻壳生物炭抑制酸性农田土壤N2O排放

为探明在土壤环境有利于氨氧化作用发生的条件下，稻壳生物炭对酸性农田土壤N₂O排放的影响，将生物炭分别按质量比0%（对照）、2%、5%和10%与土壤充分混匀，开展为期17d的室内静态土壤培养实验，研究土壤N₂O排放速率的日变化以及整个培养期间的N₂O累积排放量.同时，测定了培养终态土壤样品的pH值、NH₄⁺-N、NO₃^--N、NO₂^--N和溶解性有机碳（DOC）含量，分析稻壳生物炭对土壤N₂O排放影响的机理.结果表明，不同稻壳生物炭添加量均显著抑制了酸性农田土壤的N₂O排放（P<0.001），且以5%和10%处理的抑制作用最明显；与对照处理相比，2%、5%和10%处理的N₂O累积排放量分别减少了87.68%、94.59%和96.90%.培养前后土壤pH值、NH₄⁺-N和NO₃^--N含量的变化表明，稻壳生物炭显著促进了土壤的硝化作用，尤其是5%和10%处理.线性回归分析表明，土壤N₂O排放速率与NO₂^--N含量显著正相关（P<0.01），且NO₂^--N含量对N₂O排放速率的解释程度为45%.由于稻壳生物炭促进了土壤的硝化作用，使NO₂^-更易转化为NO₃^-，减少了NO₂^-积累，进而减少了通过硝化菌反硝化作用途径产生的N₂O.培养结束时，5%和10%处理的DOC含量显著高于对照处理，但培养过程中，稻壳生物炭并未显著促进土壤有机碳矿化.

Rice husk-derived biochar inhibited N2O emission from acidic arable soil under the condition of facilitating ammonia oxidation

The objective of this research is to examine the effect of rice husk-derived biochar on nitrous oxide (N₂O) emission in acidic arable soil. The indoor static soil incubation experiment was carried out for 17days after evenly mixing biochar (0% (control), 2%, 5%, and 10% in the mass ratio) with the soil sample to investigate the diurnal variation of N₂O emission rate and the cumulative N₂O emission of the soils. Meanwhile, to unravel the mechanisms that control N₂O emission from the soil amended with biochar, the pH, NH₄⁺-N, NO₃^--N, NO₂^--N, and dissolved organic carbon (DOC) contents of the soils were determined at the end of incubation. The results indicated that the rice husk-derived biochar significantly (P<0.001) inhibited N₂O emission of the acidic arable soil under the condition of facilitating ammonia oxidation, especially for the 5% and 10% treatments. Compared with the control, the cumulative N₂O emission of the 2%, 5%, and 10% treatments decreased by 87.68%, 94.59%, and 96.90%, respectively. The changes of pH, NH₄⁺-N, and NO₃^--N contents of the soil amended with different amounts of biochar before and after incubation showed that the biochar promoted soil nitrification process, especially for the 5% and 10% biochar addition rates. The linear regression analysis indicated that N₂O emission rate was significantly (P<0.01) positively correlated with NO₂^--N content at the end of incubation, and NO₂^--N content could explain 45% variance of N₂O emission rate. The biochar-induced nitrification enhancement that accelerated the conversion of NO₂^- to NO₃^- resulted in N₂O emission decrease by nitrifier denitrification pathway. DOC contents of the 5% and 10% treatments at the end of incubation were significantly higher than the control. However, organic carbon mineralization was not enhanced with biochar addition during the incubation.