氨氧化过程中稻壳生物炭抑制酸性农田土壤N2O排放

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

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.

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.