不同生物质炭对酸化茶园土壤N_2O和CO_2排放的影响

Effects of different biochars on N_2O and CO_2 emission from acidified tea field soil

为了研究不同生物质炭对酸化茶园土壤温室气体排放的影响,采用原料为小麦秸秆、柳树枝、椰壳3种生物质炭,通过室内培养试验来探究不同生物质炭对茶园土壤性质及N_2O、CO_2排放特征的影响。试验中生物质炭添加量为20 g·kg^(-1),同时设置了施氮肥处理,采用尿素作为外加氮源,施氮量为100 mg·kg^(-1)。结果表明,施加生物质炭提高了酸化茶园土壤pH值,柳树枝生物质炭处理土壤pH值最高为6.71,显著高于其他处理。不同生物质炭对土壤DOC含量的影响效果存在差异,柳树枝生物质炭使土壤DOC平均含量增加了95.6%,椰壳生物质炭使土壤DOC含量降低36.1%,小麦秸秆生物质炭则影响不显著。生物质炭通过抑制土壤硝化和反硝化作用降低土壤N_2O的排放,椰壳生物质炭降低N_2O排放比例达91.7%,减排效果最显著。在施氮条件下柳树枝生物质炭对土壤N_2O的减排效果显著低于小麦秸秆和椰壳生物质炭。土壤CO_2的排放通量与pH值、DOC含量均呈极显著正相关,生物质炭促进了土壤CO_2的排放,柳树枝生物质炭处理CO_2的排放显著高于其他处理。此外,外加氮源降低了土壤pH值,增加了土壤N_2O的排放,但是对土壤DOC含量变化无显著影响。

An incubation experiment was conducted to determine the effects of the addition of three kinds of biochars （wheat straw, willow branches, and coconut shell） on acidified tea field soil properties and greenhouse gas emissions. In this experiment, the amount of biochar was 20 g·kg-1, whereas urea was used as an additional nitrogen source for nitrogen fertilizer treatment at the rate of 100 mg· kg-1. The results showed that biochar addition was beneficial to improve the pH value of acidified tea field soil, and the soil pH of the willow biocbar addition treatment was 6.71, which was significantly higher than that of the other treatments. Significant differences were noted between the biochar treatments for soil dissolved organic carbon（ DOC ） content. Compared with that of the control treatment, the soil DOC content increased by 95.6% in the willow bioehar treatment and decreased by 36.1% in the coconut shell biochar treatment, whereas no significant difference in DOC was noted in wheat straw biochar（P〉0.05 ）. The reduction of soil nitrification and denitrification rate caused by biochar applica- tion might have reduced soil N20 emissions, and the application of coconut shell biochar reduced N20 emissions to 91.7%, which was the most significant reduction. When combined with nitrogen application, willow biochar treatment caused significantly higher N20 emissions than those from the other biochar treatments. Compared with N20 emissions in wheat straw and coconut shell biochar treatments, the N20 e- missions in willow biochar treatment were considerably more sensitive to nitrogen addition. Biochar addition promoted C02 emission from the soil, with the highest C02 emissions from the willow biochar treatment and soil C02 fluxes having significant positive correlation with pH val- ue and DOC contents. Moreover, nitrogen addition reduced the soil pH value and increased N20 emission, but had no significant effect on soil DOC content.