过量施肥对设施菜田土壤菌群结构及N2O产生的影响

【背景】N_2O是一种很强的温室气体,其温室效应强度大约是CO_2的265倍。土壤氮肥施加量是影响N_2O排放的重要因素,而厌氧条件下微生物反硝化则是N_2O产生的重要途径。【目的】研究过量施肥条件下蔬菜大棚土壤菌群结构变化及其对N_2O气体排放的影响。【方法】利用自动化培养与实时气体检测系统(Robot)监测土壤厌氧培养过程中N_2O和N_2排放通量,比较过量施肥和减氮施肥模式下土壤N_2O排放模式的差异。通过Illumina二代测序平台对这2种不同施肥处理的土壤微生物群落进行高通量测序,研究不同施肥量对土壤菌群组成的影响。【结果】过量施肥土壤中硝酸盐的含量大约是减氮施肥土壤的2倍,通过添加硝酸盐使2种土壤的硝酸盐含量均为60 mg/kg或为200 mg/kg时,过量施肥土壤在厌氧培养前期N_2O气体的产生量及产生速度都明显高于减氮施肥土壤。另外,过量施肥导致土壤菌群结构发生显著改变,并且降低了土壤微生物的多样性。相对于减氮施肥,过量施肥方式富集了Rhodanobacter属的微生物。PICRUSt预测结果显示,传统施肥没有显著改变反硝化功能基因相对丰度。【结论】长期过量氮肥施用显著增加了土壤N_2O的排放,可能原因是施肥改变了包括氮转化相关微生物在内的土壤菌群组成,从而影响了土壤N_2O气体的形成与还原过程。

Effect of overuse nitrogen fertilizer on bacterial community and N2O emission from greenhouse soil

Background] N2O is a powerful greenhouse gas with a 265-fold stronger warming potential than CO2. Fertilization plays an important role in affecting N2O emission from soils driven by bacterial community, and denitrification is the major source of N2O under anaerobic conditions. Objective] To investigate N2O emission and greenhouse soil bacterial community response to the overuse of nitrogen fertilizer. Methods] Robot system was used to monitor the denitrifying gas (N2O and N2) kinetics of soils during anaerobic incubation, and compare the difference of N2O emissions between traditional fertilization and reduced nitrogen fertilization. The soil microbial community structure was analyzed by sequencing the 16S rRNA gene V3?V4 region using Illumina MiSeq. Results] The nitrate concentration in conventional nitrogen fertilization soil (CNS) was about two folds higher than that in reduced nitrogen fertilization soil (RNS). CNS showed higher N2O accumulation and emission rate during earlier anaerobic-incubation stage although the nitrate content was adjusted to the same level in both types of soil. Traditional fertilization significantly changed the bacterial community structure, and decreased the microbial diversity. Although Rhodanobacter was the most abundant genus both in CNS and RNS, it was enriched by traditional fertilization. However, relative abundance of denitrifying functional genes (narG, nirK, norB, nosZ) had little response to the overuse of fertilizer. Conclusion] Traditional fertilization reshaped the bacterial community in soil. Overuse nitrogen fertilizer influenced N2O emission from soil via changing the microbial community including the microbiota related with nitrogen transformations.