长期施肥对稻田土壤微生物群落结构及氮循环功能微生物数量的影响

Effects of long-term fertilization on the microbial community structure and the population of N cycle-related functional microorganism in paddy soil

【目的】稻田是陆生生态系统中重要的氮库之一,在氮素生物地球化学循环中具有重要地位。研究不同施肥处理对稻田土壤微生物群落结构及其功能的影响具有重要意义。【方法】田间试验位于江苏省金坛市,在取样时试验已进行了6年。施肥处理包括:不施肥对照(CK)、施化肥(CF)、化肥+猪粪混施(CMF)、化肥+秸秆混施(CSF)。采用高通量测序和定量PCR方法测定稻田土壤微生物群落结构及氮循环相关功能微生物数量。【结果】在施用肥料6年后,土壤全碳、可溶性有机碳、全氮、铵态氮和硝态氮含量均不同程度地提高。与CF相比,CSF和CMF处理土壤pH升高,全碳、可溶性有机碳与养分含量升高。CK与施肥处理的土壤细菌群落结构差异明显,不同施肥处理的细菌群落结构之间有明显差别。聚类结果显示,CK与CMF处理细菌群落聚类更接近,CF处理和CSF处理细菌群落结构更为接近;与CK相比,CF、CMF、CSF处理土壤中氨氧化细菌(AOB)和铁氨氧化微生物Feammox A6的丰度显著提高,其中Feammox A6分别增长87.6%、158%和157%。冗余分析结果表明,施肥过程及其对土壤化学性质的改变显著影响土壤细菌群落的组成和分布。【结论】施肥导致的反应底物(NH4+、NO3-含量)及土壤理化性质的差异,是土壤微生物群落结构和功能微生物数量响应的主要决定因素。不施肥与化肥配施猪粪的土壤细菌群落聚类更接近,施化肥与化肥配施秸秆的细菌群落结构更为接近。施肥对氨氧化细菌AOA数量影响不明显,但显著提高氨氧化古菌AOB和厌氧铁氨氧化功能微生物Feammox A6的数量,特别是有机肥(猪粪、秸秆)提高Feammox A6数量的效果大于化肥。长期单施化肥土壤中厌氧氨氧化细菌丰度显著降低,反硝化功能基因nirK、nosZ丰度显著增高;化肥配施猪粪土壤中的厌氧氨氧化细菌丰度变化不明显,反硝化功能基因narG、nirK、nosZ丰度显著增高;化肥配施秸秆处理厌氧氨氧化细菌丰度变化不明显,反硝化功能基因nirK、nosZ丰度显著增高。

【Objectives】Paddy field is regarded as one of the important terrestrial nitrogen(N)reservoirs.Microorganism community and quantity play an essential role in N biogeochemical cycle and are regarded as indicators of soil fertility.Thus,we studied the effects of different fertilizer treatments on the structure and function of soil microbial communities in a paddy field.【Methods】This study was conducted in a long-term paddy field experiment in Jinhua City,Jiangsu Province.The treatments on the field include:no fertilizer application(control,CK),pure chemical fertilizer(CF),chemical fertilizer plus crop straw(CSF),and chemical fertilizer plus pig manure(CMF).Soil samples were taken in the sixth year of the experiment,while the microbial community structure and the population of N cycle-related functional microorganisms were measured using quantitative PCR and high-throughput sequencing.【Results】The CMF and CSF treatments significantly increased the total carbon(TC)and soluble organic carbon(DOC)contents more than CF did,whereas total nitrogen(TN),NH4^+-N and NO3^--N increased in similar pattern under the three fertilization treatments.Cluster analysis showed there were differences in soil bacterial community structure between CK and fertilization treatments while soil pH and NH4^+-N and NO3^--N content were the dominant factors.The bacterial community clusters of CK and CMF treatments were close,while the bacterial community structure of CF and CSF treatments were also close.Compared with CK,the abundance of ammonia oxidizing bacteria(AOB)and iron ammonia oxidizing microorganism(Feammox A6)significantly increased in CF,CMF and CSF treatments.Feammox A6 increased by 87.6%,158% and 157%,respectively.【Conclusions】Long-term fertilization affected soil chemical properties,and the NH4^+,NO3^- contents and soil pH were dominantly responsible for the soil microbial community succession and composition.The cluster of microorganism community under combined application of chemical fertilizer and pig manure was close to that of control,while the clusters of soil microorganism community structure under both pure chemical fertilization and combined application of chemical and crop straw were close.Abundance of AOA did not change with long-term fertilization,but abundance of AOB and Feammox A6 increased.Chemical fertilizer plus pig manure or straw increased Feammox A6 population more than pure chemical fertilizer.The gene copies of denitrification functional groups(nirK,nosZ)were significantly higher under pure chemical fertilization compared to other treatments.