不同施氮水平对冬油菜根际微生物群落特征的影响

Effects of different levels of nitrogen application on the characteristics of rhizosphere microbial communities of winter rape

【目的】探究冬油菜根际微生物群落特征对不同施肥的响应,确定油菜氮肥适宜用量,为土壤培肥和调控土壤生态功能提供理论依据【方法】田间试验在油菜种植区(武穴)开展,在秸秆还田条件下设置5个处理:不施氮肥(SN0)、N 120 kg/hm^(2)(SN120)、N 180 kg/hm^(2)(SN180)、N 240 kg/hm^(2)(SN240)和N 300 kg/hm^(2)(SN300),采用16S rRNA和ITS高通量测序方法,分析根际土壤细菌和真菌群落结构及其功能变化,同时测定土壤理化性质和作物产量。【结果】1)与不施氮处理(SN0)相比,施氮处理降低了根际土壤有效磷含量(24.63%~35.10%)和速效钾含量(39.67%~59.77%),提高了全氮(6.18%~14.60%)和碱解氮含量(7.18%~34.99%)。SN180处理提升土壤全氮和碱解氮含量的幅度最小,SN300处理提升幅度最大。随着氮肥的增加,有机碳含量呈增长趋势,pH呈下降趋势,油菜产量先增加后减少,SN180产量最高。2)随着施氮量的递增,细菌的Chao1指数呈递增趋势;与SN0处理相比,SN180处理提高了真菌Shannon指数7.20%。施氮肥改变了细菌和真菌群落结构。与SN0处理相比,SN180处理提高了子囊菌门、担子菌门和拟杆菌门相对丰度,降低了被孢霉门和酸杆菌门相对丰度,减缓了鞘氨醇单胞菌和芽孢杆菌属的减少趋势,富集了红假单胞菌属(Rhodopseudomonas)和线黑粉酵母属(Filobasidium)。与SN0处理相比,施氮处理均降低了化学异养、固氮、芳香化合物降解和几丁质分解功能菌群的丰度,同时降低undefined saprotroph丰度。3)环境因子与群落关联网络分析和RDA分析显示,土壤有机碳(SOC)、碱解氮(AN)、全氮(TN)和有效磷(AP)含量是影响真菌群落的主要环境因子,SOC和AP含量是细菌群落的主要影响因子。无色穗孢属(Achroiostachys)与SOC含量呈负相关,与AN呈正相关。Emericellopsis与AN和TN含量呈显著负相关,与pH呈显著正相关。SOC与类诺卡氏属(Nocardioides)显著正相关,与厌氧粘细菌属(Anaeromyxobacter)显著负相关。【结论】从产量、群落多样性及富集有益微生物角度综合分析,冬油菜施用N 180 kg/hm^(2)是较合理的氮肥用量。

【Objectives】To investigate the response of inter-root microbial communities of winter oilseed rape to different fertilizers,and to determine the appropriate amount of nitrogen fertilizer for oilseed rape,in order to provide a theoretical basis for soil fertilization and regulation of soil ecological functions.【Methods】The field experiment was carried out in the oilseed rape planting area(Wuxue),and five treatments were set up under strawreturning conditions,namely,no nitrogen fertilizer(SN0),nitrogen fertilizer N 120 kg/hm^(2)(SN120),nitrogen fertilizer N 180 kg/hm^(2)(SN180),nitrogen fertilizer N 240 kg/hm^(2)(SN240) and nitrogen fertilizer N 300 kg/hm^(2)(SN300).The community structure and functional changes of bacteria and fungi in rhizosphere soil were analyzed using 16S rRNA and ITS high-throughput sequencing methods,while soil physicochemical properties and yield were determined.【Results】1) Compared with SN0,nitrogen fertilizer application reduced available phosphorus(24.63%-35.10%) and available potassium(39.67%-59.77%),and increased total nitrogen(6.18%-14.60%) and alkali-hydrolyzed nitrogen(7.18%-34.99%) in rhizosphere soil.SN180 increased soil total nitrogen and alkalihydrolyzed nitrogen to the smallest extent,while SN300 increased the most.With the increase of nitrogen fertilizer,organic carbon showed an increasing trend,pH showed a decreasing trend,and yield increased first and then decreased,with SN180 having the highest yield.2) With the increase of nitrogen application,Chao1 index of bacteria showed an increasing trend.Compared with SN0,SN180 increased the Shannon index of fungi by 7.20%.Application of nitrogen fertilizer changed the community structure of bacteria and fungi.Compared with SN0,SN180 increased the relative abundance of Ascomycetes,Basidiomycetes and Bacteroidetes,decreased the relative abundance of Mortierellomycota and Acidobacteria,and slowed down the decreasing trend of Sphingomonas and Bacillus.Rhodopseudomonas and Filobasidium were enriched.Compared with SN0,nitrogen fertilizer application reduced the abundance of chemical heterotrophic,nitrogen fixation,aromatic compound degradation and chitin decomposition functional bacterial groups,and also reduced the abundance of undefined saprotroph.3) The analysis of environmental factors and community association network and RDA analysis showed that soil organic C(SOC),alkali-hydrolyzed N(AN),total N(TN) and available P(AP) were the main environmental factors affecting the fungal community,and SOC and AP were the main environmental factors affecting the bacterial community.Achroiostachys was negatively correlated with SOC and positively correlated with AN.Emericellosis was significantly negatively correlated with AN and TN,and significantly positively correlated with pH.SOC was significantly positively correlated with Nocardioides and negatively correlated with Anaeromyxobacteria.【Conclusions】From the perspective of yield,community diversity and enrichment of beneficial microorganisms,applying nitrogen fertilizer of N 180 kg/hm^(2) is a reasonable amount for winter rapeseed.