长期不同养分缺乏对冬油菜土壤微生物群落组成及多样性的影响

Effects of long-term different nutrient deficiency on the composition and diversity of soil microbial community in winter oilseed rape

为探明长期不同养分缺乏对冬油菜根际与非根际土壤细菌和真菌群落组成结构及多样性的影响,以江汉平原中稻-冬油菜田间定位试验为研究对象,选取施磷钾肥不施氮肥(-N)、施氮钾肥不施磷肥(-P)、施氮磷肥不施钾肥(-K)和施用氮磷钾肥(NPK)4个处理,于成熟期采集各处理冬油菜非根际土壤(标记为0)和根际土壤(标记为1)。基于Illumina MiSeq高通量测序技术对土壤样本的细菌16S rDNA和真菌ITS进行扩增、测序,并结合生物信息学分析根际和非根际土壤中细菌和真菌群落组成和多样性。结果表明:长期养分的投入缺乏造成土壤pH和养分含量均有不同程度的降低。相比非根际土壤,冬油菜根际土壤的有机质、有效磷和速效钾含量有富集的趋势,而缓效钾差异不显著。长期平衡施肥(NPK处理)条件下,油菜根际土壤的细菌多样性比非根际土壤高,而根际真菌多样性低于非根际土壤。门分类水平上,各处理土壤中的细菌优势物种是绿弯菌门、酸杆菌门和变形菌门,平均相对丰度分别为30.9%、25.7%和17.6%;真菌优势物种是子囊菌门和担子菌门,平均相对丰度分别为52.0%和6.3%。相比NPK处理,-N、-P和-K处理对冬油菜根际和非根际细菌、根际真菌群落分布有显著影响,但对非根际真菌群落分布无明显作用,从而导致各处理的优势属种类型和相对丰度差异显著。冗余分析结果表明,pH、速效钾和有效磷含量对土壤细菌群落结构的影响最为显著,而有机质和碱解氮含量对真菌群落结构的影响最为明显。可见,长期不同养分缺乏会显著改变冬油菜根际细菌和真菌群落的组成结构及其多样性,尤其是缺磷、缺氮,其次是缺钾。因此,平衡施肥仍是维持农田微生物生态系统平衡与稳定的重要措施。

To explore the effects of different types of nutrient deficiency on the composition of bacterial and fungal communities and diversity in the rhizosphere and non-rhizosphere soil of winter oilseed rape,a long-term field experiment on fertilizer effect with paddy-upland rotation was carried out on a Jianghan plain in 2011.Four treatments were set up:phosphate and potassium application but no nitrogen fertilizer(-N),nitrogen and potassium application but no phosphate fertilizer(-P),nitrogen and phosphate application but no potassium fertilizer(-K),nitrogen,phosphorus and potassium fertilizer application(NPK).At the maturity period of winter oilseed rape,samples of non-rhizosphere soil(marked as 0)and rhizosphere soil(marked as 1)were collected from each treatment.Amplification and sequencing of the bacterial 16S rDNA and fungal ITS in soil samples were checked based on Illumina MiSeq high-throughput sequencing technology.Community composition and diversity of bacteria and fungi in rhizosphere and non-rhizosphere soil were analyzed using bioinformatics.The results showed that the soil pH and nutrient content decreased to varying degrees because of the long-term nutrient deficiency.The content of organic matter,available P,and available K in winter oilseed rape rhizosphere soil tended to be greater than in non-rhizosphere soil,but the change of available K content showed no significant difference between treatments.Under balanced fertilization conditions(NPK treatment),the bacterial diversity of rhizosphere was greater than that of non-rhizosphere soil,while the fungal diversity of rhizosphere soil was lower than that of non-rhizosphere soil.At the phylum level,the dominant species of bacteria were Chloroflexus,Acidobacteria and Proteobacteria,with an average relative abundance of 30.9%,25.7%and 17.6%,respectively;The dominant species of fungi were Ascomycota and Basidiomycota,and the relative abundance averaged 52.0%and 6.3%.For-N,-P and-K treatments,the distribution of the rhizosphere and the non-rhizosphere bacterial and rhizosphere fungal communities changed significantly,but the distribution of non-rhizosphere fungal communities was stable,compared with NPK treatment,which induced significant differences in types of species and relative abundance among the four treatments at the genus level.The results of redundancy analysis showed that pH,available P and available K content had the most significant effects on bacterial community structure,while organic matter and available N content had the most significant effect on fungal community structure.Long-term nutrient deficiency could significantly change the community structure and diversity of bacteria and fungi in the rhizosphere of winter oilseed rape.Phosphate fertilizer and nitrogen fertilizer were found to have the greatest impact on microbial communities,followed by potassium fertilizer.These findings show that balanced fertilization is still an important measure to maintain the balance and stability of the farmland microbial ecosystem.