减氮对麦玉轮作农田土壤反硝化细菌群落结构和多样性的影响

Effects of nitrogen reduction on community structure and diversity of denitrifying bacteria in wheat–maize rotation farmland

探究减氮对华北地区麦玉轮作农田土壤反硝化细菌群落结构和多样性影响,为华北地区麦玉轮作农田氮肥管理提供技术支持,本研究以不施氮为对照(CK),设置2个施氮量,分别为常规施氮量(纯氮300 kg·hm^(-2),N2)、减氮20%(纯氮240 kg·hm^(-2),N1),提取土壤DNA,用nirS(细胞色素cd1-亚硝酸还原酶)、nirK(Cu-亚硝酸还原酶)引物扩增后采用MiSeq PE300测序技术,研究施氮量对麦玉轮作农田土壤性状及nirS、nirK反硝化细菌群落结构及多样性的影响。结果表明,3个处理nirS、nirK反硝化细菌α-多样性指数无显著差异,nirS反硝化细菌α-多样性高于nirK。减氮显著影响nirS、nirK反硝化细菌物种组成。减氮对nirS、nirK反硝化细菌门水平及nirK纲水平物种组成无显著影响,但显著降低了nirS反硝化细菌Deltaproteobacteria(δ-变形菌纲)相对丰度;减氮显著影响nirS、nirK属水平物种组成。硝态氮、速效磷、pH值是影响土壤nirS反硝化细菌属水平群落结构主要环境因子;pH值是影响土壤nirK反硝化细菌属水平群落结构的主要环境因子。研究表明,适量减氮不影响反硝化细菌α-多样性,但显著影响反硝化细菌属水平群落组成和群落结构,减氮主要是通过影响土壤性状及微生物群落结构进而影响农田土壤N2O排放。

To provide technical support for nitrogen fertilizer management in wheat–maize rotation farmland in North China Region,we investigated the effects of nitrogen reduction on the community structure and diversity of denitrifying bacteria communities.With no nitrogen application as control(CK),two nitrogen application rates were set,namely the conventional nitrogen application rate(300 kg·hm^(-2),N2)and nitrogen reduction rate of 20%(240 kg·hm^(-2),N1).Thereafter,soil DNA was extracted,amplified with nirS and nirK primers,and MiSeq PE300 sequencing technology was subsequently used to study the effects of nitrogen application rate on soil properties and nirS and nirK denitrifying bacteria community diversity in wheat–maize rotation farmland.The results demonstrated that,no significant difference in theα-diversity index of nirS and nirK denitrifying bacteria was observed among the three treatments,and theα-diversity of nirS denitrifying bacteria was higher than that of nirK.Nitrogen reduction significantly affected the species composition of nirS and nirK denitrifying bacteria.Moreover,it had no significant effect on the phylum level species composition of nirS and nirK denitrifying bacteria and the class level species composition of nirK denitrifying bacteria,but significantly reduced the relative abundance of Deltaproteobacteria of nirS denitrifying bacteria.Further,it significantly affected the genus level species composition of nirS and nirK denitrifying bacteria.Nitrate nitrogen,available phosphorus,and pH were the main soil environmental factors affecting the community structure of nirS denitrifying bacteria.pH value was the main soil environmental factor affecting the community structure of nirK denitrifying bacteria.In conclusion,moderate nitrogen reduction did not affect theα-diversity of denitrifying bacteria,but it significantly affected the community composition and structure of denitrifying bacteria at the genus level;thus,nitrogen reduction mainly affects N2O emission in farmland soil by affecting soil properties and microbial community structure.