改良剂对酸性植烟土壤固氮菌群落结构和丰度的影响

【目的】研究不同改良剂对酸性植烟土壤固氮菌群落和丰度的影响,从固氮微生物角度为改良剂的筛选及其推广应用提供科学依据。【方法】采用田间单因素随机试验,设4个改良剂处理,分别为硅钙钾镁(T1)、白云石粉(T2)、硅钙钾镁+生物炭(T3)和白云石粉+生物炭(T4),以不施用改良剂为对照(CK)。烟叶旺长期进行烟株农艺性状调查并采集根际土壤样品,以nifH基因作为分子标记,应用荧光定量PCR和高通量测序技术,研究不同处理的土壤固氮菌丰度和群落结构变化特征,并分析土壤固氮菌群落结构变化的主要驱动因素。【结果】施用不同改良剂普遍提高了烟株农艺性状及土壤p H、有机碳含量和C/N。施用改良剂可显著提高土壤固氮菌nifH基因丰度(P<0.05,下同),T1、T2、T3和T4处理分别较CK提高2.97、3.32、4.68和3.81倍。施用改良剂也提高了土壤固氮菌群落α多样性,且Chao1、ACE、Shannon和Simpson指数均以T3处理最高。相关分析结果表明,固氮菌丰度、Chao1和ACE指数与土壤pH呈显著正相关。在门水平上,共获得5个类群,其中放线菌门(Actinobacteria)、蓝藻门(Cyanobacteria)和厚壁菌门(Firmicutes)为优势类群。改良剂施用对固氮菌群落结构有显著影响,优势门和属发生变化,硅钙钾镁+生物炭处理显著增加放线菌门、蓝藻门、慢生根瘤菌属(Bradyrhizobium)和固氮螺菌属(Azospirillum)相对丰度。冗余分析结果表明,土壤pH、有机碳、硝态氮和C/N是驱动固氮菌群落结构变化的主要因素。【结论】硅钙钾镁+生物炭混施处理对缓解土壤酸化、改善烟田环境、促进烟株生长及提高固氮菌nifH基因丰度、群落α多样性和优势类群相对丰度效果显著,适合在酸性植烟土壤中推广应用。

Effects of amendment application on structure and abundance of nitrogen-fixing microbial community in acidic tobacco-planting soil

【Objective】To study the abundance and structure of nitrogen-fixing microbial community in different amendment application in acidic tobacco-planting soils,and to provide a scientific basis for selecting the amendment and applied in flue-cured tobacco production from a microbiological point of view.【Method】Open-field random test involving a single factor was performed. Four soil conditioner treatments were set,namely,silicon-calcium-potassium-magnesium(T1),dolomite(T2),silicon-calcium-potassium-magnesium and biochar(T3),dolomite and biochar(T4). The treatment without soil conditioner was the control(CK). Agronomic traits were investigated during the exuberant growing period,and rhizosphere soil samples were collected. The fluorogenic quantitative real-time PCR technique was adopted in the experiments using the high-throughput sequencing platform to target the nifH gene. The abundance,nitrogen-fixing microbial community composition in acidic tobacco-planting soils werestudied under different treatments. The driving factors for structural changes in the diazotrophic communities of the soil were identified.【Result】The application of different soil conditioners generally improved the agronomic traits of tobacco plants and soil pH value,organic carbon content and C/N ratio. Soil conditioners significantly improved the nifH gene abundance in soil nitrogen-fixing bacteria(P<0.05,the same below). T1,T2,T3 and T4 treatments achieved 2.97,3.32,4.68 and 3.81 times increase compared with CK,respectively.Soil conditioners also increased the α-diversity index of the soil nitrogen-fixing bacterial community. Of all treatments,T3had the highest Chao1,ACE,Shannon and Simpson indexes. The results of correlation analysis showed that the abundance of nitrogen-fixing microbial community,Chao1 and ACE indexes were significant positively correlated with soil pH. On the phylum level,five phyla were identified. Proteobacteria,Cyanobacteria,and Firmicutes were dominant phyla.In contrast,the amendment addition altered the nitrogen-fixing microbial community structure with shifts in the phyla and dominant genus,with significantly higher Proteobacteria,Cyanobacteria,Bradyrhizobium and Azospirillum in the siliconcalcium-potassium-magnesium and biochar. Soil p H,organic carbon,nitrate nitrogen and C/N were the key factor correlated with change in nitrogen-fixing microbial community structure. The results from redundancy analysis showed that soil pH,organic carbon,nitrate nitrogen and C/N were the key factors correlated with change in nitrogen-fixing microbial community structure.【Conclusion】Mixed application of silicon-calcium-potassium-magnesium and biochar has multiple effects:alleviating soil acidification,improving tobacco field environment,promoting tobacco plant growth,and increasing nifH gene abundance,α-diversity index,and relative abundance of dominant species in soil nitrogen-fixing bacteria. This fertilizer combination is worthy of wider application in acidic tobacco-growing soils.