红壤旱地一株自生固氮菌的筛选鉴定及其固氮能力评估

为了鉴定从红壤中分离得到的一株自生固氮菌,并探讨其固氮能力。采用形态观察、生理生化测定和16S rDNA基因序列分析的方法研究了菌株的分类地位,采用乙炔还原法测定其固氮酶活性,并在室内培养条件下,通过花生、玉米的幼苗盆栽试验研究菌株对土壤MBN、矿化氮和植株氮素积累量的影响。结果表明：从种植于红壤的玉米根际,筛选出15株自生固氮菌,以菌株CM12固氮能力最强,初步鉴定CM12为伯霍尔德杆菌属(Burkholderia sp.),固氮酶活性达C₂H₄ 39.1 nmol/(h·mL)。室内培养试验结果表明,接种CM12菌株的处理,花生和玉米土壤MBN含量较CK处理分别提高了2.38和2.37倍,其中种植花生体系中,接菌处理与施用化学氮肥处理土壤MBN含量无显著差异。接种固氮菌影响了旱地红壤NO₃^--N和NH₄⁺-N比例,降低了土壤中NO₃^--N含量,且种植玉米体系中土壤NO₃^--N含量降低较明显。固氮菌短期接种增加了花生根系和玉米地上植株的氮素积累量。研究结果为该菌株在红壤旱地实际生产中的应用提供了理论基础。

A Strain of Abiogenous Azotobacter in Upland Red Soil: Isolation, Identification and Nitrogen Fixation Capacity Evaluation

To identify a strain of abiogenous azotobacter isolated from red soil and to explore the nitrogen fixation capacity of the strain, morphological observation, physiological and biochemical determination and 16S rDNA sequence identification were used to study the taxonomic status of the strain, and acetylene reduction method was used to determine nitrogenase activity. A peanut and maize seedling pot experiment in greenhouse condition was conducted to study the effect of abiogenous azotobacter on soil microbial biomass nitrogen (MBN), mineralized nitrogen and nitrogen accumulation. The results showed that: 15 azotobacter strains were isolated from maize rhizosphere in red soil, and the strain CM12 had the strongest nitrogen fixation capacity, which was classified as Burkholderia sp.. The nitrogenase activity of CM12 was C2H4 39.1 nmol/(h·mL). The pot experiments showed that, inoculation with CM12 significantly increased MBN content by 2.38 and 2.37- fold in the soil planted with peanut or maize, respectively, compared with the control. In the peanut system, MBN content had no significant difference between CM12 and chemical nitrogen fertilizer application. Abiogenous azotobacter inoculation affected the ratio of soil NO3--N and NH4+-N, decreased the content of soil NO3--N, and the decrease was obvious in maize planting system. Nitrogen accumulation of peanut roots and maize seedlings increased after short-term application of CM12. These results provided the theoretical basis for the application of the strain in the agriculture production in upland red soil.