Abstract:

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.

Key words: upland red soil, abiogenous azotobacter, nitrogen-fixing, peanut, maize