STUDY OF PHYSICO-CHEMICAL PROPERTIES OF SOIL AND CHARACTERIZATION OF Azotobacter sp. FROM PANCHAKANYA FOREST AND IT’S SURROUNDING AREA.

Abstract

The forest ecosystems provide critical and diverse services and values to human society. As primary habitat for wide range of species, forests support biodiversity maintenance and conservation. We cannot understand about forest without the knowledge of forest soil. Therefore, the main objective of this study is to study about the physical, chemical and microbiological properties of soil of Panchakanya forest and its surrounding area. 30 soil samples from 5 different locations of Panchakanya forest and 5 different locations surrounding Panchakanya forest were collected and analyzed for physical properties (moisture content, water holding capacity, pH, bulk density, electric conductivity), soil texture (sand, silt and clay) and chemical properties (carbon, nitrogen, potassium, phosphorus, soil microbial biomass carbon and soil microbial biomass nitrogen). Total plate count was done to study about the microbial load of each sample. Different species of Azotobacter was isolated and identified according to Bergey’s Manual of Systematic Bacteriology. To establish the correlation between the physico-chemical variables and organism, the canonical analysis (CA) was performed. Most of the soil samples were loamy sand having mean moisture content of 24.33%, mean water holding capacity of 60.5% mean bulk density of 1.24 gm/cm3 and mean electric conductivity of 0.246mS/cm. Most of the soil samples were slightly acidic to neutral. The value of mean soil nitrogen was 0.1016%, organic carbon was 1.99%, mean phosphorus content was 2.278mg/l, mean potassium content was 44.85ppm, mean SMBC was 808.75 mg/kg and mean SMBN was 16.108 mg/kg. The value of total plate count ranged from 9×105 cfu/ml to 79×107 cfu/ml. After the study of colonial characteristics and microscopic examination, 27 isolates of Azotobacter were found. Further biochemical tests confirmed 20 isolates of Azotobacter sp. And among them 10 species were A. chroococcum, 6 species were A. vinelandii and 4 species were A. beijerinckii. The canonical analysis suggested that the physico-chemical variables such as soil texture (sand, silt and clay), organic carbon, pH, bulk density, potassium, nitrogen and electric conductivity are highly associated with organism (TPC) but negatively related to soil microbial vii biomass carbon. In the contrary, variables of gravel, soil microbial biomass nitrogen and moisture content are not associated with organisms.