Abstract

Availability of heterotrophic soil bacteria and an associative micro-aerophilic nitrogen fixing Azospirillum, from the rhizosphere of different crop plants, was studied. Microorganisms were reported from root and rhizospheric soil (from twenty-seven different samples collected from Chhattisgarh, India) of different crop plants. The amount of total heterotrophic bacteria, in different samples, varied significantly from 3.01×10⁸ to 4.90×10⁸ in rhizosphere and from 1.11×10⁸ to 2.91×10⁸ in root tissues. Azospirillum population significantly varied from 3.81×10⁸ to 4.90×10⁸ in rhizosphere and from 2.09×10⁸ to 2.88×10⁸ in root tissues. Rhizospheric soils were found to harbor the highest population of heterotrophic soil bacteria and Azospirillum in comparison with plant tissues. Nitrogen, phosphorus, potash, organic matter (OM) and pH value have significant positive correlation but electrical conductivity (EC) have non-significant effect with total heterotrophic bacterial population. Based on the correlation co-efficient (r) value, all significant positive correlation has been grouped in three categories viz; strong (r = >0.5), medium (r = >0.4 but <0.5) and weak (r = <0.4). Thus, in the present study, N, OM and rhizospheric pH have strong significant positive correlation with total heterotrophic bacterial population while P and K content have medium correlation with bacterial population.

Key words: Heterotrophic bacteria, rhizosphere, Azospirillum, nitrogen fixing bacteria, correlation, regression.