The main factors that influence the growth of the Azotobacter are:
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Temperature: It is a mesophilic bacterium which can withstand at temperature between 25°C-30°C.
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Humidity: The cell of the Azotobacter requires high humidity and lower intracellular osmotic pressure.
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Aeration: It require the continuous oxygen supply as it an aerobic bacteria. But it can also multiply in micro aerophilic conditions.
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Salt: The viability of the microorganisms in the soil depends on the high salt concentrations.
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pH: The pH has an important influence on the metabolic activity of the Azotobacter. The optimum pH for the growth of bacteria is just above the neutrality that is between 7.2 - 7.6.