Because of their huge numbers and direct access to soil organic matter,free living microorganisms such as Azotobacter typically fix more nitrogen per hectare of land than do nitrogen-fixing bacteria living in plant roots.

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Free-living microorganisms like Azotobacter generally fix less nitrogen per hectare of land compared to nitrogen-fixing bacteria living in symbiosis with plant roots, such as those in the Rhizobium genus with legumes, because the symbiotic relationships allow for more efficient nitrogen fixation due to the direct energy supply from the plant to the bacteria.

Because of Their Huge Numbers and Direct Access to Soil