The bacteria found in soil that “fix” nitrogen when they settle inside the nodes of legume roots. Rhizobia are most likely present in areas where legumes have grown for two or more years, while areas without legumes may be lacking. To test for rhizobia, plant two different legumes and fertilize one with nitrogen. If the node development on both plants is the same, rhizobia are present. If the non-fertilized legume does not produce as many nodes as the fertilized plant, you likely will need to inoculate your soil by hand with the appropriate rhizobia.
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