I have been told that they exist in areas where the plants that host them grow naturally. Like the Rhizos that attach to oak tree roots, are avalable in the woods near oak trees. That may not help your particular need, if not others will answer.

Rhizobacteria, generally Nitrogen fixing on legumes, can be present in good healthy soils, or you can purchase innoculants to coat the seeds. I have yet to find a good source of information on how to produce, or grow, those bacteria except to make the soil into a good healthy soil well endowed with organic matter.

Bob, if I knew more about your goals, I might be able to help direct you to some information.

Different forms of beneficial (essential) bacteria have been cultivated and available commercially for a very long time.

For the vast majority of us, fostering a healthy natural soil is the best way of encouaging a good population of beneficial bacteria species.

Something sort of neat, is that there are thought to be soil micro-organisms that can fix nitrogen, that do no rely on the well known, symbiotic legume relationship. Haven't looked into it further, as it was only a cursory read. M

From Steve Solomon.....

"Rhizobia are not capable of being active in compost piles, but another class of microbes is. Called azobacteria, these free-living soil dwellers also make nitrate nitrogen."

Lloyd

Here is a link that might be useful: Curing the Heap

Thank you so much for that link pt03. I read the entire article and bookmarked it. A lot of other very informative articles and books there. :)