Soil Probiotics

12 Aug

After a few long weeks at the laminar-flow hood, with literally hundreds of Petri plates inoculated, I’m ready for a day in the literature and at my computer – not something I find myself saying terribly often.  With that in mind, I’d like to finally address a comment I received on one of my very first posts last year regarding a topic I consider fun, in that sort of twisted, soil microbiologist way – something with a happy ending that leaves us all with a warm fuzzy: plant-microbe-interactions.  Here’s the original comment/question:

 “We are wanting to start a vegetable garden this coming spring and I think that there are good microbes that can encourage growth and/or enrich the vegetables that we want to grow. How do I find out if there is a fertilizer available that I can use that actually uses natural microbes to encourage the growth of my garden that is not harmful but beneficial?”

–  Sue Sullivan 

While it’s taken me some time to get to this question, we’re now beginning to see the summer draw to a close for most of the northern hemisphere and once again, many of you avid gardeners are already thinking about your plans for next year.  So, today I get the chance to introduce one of my favorite groups of microorganisms: plant growth-promoting rhizobacteria (PGPR).  That’s a long term for those microbes we find growing in and around the roots of plants that actually aid plant growth.  There’s some new research out this year demonstrating that these organisms may not simply enhance the growth of the plant (which we’ve known for some time by means of nutrient delivery and pathogen suppression), but may also increase the actual quality and nutritional content of the fruit or crop produced as well (see citations 1, 2, and 3 below) .  Very cool stuff!

These amazing little PGPR critters are getting more and more attention as people gradually realize that many of our agricultural practices (factory farms, etc) are simply not sustainable in the long term.  As such, we can thank the organic gardening movement for making non-chemical fertilizers, like PGPR soil amendments, more and more readily available to Joe-public.  So first, let me direct you to some great resources for very general information on “soil probiotics” or beneficial soil microbial inoculants:

Next, and more specifically answering the question posed in the comment, below are a few links to commercially available soil inoculants.  Disclaimer: I have never personally used nor tested any of these products and cannot attest to their quality or efficacy – but they sound pretty cool.  


Stay tuned for my review of a nice PGPR article later today.

Good luck and happy gardening!


  1. Akca, Y. and S. Ercisli (2010).  Effect of plant growth promoting rhizobacteria (PGPR) inoculation on fruit quality in sweet cherry (Prunus avium L.) cv. 0900 Ziraat.  Journal of Food Agriculture & Environment, 8(2): 769-711. 
  2. Kang, et al. (2010).  Effect of Burkholderia sp KCTC 11096BP on some physiochemical attributes of cucumber.  European Journal of Soil Biology, 46(3-4)264-268.  Doi: 10.1016/j.ejsobi.2010.03.002
  3. Ordookhani, et al. (2010).  Influence of PGPR and AMF on antioxidant activity, lycopene and potassium contents in tomato.  African Journal of Agricultural Research, 5(10): 1108-1116. 

One Response to “Soil Probiotics”

  1. Joshua July 30, 2011 at 11:45 am #


    Thanks for all that you put into your blog… it is a great resource!

    I am wondering if you might have some thoughts on a question I have run into recently…

    I am a farmer from California, currently visiting my in-laws in rural Colombia, South America. I was invited to attend a local agroecology workshop. Interestingly, it focused on the preparation of a ‘beneficial microbial brew’. It was presented as an organic alternative for soil fertility. It consisted of leaving cups of rice in ‘virgin’ forested areas (healthy ecosystems) for a couple weeks. The rice was then collected and mixed with molasses, yogurt, bakers yeast, flour and water… it was then separated into two piles, one is fermented and the other is left exposed to oxygen and prepared like compost. After a couple more weeks, the two piles are mixed together, more molasses and water are added – and there you have it!…

    It is suggested that the healthy microbial populations in the forested areas benefit the agricultural fields. It is also used to lessen odors where animals are raised and to speed up composting.

    Our approach to organic agriculture in the States usually uses other methods to create conditions for healthy microbial populations in our soil. The approach presented here is new to me. Including the idea that LOCAL beneficial microorgaisms are better adapted to local soils. I have tried to read up about it but have found varying opinions. The debate seems similar in some ways to your blog on probiotics. Manufacturers of the product promote its numerous capabilities. More traditional farmers and agronomists have little to say about these methods… One article from ATTRA (Appropriate Technology Transfer for Rural Areas) said, “these products perform best when the soil is at or near optimum conditions to begin with.”

    I don’t know if any of this is interesting to you, but as somebody who dedicates much of my life to making sure there is life in my soil – this stuff is fascinating!

    I have never responded to a blog before, but it seems like these questions might be things you have run across… please let me know if you happen to have any thoughts. I appreciate you taking the time to read all this…


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