Probiotics For the Soil: Brew Your Own Local, Indigenous Microbes

Reader Contribution by Toby Grotz
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The importance of soil health was recently emphasized by Robert Kremer in his presentation to the Cover Crop Research Symposium in Columbia, Missouri. During a day long seminar devoted to cover crops and the No Till methods of Agriculture, the importance of the subsurface ecosystem for plant health and crop yields was highlighted.

This USDA Soil Food Web graphic shows the importance of microbes in the soil.

Soil microbes provide numerous benefits to plants. These include suppression of pathogenic bacteria and fungi, and absorption of nutrients. If your soil is in poor condition as a result of chemical farming, or industrial agriculture, in addition to increasing organic matter, you may want to consider giving your soil a boost by adding local indigenous microbes. The recipe for creating a brew of your own batch of microbes is given below and is a chance to introduce you, and if you have them, your kids to the subject of microbiology.

Soil amendments are often peddled as a magic bullet. When it comes to building soil thee are no shortcuts. In order to increase the organic content of the soil, the research presented at the Cover Crop Symposium indicates that it takes 10 years to increase organic matter by one percent. A test of compost tea, soil microbes, and a control plot showed no difference in productivity as detailed in an research paper in the February, 2009 issue of HortScience Journal but there was no testing of nutrient values after harvest. A soil scientist that I spoke with at the conference suggested that just spraying the soil with a molasses solution, which provides and excellent food for soil microbes, would probably produce the same results. There is a possibility that local, indigenous, soil microbes might be of more benefit than commercially viable microbe preparations. Here is a recipe we tested at the Creek House Norganic Community Garden in Kansas City.

Make Your Own Soil Microbe Mix!


Molasses – unsulphered – (Our tests of every brand we could get our hands on found that Plantation Blackstrap brand produced the most active cultures) For bulk orders contact Organic Fertilizers Inc

Water – filtered or distilled

Dirt from undisturbed pasture, bottom land, prairie, Harvested every six inches from a 3 foot deep hole.


When soil temperature reaches 60 degrees or more, using post a hole digger make a hole 3 feet deep, taking a dirt sample every six inches.

Clean Gallon Jug with Hot Water and Soap, Rinse well.

Add 2 cups hot to the touch water.

Add 2-1/2 oz molasses – = 2-1/2 shot glasses – this yields an approximate 2% solution.

Fill the bottle ½ full with cool non chlorinated water.

Mix the soil samples, add 1 cup dirt to the bottle, shake, then fill bottle with water 2 inch below neck.

Wait until foaming stops – about 2 weeks at 90 F, or pH = 3.5 – 4.0 (pH test papers widely available)

Using Homemade Soil Microbe Mix

One part Microbe Mix to 20 parts water. Use as foilar spray, on new and established seed beds

The photo shows typical leaf sizes from our test of local, indigenous microbes on 100 foot row of sweet potatoes. After brewing as described, the microbe mix was applied without dilution using 4 gallons on half the row. The other half of the row was not treated. No other fertilizers or soil amendments were applied.   The treated side of the row produced larger leaves.

More Information

Sustainable Agriculture Research and EducationCover Crop Symposium

Application of Two Microbial Teas Did Not Affect Collard or Spinach Yield