Saturday, March 28, 2009

Compost Tea vs EM1 Microbial Inoculant

Why is it that people are always looking for which thing or gadget is better? It might be human nature to look for the "next best thing" or "which is the best". I often find myself looking at how to combine things and "get the best of both worlds". There are always pros and cons for everything. Let's take a look at compost tea vs EM1 Microbial Inoculant.

This is fresh in my mind because it kept coming up at the Organic Growers School in Asheville, North Carolina.

This is a compost tea brewer (pictured above, right) used at Harding Golf Course in San Francisco. They make aerated compost tea and add a little bit of Activated EM-1 just before they apply it to the course.

Compost Tea (Pro)
  • Low cost to produce.
  • Great way to get beneficial fungi and protozoa for soils and plants.
  • Can be brewed on site.
  • Easy to apply.
Compost Tea (Con)
  • Could brew pathogens without knowing.
  • Inconsistent quality
  • Requires an aeration unit and tank to brew
  • Very short shelf life. ( 24 hours or less)
  • Almost entirely aerobic microbes, lacks facultative microbes.
EM1 Microbial Inoculant (Pro)
  • High quality, consistent product.
  • Easy to brew/increase populations (Activation)
  • Can be brewed on site or shipped ready-to-use
  • Easy to apply
  • Contains large populations of facultative microbes, enzymes, trace minerals, vitamins, and organic acids
  • Long shelf Life (about 1 year with the EM-1 and 30+ days for Activated EM-1)
  • Multiple uses beyond horticulture (inoculate compost, odor control, improves water clarity in irrigation ponds, etc)
EM1 Microbial Inoculant (Con)
  • Does require repeat purchases of "seed" product (EM-1)
  • Cost is $3-$4 per gallon for Activated EM-1 (the material you actually apply)
  • Does not contain much fungi (yeasts only) or any protozoa
  • Requires the purchase of a sugar source
Get the Best of both! Combine the two. Here's how:
  1. Following compost tea brewing instructions
  2. After aeration cycle is complete (up to 24 hours), turn off aeration.
  3. Add Activated EM1 Microbial Inoculant at a rate of 1 part AEM-1 to 50 parts Tea.
  4. Follow suggested tea application rates.
This gives you the facultative microbes, aerobic microbes, beneficial fungi, and protozoa groups in one inoculant. The microbes in the activated EM-1 will slowly release small amounts of oxygen into the liquid extending the life of the tea without requiring further aeration.

If you are experienced with compost tea already, you will notice improved results. TeraGanix has heard from several growers that they have had higher levels of nutrient values (vitamins, shelf life, higher brix, etc.) in a variety crops. You'll see why Dr. Higa has answered the question, "What is the best inoculant?" with "All of them mixed together."


Dave said...


Great post! My family have been using both compost tea and EM (though not plain "vanilla" activated EM) for a numbe of years in commercial-scale banana farming in Australia. The results have been outstanding with pest management, sugar production (sweetness), and cold tolerance all showing significant improvements over conventional methods.

Understanding the science behind how and why the two complement each other is something that we're lacking in more than I like and this has helped. Do you know the sources of any more detailed info that I can review?



TeraGanix said...

Sorry for such a long delay in replying. For information specifically on EM, I would look through EMRO Japan's database at

Most of the experiences we have are on the farm feedback from farmers. I don't think at this stage many people have invested the capital it requires to research on aerated compost teas. It appears it is a lot of intuitive approach. They know compost tea has benefits and they know EM1 has benefits, so their questions are more of, "Will they work together?" The answer is a resounding, "Yes!"