The ABC’s of Compost Tea and the Soil FoodWeb Part II

The ABC’s of Compost Tea and the Soil FoodWeb Part II

In Part I of our series on Compost Tea, we had a brief discussion on the Soil Food Web and compost. We learned that these are tools we can use to restore the biology to our soils. Now would be a good time to talk about the microorganisms within the Soil Food Web, their roles, and then we can move on to brewing compost tea.

Healthy biologically active soil is home to billions and billions of microorganisms, and the four that represent building blocks for healthy soil are Bacteria, Fungi, Nematodes, and Protozoa. One teaspoon of healthy garden soil can contain up to a billion bacteria, yards of fungal hyphae, thousands of protozoa, and dozens of nematodes. Truly an incredible amount of life, all invisible to the naked eye, simply living and going about their daily routines. Let’s take a quick look at each group.

Bacteria are tiny, one-celled organisms and fall into four functional groups; Decomposers, Mutualists, Pathogens, and Lithotrophs. We are most concerned with Decomposers (which break down materials) and Mutualists (which form symbiotic relationships with plants), and want to avoid Pathogens (the bad guys) for obvious reasons.

Flagellate next to bacteria (long black line) amidst small bacteria cells and yeast cells. 500x magnification

Fungi are microscopic cells that grow as long threads or strands called hyphae, which push their way between soil particles, roots, and rocks. Fungi perform important services related to water dynamics, nutrient cycling, and disease suppression.

Nematodes are non-segmented worms typically 1/500 of an inch (50 µm) in diameter and 1/20 of an inch (1 mm) in length. Nematodes mineralize, or release nutrients in plant-available forms.

Ciliates seen at 500x magnification

Protozoa are single-celled animals and are classified into three groups: Ciliates, Amoebae and Flagellates. Protozoa play an important role in mineralizing nutrients, making them available for use by plants and other soil organisms.

(Information provided from papers written by Dr. Elaine Ingham, Soil Foodweb Oregon LLC. Pictures captured from “Compost, Soil & Compost Tea Organisms” DVD, Available at )

Still with me? Good.

Bacteria and Fungi are the holder of nutrients, and nematodes and protozoa are the releasers of nutrients. In short, the nematodes and protozoa eat the bacteria and fungi, and poop out nutrient rich material. Always comes back around to manure, doesn’t it?

Growing and re-establishing these organisms in poor soils is essential to re-energizing the Soil Food Web. The numbers present and needed of each of these groups of organisms differs, depending on the existing soil ecosystem, and the type of crop one intends to grow. Perennial plant ecosystems (forest, tree and shrub landscapes and perennials) are generally fungal, while annual plant ecosystems (annuals and vegetables) are generally bacterial. Grass ecosystems (great plains, lawns and turf) tend to be slightly bacterial. These compositions are important to note whether making compost, steeping Leachate or brewing Compost Tea. By building the correct soil organism communities, we provide plants an environment they can easily exploit, giving them the best opportunity to thrive. This is the essence of the organic process.

You may be asking, “How can a plant exploit?” Great question. Plants actually attract beneficial microorganisms. Say what? That’s right, plants, by releasing nutrients called exudates through their root walls into the rhizosphere (an area of only a couple of millimeters wide surrounding the root), attract the organisms they need to survive. The exudates attract bacteria and fungi that will in turn supply the plant with the nutrients it needs. Pretty cool eh? The plant actually attracts and feeds the certain bacteria and fungi that produce, or help the plant find the nutrients it needs to survive. It’s gardening on a microscopic level.

You now have a very basic understanding of the Soil Food Web. As with any complex subject, it can not adequately be covered in short blog posts. I will be providing you with suggested reading material and reference links at the end of the series.

In part III we will look at the brewing process.


Read Part III Here!


All the best,


5 thoughts on “The ABC’s of Compost Tea and the Soil FoodWeb Part II

    1. I’m glad you are enjoying this series Whitney, It’s hard to fit so much info into short blog posts, and still make sense.
      Thanks for visiting and leaving a comment! Scott

  1. A bit late here to reply. I was interested in your
    microscope studies. I prepared some compost tea, and we examined it under a 40 X TAFE Rural skills microscope with screen. Used for wool classification studies. I am doing my Diploma for Organic Agriculture.

    Probably not the best time of year as the rain water
    I used and aerated was freezing cold when I took samples of it to TAFE. Surely the temp of the brew
    would encourage the growth of microbes. And the water was very cold and I took the samples from the top of the bin, might have been better getting it
    lower down. I used compost and worm farm residues.
    Added molasses, blood and bone, Seasol, dog biscuits,
    and a handful or two of dynamic lifter pellets. And a teaspoon of sea salt. Aerated for 48 hours. But this morning the water felt colder than when I first filled the garbage bin.

    However, we found several moving critters, but also
    a round shape with a nucleus that pulsated, and seemed to change colour. They were of different
    dimensions. Because of the pulsating action I felt it was alive. Any ideas? Others thought it was just an air bubble on the slide.

    I’m going to the hospital pathology department and they are lending me a higher magnitude microscope.

    Kind regards

    Pat from Armidale NSW

    I asked a botanist I know and pathologist, and they
    felt the pulsating might be a feeding mechanism in the microbe.

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