The Science

Working with Nature, Naturally

We need to understand that working with biology is more dynamic than working with chemicals. The sheer number of variables: from compost age to compost tea recipe, starting soil conditions to annual variations in climate, human disturbances to organic soil amendments… will all influence the end result. Working with nature takes time. It’s not as simple as adding a known amount of nitrogen, but rather, fostering an environment for nitrogen-fixing bacteria and the soil food web to make nitrogen available to plants. The more we learn, the better we get at helping nature do the work. One thing is for sure, the spin-off benefits of working with nature and soil biology are more than just plant health care, it’s people care, and earth care. Carbon capture, biodiversity, and cleaner food/environment are just some of the major benefits.

The Soil Food Web

The physical and chemical properties of soil are important. Any soil test will automatically focus on pH, nutrient availability, and a few other metrics. What is often overlooked is soil biology – that is, the life in the soil. Most of it is microscopic – no wonder it is so poorly studied and understood!

In the last few decades, the use of the microscope and standard procedures for enumerating microbes have become more accessible. We can now examine a soil, compost, or even compost tea under the microscope and understand how biologically healthy it is. Biological health is determined by microorganism abundance, diversity, the abundance of pests/pathogens, and if the groupings of microbes are correct for the plants we wish to grow.

The soil food web is like the terrestrial food web. It is a community involving predators and prey, with all players needed for a healthy ecosystem. Bacteria and fungi make up the base of the food-web, feeding on exudates (carbohydrates and sugars) put out by the plant, in a symbiotic relationship. Bacteria and fungi are responsible for making glues and binding microaggregates together to increase pore spaces, oxygenating plant roots and retaining more water in drought conditions. These bacteria and fungi also chip away at organic matter and sand/silt/clay, breaking chemical bonds and making nutrients available to plants. But it is only when they are fed upon by predators, that the nutrients are released. This all happens in the rhizosphere, in quantities and qualities dictated by the plant!

Soil Microbe Succession Influences Field Succession

Plants are associated with certain microbial communities. Grasses are composed of bacterially-dominated soils, and forests are composed of fungally-dominated soils. This is the way plants co-evolved with soil microbes, and the pattern we aim to mimic when we restore soils with biology. That is why it is important to use a microscope to understand the proportion of fungi to bacteria (also known as the fungal to bacterial ratio, F:B).

Chemical versus Organic Fertilizers

Synthetic fertilizers may have a time and place. For plants that don’t have enough soil to work with, or really stressed plants that need an immediate boost of a limiting nutrient, a correctly applied synthetic fertilizer can help a plant recover quickly. But too much synthetic fertilizer is never a good thing. Excess available nitrogen can quickly burn plant roots, harming or killing the plant. Nitrogen causes green leafy growth, which can sometimes attract pests. In addition, too much synthetic fertilizer, applied incorrectly, can leach through the soil and run-off in to water bodies, where it is known to cause algae blooms and decrease water quality.

Using a synthetic fertilizer is a bit like giving yourself a cheeseburger. One here and there is fine, but too many and we don’t want to get off the couch and exercise the various other aspects of a healthy lifestyle. An organic soil program is like a healthy lifestyle regimen.

In a natural system, where organic matter is broken down by microbes which releases soluble nutrients in the rootzone slowly, plants must work for their food. They put out up 40% - 50% of the energy they obtained through photosynthesis in to the soil in the form of root exudates, to feed soil microbes, which in turn feed the plant. Plants growing this way have larger root systems, better access to micro-and-macro nutrients, and increased pest resistance and drought tolerance, than plants grown with chemicals. No excess nutrients are created and leeched away.

Living Soils = Healthier Plants, People and Planet

Forests support immense biomass, all without the help of humans. Now, we look back to the natural forest for advice on how to manage our urban soils (and plants).

During the industrial/agricultural revolution, chemical control and mechanical methods of growing plants was seen as progress. Indeed, it helped us feed larger populations at lower costs to the farmer. But times are changing. Our soils are losing their natural fertility, structure, and even quantity (as they are easily compacted and eroded and washed-away). Our food is becoming less nutritious, and our planet is suffering.

Similar to agricultural soils, urban soils are stressed. They are exposed to more chemicals, salts, compaction, heat extremes, and other stressors. As we scrape organic matter away, we are further stressing the life in the soil, giving them nothing to feed on. Urban soils are composed of little more than bacteria. Urban trees, in particular, struggle with a lack of fungi in the soil, often making them dependent on synthetic fertilizers and prone to pests, disease, and failure.

There is more and more need to shift to a soil regenerative approach to growing plants. We are finding the amazing spin-off benefits of working with soil microbes: improved plant resilience to drought, enhanced ability to resist/recover from pest attacks; increased nutritional content of our food; soils that stay in place, decompose organic matter, self-regulate and improve on their own, soils that hold more water, are better aerated, and better support plant roots; the discovery of disease-fighting antibiotics, fungicides, and other medicinal microbes, improved gut-health; increased biodiversity, and of course less need to mine and synthesize an unsustainable resource (phosphorus and nitrogen mining/synthesizing).

By working with nature, you become an environmental steward of your land, to the benefit of all.

About our Compost Tea

Compost tea is a tool in our toolbelt for restoring soils to their optimal performance. We use a biologically active compost, which contains the whole soil food web, as an inoculant. We bubble this compost in well water, and add certain microbial foods to increase the number of certain microbes that your soil is lacking, for the plants you wish to grow. The resulting solution is packed full of beneficial microbes that are ready to reproduce in your soil!

When the microbes are injected, surface drenched, or sprayed on plant leaves, they start to work away on organic matter, parent material, and plant exudates. The plant will start to cater it’s exudates to favour microbes that bring it the nutrients that it needs, creating a natural-selection pressure. The beneficials will continue to grow in number, so long as the soil environment isn’t too harsh. This is why we encourage using other “tools” to help restore the soil, including adding organic matter, to create a favorable new home for the microbes.

There are a few different products on the market that may claim to be compost tea. At Shady Lane, we only make the highest quality compost tea, that is actively aerated to ensure the growth of beneficial microbes and discourage the growth of any detrimental microbes. We create custom-brews for different plant successional stages, and add mycorrhizal inoculants for trees. All our brews are quality-controlled using the microscope.

Proof that compost tea works

The microbial world is still a bit of a mystery. Of the billions of microbes that make up a teaspoon of soil, many of them are unnamed and haven’t been studied. One thing’s for sure, the theory is incredibly supportive of restoring soil with microbes. Urban soils are lacking in life, and compost tea is full of it. Diversity is key, and a compost tea contains the full suite of soil food web microorganisms and hundreds to thousands of different species.

Below are a few examples of the use of compost tea.

When four different concentrations of compost tea were tested on soybeans, the root and shoot growth of the soybeans increased significantly at the higher compost tea concentration, and root nodule formation was higher by 7.25 times than the lower concentrations (Kim et al. 2015).

The following table by Eudoxie and Martin (2019) summarizes the effects of actively aerated compost tea (ACT) on various crop plants from several different studies. The responses of a properly made compost tea were always positive.

There are many more examples of case studies where compost tea has an overwhelmingly positive effect on soil health and plant production. We are currently working on our own studies to support the practice of using compost tea in urban settings and on trees.

Research and Development

We actively collect baseline data on leaf chlorophyll fluorescence and soil microbiology. By measuring “before” and “after” a treatment has been applied, we hope to gain a greater understanding of the use of compost tea and other organic soil amendments. If you are interested in working with on us on any type of research, please reach out to us.

Let’s build soil together!

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Connect with our soil biologist to discuss a potential project.

References and Resources

Primary literature

Amen, M.T., El-Seedy, M., Salama, A.S.A., and Elakhdar, I. 2016. Potential Impact of Compost Tea on Soil Microbial Properties and Performance of Radish Plant Under Sandy Soil Conditions – Greenhouse Experiments. Austalian Journal of Applied Sciences, 10(8):158-165.

Battini, F., Cristani, C., Giovannetti, M. and Agnolucci, M. 2016. Multifunctionality and diversity of culturable bacterial communities strictly associated with spores of the plant beneficial symbiont Rhizophagus intraradices, Microbiological Research 183(2016) 68-79.

Eudoxie, G. and Martin, M. 2019. Organic Fertilizers: Compost Tea Quality and Fertility. IntechOpen. Doi: 10.5572/intechopen.86877

Ferreira de Araujo, A.S., Jose de Melo, W. 2010. Soil microbial biomass in organic farming system (Review). Ciencia Rural, Santa Maria. 40(11): 2419-2426.

Kim, M.J., Shim, C.K., Kim, Y.K., Hong, S.J., Park, J.H., Han, E.J., Kim, J.H., and Kim, S.C. 2015. Effect of aerated compost tea on the growth promotion of lettuce, soybean, and sweet corn in organic cultivation. The Plant Pathology Journal. 31(3): 259-269.

Lanthier, M., and Peters, S. 2013. Microbial Content of Actively Aerated Compost Tea after Variations of Ingredients or Procedures. Acta Hort. 1009, ISHS.

Legein, M., Van Beek, Wannes, Muyshondt, B., Wuyts, K., Samson, R., and Leeber, S. 2022. Compost Teas: Market Survey and Microbial Analysis.
BioRxiv. Doi: https://doi.org/10.1101/2022.08.05.503013

Leitao, A.L. and Enguita, F.J. 2016. Gibberellins in Penicillium strains: Challenges for endophyte-plant host interactions under salinity stress. Microbiological Research, (183) 8-18.

Rashid, M.I., Muhawar, L.H., Shahzad, T., Almeelbi, T., Ismail I.M.I., and Oves, M. 2016. Bacteria and Fungi can contribute to nutrients bioavailability and aggregate formation in degraded soils. Microbiological Research, 183(2016) 26-41.

Scharenbroch, B.C., Treasurer, W., Catania, M., and Brand, V. 2011. Biological Properties and Denitrification in A and Bt Soils. Aboriculture & Urban Forestry, 37(6):269-277.

Books