7 Tips for Introducing Compost Teas

Evidence suggests that a healthy rhizosphere helps fight pests and pathogens while also increasing uptake, immunity, and plant vigor.

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Elaine R. Ingham and Jeffrey Lowenfels’ popularization of activated compost tea (ACT) and beneficial microbes helped trigger a paradigm shift in cannabis farming. Liquid ACTs fertilize soils with water, compost, and micro-organisms favorable for crops. Evidence suggests that a healthy rhizosphere teeming with beneficial fungi, bacteria, and other microbes from ACTs, helps fight pests and pathogens while also increasing uptake, immunity, and plant vigor.

Here are seven tips to help you introduce ACTs into your cultivation cycle.

1. Use contaminant-free ingredients.

Thoroughly research each ingredient to ensure they are free of antimicrobial preservatives. River, lake, spring, rain, or distilled water usually work best. Dechlorinate tap water using sodium thiosulfate, which dissipates chlorine and chloramine while also tying up numerous heavy metals.

2. Inoculate your ACTs.

Inoculants include compost, worm castings, powdered mycorrhizae, or any other source of dormant or living microbes. The chosen microbial inoculant critically impacts the efficacy of any ACT. Basic understanding of microbes is a valuable tool for those brewing teas.

3. Get familiar with endomycorrhizae.

These fungi insert themselves into the cortex of the cells of roots and populate the rhizosphere through a process called intracellular colonization. As asexual fungi, they compose the vast majority of mycorrhizae, and exist on the roots of 70% to 90% of all plants. These beneficial fungi increase uptake of both nutrients and water in cannabis gardens. However, Ingham believes that mycorrhizae best inoculate teas when added just prior to application, as they must quickly find roots to survive.

4. Don’t sleep on beneficial bacteria.

Beneficial bacteria, protozoa, and many other microbes play differing roles. For instance, some bacteria fight pathogens while others battle pests. Beneficial protozoa release natural nitrogen after digesting invasive protozoa, bacteria, and fungi. Therefore, microbes make nutrients more bioavailable, boost immunity, increase growth rates, and provide additional nutrition while being an integral component of any integrated pest management program.

5. Feed your microbes.

Although recipes vary, other ACT ingredients include food sources to encourage microbes to multiply versus parasitizing each other. One of the most affordable and effective sugars is unsulfured blackstrap molasses, which provides a stable food source during bubbling (when the “tea” is agitated and activated with air which initiates the breeding process). Other foods or ingredients may include kelp, humic acids, fish hydrolysate, natural nutrients (plant compost, mulch, etc.), or other sugars. Choose food sources based on the microbes you are using. Do not overly “spice” a recipe, as various microbes have differing parts per million thresholds that cannot be exceeded for them to survive and multiply. Excessive mineral salt levels kill beneficial microbes, for example.

6. Consider recipes for specific growth stages.

Introducing natural nutrient sources most critical for corresponding growth stages promotes the bloom of beneficials that coincide with that mineral. Many brewers introduce a nitrogen source for the vegetative stage followed by a phosphorus input for flowering. After all, nitrogen fixing bacteria munch nitrogen sources while phosphorus solubilizers chomp on sources of phosphorus, therefore making both nutrients more bioavailable.

7. Maintain a correct environment.

Brew teas for 24 to 48 hours at temperatures between 60° to 80° F. Maintain constant aeration and circulation with an air pump or stone to prevent aerobic beneficials from becoming anaerobic. Be aware that large bubbles may destroy hyphae (the long, delicate filaments of a fungus) if your goal is a fungal-dominant ACT. Use a 400-micron bag or strainer when filtering tea so as to not remove beneficial fungi and apply as soon as possible. The tea will turn anaerobic after approximately four hours without aeration.

Kevin Horvath consults nationwide under the banner of Botanic Assassin. He specializes in garden inputs and draws upon a vast network of industry professionals. Kevin credits his many mentors, especially Tim F.H. Allen, Scott Ostrander, Newton Hayes, “Uncle” John Picirrilli, and Chip Baker for being significant influences upon his career.

September 2021
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