DIY Soil Fertility – Part 3: Compost Tea

Welcome to DIY Soil Fertility For Homesteads!

This post series covers the many ways you can build fertility, create soil, cycle nutrients and take responsibility for “waste” streams on your property – all with materials and substrates you are likely buying already or can be sourced for free or very low cast. These systems all integrate with one another to enable you to in-source your soil fertility inputs instead of relying upon centralized commodity supply chains. By employing these systems together in an integrated system you will improve nutrition (for soil and humans) and save dollars, while making living soil fertility enhancers better than anything you can buy at the store. The posts are written from our own experience and are geared towards the DIYer, though options are provided for ready-to-go purchased systems as well. Check the link tree below or at the bottom of the post to explore the rest of the series!

What Is Compost Tea?

Compost tea is nutrient and microbe rich liquid that is aerobically brewed to maximize the number of beneficial microbes, fungi and bio-available nutrients for the soil food web and plants. Basically it’s an immune-boosting, growth-enhancing, nutrifying power drink for your garden!

Why Brew Your Own Compost Tea?

The benefits of regular application of compost tea to any garden, orchard, food forest or otherwise preferred group of plants are innumerable. Below is a short list of known benefits, and we are still learning about more every year.

• Aerobically brewed compost tea is an excellent way to grow your own beneficial microbes and fungi for application to your landscape. Instead of applying yards of imported compost to your garden every year, regular compost tea application can be just as, if not more, effective in boosting soil health and production yields simply by making sure that the biology in your soils is optimal.
• Compost tea is a great way to stretch valuable but typically limited amendments like worm castings, kelp extracts, mycorrhizal inoculants and finished compost itself. By brewing a tea in aerobic conditions for 12 – 48+ hours you can dramatically expand the number of beneficial microbiota in the mix – effectively making a beneficial probiotic tea that can be sprayed on plants or fed directly into the soil.
• Regular compost tea application to damaged or healing soil (i.e. every annuals-based garden) is one of the best ways to quickly build soil structure. Healthy soil structure increases resistance to wind erosion and enhances porosity to improve infiltration during heavy rain events (and thus minimize flooding and top soil loss). Better soil structure (a consequence of a diverse and healthy soil food web) increases drought resistance as well. A well-structured soil is able to hold onto more water for longer, thus enabling plants to weather tougher conditions than those in less healthy soils.
• Compost teas are known to improve yields (often quite dramatically) for both annuals and perennials. They help jump start and/or reinforce the soil food web (community of micro and macro-organisms) that makes for healthy plants having access to the nutrients they need when they need them – without the need for outside inputs!
• Compost tea application is known to improve plant immunity to various pests and diseases – again, simply by ensuring that necessary nutrients are available at the right time and in the right amounts to the plants.
• Compost teas reduce and ultimately eliminate the need for fertilizer application in concert with other soil-tending practices (like no-till gardening, polyculture, crop rotation etc). A strong soil life community, with a healthy dynamic balance between bacteria, fungi, protozoa and nematodes, will be able to supply all necessary nutrients to a growing plant without the need for external inputs.

How Does Compost Tea Brewing Work?

By brewing various nutrient and microbe-rich inputs in well-aerated, clean (i.e. non-chlorinated) water at moderate temperatures for a half-day or more (12+ hours), the number of beneficial microorganisms per unit volume can be dramatically increased – by many orders of magnitude. Brewing is an effective way to stretch and expand valuable inputs and maximize their impact in your garden or the broader landscape.

Critical Step #1: Make Sure Your Water Supports Life!

First thing is to ensure that the water you are going to brew with is free of biocides.

If you are using tap water from a municipal supply to brew your compost tea, it will most likely have either chlorine or chloramine in it. A good place to begin is the Environmental Working Group’s Tap Water Database where you can look up water utilities by area code and see what testing has been done and what chemicals are being added (intentionally or not) to your water supply. You may need to call your local water utility to get an accurate and up to date list of what they use to treat the water in your area.

The most common additions to tap water are chlorine and chloramine. Chlorine can be removed by bubbling or by simply allowing the water to sit exposed to the air for a few days. Chloramine cannot be bubbled out of the water and will not evaporate. It can be bound, and thus made inert, by adding water soluble humic acid to your tap water before brewing (this will prevent the chloramine from killing all of the beneficial microbes you are trying to create more of).

To test for the presence of chlorine and chloramine yourself, and thereby confirm your water is ready to grow microbes instead of kill them, you can use a chemical called DPD (N,N-diethyl-p-pheylenediamine), which will turn pink in the presence of chlorine or chloramine. If chloramine is present in your water supply you will need to test how much humic acid is needed to neutralize all chloramine prior to brewing through successive rounds of using the DPD packets and looking for the pink color (it will fade as concentrations of free chloramine are bound by the humic acid).

Of course, the easiest way to avoid all of this rigamarole is to use rainwater or springwater if you have access to them! If you have a well, your water might also be good to go straight out of the ground, however if your tap supply has any softeners or chemicals, or is known to be contaminated to begin with, these factors should be taken into account before brewing your compost tea!

Critical Step #2: Actively Oxygenate Your Tea!

Aeration is critical when brewing a good compost tea. Old-school biodynamic methods (pre-electricity) speak of old men stirring giant casks of liquid with long wooden spoons, whistling and singing while they worked, to create and maintain a vortex to help aerate the solution. Nowadays we have electrical pumps and air compressors to either create a vortex or inject compressed air into the tea and let the bubbles oxygenate the water column as they rise to the surface.

Saturating the solution with oxygen is necessary in order for the dramatic increase in beneficial microbes to occur. Microbes and fungi respire like any other creature, and actively aerating the compost tea, along with providing some nutrients for them to feed upon, enables them to exponentially increase their numbers.

Compost teas therefore have a very limited shelf life – they generally need to be used within a few hours of stopping aeration or the microbes and fungi within will begin to perish and the solution will begin to turn anaerobic. This is why brewing your own makes so much sense!

How To Use Compost Tea

Compost tea is applied to gardens and landscapes in two different ways – as a foliar feed and as a soil drench. There are several methods to apply the tea for both foliar and soil drench use cases.

Foliar feeding is the application of the compost to to the above ground parts of the plant – namely leaves and stems. It is typically accomplishing by spraying – which, depending on the scale of the operation, can be achieve in many ways – a squirt bottle, a hand-held pump-sprayer, a backpack sprayer, or an ATV or tractor-borne sprayer. The aim with foliar feeding is to cover as much of the plant surface area as possible in a fine mist of the compost tea. This serves numerous beneficial functions, like colonizing the plant surface with beneficial microbes (helping to ward off pests) and allowing the plant to absorb nutrition through the stomata in its leaves. Compost tea will generally need to be strained through a fine mesh bag (either a compost tea brewing bag or a nut milk bag) to remove any particulate that could clog the sprayer – reference the sprayer model you have to know what micron count of mesh to use.

Applying compost tea via soil drench means applying the tea directly to the soil. This application is designed to feed the soil food web and roots of the plant. Depending on the scale of the operation, it can be done with a watering can, a garden hose with a siphon injector, a Mazzei injector for drip irrigation or pressurized injection into irrigation lines for broad-acre application.

Compost tea brews can be tailored to their target application. For example, indigenous fungi might be favored in a brew meant for feeding the soil in a permaculture orchard, or a microbe-heavy brew with bio-available plant nutrients might be favored for foliar feeding an annual garden bed.

Different Brewing Set Ups

DIY Homestead Scale Compost Tea Brewing

Making your own compost tea brewing set up is quite simple. Below we detail the system we use at Honey Badger Nursery. It employs a single air compressor that pushes compressed air through two bubble snakes, each capable of aerating a 5 gallon bucket of compost tea, for a total of 10 gallons of brewing capacity per batch. The great thing about having two buckets is that we can brew different recipes (maybe one for soil drench in our air pruning beds, another for foliar application in the annual garden) simultaneously.

What You Need To Build Your Own 10 Gallon Brewing Set Up

• Parts for air compression
  • (1) 1110 GPH air compressor -purchase from VIVOHOME on Amazon or TeaLab
  • (1) 3/8″ Barbed T fitting
  • 10′ of 3/8″ clear poly tubing
• Parts for (2) bubblesnakes
  • (2) 3/8″ barb to 3/4″ MPT fittings
  • (2) 3/4″ Slip x FPT PVC fittings
  • (2) 3/4″ PVC couplings
  • (2) 3/4″ PVC end caps
  • (1) 10′ stick of 3/4″ PVC pipe(SCH40)
• Parts for brewing
  • (2) 400 micron mesh bags
  • (2) 5 gallon buckets
• Tools
  • Fine sand – for filling the PVC pipe prior to heat bending
  • Pyrex baking dish (9×9″) – for heating sand in oven
  • Torch – for heating outside of PVC pipe
  • Tape – duct or painters, for keeping sand in pipe

Farm-Scale Compost Tea Brewing

Vortex Brewer With Conical Tank – This style of vortex brewer utilizes compressed air to lift and oxygenate the water from the bottom of the tank, ultimately creating a vortex that helps to further aerate the mix. Kits are available to build your own (DIY instructions PDF) or they can be shipped ready to brew.

In Summary

Brewing your own compost tea is one of the lowest hanging fruit available to any home gardener, homesteader or farmer to quickly and powerfully increase the vitality of the soil food web and the trees and plants that grow amongst it. Brewing set ups can be scaled to practically any usage level, and can be made on the cheap with simple materials or be complex and capable of producing precision mixes geared towards specialty crops and landscapes. Inputs can be obtained for free or made on your own with vermicompost, thermophilic compost, indigenous microorganisms (IMOs), foraged or farmed fungi, kelp and other plant extracts and more.

Start brewing compost tea today!

Explore The Entire Soil Fertility Series