How to Make Compost Tea

When brewing compost tea there are some general guidelines that will help ensure successful home brewed compost teas.  Below you will find our recommendations for home brewing compost tea. 

Best Location for Brewing Compost Tea:

  • Choose a location that can tolerate a few spills.
    • Brewing compost and garden teas can be messy at times.
  • Place your brewer on a flat and level surface located near a power outlet.
  • Provide a stable environment such as a basement, barn, garage or shaded location outdoors.
    • If possible choose a location that can maintain a temperature between 55°-80°F.

Water:

  • Always start with pure filtered water
  • Microbes in compost are highly sensitive to anti-microbial agents found in many municipal water sources.
    • Chlorine, fluoride, chloramine and fluorine tare some of the potential additives in many municipal water sources.
  • If you have a municipal water source you can at the least evaporate as much chlorine as possible.
    • This can be achieved by allowing your water to sit in an uncovered bucket / brewer overnight or you can aerate your water for 15-30 min prior to use.
  • Chloramine & fluorine cannot be evaporated and are best removed thru filtration. Please note that not all filters are capable of removing these harmful chemical agents. Fresh, clean rainwater can be a great alternative to the tap.
  • Humic acids added to water (prior to your sensitive compost) can help to bind these harmful chemical agents and immobilize their harmful affects.  Here are two recommendations to accomplish this:
    • Add 1 tsp of Soluble Humic acids per gallon or 1 tbsp per 5-gallons of water
      • After the humic acid is fully dissolved you can proceed with adding your compost tea ingredients to your brewer
    • Good quality compost contains sufficient humic substances to assist in mitigating the harmful affects of the above-mentioned additives. More on this in the section on compost extracts; below.

Temperatures

  • The ideal temperature range for brewing compost tea is between 60° - 80°F
    • An aquarium heater can be used to maintain constant temps for more precision brewing and reduced brew times
  • High temperatures can kill or limit a diversity of microbes.
  • Low temperatures will slow microbial activity and limit a diversity of microbial growth.
    • Do not to exceed a water temperature of 95°F
  • Brewing in a temperate environment is a pretty safe option
  • Match your water temperature to the temperature of the soil or leaf zone where the tea is to be applied.
    • The microbes that are cultivated in your compost teas are more likely to remain active when applied to the soil or a leaf surface that is a similar temperature as your tea.

Ensuring A Quality Extraction:

    In brewing compost teas we are attempting to transfer the multitudes of beneficial microorganisms and soluble nutrients, from good quality compost, into a solution that can easily be applied to soil and plant surfaces.  The compost serves as a starter agent, much like yeast is to bread. Water is the medium or carrier and food sources (soluble kelp powder, Humic acid, liquid fish fertilizer, etc.) serve as a catalyst to feed active and dormant organisms present in the compost. Aerating the compost will further help to promote the growth of the organisms present in the compost.  There are two primary methods that we recommend to produce quality compost teas.

Filter Bags

Filter bags are used to contain compost and dry ingredients. Using a filter bag will keep your brewer cleaner, but is not necessary. You can just place compost in a bucket or barrel to keep it super simple.

  • 400-micron filter bag used for compost
    • Use the 400 micron mesh filter bag to contain compost when brewing compost teas
    • 400-micron mesh will allow the full array of organisms, present in compost to easily pass into the liquid
  • 150-micron elastic strainer bags provide a high level of filtration
    • Use the 150 micron bags to filter fertilizer/ garden teas at the end of the brewing cycle
  • 100-micron mesh bags can be used to contain dry, powdered or plant-based ingredients when brewing fertilizer/ garden teas
    • Add dry ingredients and tie-off the opening with the drawstring

I. Compost Extract:

    Compost extracts can be made in minutes and applied immediately, making them very convenient if there is not enough time to brew aerated compost tea.  Compost extracts will provide a similar concentration of the microbes found in your compost. You can use compost extracts as a soil drench, root dip when transplanting or to inoculate; compost heaps, potting and planting mixtures.

How to Make A Compost Extract:

  • Fill your brewer with 4 – 5 gallons of chlorine free water or aerate municipal water as described above
  • Place 2 – 4 cups of compost into a 400-micron filter bag
    • The filter bag will help to keep your brewer cleaner, but is not necessary. You can just stir the compost in a bucket or barrel to keep it super simple.
  • Place the compost bag into your bucket / vessel and aerate, gently massage or stir for 1 – 5 minutes (whatever works for your situation)
  • Remove the filter bag and use the coffee brown liquid compost
    • Teas can be further energized by stirring rhythmically, alternating between clockwise and counter-clockwise stirring. Stir in one direction until a vortex is formed for 1 min before changing directions.  

Using Compost Extracts for neutralizing chemical agents in municipal water

    Compost extracts can also provide the necessary humic acids to help immobilize the harmful affects of chemical agents found in some municipal water sources. If you are using a compost extract for the humic acids to help with your municipal water then follow these steps.

  1. Make a compost extract as mentioned above
  2. Remove the tea bag and discard the compost onto a compost heap or mix into soil
  3. Use this liquid to brew a batch of aerated compost tea

II. Aerated Compost Tea (ACT)

   This method of brewing is also referred to as actively aerated compost tea (AACT) and will cultivate the greatest concentration of microbial life in your teas. Aerated Compost Tea or Actively Aerated Compost Tea can be applied as a soil drench or a foliar spray.

  • Fill a 5-gallon bucket with water
  • Add the any liquid or soluble tea ingredients such as soluble kelp powder, Humic acid, liquid fish fertilizer, etc. into the water and aerate for a minute or two prior to adding your compost
  • Place the recommended amount of compost into a 400-micron filter bag
  • Place the compost bag into your bucket or barrel of chlorine free water and aerate for 12 - 24 hrs
  • The compost bag can be removed after 12 - 24 hours
    • The bulk of the beneficial organisms from the compost are now suspended in the water
    • Do not squeeze or press the 400-micron filter bag as you may force sediment thru the mesh that could clod your air-diffuser and/ or spray nozzles
  • Brew your compost tea for the recommended minimum or maximum time and serve fresh

 Customize Your Compost Tea for Plant Types, Disease, or Pest

 These are general guidelines; recipes may need to be adjusted according to active biology present in your compost.

  • All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios): 
    • This is the most effective tea for all types of plants and soils: Use on most vegetable crops, grasses and pastures, flower and herb gardens, berries, fruit trees or to manage some pest and pathogen outbreaks.
  • Fungi/ Humus Tea: Use on deciduous and conifer trees, orchards, vine crops shrubs, acid-loving plants, or to manage pathogen outbreaks. Fungi dominated teas can also be used to enhance the growth of moss.
  • Bacterial Tea: Use on brassica family crops or to help manage pests.

Brew Times:

  • Temperature of both water and the outside environment will affect your brewing times
    • When ambient air temperature is above 60°F brew for 12-24hrs
    • At temperatures below 60°F extend brew times generally 48-72 hours      
  • All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios): Brew for 12 - 36 hours to encourage a more balanced life within the compost tea.
  • Bacterial Teas: Brew for 12 - 24 hours to encourage bacterial biomass.
  • Fungi/ Humus Teas: brew for 36 - 48 to encourage a fungal biomass. After 48 hours compost tea begins to express protozoa dominance, which mainly feed on bacteria.

You may use the minimum brew times if you are starting with a few quarts of a good quality compost tea from a previous batch. Think of this like a bread starter

Sanitation:

 Clean your brewer, air diffuser, watering vessels, and/ or spray applicators immediately after each batch of tea or application

  • Thoroughly clean brewer bucket, air hose, air diffuser and spray applicator after each batch of tea
  • Use dish soap and a scrub brush to clean all residue known as bio-slime from all of your components before storing
  • “No Rinse Cleansers”, such as One-Step, used to sanitize bottles and equipment for the home brewing of beer and wine making works well to thoroughly sanitize your equipment
  • Baking soda makes an excellent abrasive cleaner
  • Hydrogen Peroxide can also be used to sanitize your equipment

Further Reading:
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