Are you a gardener or agricultural professional looking for a useful material for plant production, or hoping to avoid chemical treatments that are too often assumed to be the standard for growing plants? Are you looking to return to the ancient roots of nutrient management and disease control? Or do you simply want to avoid the financial burden of purchasing bags of fertilizers and other soil amendments?
No matter what your rationale is, there is one answer: compost tea.
What is compost tea?
Compost teas are liquid versions of the solid compost material. They contain soluble plant nutrients and a complex community of beneficial microorganisms. While there are an infinite number of ways to prepare compost teas, basically all teas begin by mixing compost in water in order to extract plant nutrients and microorganisms. Liquid teas can be applied as soil drenches, foliar sprays or incorporated into irrigation systems.
Compost teas have gone by many different names. Some of the earlier names are slurries, watery fermented extracts, compost steepage, and amended extracts. In the last few decades, compost “teas” and “extracts” have been used interchangeably to describe the simple product of putting compost in water and extracting microorganisms and soluble plant nutrients. While there are some semblances to the tea you drink, such as its color, steeping process and optional use of a bag, the goal of making compost tea is to extract a part of the whole.
There are two diverging methods for preparing compost teas: aerated or non-aerated. The costs and benefits for each method are described below as well as instructions for at-home preparation. Aerated compost extracts are actively aerated with oxygen using a blower, bubbler or any other device used to force air into liquid. Alternatively, NCEs are not actively aerated but occasionally mixed or stirred to re-suspend solid materials that have settled to the bottom.
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Why use compost tea?
Plants require up to 17 micro- and macronutrients for growth and reproduction. When compost is placed in water, soluble nutrients are released into the solution and are readily available after the liquid is applied. The liquid environment, containing organic matter and other nutrients, is perfect for encouraging microbial growth. Bacteria and other microbes are attracted to germinating seeds and developing roots. Plants release a variety of exudates into the soil that are consumed by microbes. In return, specific microorganisms will release metabolites and other by-products of growth and reproduction that benefit plant production by suppressing plant diseases and increase nutrient turnover.
Compost extracts have been used for centuries because they work. While extracts can be variable and unpredictable, they will promote plant growth.
How to Make Aerated Compost Teas
What you’ll need:
- 6.5 gallon bucket with lid
- Aquarium air pump
- 3 to 6 feet of aquarium hose/tubing
- One T-valve or cross-valve (to increase the number of available air streams
- Aquarium airstones or bubblers (optional)
- 5 gallons of water
- 2-4 cups of mature compost, sieved through ½” mesh or smaller
- One nylon stocking, sock, or another porous bag-like material to hold the compost
Directions:
- Obtain the materials for preparing 1:20 to 1:40 (compost:water, v:v) ACT.
- Add tap water to the bucket and let sit over night to remove chlorine (you can also use rain water).
- Start aerating the water.
- Put mature compost in the bag and place the bag in the bucket.
- Initially stir or gently massage the contents of the bag.
- Let sit and aerate for 1 hour to 3 days. The longer the extraction period the great the potential for nutrients and microbes to be released into the water.
- After extraction, filter the liquid through cheesecloth, strainer, or a new nylon stocking.
- Apply the liquid immediately after preparation as a soil drench or as a foliar application. The liquid can also be further diluted with dechlorinated water as needed.
How To Make Non-Aerated Compost Teas
What you’ll need:
- 6.5 gallon bucket with lid
- 5 gallons of water
- 2-4 cups of mature
- compost, sieved through
- ½” mesh or smaller
- Long-handled instrument for stirring
Directions
- Obtain the materials for preparing 1:20 to 1:40 (compost:water, v:v) NCT.
- Add tab water to the bucket and let sit over night to remove chlorine or else use rain water.
- Put mature compost in the water.
- Vigorously stir the solution for about 2 minutes.
- Stir daily or twice daily for 7 to 10 days.
- After extraction, filter the liquid through cheesecloth, strainer, or a nylon stocking.
- Apply the liquid as a soil drench or as a foliar application. The liquid can also be further diluted with dechlorinated water as needed.
There is no one right way to make ACE or NCEs just as there is no one right way to make compost. Find a system that is effective, efficient and does not negatively impact plant production. It is more important not to cause damage to plants than it is to increase production. Often, the benefits of compost extracts are too small to observe but they still exist.
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The use of compost tea and compost are key aspects of a regenerative organic system, returning nutrients to the soil without the use of synthetic fertilizers. Share this post with other gardeners or farmers and watch the results grow!
Rick Carr is the Farm Director and former Compost Production Specialist for Rodale Institute. Compost-related questions can be directed to Rick.Carr@RodaleInstitute.org