My Compost Tea Stinks: What To Do When Compost Tea Smells Bad

By: Amy Grant

Using compost in conjunction with water to create an extract has been used by farmers and gardeners for hundreds of years to add additional nutrients to crops. Today, most people make a brewed compost tea rather than an extract. Teas, when properly prepared, do not have the dangerous bacteria that compost extracts do. But what happens if your compost tea smells bad?

Help, My Compost Tea Stinks!

If you have smelly compost tea, the question is whether it is safe to use and, more importantly, just what may have gone wrong in the process. First of all, compost tea should not have an unpleasant odor; it should smell earthy and yeasty. So, if your compost tea smells bad, there is a problem.

There are many different “recipes” for compost teas but all of them have three basic elements: clean compost, inert water, and aeration.

  • Quality compost made up of yard and grass trimmings, dry leaves, fruit and veggie leftovers, paper products, and untreated sawdust and wood chips are suitable as clean compost. Worm castings are also ideal.
  • Pure water that does not contain heavy metals, nitrates, pesticides, chlorine, salt, or pathogens should be used. Keep in mind, if you are using tap water, there is likely a high concentration of chlorine. Let it sit overnight, just as you would when preparing a fish tank.
  • Aeration is important for maintaining oxygen levels, thereby increasing microbial growth — the good stuff. You may also decide to add a number of other additives such as molasses, fish-based products, yeast, kelp, or green plant tissues.

All of the above are crucial elements in brewing compost teas, but you should pay attention to several other issues as well in order to avoid a bad compost tea odor.

  • You want only soluble components to enter the water, so the size of the tea bag, whether an old nylon stocking, burlap or finely woven cotton, or silk bags is important. Be sure to use untreated material for your bag.
  • You want to have the proper ratio of compost to water. Too much water and the tea is diluted and will not be as viable. Likewise, too much compost and the excess of nutrients will foster bacteria, leading to oxygen depletions, anaerobic conditions, and smelly compost tea.
  • The temperature of the mix is also crucial. Cold temps will slow the microbial growth while temperatures that are too high may cause evaporation, inhibiting the microorganisms.
  • Lastly, the length of time your compost tea is brewed is paramount. Most teas should be of good quality and should be used in 24 hours. Well-aerated teas require shorter brew times while those created under more base conditions may need to steep for a few days to a few weeks.

Can You Use Smelly Compost Tea?

If your compost has a nasty odor, don’t use it. It may actually harm the plants. Chances are good that you need better aeration. Insufficient aeration is allowing harmful bacteria to grow and these guys stink!

Also, use most teas within 24 hours. The longer it sits, the more likely dangerous bacteria will start to grow. The proper ratio of pure water (5 gallons (19 L.)) to clean compost (one pound (0.5 kg.)) will create a concentrated concoction that can be diluted prior to application.

All in all, making compost tea has many benefits from disease prevention to boosting the nutrient absorption of plants and is well worth the effort, even if you have to experiment a little along the way.

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Read more about Composting Basics

Home Brewed Compost Tea

Gardeners know that compost works wonders by nourishing soil and plants. Compost improves soil structure, helping it drain well, yet still hold adequate moisture for plants. It makes nutrients more available to plants adds important microbes to the soil and improves the workability of soil. But compost can be heavy and bulky to transport and spread. Compost tea offers the benefits of compost in a lighter-weight package. It's a liquid version of compost, making it easier to apply to plants and soil. Plus, nutrients are more readily available.

The traditional method of making compost tea uses water to extract nutrients from the compost. The technique can be traced as far back as 4,000 years ago in ancient Egypt. It's very simple: Suspend a burlap sack filled with compost in a bucket or barrel of water and stir occasionally. The longer the compost is left to steep in the barrel or bucket or the more compost you use in relation to water, the more concentrated the liquid. This produces an extract of the compost.

Brewing compost tea is a more active process. By adding a food source, such as molasses, and adding more air to the mixture, you not only extract nutrients from the compost, but also grow a diverse population of beneficial soil microbes within 1 to 2 days. Adding the microbe-rich liquid to your soil boosts the number of 'good guys' and provides many benefits, such as increasing the uptake of nutrients and protecting plants from disease.

To make a simple compost extract, add 1 gallon of finished compost to a 5-gallon bucket. Fill the bucket to within 6 inches of the rim with water and stir it occasionally. After 3 to 7 days, strain the liquid through cheesecloth into another bucket, and use straight or diluted when to water your plants.

Commercial compost tea brewing systems make this process easy by supplying all the compost, equipment, and instructions you'll need. However, you can brew your tea with components you purchase at a pet supply store or hobby shop. It all starts with good, healthy, finished compost. You can use your own compost if you make sure your pile heats up to 140oF to kill harmful pathogens and weed seeds, or you can purchase commercially made compost.

Here's how to make a home brewed compost tea:

Add 1 gallon of compost to a 5-gallon bucket. Next, add air and food to the bucket. Attach air tubes to an aquarium pump and dangle it in the compost, keeping the pump outside the bucket.

Add 1 ounce of molasses to the compost, fill the bucket with water, and stir. Turn on the pump and let the mixture percolate for 1 to 2 days.

After brewing, strain the tea through cheesecloth, pouring the mixture into another bucket. For best results, use the tea soon after making it - aerobic microbes will die within 12 hours without the benefit of aeration and a food source.

Whether you make compost extract or compost tea, it should smell sweet and earthy. If it has a foul smell, then it may contain harmful microbes, and you shouldn't use it on your plants. Even better, to be sure your brew is free from pathogens, have your compost tested at one of the national labs that offer this service.

You can use a watering can or a garden sprayer to apply compost tea. If you're using a sprayer, filter the tea a second time through a cloth mesh or cheesecloth-like bag to strain out any pieces of organic matter.

Clean out your hand-held pump sprayer and fill with an appropriate mixture of tea. The rates of application will vary depending on your gardening situation. On poor soil it should be used straight, while on fertile soil it should be diluted - one part tea to 10 parts water. Apply it every two weeks.

Charlie Nardozzi is an award winning, nationally recognized garden writer, speaker, radio, and television personality. He has worked for more than 30 years bringing expert gardening information to home gardeners through radio, television, talks, tours, on-line, and the printed page. Charlie delights in making gardening information simple, easy, fun and accessible to everyone. He's the author of 6 books, has three radio shows in New England and a TV show. He leads Garden Tours around the world and consults with organizations and companies about gardening programs. See more about him at Gardening With Charlie.

How Does Compost Tea Work?

You may be wondering why you should use compost tea when you already add compost to your soil. Adding compost to your garden adds nutrients to the earth, but it’s part of a long-term maintenance process.

On the other hand, compost tea delivers all of those beneficial nutrients you get in compost, only faster. That’s because when you add compost to water and let it “brew,” it steeps out the nutrients and makes them more available to the plants. Kind of like a vitamin makes certain elements more available to your body.

Healthy Roots

Drenching with compost tea is a great way to quickly deliver organic fertilizer and beneficial organisms from compost to a plant’s root zone. Simply pour the tea mixture to the soil in the area below the plant’s leaves (or under the “drip line”). The liquid tea will carry beneficial bacteria, fungi and other microorganisms down to the area around the roots.

Once there, the bacteria will help unlock nutrients that are already in the soil but were previously in a state the plants couldn’t use (ex. converting unusable ammonium nitrogen to nitrite, then to useable nitrate). The mycorrhizal fungi will create a symbiotic relationship with plant roots that will benefit both the fungus and the plant. In exchange for some of the carbon in the roots, mycorrhizae will extend further into the soil to bring back nutrients for the plant. Some estimates suggest that mycorrhizal fungi can extend a plant’s reach in the soil by 95%!

Worm Tea

Worm Tea can outperform ANY chemical fertilizer known, increasing both plant size and yield. The synergy developed as the Worm Tea interacts with the microbes and protozoa in the soil and the plant’s roots. The organisms contained in it produce all the hormones, vitamins, nutrients, enzymes, amino acids, and minerals needed for plants in all stages to thrive.

Use worm tea to inoculate potting soil when starting new plants or seedlings and remedial treatment for any plants or shrubs growing in soil damaged by prolonged chemical treatments. Worm Tea is natural and will never burn or damage plants or soil.

The microbes in Worm Tea turn any organic matter in the soil into humus, effectively storing energy for later use. This is a basic part of soil fertility.

Worm Tea is a good source of nutrients for your plants. It is alive, containing various beneficial bacteria and fungi that help improve the soil and anything planted in it. For this reason, use your freshly brewed worm tea as soon as possible.

A couple of quick notes. Worm Tea is only as good as its ingredients. You must use the tea as soon as possible because the organisms last only a few hours out of their food source.

My formula for Worm Teas

10 gallons of de-chlorinated and de-chloramine water

1 1/2 cups of worm castings

1/2 of dried sea kelp or you could use liquid sea kelp (more expensive)

2 cups of un-sulfured molasses

1 aquarium aerator with stone

Place the aquarium aerator into the 10 gallons of water. Run aerators for 24 hours to remove chlorine or add a fish water conditioner to remove both chlorine and chloramines. If chlorine or chloramines are present, they will kill off the bacterial you want to grow.

Put the worm castings, sea kelp, and compost in a half nylon stocking.

Pour in the molasses into the water and stir until mixed.

Attach nylon stocking full of ingredients to the water container’s side and place it into the water. Submerge the nylon into the water. Continue to pump air into the mixture via the aquarium air pump for two days.

Once you have brewed your worm tea for two days, worm tea has a short lifespan. Use it within 8 to 10 hours.

Another great product you can make is Garrett Juice. The receipt is below.

Garrett Juice

Garrett Juice evolved over the years as I would tell readers and callers how to make a compelling foliar feeding mix. The mix has always had compost, tea, molasses, and seaweed, but the other ingredients have varied. Through trial and error, we came to the essential mix we use today. As always, my formulas are for making the mix at home, but commercial products are on the market for convenience.

To make your own, here are the instructions:

Mix the following in a gallon of water.
Garrett Juice (ready to spray):


Beginner brewers should get their feet wet by trying their first batch in a 5-gallon pickle bucket. As your interest and compost tea needs grow, you can always brew in a bigger container. Repurposed plastic drums, trashcans and other containers have been used for successfully brewing compost tea. Remember, the bigger the container, the more oxygen and compost you’ll need.

Depending on the types and proportions of each ingredient added, brewing compost tea can take anywhere from one to three days. Remember, UV rays kill microbes, so brew your tea out of direct sunlight. Finished tea looks a bit like coffee and smells really sweet and earthy. Use your tea within four hours to keep your microorganisms alive. Need more time? Keep the air pump running or refrigerate until you’re ready to use.

Watch the video: Poseidon 4 compost tea vortex style hurricane brewer 32 gallon.

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