Compost tea has created a lot of controversy in the gardening community in recent years, with some gardeners swearing by it and others entirely opposed to it.
While it has been used in the past to add nutrients to soil, the focus has shifted to the microbes that are contained in the tea and their ability to cure certain common plant diseases.
There is little scientific evidence supporting recent claims that compost tea can help eliminate disease, but it can still be beneficial for use on plants where adding compost is not practical – like pot plants or trees.
In this article, I will be taking you through the uses, types and benefits of compost tea. I’ll also include a step-by-step compost tea recipe for making your own.
- Related article: How to Start Composting
What is Compost Tea?
Simply put, compost tea is water that has been brewed in compost. It’s basically compost in liquid form.
The compost transfers some of its nutrients and beneficial microbes into the water, which can then be used to water your plants. It acts as an organic fertilizer to make healthy soil.
The brewed tea contains bacteria, fungi, protozoa, and potentially nematodes that have all been found in composts.
These beneficial microorganisms work together to break down organic matter such as leaves, grass clippings, manure, food scraps, etc.
This process helps create healthy soils because the microbial activity increases aeration and improves drainage. It also reduces the need for chemical fertilizers.
Compost tea and this method of nutrient transfer has been around since early Roman Empire.
Benefits of Using Compost Tea
As mentioned above, there isn’t much research done on how effective compost tea actually is at treating specific plant problems.
However, many people swear by using it as an alternative to fertilizing their gardens and other benefits.
These are the core benefits that people see:
- Replaces expensive fertilizers.
- Some believe it can suppress diseases and help plants breakdown toxins.
- Organic – If you have ensured your organic compost is completely organic, then your compost tea will be too!
- Improves soil structure for nutrient and water accessibility and retention with the beneficial organisms.
- Easy to make.
Compost Tea Ingredients and Supplies
There are various recipes for making compost tea that vary from just adding compost in a burlap sack to a bucket of water to more complicated versions.
Below is a simple compost tea recipe that does have some additives as well as compost.
To make compost tea you will need:
- Non-Chlorinated water – rainwater is best, but you can use tap water if you allow it to sit for 24 hours before using.
- 2 cups of compost – Make sure the finished compost is fully ready, it should only have an earthy smell to it. Any bad smell will indicate that it is not ready to be used yet.
- 1 tablespoon of unsulfured molasses (does not contain the preservative “sulfur dioxide”)
- 1 tablespoon of liquid kelp fertilizer
- 1 teaspoon of liquid fish fertilizer, like humic acid or fish hydrolysate. This is added to feed the bacteria and fungi.
- A bucket to brew the compost in
- A porous cloth, like a nylon stocking or burlap sack, to hold the compost and act as a filter, like a tea bag. Steps for a DIY Compost Tea Brewer in the next section.
How to Make Compost Tea
Step 1 – Make sure your compost is ready. It should resemble a rich soil, with no visibly recognizable organic materials. It should not smell bad, be too wet, or have twigs or eggshells still in it.
Step 2 – Fill your bucket with non-chlorinated water. If you are using tap water, then make sure you leave it out for at least 24 hours before using it. Rainwater is always best to use if you can.
Step 3 – Add the compost, unsulfured molasses, and liquid kelp/fish fertilizers to your bucket and then strain it through your porous material. If you are aerating your compost tea, add your airstone and start the pump at this stage.
Step 4 – Leave it to brew for about 24 hours. If it starts to smell, then this means there is a build-up of harmful bacteria, and you won’t be able to use it on your plants.
Step 5 – Once it’s ready, use it immediately.
An alternative to Step 3 and using a loose piece of porous material would be to make your own DIY Compost Tea Bag. It is a lot less messy to make a bag out of your material and add your ingredients to that, much like a teabag.
- Using a stocking or a pair of tights is ideal.
- Tie some sting to the end of your compost teabag that’s left outside of the bucket and water. This allows you to easily remove the teabag from the bucket without having to fish about in the tea.
How to Use Compost Tea
It is usually used diluted at a ratio of around 1:4 with water. You can add it to the water in your watering can when you water your plants, and use it on the plant roots as well as foliage.
It is possible to pour it directly onto the soil if you feel your plants are in need of an extra nutrient boost. Some will also use it with a sprayer to spray it on foliage to improve the plant’s health and prevent disease.
You can also use this tea on your houseplants. It is a great way of giving them some nutrients that would normally be provided by compost being dug in regularly, or added as mulch.
Any plants where adding compost is not practical will benefit from watering with compost tea.
Types of Compost Tea
As well as aerated and non-aerated compost teas, you can make plenty of other kinds depending on what nutrients you want. Most of these teas are made in the same way with different food sources:
- Manure tea – Fresh manure is too strong to use on plants directly, so make sure your manure is at least three to four months old.
- Eggshell tea – Rich in calcium. Add the eggshells to boiled water and leave overnight before using. This will help any plants suffering from blossom end rot.
- Fresh plant tea – Use plants that are rich in nutrients, like nettle and comfrey, and leave to brew for a week. This fertilizer does smell rather bad, but it is a great fertilizer.
Compost Tea Tips
Here are some composting tips to keep in mind while making compost tea:
- Make sure you use pure water that does not contain any chemicals. Ideally, use rainwater, but if you do have to use tap water, then leave it out for 24 hours to allow the chemicals to evaporate.
- Don’t leave the tea to brew for too long. If you aren’t using a pump to aerate it, give it a stir now and again.
- Don’t use bad compost. Make sure your compost has a nice earthy smell, and isn’t too wet or slimy.
- Put your compost in a bag. This helps eliminate the need to strain the tea.
- If you have access to fresh air, then you should definitely try making aerated compost tea. Aeration helps oxygenate the tea which makes it more effective. The only downside to aerated compost tea is that it takes longer to prepare than non-aerated compost tea. Aerated compost tea has been known to contain up to 10 times more beneficial microorganisms than non-aerated tea.
- Use your compost tea as soon as it’s ready. Leaving it too long may cause harmful bacteria to build up.
Compost Tea Final Thoughts
Compost tea can absolutely add beneficial nutrients to your soil. There is a line of thought: why use compost tea when you can use perfectly good compost?
While I tend to agree with that statement because you can add a layer of compost to the top of the soil, then water in the nutrients. Sometimes this may not be a practical solution.
Compost tea must be made correctly to be beneficial, and sometimes may contain harmful pathogens. As a general rule, if compost tea smells bad, then don’t use it.
Compost Tea FAQs
Can you burn your plants with compost tea?
Yes, it’s possible to burn your plants with compost tea if the original compost was not well-balanced and too high in nitrogen. Compost that is manure-based usually has high levels of nitrogen. You can dilute it more before using it to help prevent burning.
What other types of compost teas are there?
Other types of compost teas include manure tea, fresh plant tea, and eggshell tea. These all work differently, but they’re all good compost teas.
What are the benefits of compost tea?
There are many benefits to using compost tea to improve the soil. It can act as a replacement to expensive fertilizers. There’s potential in it helping prevent plant diseases and breaking down toxins. It helps to improve soil structure for nutrients and water retention.
Why Is Compost Tea Even Better Than Compost?
When used properly, compost tea works better than compost itself. Compost tea contains about ten times more beneficial microbes than regular compost. That means it will break down faster and provide even greater nutrient value.
How long does it take to brew compost tea?
Brewing compost tea usually takes 24 hours. If you brew it for too long, harmful bacteria like E. coli and salmonella will start to be introduced.
What is aerated compost tea?
Aerated compost tea is brewed from compost, but uses an airstone or similar to actively add oxygen to the tea as it’s brewing. Microbes use up oxygen in the tea, which leads to anaerobic conditions. Aerating will help increase the beneficial microbes to prevent the bad ones.
Does compost tea need molasses?
Molasses isn’t necessary in compost tea, but some people prefer adding it. Molasses adds sweetness and minerals to feed the beneficial microorganisms.
Can I use compost tea everyday?
You shouldn’t use compost tea every day. Using compost tea on a daily basis could lead to overuse of fertilizer. This would eventually kill off any remaining beneficial organisms. Instead, it’s recommended to add compost tea once per week on average. You can use trial and error to see what’s best for your plants and garden.