Why Does Compost Tea Foam?

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Turning your compost into tea is one of the best ways to unlock its benefits. This mixture has plenty of nutrients, making it an ideal fertilizer for your garden. But when you are creating it, you might notice a layer of foam forming on top. So, why is this happening?

Several elements are responsible for making compost tea foam. These are; aeration, stirring the mixture, and the nutrients in the tea. Many people think that foam is an indication of the quality of the tea. But this is a myth. The key is preparing it properly and giving the beneficial bacteria the environment they need to thrive.

Having a bit of foam on your compost tea is normal. Keep reading to learn more about what the foam means and how you can create a healthy compost tea mixture.

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Why Does the Foam Occur?

Foaming is a normal response to the aeration used when making compost tea. This is most common when making aerated compost tea. This is where oxygen is added to the mixture, often through an air pump. The oxygen, combined with the bubbling of the water, is what is responsible for the foam.

There are a few reasons why it’s recommended to aerate the tea. First, it will speed up the brewing process. What used to take weeks will be ready in two to three days. Plus, it can help activate the aerobic organisms present in the compost. It can also be a way of preventing disease. Finally, adding oxygen will allow the worms to survive the process.

The good news is that foam isn’t something to be concerned about. It’s the sign of a good compost tea. It means that there are plenty of amino acids and carbohydrates present in the tea. This is what is needed for your plants to grow strongly. The nutrient levels will also determine the amount of foam you will receive. For example, a mix that is high in carbohydrates tends to foam for longer.

Controlling Excess Foam

Usually, the amount of foam you receive isn’t a problem. It doesn’t indicate the quality of the tea. But if you are receiving an unusually high amount of foam, there might be a simple explanation. The most common culprit is dead earthworms in the compost mixture.

They will be releasing higher levels of organic acids and carbohydrates. It is this process that is causing the bubbling to occur.

If it becomes a problem, you can use a small amount of vegetable oil to control the foaming. You want to avoid using commercial defoamers. These will reduce the amount of foam. But they will also kill the bacteria.

What Happens if the Compost Tea Isn’t Foaming?

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When making compost tea, it’s common to see a layer of foam forming. This is how you know the aerobic bacteria is being activated properly. There are a few reasons why this might not be happening. Explanations include:

Not enough time to start foaming. Most recipes will require you to aerate the tea for several hours. So, don’t be alarmed if it doesn’t start foaming immediately.

You missed the foam period. Another simple explanation is that you missed the period where the foam was being formed.
Not the right mix of nutrients. It’s also possible that you don’t have the right nutrient mix to cause foaming.
Too much aeration. Sometimes, you can leave the tea to aerate for too long. Without any food, the beneficial bacteria can die off.

Generally, though, the compost tea isn’t foaming doesn’t necessarily present a problem. In most cases, the worm tea will still benefit your plants.

The exception is when you have left it to aerate for too long. Though it won’t harm the garden, it won’t bring the growth you expect from correctly brewed compost tea. Remember, you need to add food for the bacteria to consume. There are a few types of food that you can use, including:

Molasses. You’ll need to add between one to two teaspoons.

Fish hydrolysate. Usually, you’ll only need to use half a teaspoon
Kelp meal. Again, you’ll need to add half a teaspoon

If this works, the mixture should start foaming again.

When is the Compost Tea Ready to Use in the Garden?

Though the foam is a common reaction when making compost tea, it isn’t the best way of judging when the compost tea is ready to use in your garden. In most cases, you’ll need to keep the mixture at 75 degrees Fahrenheit (23 degrees Celsius). Keep it away from extreme temperature variations.

It should take between 12 to 48 hours to brew. If you are using a commercial device, you can consult the owner’s manual. It will often tell you how long it will take for the brew to be ready. Don’t forget to stir the brew regularly during the steeping time. This stimulates the bacteria. As long as you stick to the recommended brewing time and follow a good recipe, you shouldn’t have any problems.

Another way to tell when the compost is ready is by smelling it. If it starts to smell like ammonia, it has been brewing for too long. This is a sign that the bacteria have started to die. If you don’t intervene, the mixture will turn into a monoculture, with one type of bacteria dominating. This eliminates a lot of the benefits gained from making compost tea.

Once the tea is ready, it’s time to add it to the garden. Ideally, you should do this a few hours after you have finished the brewing process. Remember, the longer it remains brewing, the less diverse the bacterial mix will become.

Ways to Care For Bacteria in Compost Tea

Foaming is a good sign that your bacteria are happy and productive. There are a few simple ways to encourage the growth of positive bacteria. These include:

Preparing the water. If you are using tap water, it will usually contain a high amount of chlorine. This has the potential to kill beneficial bacteria. Thankfully, the solution is simple. You just need to heat and aerate the water for a few hours.

Space the bubblers evenly. By doing this, you will be able to make sure that every part of the pot is getting access to oxygen. You will often have to check their positioning each time you stir, as there is a chance that you can knock them out of position.
Use high-quality compost. When you are making compost tea, you will be encouraging bacterial growth. In most cases, these will be beneficial bacteria, helping your garden thrive. But there is also a risk that you could be encouraging harmful bacteria with E. coli. Aerating the mixture will also reduce the chances of this.

As long as you keep these tips in mind, you should be able to create a high-quality compost tea.

Final Thoughts

If you want to get the most out of your compost, you should consider turning it into tea. This mixture contains plenty of beneficial nutrients to support healthy plant growth. Plus, it’s easy to create at home. Though the foam is often used as a benchmark to find a healthy mixture, this isn’t accurate. Instead, it’s better to pay attention to how the tea is being created and the ingredients you are using to prepare it. The ultimate test, though, is how the plants respond when given the tea.

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