How To Make Simple Compost Tea

Compost tea is traditional compost steeped in water, to create an extract for use as a soil drench or foliar feed. The brew packs a nutritional powerhouse for soil, roots, and leaves, introducing healthy fungal colonies (think of how probiotics benefit the digestive system) and beneficial bacteria to cannabis plants. 

Some of the benefits of compost tea

The brew packs a nutritional powerhouse for soil, roots, and leaves, introducing healthy fungal colonies (think of how probiotics benefit the digestive system) and beneficial bacteria to cannabis plants. The results are a boost in plant growth and protection from disease. Farmers have used compost tea for generations as a cheap and effective means of adding nutrients to plants; however, the cannabis community only woke up to compost tea’s potential within the last decade or so.

Though not all growers agree on whether compost tea is any more effective than ordinary compost, some cultivators have pinpointed these potential benefits:

  1. Reducing the presence of weeds and pests, which consequently helps cannabis plants fend off diseases such as blight. Compost tea may shield marijuana from pathogens that could harm or even kill the plant.
  2. Infusing the cannabis plant with a strong dose of nutrients, which can potentially increase plant size due to a strengthened immune system from a diversity of trace minerals.
  3. Eliminating the need for chemical fertilizers that ultimately harm the soil and the environment when contaminated water leads to runoff and seeps into public water supplies. With compost tea, you are creating something 100% organic, which facilitates a thriving and self-sustaining ecosystem.
  4. Maximizing water retention in the soil, meaning less wasted water.
  5. Improving the overall health of the plant with a beneficial cocktail of fungi, bacteria, protozoa, and nematodes of multiple species.

How long does it take to brew compost tea?

It only takes about 24-36 hours to make either kind of compost tea noted above. Any longer than that and your concoction will be in danger of collecting some not-so-friendly bacteria like E. coli and salmonella. The microbes within will use up all the oxygen, which creates anaerobic conditions and increases the likelihood that bacteria, viruses, and molds will thrive.

What is aerated compost tea?

Aerated compost tea, also known as aerobic compost tea or actively aerated compost tea is exactly what it sounds like: regular compost tea that is mixed with a lot more oxygen. The theory is that if microbes use up oxygen quickly, which begins to create anaerobic conditions, then aerating the compost will produce larger populations of good organisms faster and prevent the bad ones. This is done by using an aerating pump like the ones used in fish tanks to create a bubbling action in the liquid.

What other types of compost teas are there?

  1. Plant tea: Instead of soaking compost, a plant that has nutritious properties is soaked in water to extract those nutrients. The most common plants used are comfrey and nettle, which can add valuable nutrients like phosphorus and potassium to the soil.
  2. Manure tea: This is a very common fertilizer used by farmers, which is a mixture of various aged manures soaked in water. It’s not really the best home project as it becomes very stinky.
  3. Commercial microbial tea: Just add water! These instant tea mixes are usually designed to combat specific plant issues, but proponents of homemade compost tea believe that they do not have enough microbes to be worthwhile. However, they are technically much safer because they are free from bad bacteria.
  4. Compost leachate: There is a fine line between compost leachate and regular compost tea because both require compost to sit in water. However, leachate is created when water leaches through vermicompost (worm compost) or your compost bin and out the bottom. Because it’s not fermented, it is considered to be only valuable for the nutrients it contains, rather than the living microbes. The Green Cone, a solar waste digester, is one such composter effective at creating nutrient-rich leachate for surrounding plants.

How do you make compost tea to enhance your cannabis harvest? Here is an easy compost tea recipe, complete with all the necessary steps and ingredients.

What is the best compost tea recipe?

To whip up the best compost tea to strengthen your cannabis plants and make them more resilient, you’ll need five main ingredients:

  • Compost: The first and most important ingredient is composted with a rich biome of nutrients and microorganisms. The more developed the compost’s fungal colonies, the stronger the compost tea will be. Organic compost from local sources provides the best foundation for this recipe.
  • Kelp: This sea ingredient feeds the fungal colonies and aids in development, ultimately activating the potency of compost tea.
  • Molasses: More commonly used as an ingredient in baking, molasses feeds the helpful bacteria, encouraging them to proliferate and maximize the benefits of compost tea. For an extra infusion of potency, try blackstrap molasses, which is saltier and more bitter than the ordinary kind, making it better for brewing compost.
  • Worm Castings: Though not the most appetizing ingredient, worm castings are dense in easily absorbed nutrients and introduce a host of microorganisms to the tea.
  • Fish Hydrolysate: Like kelp, fish hydrolysate feeds fungi, but it also contains nitrogen and chitin, the latter of which serves as an immune booster to marijuana plants.

Once you’ve gathered these ingredients, you’ll need a few supplies before the tea brewing begins.

Building a DIY Compost Tea Brewer

For the simplest kind of compost tea brewing, all you need is:

  • A 5-gallon bucket
  • Porous fabric, such as a nylon stocking or porous cloth for filtering the compost
  • Enough non-chlorinated water to fill the bucket
  • A sprayer or plastic watering can

For aerated compost tea, you will need everything above, plus:

  • An air pump
  • An airstone (aquarium bubbler)

You can make your own non-chlorinated water by collecting some rainwater or simply letting tap water sit for 24 hours. Fill up the bucket, and when it’s ready you can add the inoculant.

Many people dump the compost straight into the bucket and then just strain it through a burlap bag to separate the tea from the solids. However, it’s easier and very little work to put the ingredients into a nylon stocking or porous cloth tied into a bag. Make sure you have a rope or long end to pull it up so you don’t have to put your hand in the tea. If you are using an air pump, drop in the airstone and fire up the air pump.

Now, let it sit for about 24 hours. Too much longer than that and bad bacteria will start to take over. In fact, if it starts to stink then you’ve gone too far and it needs to be thrown out. Once you’re ready to use it, your tea needs to be used within four hours so that the active microorganisms won’t start to die.

Steps to making compost tea

The three steps to making compost tea are straightforward:

  • Build the brewer: Place the aquarium bubbler in the bottom of the bucket and use plastic tubing to attach it to the air pump outside the bucket. Fill the bucket with non-chlorinated water.
  • Fill the teabag (aka the mesh bag):  Remove any worms from the compost before you proceed with this step. Then, pour the tea ingredients into the mesh bag. 
  • Brew the tea: Carve out at least a 24-hour period to let the pump run continuously and brew the tea. Be prepared to apply the compost tea to the soil as soon as possible, preferably within 36 hours of adding the bag to the brewer.

There is an optional fourth step. You can supplement the compost tea with items in addition to the kelp, molasses, and castings. Try a biologically active product such as Actinovate along with supplemental food for fungi and bacteria, if desired.

Once the compost tea has brewed, apply it to the soil. You can also spray some of the mixtures onto the leaves for a more thorough treatment. This usage varies from plain compost, which is applied only to the soil and doesn’t directly reach every part of the plant. Foliar spraying is one benefit of compost tea, offering a more well-rounded treatment than might otherwise be possible.

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