Worm tea, also known as casting tea, worm leachate, and worm wee, is another one of nature’s miracles. Filled with trace minerals and large colonies of aerobic bacteria, applying this to your plants is like giving someone a shot of penicillin (alright, maybe that’s a bad analogy but you get the idea).
Tea is made by soaking worm castings in warm water for a couple of days. The idea here is to not so much transfer trace minerals to the tea but to create a condition where aerobic bacteria can thrive.
This bacteria once applied to the root system of your plants, is the true nature miracle. If conditions are right, bacterial growth will explode and top out after 48 hours or so at which time it can be diluted and applied to your plants.
As a side note I used to brew my own beer with a much similar method. I created the perfect conditions for fermentation to begin and work in and I could always see this happening by the huge head of foam on the wort (as we called it) indicating vigorous yeast action.
The same goes for worm tea, while it is fermenting, so to speak, it will acquire a foamy head indicating huge bacterial growth. But have no fear for this is aerobic or ‘good bacteria.
Here is a good recipe for worm tea:
- 5 gallons of water, preferably rain water or well water (let chlorinated water sit until the chlorine dissapates),
- one half cup molasses,
- approximately a 1 pound of worm castings placed in a burlap bag,
- an aquarium air-bubbler.
The water you use should be around 70 degrees Fahrenheit (21 C) and a burlap bag is used because it is more ‘open’ than a stocking which may filter out some needed microbes. The molasses is food for an exploding bacterial population and the air bubbler aerates the solution to encourage bacterial growth.
Let the solution sit outside and out of the sun because UV rays will kill the bacteria you are trying to grow. You will soon begin to notice a head of foam on the solution indicating bacterial growth.
Keep the air bubbler going the whole time and after 48 hours bacterial populations will top out at which time you can use the solution as a foliar spray or water your garden with a diluted mix of 1:5, which means 1 part worm tea to 5 parts water.
Letting the solution ‘ferment’ for longer than 48 hours is not in your best interests. As bacterial populations begin to die anaerobic bacteria may move in and take over.
As a final note, aerobic bacteria do not have a bad smell but anaerobic bacteria will smell bad so use your nose as a general indication of the health of your solution.
Worm castings, otherwise known as worm excrement, worm humus or worm poo, is actually extremely beneficial to your garden – and to your hydroponics system the same as any other excrement or manure. It contains trace minerals and nutrients vital to your plants as well as humic acids that have been linked with increased plant growth.
When a worm eats and digests organic plant matter it excretes castings containing nitrogen that has been ‘fixed’ to make it usable to your plants. This is what a compost pile does; aerobic bacteria fix nitrogen through the composting process.
Fixed nitrogen, a mineral salt, dissolves in water into ions, and plants uptake this for nutrients. Does this mean that worm castings by themselves can be a soil substitute? No, it does not contain all the needed nutrients, just some.
In fact, the NPK rating of castings has been tested periodically and they average around 2-2-2 or 3-1-1 depending on the diet of the worms that created them. This makes castings a good soil adjunct but not a soil substitute.
Worm poo has gone through its own ‘composting’ process in the digestive system of the worms so is rich in bacteria – good bacteria known as aerobic bacteria. This is far more important to us who grow plants than the minerals found in castings.
Bacteria in the human intestines live with us in a symbiotic relationship; while not something we want in our food and digestive tract, in our gut this bacteria helps suppress disease and bolster our immune system. The same occurs in a plant root system.
Aerobic vs Anaerobic Bacteria
Aerobic bacteria take in oxygen and excrete carbon dioxide. These microbes live in a symbiotic relationship with a plant helping it maintain good health.
Anaerobic bacteria, on the other hand, do not need oxygen to survive. This grouping of ‘bad’ microbes can actually hurt your plant by stunting growth, damaging root systems, and promoting disease.
A well-drained garden will contain large colonies of aerobic bacteria and this includes hydroponics systems. This is why I never run hydrogen peroxide through my system to kill bacteria.
Keep the system clean and flush with water to promote the growth of aerobic bacteria while discouraging anaerobic bacteria from taking hold.A colony of beneficial bacteria in the root system of a plant will also bolster the plant immune system and help the plant uptake water more efficiently. Worm poo is loaded with this beneficial bacteria.
This brings us to the second use of worm castings, making worm tea, which is, in my opinion, the best use of worm compost.
Worm tea will transfer huge amounts of aerobic, beneficial bacteria to the root system of your plants and can be used as a foliar spray as well. It will suppress insect attacks due to a high amount of chitinase which damages insect exoskeletons.
This makes worm tea an effective insect repellent and possibly a bio fungicide of sorts. When worm tea microbes are sprayed onto plant leaves they may possibly be competing for food resources with other not-so-beneficial bacteria and maybe even fungus helping to eliminate them.
So the question remains…can worm tea and worm castings be used in a hydroponics system? They certainly could in a Mittleider hybrid system but would not do so well in a closed hydroponics system.
Particulate matter in the tea would tend to clog water pumps even if strained off. And since worm tea would contain some mineral salts which are the trace nutrients found in worm excrement it is possible a toxic amount of salts could build up quickly and damage your plants.
What is the level of mineral salts in worm compost? It all depends on the diet of the worm. A diet consisting of animal manure mixed in urine would result in a high concentration of mineral salts. Chicken manure is notorious for this.
Using worm tea in a passive hydroponics system or container system would work well as long as the system and plants are flushed often and we do this anyway as part of routine hydroponics maintenance.
So how does one obtain a relatively free source of worm castings? Get a worm farm and use the worm compost for your plants or sell the worms as fishing bait…build yourself a profitable business.
Even though the types of worms used in a worm farm are not necessarily what you would find out in your yard they are relatively inexpensive and will reproduce so a worm farm could be self-sustaining.