Actively aerated microbial compost tea is a water based, oxygen rich and cultured, containing large populations of beneficial aerobic bacteria, nematodes, fungi, and protozoa, which can bioremediate toxins in soils. This brew can be used as a fertilizer on flowering beds, vegetable beds, indoor plants, and crops of all sorts to increase growth, resilience and yields.
Compost tea is relatively easy, cheap and fun to make — it is also a really great activity to do with kids. It requires an inoculant of beneficial bacteria and fungi, some key food sources, dechlorinated water, oxygen and agitation.
Inoculating Compost Tea
Worm castings and aerobic compost are the best inoculant choices. Worm castings are a great inoculant because worms use bacteria instead of digestive acids in their stomachs to break down food. The castings are rich in beneficial microorganisms, which have been found to be effective in breaking down certain contaminants in the soil. Worm castings are also a source of humic acid.
The trick to making compost tea is using mature, diverse, well decomposed, fungal-dominated compost that doesn’t contain any dangerous pathogens. You want an incredibly biologically active compost, as the tea can only amplify the biology already present in the compost.
Use natural unchlorinated water from a mature pond or from your borehole. Chlorine will kill the beneficial bacteria in the compost tea. You’ll need around 11 litres of water to make the tea. If you don’t have access to non-chemically treated water, let the water sit out in the sun and fresh air for several hours. This will allow most of the chlorine in the water to break down.
Feeding Your Compost Tea
To create a tea rich in both bacteria and fungi, which is ideal for the remediation of contaminants in soils.
Such as unsulphured molasses, fruit juice, cane syrup and fish emulsion. Food for fungi include complex sugars, amino sugars and complex proteins. The most commonly used compost tea food sources for fungi are fish hydrolysate, kelp/seaweed and humic acid. Some additional food sources include fulvic acids, soybean meal, oat bran, oatmeal, fish oils, cellulose, lignin, cutins, rock phosphate dust, fruit pulp (oranges, apples and blueberries) and preservative free aloe vera extract. The more diverse, the greater the species of microorganisms likely to be present.
Compost Tea Recipe
Ingredients and Supplies
- 19 liter clean bin
- un-chlorinated water such as rainwater, pond or borehole)
- 1 cup of worm castings and/or aerobic compost inoculant
- 1/4 cup of food comprising of one or a combination of: unsulphured molasses, humic acid (1 tablespoon), fish hydrolase and kelp.
- 1 compost tea bag which can be made with a nut milk bag
- air pump
- backpack sprayer
Making Your Compost Tea Bag
For optimal extraction, don’t place the inoculant in the bag and not directly in the water.
Aeration and Agitation
Use an air pump to keep your tea sufficiently oxygenated.
You need both aeration and agitation for effective compost tea brewing. It’s the breaking of the surface of the water that gets oxygen into it. So instead of a lightly bubbling compost tea, you should aim for more of a rolling boil, or churning. To achieve this, you may have to play around with a few different air pumps. Try a high-pressure 3.9 psi, high-volume air pump 17 gallons per minute. Avoid using air compressors as they can damage microorganisms.
Considerations also need to be taken into account for the power source. The pump will need to be on 24/7 to aerated the tea
How to Make Compost Tea
Pretreat your compost to increase its inoculant and fungal power. To increase the effectiveness of your brew, add some humic acid or fish hydrolase to your inoculant. Place the ingredients in a shallow tray and mix it well. Leave it to sit for three days out of direct sunlight. This encourages fresh microorganism, making it more biologically active.
Fill a bucket with water. Ideal water temperature: 12-26’C.
Attach the aerator to the pump. Attach one end of a flexible tube to the aerator in the bottom of the bucket. Attach the other end of the tube to the pump outside the bucket. You can either leave the pump on the ground beside your tea, or clip it to the side of the bucket.
Make sure there is enough oxygen and agitation moving through your liquid; if not, get a more powerful pump or move to the gang valve and three-bubbler approach. Make sure the brew is churning or rolling boil.
Put inoculant in the nut milk/mesh bag, tie off the end and suspend it in the water.
Add the food.
Let the whole brew bubble for 24 hours and for no longer than 36 hours. After 36 hours, if the tea received insufficient oxygen or too much food, anaerobic organisms will overcome the beneficial aerobic organisms. It will be obvious if the tea went anaerobic, because it will stink!
If the brew becomes anaerobic, pour it into your bannan circle or worm bath and start over.
The mixture is ready, pour it through a fine sieve to remove any debris and sediment that may block backpack sprayer. Avoid using any metals while making and spreading your compost tea as it may harm the more delicate beneficial bacteria and organisms
Make sure to clean your bucket and pump for your next round of tea. Use a non-toxic, environmentally friendly, biodegradable cleaner.
Applying Compost Tea
Apply your compost tea within four hours of turning off the bubbler. Without oxygen your aerobic microorganisms will begin to die. You can apply it directly onto the contaminated and damaged land, a spill area or onto your phytoremediating plants to increase their health. It is best to apply your tea to moist soil or after a rain, on a cloudy morning or in the evening as some microorganisms do not like the baking hot sun. If you are applying your tea with a sprayer, make sure that the sprayer doesn’t need too high a pressure and that the velocity of the spray is slow — the microbes you are working with are delicate and require gentle treatment.
Use a digging fork to loosen the soil lightly and give the microorganisms a way to move more rapidly down to where the contamination may be.
Use about 4 liters of tea per 90 square meters of contaminated land. When you are using tea for remediation, drenching the soil instead of spraying plants. Apply the tea repeatedly, waiting two weeks to one month between applications.
If you are going to be making large brews of compost tea, you can use a rain tank-sized container. Just make sure to adjust the proportions of inoculant and food and get a strong enough pump or two to ensure the tank is properly oxygenated and agitated.