by Arielle Illia
Brewing Compost Tea
If you are fond of gardening you more than likely understand the vitality of amending your soil with compost. We know that well aged compost plays a role in a healthy soil food web and promotes long term soil health but you may not be as familiar with compost tea's value, or what exactly brewing a batch of this tea, rich in microorganisms, entails. Believe me when I say, this tea IS worth your while and extremely gentle to plants and soil that you simply cannot over fertilize.
As gardeners we want our plants to thrive, we want strong leafy growth, big blooms, an abundance of fruits and large yields from vegetable crops, compost tea is the answer to your desires. So what is compost tea exactly? Compost tea starts with a microbial inoculant that is steeped in water, adding food sources and oxygen then provide ideal conditions for the aerobic beneficial microorganisms to proliferate, these microorganisms include bacteria, fungi, protozoa and beneficial nematodes. The results of regular applications of compost tea are notable, benefits include healthy plant growth and increased plant immunity, not to mention this tea is simple to brew and fun to broadcast, so why not supplement your current fertilizing schedule with compost tea?
Okay, so you want to get brewing (or at least try a batch I hope), the first thing you will need is a container or bin of some sort, we use a 35 gallon plastic garbage bin, we used a modified version of online design plans provided by Oregon State University:
Next you will need to fill this container with the appropriate amount of water for your brew, for this batch we fill approximately 30 gallons (you will need to account for bubbling that may spill over). If you are using tap water you can aerate your water for 30 minutes prior to adding ingredients in order for chlorine to off-gas. Our farm's water source is derived from a spring, if you have spring water or well water access you can skip this step.
Now we're ready to add our ingredients.
The first ingredient is a biologically active source of microorganisms, typically worm castings (good bacteria source) and/or well balanced compost (good source of fungi), we use a 1:1 ratio of each for our tea and for this recipe that is equivalent to 10 cups total. These ingredients are placed in a nylon mesh bag specifically designed for brewing compost tea (microns is important because the microorganisms need to be able to move freely out of the bag).
The next step is adding a food source for the microorganisms, unsulphured molasses is commonly used to feed the bacteria, we now add 10 tablespoons directly to the water.
Kelp meal is added as a fungi food source, we apply 10 tablespoons dry kelp meal into the mesh bags (if using liquid kelp meal, instead apply directly to water).
Now that your recipe is complete, it’s time to start brewing!
We fasten our mesh bags to the pvc pipe fully submerged in the water. An air pump is used to aerate the compost tea by means of pvc piping with small holes drilled throughout.
The degree of aeration is relative; you want to aim for a boiling or churning to knock the microorganisms free from the compost and/or worm castings. Brew your compost for a minimum of 24 hours but not longer than 36 hours, at this point or if at any time the air pump is shut off the microorganisms will begin to die.
Once done brewing, you will most likely see a frothy layer of bubbles. You ideally want to apply compost tea rapidly after the air pump has been turned off (within a few hours is okay). You can distribute by a watering can, pump sprayer or an electric sprayer, we prefer the latter method for applying a fine mist and since we are covering a good amount of square footage.
Generally foliar application is best for plant absorption and once the leaves are saturated the residual compost tea drips to the soil beneath. I typically spray each plant for a few good seconds then move on, but remember you can't overdo it so spray to your heart's content.
Compost tea is a wonderful fertilizer for indoor plants, flowers, trees, shrubs and vegetable gardens; you name it. It is also economical and convenient as it can be brewed on a small or large scale dependent upon your needs. We apply compost tea to our fruit and nut trees, the garden and flowers and shrubs every 2 weeks during the spring and summer months.