Compost Tea: A Brew for Your Garden - October 13, 2004
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
Compost tea is a liquid fertilizer made from compost and has many additional plant benefits beyond providing nutrients. Compost tea is easy to make at home using low-tech, readily-available equipment. There is much to learn about making good compost and compost tea. So, let’s learn a little more about compost, compost tea, and then get brewing.
Your compost pile is full of living beneficial microorganisms (bacteria, protozoa, fungi, predatory nematodes, etc.) that recycle nutrients from kitchen and yard waste to release plant available nutrients and organic compounds back into the soil environment. The microorganisms present in your compost pile are always locally-adapted because they were present when you added the raw materials, contributed to decomposition, and persisted throughout the breakdown process. Compost tea is simply a method to multiply these beneficial organisms and introduce them back into your garden environment.
There can also be plant pathogenic (disease-causing) microorganisms present in compost. The trick to good compost and compost tea is to minimize these “bad actors” and promote the beneficial ones. Beneficial microorganisms thrive in oxygen-rich, well-aerated compost piles. When making compost tea, you should always start with sweet-smelling, well-decomposed compost. Worm compost makes excellent compost tea.
Aerobic bacteria are the basis of the compost pile food web and essential to producing good compost teas. When applied to the foliage and the soil, aerobic bacteria present in compost tea will benefit plants by inoculating the soil and plant surfaces with beneficial bacteria. This benefits plants by increasing competition with pathogenic organisms for nutrients, food, and living space. Some beneficial bacteria also produce antibiotics that further reduce pathogens.
Materials needed to make compost tea are: two five-gallon plastic buckets, aquarium tubing (8 feet or so), a gang valve to split the tubing into three outlets, three air stones (bubblers), an aquarium pump large enough to run three air stones, some unsulfured molasses, an old pillowcase or nylon stocking to strain the mixture, and an inexpensive sprayer to apply the finished tea. Attach the air stones to the manifold so that they are evenly spaced from each other in the bottom of a bucket and connect the remaining hose to the pump. The aquarium equipment ensures adequate aeration to promote the aerobic bacteria and the molasses provides a food source.
Compost tea takes about three days to make. Time it so that you have time to apply it when ready. To make the compost tea, fill a bucket almost full with water and run the aquarium pump for one hour to drive off chlorine (not necessary with well water). Take the air stones, manifold, and pump from the water and place in the other bucket, then fill it half full of high-quality, well-decomposed compost. Add aerated water to within 4 inches of the top and plug in the pump. After the compost/water mixture is bubbling, add one ounce unsulfured molasses and stir mixture with a stick of wood. Check the position of the air stones after each stirring.
Continue aerating the mixture for three days stirring when convenient (a few times per day). The finished tea should smell sweet and earthy. If the mixture smells foul, add a second pump to provide additional aeration. After three days, unplug the pump and let settle for 20 minutes before straining/decanting into the other cleaned bucket or directly into your sprayer. This method should yield about 2˝ gallons of tea. Apply immediately to the foliage of your garden, orchard, or landscape.
One application at the beginning of the growing season will get your garden off to a good start. You can apply as often as you like (three or four times during the season will probably be adequate). Lindsay Schram, Verde Valley organic gardener (and Master Gardener), uses compost tea at her farm and frequently promotes its benefits. She has attended courses taught by Dr. Elaine Ingham (compost tea expert/scholar) and will be demonstrating compost tea preparation at the Arizona Highlands Garden Conference October 18 and 19 at Cliff Castle Conference Center. Happy brewing!
The University of Arizona Cooperative Extension has publications and information on gardening and pest management. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at firstname.lastname@example.org and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
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