The Organic Corner: June Bulletin 2009
Some thoughts on Actively Aerated Compost Tea
Excerpts from an article by Jeff Lowenfels; Jeff has given his permission to this for use of parts of this discussion.
When I write about compost tea and promote its use to return biology to soils, I am speaking only of “Actively Aerated Compost Tea” (AACT); a term applied to the resultant of mixing compost, humus or vermin-products with non-chlorinated water and aerated twelve to thirty-six hours (depending on the brewer). Appropriate microbiological nutrients can be added, but don’t have to be, to increase the population or size (in the case of fungi) of microbes during the process. The mixture must remain aerobic for the entire brew. I am not referring to compost leachate, the liquid that oozes out of compost when it is squeezed or becomes too wet. This might have a tiny bit of nutrient value, but contains relatively few micro-organisms from the compost. This is because it takes energy to remove bacteria and fungi from the compost.
Then there is compost extract. This is not AACT. This is the stuff produced by soaking a bag of compost (or, God forbid, manure) in water for a week or more. Except for an aerobic surface, most of the biology is anaerobic with none of the diversity of beneficial, aerobic micro-biota—the hallmark of AACT. I don’t consider these safe nor do I call them compost tea.
Manure teas? I won’t even use manure in my compost, much less soak a bag of it to make a tea. Using manure for anything in the yard and garden is asking for pathogens and e. coli in particular—not to mention a great way to apply things that don’t degrade in compost like tetracycline and other antibiotics used in animal feed and on animals. I don’t advise it for compost or for AACT.
Unless you add organic matter or nutrients you can’t fundamentally change the microorganism make-up of soil for the better for any significant length of time. A competent compost tea program includes the addition of “microbe foods” (inappropriately called “fertilizers”) as well as application of compost tea. Using compost tea is only part of a program to get soil biology where you want it.
Next, add compost and the appropriate mulches as well to restore life in soil that has been damaged by chemicals. Adding good compost works and is terrific to use, I would suggest that addition of active aerated compost tea (yes, along with microbial food or organic matter) will speed that process up. One teaspoon of compost has 1 billion bacteria. Compare this to the 4 billion in one teaspoon of AACT. You just need to look at soil before and after application of a soil drench of compost tea to know it imparts microbiology to impacted soils. And you don’t have to wait a year. Think about it: AACT works faster because the microbiology is not bound up in the humus of the compost.
This is not to say the stories about the use of compost tea, the home studies and comparisons that are not considered “scientific” are not extremely useful and shouldn’t continue. After all, it’s only been about eight or 10 years since folks have started to seriously use AACT and there have been vast improvements in systems and understanding the role of nutrients. Those of us involved with AACT have seen far too many “before” and “after” pictures of farms, golf courses, lawns, and vegetable gardens—and know of far too many stories of those who have rescued and then maintained gardens, farms and yards for several years now with only the use of AACT and a suitable food to sustain the micro herd. These were not parts of scientific studies, alas, but they are real life usages where real money was used.
Editor Note: In my third season of AACT—-my lawn never looked better; my arborvitae, that were on their way out are now the talk of the neighborhood and my exhibition dahlias have been outstanding as to size- form and color.
The reported successes with AACT should heighten the desire to see well-executed experiments to test and perfect what is a relatively new practice. I know they did for me and I have made and used AACT to repair years of chemical abuse in my yard. I use it on all starts and new plants and conduct experiments constantly. Add me to the voices who claim “the stuff works” based merely on personal experience. But I have to tell you, hundreds of my neighbors agree.
Let’s do the studies. However, let’s do them properly. Not any old tea is Compost Tea!
Finally, using AACT alone is not going to work. You must have sufficient organic matter in the soil to feed the soil food web critters you are introducing. This is why it is critical to add microbe foods (legally “fertilizers”) to keep the herd you’ve installed happy. Instead of thinking ‘application’ when using AACT, think ‘inoculation’ or ‘introduction.’ Once they are they are need to keep them alive and you do that making sure they have lots of organics to consume.”
Note: If you are really interested in learning all about your soil and the life that’s part of a healthy soil please get a copy of Jeff’s book. “Teaming With Microbes—a Gardeners Guide to the Soil Food Web” by Jeff Lowenfels & Wayne Lewis—Timber Press. Jeff and Wayne have made a complex subject very understandable to a non- pro like me. Once you read this book you will never look at your soil in the same way. Following the suggestions in the book I now have a very healthy soil full of life with worms all over the place. In three seasons my garden has never looked better and plants (dahlias) are outstanding. I no longer roto-till and can drive my dahlia support stakes in 14” by hand. Do yourself and your garden a favor —get the book and have a safer and better garden.
No chemicals and no poisons needed!