Aerated Compost Tea: Does it Work?

There’s a lot aerated compost tea brewers on the interwebs!

I’ve been asked by Urban Farm Magazine to write a short piece on the pros and cons of aerated compost tea (ACT for short). I’ve been sifting through the peer reviewed literature on the subject. Most of the studies show, at best, mixed results. And, honestly, my bias is against gardening techniques that require gadgets or novel techniques with no analog in nature. I’ve also tried it myself and found that a thick mulch of plain compost seems to work better.

That being said, I want to present a balanced story. I’m interested in hearing from readers about their ACT experiences. Have you tried it? Do you think it works? Or are you skeptical? Leave a comment or send me an email with your name, where you live and whether ACT did or did not work for you. I’d like to gather some anecdotal reports for the story and your help is greatly appreciated.

For those of you not familiar with ACT, here’s a good explanation with some resources via Permaculture Magazine: What is compost tea (and how do you make it)?

On the con side of ACT, horticulturalist Linda Chalker-Scott has a set of pdfs as well as a long list of ACT studies on her gardening myths page.

The Fine Art of Worm Grunting


For your Monday viewing pleasure we have two videos showing worm grunting in Florida.

Worm grunting is a technique used to lure worms out of the soil to collect as fishing bait. Basically, you take a stick (called a “stob”), pound it into the ground and rub a metal rod (known as a “rooping iron”) against the top of the stob. The deep vibrations are said to mimic the sound of burrowing moles, the natural predator of worms. When they sense the vibrations, the panicked worms crawl to the surface of the soil. (The high population of earthworms in the area profiled, upwards of 1 million per acre, makes grunting a sustainable practice.)

In England, grunting is called “worm charming”. And yes, there are competitions–in Sopchoppy, Florida, Shelburne, Ontario, and South Devon, England.

Kelly adds: Attn: geeks! After viewing, shall we discuss whether Dune author Frank Herbert knew about grunting…er…thumping? Were the Shai-Hulud fleeing even more terrifying SandVoles?

What Are Your Favorite Compost Materials?

Root Simple’s new composting game for your Xbox!

I wish I could source compost pile materials from our yard. But lead and zinc contamination in our soil make that a dodgy proposition without doing a lot of expensive lab tests. And I never seem to have enough materials even for our modest vegetable garden. So in the past I’ve used:

  • horse bedding
  • chicken manure from our own chickens
  • alfalfa hay (kinda spendy these days)
  • straw (takes a long time to break down)
  • spent grain from a local brewery
  • vegetable scraps from the farmer’s market

Once again I’ve got to build another pile and I’m interested in hearing from readers about compostibles you’ve used. Do you have a good source for stuff to compost? What are some of the things you’ve managed to scavenge? Comments!

Tips on Composting from Will Bakx of Sonoma Compost

Sonoma Compost’s composting operation.

On Thursday at the National Heirloom Exposition, Will Bakx, soil scientist and operations manager of Sonoma Compost, gave a rapid fire lecture on the nitty gritty details of composting. Here’s some of his useful tips:

Temperature and Turning
Compost should stay above 131ºF for 15 days to kill pathogens. Bakx recommended getting a thermometer to check the temperature every day during the initial period and using Sonoma Compost’s handy Temperature/Turning Sheet (pdf) to keep track of the temperature of the pile. If the pile dips below 135ºF, turn it. If it doesn’t get up to temperature, add more nitrogen containing materials. If it gets above 163ºF, add more carbon containing materials. After the initial turnings just let it sit unless you have to turn to add moisture.

Bakx believes that you should turn as little as possible, just enough to achieve that first period of 15 days above 135º F. I really like the simplicity of this method and will definitely use the turning sheet the next time I build a pile. I really makes it clear when you should turn and how often.

Moisture
Lack of moisture, according to Bakx, is the number one mistake made by beginning composters. He suggested an ideal moisture range between 40-­‐60%. You can check the moisture level using the following technique:

Take handful of material. Squeeze firmly
Water escapes: >60%
Shiny ball: 55%–60%
Ball remains when tapped: 50–55%
Ball falls apart when tapped: 45–50%
No ball forms: 40–45%
Unless hand feels powdery dry: <40 p="p">

Bakx has drip irrigation set up on his large windrows, something I might try with my pile the next time.

Pile Size
The mimimum size for a compost pile is 3 x 3 x 3 feet or larger.

Things not to add

  • Ash–our soils tend to be alkaline in California and ash will raise pH. A small amount is ok.
  • Cardboard–Bakx is afraid of the glues and said that he is very conservative about what he ads to his compost.
  • Toilet paper–because of metals (I’ve been unable to verify this–if any of you know about this issue, please leave a comment.

Alleopathic plant material such as eucalyptus leaves and walnut leaves, on the other hand, are ok to add. Bakx cited studies where plants were successfully grown in leaf litter made entirely out of eucalyptus leaves. He suggested keeping such alleopathic material to less than 15% of the pile.

Web links
Sonoma Compost’s website: www.sonomacompost.com
Sonoma Compost’s Simple Guidelines to Composting (pdf)
Sonoma Compost’s Temperature/Turning Sheet (pdf)
An online carbon/nitrogen ratio calculator

Comopost, Compost, Compost

As if I didn’t need a reminder of how important compost is to a vegetable garden, note the tomato above. It’s on its way out, but it grew with no supplemental water in hard-packed clay soil contaminated with lead and zinc in a hot side yard. Why did it do well while the rest of my vegetable garden did not do as so good this summer?

Homemade compost.

I didn’t have enough compost for the rest of the veggie garden so I bought some at a nursery. The homebrew compost obviously had much more life in it. 

And life is the point. Soil is a living thing. Plants, particularly vegetables, need microbial life to thrive.

For more on the importance of microbial life read the USDA’s soil biology primer written by Dr. Elaine Ingham.