Austin is very big on organics, and many nurseries are selling
freshly
brewed compost teas at $7/gal. It's being praised by a local garden
guru
as the very grail of gardening. This guru also promotes
"paramagnetism"
for more vigorous roots.

Yes, on Long Island you can buy homeopathic, magnetic compost tea!
That's right, I said magnetic; it contains ground-up magnets. And I
said homeopathic: one teaspoon of tea to 100 gallons of water, but be
assured that the "vibrations" from the compost molecules are
transforming the water, and making your lawn green and healthy.

On Long Island, we had to understand compost tea because our growers
were hypnotised by it (as well as electrostatic generators and cow
horns that focussed bioenergy). We also had a lawn-waste compost
industry that was pressuring us to come up with more uses for the
stuff, so they could make a profit. So I can say a few things about
it.

1) The source matters. The lawn waste compost was poor quality and it
contained so many pesticide residues that it was inhibitory if used on
tomatoes. Whereas composted malt and barley from out fledgling beer
industry was GREAT STUFF that dramatically increased the percent
organic material and improved the texture of agricultural soil. It
also had a high microbial activity as measured by fluoroscein diacetate
assays.

2) It's true: pathogens are largely killed by temperatures that won't
kill beneficial bacteria. But it's hard for anything but a big,
professional operation to get even, consistent heating. Most
home-composters can't do it, and sloppy operations can't do it. The
risk of getting disease by using poorly prepared compost is minimal,
compared to using, say, regular soil. But it can happen.

3) I've got friends who study compost tea. They have found minimal
benefits for disease control. But the quality of tea varies from batch
to batch, and it's difficult to replicate anything. I can't say that
*no* tea works, just that it's hard to study. Especially hard to study
is "induced resistance", where mycorrhiza or compost tea or various
other things are supposed to trigger the plant's natural defenses. You
can find studies that say everything from "it works" to "it doesn't" to
"it's detrimental". I've seen studies that show that a pathogen sets
up induced resistance to itself in a host plant. Think about it. How
well can that work, if it's a pathogen?

I think everyone should have a compost heap, but I'm skipping the tea,
the magnets and the cow-horns, thanks.