Compost Tea: Does It Work, or Not?

This photo, supplied by Dan Corum at the Seattle Zoo, shows the rose gardens that are tended solely with compost tea.

I’ve long told the story of my Grandmother, Clarida Van Dyne, and her “manure” tea that she made on her dairy farm in Bradford, Maine. In recent years, as I’ve espoused the virtues of applying compost tea to the landscape to add valuable micronutrients and, most importantly, microbial life to the soil, I’ve had all sorts of feedback. Good and bad.

The official word from Cornell University, for example, is that compost tea doesn’t work. When it has measured disease suppression or the addition of “life” to the soil in terms of increase fungal or bacterial content, the illustrious New York institution insists that compost tea is bunk. Here is a passage from a 2007 article in the New York Times by Leslie Land, in which she pitted my “opinion” against that of Dr. Frank Rossi of Cornell.

To put this into context, Ms. Land was asking me how to hasten the transition from synthetic chemicals to organic solutions:

Asked if there was a way to speed things up, Mr. Tukey suggested compost tea. Applied monthly to a lawn that is also fed with organic fertilizers, it can reduce transition time to one season, he said, adding that compost tea ”is like a blood transfusion for the lawn.”

Frank S. Rossi, a turf specialist at Cornell University and a nationally recognized expert on golf course maintenance, does not share Mr. Tukey’s enthusiasm. Dr. Rossi’s research lab has evaluated compost tea’s effect on turf and found little proof of a major benefit.

And so those of us who see the results with our own eyes are left to scratch our heads, and even make a joke or two about it.

My friend, Sandy Syberg, of Purple Cow Organics in Wisconsin, told me he was heading off to California for a week of compost tea trials. “Haven’t you heard?” I asked. “Compost tea doesn’t work!”

We both shared a good laugh, but the serious question remains. Does compost tea really work?

The issue, of course, is that all compost tea is not created equally. In fact, there are probably as many variations in compost tea as there are variations in gardeners. Most essential is the quality of the compost from which the tea will be brewed. Then comes the addition of air to the brewing process, or the “feeding” of a food source such as molasses to the final mix. How much air to add? How much molasses to add? At what temperature?

It’s not all that different than brewing beer, and if you live in a state like Maine where I do, you know that dozens of different microbreweries churn out hundreds of different styles of beer that all taste differently — and all leave you feeling a bit differently both as you’re drinking, and when you wake up the next morning.

The bottom line is that the pros — the Elaine Inghams and Betsy Rosses of the world — have the compost tea literally dialed in. To even suggest that the application of their teas has no value is flat-out preposterous.

But will the tea you brew in your own five-gallon bucket have any value? Maybe. Maybe not. I have met hundreds of gardeners who swear by it and a few who don’t see the point. The good news is that it’s inexpensive, practically free, to make. And it really won’t do any harm, provided it doesn’t smell pungent or like ammonia when it’s applied. Good compost tea, like good compost, should have a sweet earthy smell. You can check out the compost tea video on the SafeLawns site: http://www.safelawns.org/video.cfm.

As for the teas you can buy at the garden center, you should ask the “fresh” question. If the tea has been capped for any period of time, the only thing living in the jugged tea will be bacteria. Fresh tea can be full of a whole rainbow of microorganisms and is definitely more likely to have a positive impact to your lawn, garden, trees or shrubs.

What’s your experience with compost tea? What pointers do you have, or comments — pro or con — to add to the debate? I’d love to hear them.