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How to Make and Use Compost Tea

TOH landscape contractor Roger Cook shows how to get a beautiful, maintenance-free lawn using a natural liquid fertilizer

Q: Can you give me the recipe for making compost tea?
John Stumpo, Detroit

Roger Cook replies: Compost tea is a natural liquid fertilizer loaded with beneficial bacteria and nutrients that reach the roots faster than traditional compost. A lawn treated with the tea grows slower, needs less mowing, and uses less water because of its deep roots.

My compost recipe is 2 parts carbon-rich "browns," such as dead leaves, to 1 part nitrogen-rich "greens," like rotted grass clippings. I put 7 pounds of it in a mesh sack and suspend the sack inside a rain barrel filled with water and fitted with an aerator. Then I add 12 ounces each of molasses, liquid kelp, and fish hydrolysate. These last two are sold by Neptune's Harvest. It takes about 24 hours to brew 55 gallons of tea, enough for more than an acre of lawn. Once it's used up, discard the compost and start a fresh batch.

Step 1

Add the Tubing

Photo by Kindra Clineff

Cut a length of ⅜-inch-diameter irrigation tubing and bend it into a ring that fits the bottom of the barrel. Join the ends with a T-fitting, and attach the remaining tubing to the T's third leg. Using a 3/16-inch bit, drill a series of holes into the top of the ring about 1 inch apart; they let air bubble up, encouraging the growth of beneficial bacteria and reducing odors.

Step 2

Place the Lid

Photo by Kindra Clineff

Drill a ⅜-inch hole in the barrel's lid, and thread the irrigation tubing up through it. Fill a nylon-mesh bag or cheesecloth with about 7 pounds of aged compost. Pull the top of the sack through the lid's center hole, and hang it from a dowel so that the sack is suspended in the center of the barrel. Place the lid over the barrel.

Step 3

Let it Brew

Photo by Kindra Clineff

Connect the barrel to the downspout. Using a stainless-steel hose clamp, secure the aerator to the end of the tubing coming out of the barrel. Once the barrel is full of rainwater, run the aerator for at least 24 hours. (If using tap water, aerate for 20 minutes before adding compost.) Leave the aerator on whenever there's tea in the barrel, to keep the bacteria alive.

Step 4

Spray the Lawn

Photo by Kindra Clineff

For lawns of 400 square feet or less, wet the grass with the tea using a pump sprayer. Use a backpack or walk-behind sprayer for larger lawns. One gallon covers about 1,000 square feet. At minimum, apply the tea in early spring, summer, early fall, and just before the lawn goes dormant, although there's no harm in letting your grass drink the tea more frequently.