Horse manure is considered hot manure because it contains more nitrogen than cow manure, but it only contains about half as much nitrogen as chicken manure. Because horse manure usually contains weed seeds, it's best to compost it before using it to make manure tea. There is no one precise formula for making horse manure tea, but several combinations of manure and water will make a useful tea, depending on the how strong you want it to be.
Put four shovelfuls of horse manure into a 30-gallon trash can filled with water. Cover this and let it sit for two to three weeks. Stir once a day. Strain and it's finished. Manure tea that is not strained can clog drip irrigation systems.
Put a bucket of horse manure into an open-weave bag and suspend it in a 40-gallon drum and let it soak. After about a month, dilute it to the color of weak tea.
Put two shovelfuls of manure into a 5-gallon bucket filled with water. Strain out the manure after a week.
Put 3 to 4 gallons of composted horse manure in old pillow cases. Tie them shut and soak them in a bucket of water for a day.
Tea Bag Method
To make straining easier, put the horse manure in a burlap bag, onion bag or similar porous bag. Tie the top and put it in the water and let it soak like a bag of tea. Every couple of days, bob it up and down to help the manure mix with water.
Anti-Bug Manure Tea
To make a horse manure tea that also doubles as a way to keep bugs away, buzz up some garlic and hot chili peppers in a blender and add them to your tea.
The Maine Organic Farmers and Gardeners Association recommends that you compost manure before using it to make manure tea. A compost pile reaching 130 degrees Fahrenheit will kill any E. coli that may be present. The association also recommends that you do not use manure tea on vegetables within two months of harvesting them and within four months of harvesting root crops.