Wonderful Worm Tea
Many misconceptions surround what is called “worm tea.” Many people think worm tea is simply water that has had castings added to it, either mixed in or encased in a pouch, tea bag style. However, real worm tea is a powerful liquid rich in microbes with a limited shelf life. The microbes are fed a food source in a method that is similar to feeding yeast when making an alcoholic homebrew. Three liquids that are frequently referred to as “worm tea” are the runoff from compost bins, water with some castings mixed in, and real worm tea. What are the differences?
The water that runs off from your compost bin is actually called “leachate.” It is full of nutrients, but the microbes are anaerobic and could be harmful to plants. Another potential problem is that leachate could be contaminated by the waste added to a compost pile such as manures and decomposing food. Therefore, although it can safely be used to feed plants, it should be diluted with clean water and only used directly on the soil, never put onto the foliage or produce of a plant.
Water with castings
This product is also known as non-aerated compost tea. Putting castings directly into a container of water, either loose or enclosed in a porous pouch, adds the nutrients of the castings to the water. Therefore, it makes a good plant food water. However, it is not technically worm tea. It does not have the same powerful effects as properly brewed worm tea.
This is the liquid gold that is produced by soaking worm castings in water with a food source and proper oxygenation. The oxygen infused into the water results in a substantial increase of beneficial bacteria and nutrients. According to the USDA “Compost Tea Task Force Report,” the “primary reason for producing compost tea is to transfer microbial biomass, fine particulate organic matter, and soluble chemical components of compost into an aqueous phase” (http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5058470).
Making Worm Tea
Okay, so now that we have established what truly qualifies as worm tea, how do you make worm tea? The document cited above points out that there are numerous recipes. The general guidelines, however, are as follows:
Ingredients: chemical-free water (rainwater is the best), worm castings, a natural food source, and oxygen.
Method: fill a bucket with water. Insert the aeration method and oxygenate the water for a couple of hours. Add the bag of castings and food source. Brew with the aerator for 24 hours. The USDA data sheet gives the following direction: “Usually compost is filled into a porous container, which is then suspended in a water-containing vessel, typically 1 part compost to 10-50 parts water. Constant mechanical energy input is used to provide aeration either by air injection directly into the water or by re-circulation of the water, typically for 12-24 hours. Compost tea additives, such as molasses, yeast extract, algal powders, when included, substantially increase microbial biomass in the aqueous phase from microorganisms extracted from the compost” (http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5058470).
Helpful hints: pantyhose, cheesecloth, a laundry bag for delicates, or any similar fabric can be used to hold the castings. An air pump like those used in home aquariums works well as an aerator. Especially good are the stone bars that produce diffused bubbles. The water should be warm, above 70 degrees, for optimal reproduction of microbes. Worm tea should be stored in a container that will not rust, but use within 90 days. Store in a dark place since sunlight will kill the microbes that are growing.
Don’t Settle for Less
The big difference between real worm tea and the other liquids is that the infusion of oxygen will increase the number of beneficial microbes into the millions, resulting in a nutrient rich broth. There is also evidence that it will deter pests and prevent some plant diseases. Information on how to use it is available in a separate post. Worm tea does require some extra work, but the benefits are definitely worth the effort!