Worm Tea – Organic fertiliser – How To Guide

In this short guide we will be introducing you to one of the most popular organic additives for plants in all stages of development.

Worm tea is the liquid concentrate of worm compost. Mineral and microbial elements are extracted from the solid compost by actively brewing and agitating in water by using an air pump. This forces oxygen into a solution that can be applied to the plant surfaces (foliar spray), soils and in a range of other ways which can not be possible or economically feasible with solid worm compost. While a compost extraction can be made by simply stirring, it's made even better if continuous oxygen is incorporated into the mix which can increase the original numbers of microbes into billions. This is known as AACT or Actively Aerated Compost Tea, in this case “worm tea”. Worm tea can be used in both hydroponic systems and in soil, as well as a foliar application.

Worm tea may not sound too appetising but your plants will really love it. You can buy this amazing fertilizer from a number of online sites but if you have a worm bin, you can make your own. Worm tea allows you fertilize with something really nutritious for your plants without adding bulk to your soil. Your plants will practically jump up and shout “Hallelujah!” when fertilized with worm castings tea, and you will be amazed with the growth and flowering results.

What do you need to get started?

• 2 cups of well composted worm castings (no large scraps, preferably sifted).
• 2 tablespoons of corn syrup or unsulphured molasses.
• Water which has been left to stand overnight or rain water.

Step by Step Instructions

1. Fill a bucket with water. Either use rainwater or let the water stand so the chlorine can evaporate out. You don’t want to kill the beneficial micro-organisms, which is the point of municipal chlorine. Using a bubbler will speed up the release of Cl- ions from the water, cutting down the time the water needs to stand.

2. Add the corn syrup or molasses to the water. This will serve as food for the micro-organisms. Try dissolve the molasses in a small volume (like half a cup) of hot water before adding it to the bucket. This prevents potential obstruction of your air bubblers.

3. Place the worm castings in the bucket by either of the following two methods:
(A) Putting the castings into a thin mesh “teabag” of pantyhose type material or a similarly sheer sock and knotting the end. The knotted end of the bag can be hung down and submerged so the tea bag is situated above the rising bubbles. Some simply dump the teabag in.
(B) Putting the castings directly in the bucket (with no tea bag) if you plan to use a watering can. Straining it through cheesecloth or mesh may be necessary when using backpack-type sprayer with nozzles that could clog easily with debris and detritus.

Please note: The particle size of your worm castings (determined by source and packaging process) play a role in making this choice. Casting particles come in sizes ranging from marble sized balls to finely ground castings. The difference in total surface area exposed to water is much larger for the finely ground which has more exposure to the aerated water.

4. Use a bubbler e.g. air stone attached to an air pump if you have one. Place the air stone in the bottom of the bucket and connect it to your air pump with some air tubing. This will aerate your solution with many small air bubbles rising up from your air stone.

5. Let water and castings bubble (or at least soak) for 24 hours. If you don’t have a bubbler, consider stirring occasionally- don’t worry you can't hurt the micro critters (microbes) by stirring. The air stone at the bottom of the bucket will cause the tea to be in constant mix – this is the best way to get a high yield tea.

6. To produce high yield tea, conditions should be desirable for the microbes to proliferate, multiplying exponentially. The microorganisms from the digestive system of the worm are extruded in their castings. These aerobic (oxygen-dependent) microbes are “good” microbes for plants (nature’s way). Bad microbes are typically anaerobic (oxygen kills them) and many give off offensive odors as they release byproducts of metabolism like hydrogen sulfide (rotten egg smell). Aerating the tea improves conditions (agitation, circulation, aeration) for the survival, reproduction and growth of the good microbes. Aeration helps suppress the presence or growth of bad “bugs” that will compete against the good ones. Use of a bubbler helps along dissolution of the molasses food as well ensuring it dissolves and diffuses faster. Some instructions for tea setups without a bubbler recommend up to three days of brewing.

7. Be sure to use your worm tea within 48 hours. Exponential populations in limited spaces eventually peak and then plunge with massive population loss. We want the tea to be biologically alive with good microbes like Bacillus subtilis. To avoid losing the beneficial microorganisms you created, use the worm compost tea as soon as possible.

8. It can be refrigerated (in a sealed, labeled container) for up to 3 days. Non-pleasing odors from the tea after initial brewing or prolonged refrigeration may signal a low quality brew which should probably be thrown away. This could be added to a composter or wormery to prevent waste.