Worm Castings Tea – PART II

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Last week I provided you with a quick overview of the topic of ‘worm (castings) tea’. This week we’ll be talking in more detail about making tea. I was originally hoping to chat about how to use worm tea as well, but that will have to wait until next week.

Just as a quick recap, worm tea is created by soaking high quality vermicompost/castings in aerated (and de-chlorinated) water for a period of time.

As I mentioned, it is also very common for compost tea practitioners to add additional nutrients to their tea blends while they brew. This not only potentially enhances the nutritional value of the end product, but also acts as a means of ‘feeding’ certain microbial groups – namely the ones you want to be dominant in your tea.

Remember, not all plants thrive in the same soil ecosystems.

For the sake of simplicity, it is helpful to think of plants as preferring either bacterial or fungal dominance. Of course, we are over-simplifying a vastly complex topic, but it’s a good place to start. Generally speaking, grass, annuals, and crops all grow best in bacterially-dominated soils – whereas trees, shrubs and perennials often prefer a soil with a greater fungal dominance.

In order to enhance either of these groups in your worm/compost tea, you’ll need to add the right ‘foods’ during the brewing process.

As I mentioned last week, the type of compost you use is also important.

Again, worm castings themselves tend to have a bacterially-dominated group of microbes – whereas vermicomposts produced from high C:N mixtures (and still containing carbon-rich bedding types of materials) should contain a much larger fungal population than ‘pure’ castings.

According to an article in Worm Digest (Issue #21, 2001; pg 22), fungal food can include nutrients such as humic acids, fish hydrolyzate, and yucca, while bacterial foods include simple sugars like molasses, brown sugar, honey, maple syrup, as well as algal extracts and yeasts. Just as it is important to avoid chlorinated water – it is similarly important to make sure that these microbial foods don’t have any preservatives in them.

As I alluded to last week, there has been some controversy regarding the use of these nutrients when brewing compost teas.

Some in the composting and organic agriculture industries have suggested that this practice can lead to the growth of pathogenic microbes in the teas. Those on the pro-nutrient side have argued that not only would there need to be pathogens in the compost to start with (thus meaning they were not really ‘quality’ composts), but also, even if there WERE pathogens in the mix initially, the vigorous aeration and proliferation of beneficial aerobic microbes (pathogens tend to thrive more in low oxygen environments) would effectively eliminate them from the tea during the brewing process.

In 2004, a ‘Compost Tea Task Force’ was put together by the National Organic Standards Board to determine whether or not there was any cause for concern. The task force concluded that there WAS indeed enough evidence to suggest that pathogens could increase in abundance to the point of posing a health risk, even if the starting numbers were very low in the compost. Of particular concern were composts made using animal wastes, and those not undergoing a thermophilic (hot composting) period (BioCycle; Nov. 2007; pg52).

Vermicomposts and castings of course fall into this potentially dangerous category (unless a ‘precomposting’ period is used) – and this is why I would suggest that all beginners refrain from adding additional nutrients when first starting out.

That being said, in all honesty I don’t see a SERIOUS threat here.

Again, it is very important to use high quality composts – and if using those made from animal wastes, make sure they are very well processed. Aside from the arguments mentioned above (from the ‘pro-nutrient’ folks), it’s also important to mention that there are numerous documented cases of vermicomposting being an effective means of eliminating pathogens from a waste material. (Perhaps a topic I will dedicate a future newsletter to).

Ok – getting back to making worm tea…

If you want to get really serious about making your own high quality castings and compost teas, there are certainly plenty of commercial compost tea brewers (large and small) available for purchase online – maybe even more than there are different commercial worm composting systems.

But just as you don’t really need to buy a fancy worm bin in order to vermicompost, you certainly don’t need an expensive tea brewer in order to make your own quality worm tea. With some basic equipment and the key principles in mind you can produce your own ‘liquid gold’ for relatively little money.

An important starting place is with the compost/castings – just as you need tea leaves to brew normal tea, obviously you’ll need some compost to create compost tea (duh!). Of course, I personally advocate making it yourself, but you can also buy it from a reputable supplier as well (the latter option can actually be a good way to ensure you are getting top quality stuff).

As far as the actual ‘tea brewer’ goes, all you really need is a 5 gallon pail and some basic aquarium equipment – an air pump, some tubing, and some air stones (which attach to the end of the tube and produce lots of tiny bubbles – helping to increase oxygenation).

To get started, simply fill your pail with water and let it sit overnight (assuming you are using tap water) – if you add aeration right away you can speed up the process, but it’s still probably¬† not a bad idea to give it until the next day before you start brewing.

When the water is ready to go you can add your compost tea bag – this can be made by wrapping 2 or 3 cups of high quality compost in cheese cloth or simply putting the compost in some type of ‘breathable’ cloth bag. You can let the tea bag sit at the bottom if you want, but for best results you should suspend it in the middle of the water column to maximize exposure to water currents and aeration.

If your bucket came with a lid you may want to put it on during the brewing process (simply drill a hole for the air tube to go through) – this will reduce the amount of tea lost due to the vigorous bubbling. It will also help to reduce the amount of light shining into the system during the brewing process.

How long you brew your tea for is up to you, but generally 1-2 days should be sufficient. i.e. Leaving it for a week likely won’t make it any ‘stronger’ (more effective).

That’s it – very straightforward stuff!

Again, you might want to learn more about the various nutrients you can add to enhance the process if you plan on getting serious with your tea brewing. For those of you who are interested in learning more, I highly recommend you familiarize yourself with the work of Dr. Elaine Ingham, of Soil Foodweb Inc…


…there is great deal to be learned just from her website alone!

Next week we’ll discuss how worm teas can be used to enhance the growth and overall health of plants, and offer protection from a wide range of plant diseases.

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