Compost Tea

Today we’re brewing up a batch of Compost Tea. To be more precise, Actively Aerated Compost Tea. Or as my kids are now calling it – Worm Poo Brew.

There are a lot of different interpretations of compost tea. I don’t like to say that most of them are wrong – but the more I’ve learnt about it the more I realise that the most effective compost tea is not most peoples idea of compost tea.


Nutrients or Life?

What do you think of when you hear the word compost – not compost tea, just compost? Living matter broken down so that plants can take up the nutrients again? A sort of organic fertiliser to feed your garden? So is compost tea just a liquid form of compost?

No, that’s the first misconception. Compost tea isn’t so much about the nutrients in the compost – as the bacteria and fungi that do the composting. We certainly can add some nutrients to the brew. But the aim of compost tea is to add life to your garden. These are the little creatures that break down dead matter into nutrients. These are the little life forms that communicate with the plant roots and swap minerals for exudates. If you get a healthy ecosystem of these guys on the leaves of your plants, there is no room for the bad guys like powdery mildew to take hold.


Aerobic or Anaerobic?

Quick primer –

  • Aerobic means lives on oxygen. You want to turn your compost piles to give the aerobic microbes the oxygen that they need.
  • Anaerobic means lives without oxygen. You want to keep your lacto-fermenting pickles or kimchi under the brine with no oxygen so that only the anaerobic guys are working.

So the next fork in the road is to aerate or not to aerate. Aerobic or anaerobic. I’m on the aerated side of the fence. We want our soil to be aerobic, so we want the aerobic microbes. The leaf surfaces will be very aerobic, so anaerobic microbes wont survive for long. I’ve done some anaerobic brews in the past – only because I didn’t have the right equipment for an aerobic brew. Anaerobic compost teas take much longer and they stink. I have heard, but have no direct experience, that anaerobic compost tea is beneficial for eliminating certain pests or diseases in certain circumstances.

I’m not really into brewing specific teas for specific circumstances – mine is more of a one size fits all brew. Aerobic brews take a bit more equipment, but it’s so easy to get hold of. I have a 50 litre barrel, a couple of air stones, air hose and a pump. That’s about it for equipment.

The main bit of equipment is the pump. These are easy to get from aquarium shops. I opted for the piston style rather than the diaphragm style. The piston type is noisier, but far cheaper. They also may not last as long as a diaphragm type, but I am only running it for 48 hrs every few months. I went with a 70l/min model – which is high for my 50l bucket. I could have gone 40 to 50l/min, but better too much than not enough.


Feed Material

The next decision is the feed material. Where do we get first generation of critters from? Most people use a good mature compost. For me, I don’t always have a mature compost pile. For me, worm casting are the best. No matter what (almost) goes into your worm bin – what comes out is a pH neutral, bacteria rich, nutrient rich, pathogen free, moist and fluffy material.

I have heard some people mention a manure tea – the problem with that is that we can be breading things are harmful to us or to the ground. If your compost has been through a good hot composting cycle, or everything has been through the gut of a worm, then you can be fairly confident that the likes of parasitic worms and e-coli are gone.


How to use it

One of the good things about compost tea is that it will never damage your plants – so you can use it undiluted. You can also dilute it to make it go further – 1 part compost tea to 4 parts rain water. I have heard it used out to 1:8, but I built my system to make much more than I need. So much, in fact, that I have a surplus. What to do with that surplus? Give it away for social capital, or sell it to pay back the system and ingredients costs.

Once you have diluted it down, the final decision is where to put it. You can put it in a sprayer and use it as a foliar spray to coat all of the leaves. Or you can pour it into the soil all the way through your garden. I like to do both. I spray first until I have done all of my plants, and then water the rest over the mulch.


What Next?

This is just a brief introduction to compost tea. It’s a fascinating aspect of gardening. Like me, you have or will trawl the internet for more information. There is a lot of garbage on the internet. The most important thing you can do with that information is to look at it critically. If it’s rubbish, throw it out – don’t waste your time. If it makes sense and suits your situation – use it. Grow something with it.

Actively Aerated (Vermi)Compost Tea works well for me. Will it work for you? It depends.

Some time soon I’ll write a post on how to actually brew the tea. Until then, happy planting.


Leave a Reply

Your email address will not be published. Required fields are marked *