Compost teas

The brewer bubbling away.
Our bubble style compost tea activator in action

Compost or manure teas are easy to make and simple to apply. They are really just a brew of nutritious organic materials that are diluted and either sprayed as foliar sprays or added to the soil at the root zone. If you’re looking for an easy and odourless, space saving way to get Nettle or Comfrey tea, check out our page on the ‘odourless compost tea press‘.

Odourless compost tea press
Odourless compost tea press
Nettle compost tea produced by this method (left) and the traditional fermentation method (right).
Nettle compost tea produced by the press method (left) and the traditional fermentation method (right).

Traditional compost and manure teas

The traditional method of making compost or manure teas is to place your compostable materials into a big bucket and cover them with water. Cover the bucket with a loose fitting lid or mesh screen. You then leave them for a couple of weeks and strain off the liquid to use on your plants. Add more water to the bucket and repeat the process.

This technique has the benefits of needing no equipment (other than a bucket) and that it is ‘set and forget’. The disadvantages are (possibly) flies and mosquitoes and (definitely smell).

Aeration (activation)

You can make a tea by simply soaking any organic material in a bucket of water for a couple of weeks but to make them extra potent, a compost tea aerator can continuously mix the ingredients by bubbling air through the solution. This gives a boost to the beneficial microbes that will break down the components of the tea into forms that are more accessible to the plants. It helps to drastically reduce the time required to make the tea.


Any organic material that can be added to a compost heap can be used. Here’s a few of my favourite ingredients –

  • Worm castings
  • Spent coffee grounds
  • Nettles
  • Yarrow
  • Comfrey leaves
  • Chicken poo
  • Animal manures
  • Molasses
  • Leaf mould
  • Bokashi liquid (from the bottom of the Bokashi bin, not the stuff you spray onto the veggie scraps)
  • Dolomite

Worm castings are a cornerstone of all of my compost teas. They are well known for their amazing range of plant nutrients. Nettles too have a formidable reputation for their nutritional content and make a well known tea in their own right.

Yarrow and Comfrey are known as ‘compost activators’. they have compounds in them that help speed the composting process through enhancing biological or chemical reactions in the compost pile. Comfrey is a dynamic accumulator and contains valuable potassium.

Chicken poo is a well known fertilizer that is full of nitrogen. That nitrogen boosts microbial activity quite well. We get pigeon poo from a free local source and that helps to add phosphorus to the mix. Check out this page for an easy way to use chook or pigeon poo on your garden.

Chook Poo percolator
Chook Poo Percolator


Molasses gives a food source to micro-organisms. This isn’t highly beneficial in the soil, as it does cause quick spikes in the microbe population that it feeds but these populations crash when this easy food source is used up. For our purposes though, it can increase microbe activity during the relatively short time we’re making the tea and help break down the organic materials into substances that can be more readily uptaken by the plants or soil biota.

Bokashi liquid adds a whole heap of new microbes to the mix. Even though the Bokashi process is anaerobic, if it is exposed to air for a while, it becomes colonized by aerobic microbes that use it as a food source.

Dolomite or rock dust has some minerals in it, but I mostly add it to the mix if it is too acidic.

For a batch of compost tea in a 60 litre bin add –

  • 200g worm castings
  • 100g Nettle leaves
  • 100g chicken or pigeon poo
  • 1/2 cup molasses
  • 1 cup Bokashi liquid
  • a good handful of Comfrey or Yarrow depending on how much is growing in the garden
  • usually a small handful of dolomite

These ingredients are added to 60 litres of rainwater and put into the compost tea brewer where air is bubbled through it overnight. It is then ready to go after filtration. Put the waste from the filtering straight onto your compost heap.

You can see from the ingredients that I reckon that the microbial population and activity is the prime driver of a good compost or tea but be creative with your mix, there are hundreds of ideas online. You can even just get existing compost and soak it in water for a couple of days before straining it and using the resulting liquid.

Bubble style aerator

This design is our oldest method of activating compost teas. It is a simple system of bubbling air through the compost tea, mixing the microbes and nutrients and giving them plenty of oxygen.

Vortex aerator

A more recent addition to our compost tea brewing repertoire is our Vortex aerator. This works by creating a spinning vortex in the compost tea which sucks down air and mixes it thoroughly. Because the liquid is always moving and is lifted to the jets by an air lift pump, it is quickly saturated with oxygen, giving the microbes a real boost. It has the benefits of the compost tea activator but with more thorough mixing of air and microbes.

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