Worm tea is a valuable by product of worm farming and an easy direct way to improve soil fertility. There are actually two ways of obtaining worm tea from your worm farm

1. Leachate

Traditionally, the dark  leachate that drains naturally through the active portion of a worm farm is collected and then diluted with water and used as a liquid manure to feed both garden and pot plants. This liquid is certainly useful for feeding plants, but its efficacy may not be quite as good as is generally assumed, for a number of reasons that will be explained later.

Bottled Worm Tea


2. Wet Mixed Worm Tea

An alternate method of obtaining good quality  Worm Tea can be considered.  Whenever the fresh worm compost (worm castings) is being harvested from the worm farm, Worm Tea can be directly produced by wet mixing some of this manure (worm poo) with a quantity of water and then pouring the resultant liquor immediately onto the soil to feed your plants. If desired the liquid portion can be separated from the remaining solid sludge with the aid of a fine sieve or  suitable cloth. This filtering or separation is only really necessary if you do not want to add too much solid material to your pot plants, but is really not worth the bother for use in the open garden.


The True Value of Worm Tea or Worm Compost

What is not often not fully appreciated, is that it is not actually the solid faecal matter (worm compost) or liquid (worm tea)  that adds most to the fertility of the garden. These ingredients  do put valuable nutriments, minerals and  trace elements into the soil and improve its texture – howevert it is actually the millions of tiny aerobic microbes or bacteria that reside in the compost or liquid that actually do most to promote fertility. This is because these symbiotic bacteria, originating in the worms’ guts have the remarkable ability to fix nitrogen in the soil.

Nitrogen Fixing

Plants need Nitrogen as a most important constituent of their composition, but although atmospheric Nitrogen (N2) is incredibly abundant in the air, it is inert and does not readily react with other elements to form compounds. Some plants (legume family) can fix nitrogen on their own, but most cannot.  However the aerobic bacteria living symbiotically with the worms in the composting process have this ability, in the presence of moisture, to combine nitrogen with hydrogen to form ammonium ions (NH4) on the roots of plants. Ammonium ions, unlike elementry nitrogen are highly reactive and readily form nitrites and nitrates and recombine with carbon, oxygen and hydrogen to form more complex organic compounds, to produce amino acids, enzyms and proteins and other long chain compounds, which are the true building blocks of living matter.


Leachate versus Wet Mixing

Because the value of the Worm Tea is largely proportional to the amount of the nitrogen fixing bacteria it contains, there is an ongoing debate as to which method of obtaining the worm tea gives the better product. The salient fact is that in the traditional process of simply collecting the the dark leachate draining through your worm farm can result in a varying quality of product as the amount of bacteria within it can vary considerably, depending on how fresh it is.Therefore many feel that the second method of wet mixing produces a more consistent and thus superior product as it is always used freshly made.

The argument in favour of the wet mixing process giving the better result over the natural leachate is fairly convincing to me for the following reasons: –

  • In the first process, the leachate running into the containing sump  initially does contain a fair amount of the desired wholesome bacteria as it drips fresh into the reservoir or sump, but the bacterial load can quickly become depleted, if the liquid in the sump is left in a stagnant condition. This is because the collected leachate will begin to lose oxygen content over time and consequently this provides a less hospitable environment for supporting large numbers of the desired bacteria. These beneficial bacterias are aerobic (oxygen loving) and once they leave the worm’s gut the microbes need to have a constant supply of oxygen in order to survive and bloom.
  • However,if we use the second method (wet mixing) to make our Worm Tea, by liquifying the fresh worm manure with added water and then immediately using the resultant liquid on the plants, then the bacteria washed out of the vermicompost simply do not have time to die back from lack of oxygen, before being added to the soil.
  • There is another factor at play too. It must also be appreciated that any bacteria population will increase rapidly (even exponentially)  in the right environment and this growth will continue until all the available food has been consumed and then the population will inevitably start to die back. In the first process of leachate collecting the resultant liquid will inevitably have to be stored for some time before being tapped off, and so in the interim the available food for the bacteria will steadily be consumed by the microbes. Consequently the bacterial count will drop off proportionately as the food is used up. So it is inevitable that the optimum bacterial load will have been diminished considerably at the point the liquid is poured into the soil. The second process (wet mixing) avoids this problem as the bacteria end up in the soil immediatelly.


Enhancing the Value by Oxygenating

In either process, the amount of bacteria available can be greatly enhanced (or revived) by putting the liquid for 24 – 48 hours into a container which is oxygenated constantly with an air pump, such as those used in fish tanks (preferably with an air stone bubbler) These are incredibly cheap and use hardly any power at all.

Air Stone Bubbler


Adding some molasses, whey or similar high energy food  to nurture the bacteria, whilst oxygenating will further beef up the bacteria count to produce optimum results. But after oxygenating, you must always use the resultant liquor straight away – don’t try to bottle it for later use – otherwise by the time you use the worm tea it will have lost oxygen and stagnated and the bacteria will all be dead and its usefulness will be considerably reduced.


Practical Economies:

The best way to use both products from your worm farm for use as a liquid fertilizer, is to use the collected leachate liquid from the bottom of your worm bins, together with some added water, to wash out some freshly harvested worm manure – instead of just using water alone. Then aerate the entire mix  for 24 hours together with some molasses. After oxygenating the mix, use it on the soil immediately, don’t give the bacteria time to die back


Liquid Manure:

  • Organic farmers use several methods (both anaerobic and aerobic) to make liquid manure from animal droppings for their commercial applications. Gardeners often use a simple anaerobic method for producing liquid manure from cow, poultry and horse manure, by simply letting the manure stand in buckets of water for a couple of weeks. This method breaks down the manure and makes it available for immediate use by the plants, moreover this also prevents the fresh manure from burning the roots of the plants, but the process takes time and is generally messy, smelly and can attract flies.
  • A faster method to activate a quantity of animal manure for making large  amounts of healthy liquid plant food for the garden would be to combine three parts cow manure with one part freshly harvested worm manure (vermicompost) and then mix the combined mass together with twelve parts of water / leachate and then aerate the mix for 24 – 48 hours with your airstone bubbler. In warm weather the cow manure will be rapidly broken down by the aerobic bacteria and you will increase the yield of liquid fertilizer considerably and moreover end up with a good mulch for your soil as an added benefit .



  • Never add municipal water directly from the tap to the worm tea at any stage, or ever put it into the worm farm itself, as this water contains chlorine and can kill off the beneficial bacteria – use only rain, river or pond water. Otherwise you can use tap water that has been standing for a couple of days in an open vessel, this will give the dissolved chlorine gas a chance to escape.
  • You need warm weather to create healthy worm tea, as the biological activity of the microbes is very slow in cold weather – but in any event this restriction is probably is of little consequence, as you would not normally be fertilizing your garden in winter.
  • Loosen the soil that you going to pour the worm tea on, with a fork, to aerate it and then keep it damp, to provide an optimum environment for the bacteria to do their work.This will also allow stray worms and hatchlings from any casings to also continue adding their contibution to soil fertility.
  • If you do not seperate the solids from the liquor, it is best to dig in the resultant sludge to below the surface of the soil. This is necessary to protect its bacterial population from the heat of direct sunlight and will also protect any stray worms.