In simple terms, what is a Compost Tea and how does it work ?
A Compost Tea is a microbial soup which contains a diverse range of microorganisms naturally found
in a healthy soil. The vast variety of microbes which include, trillions of bacteria, billions of fungi, along
with millions of protozoa and nematodes, all of which have a different role and function in the soil
ecosystem are essentially ‘shaken’ from the compost in the brewer. These organisms then utilise the
food sources added to the brew, the activating nutrients and / or additional nutrient i.e. Seaweed /
Fish hydrolysate and proliferate, increasing even further in numbers.
This microbial soup is brewed for a minimum amount of time to ensure that the different
microorganisms reach their optimal numbers, after which the suspension is filtered into a suitable
spraying vessel i.e. watering can, diluted and applied to the plants as desired.
If you are applying Compost Tea to heavily managed soils; soils which have been chemically managed
or depleted, then you are adding a ‘fresh’ input of microbes that may already be existing but you are
also adding a vast range of microbes which may be deficient in the soils, due to the chemicals and
management techniques previously utilised. These new microorganisms with repeated applications
and their natural replication will grow in number and their enzymes, toxins and vast number can be
used to support plant health and growth. However, if you are adding the Compost Tea brew to a soil
which is in a relatively good state, the brew is acting like a probiotic, topping up the diversity –variety,
adding a fresh and new input on a regular basis to compensate for those which may have been lost to
predation, died or been killed due to the management techniques applied.
The vast diversity of microbes in the soil ensures that no one species gets out of control and is allowed
to grow uninhibited. The chemical toxins that the microbes produce, stop and can even kill each other,
so they will avoid each other and their population numbers are controlled in this manner. This inhibits
one species dominating and becoming a problem to the plant or the other microorganisms. They also
predate each other and control numbers in this way. Likewise, they are all producing a vast array of
enzymes which can breakdown organic material, making the soil friable and providing it with
structure. Similarly, whilst the microbes are undertaking degradation they are releasing in their
excretory products, Nitrogen in the form of Ammonium a plant fertiliser. Other soil bacteria perform
the nitrogen cycle, releasing forms of plant accessible nitrogen Ammonium and Nitrate. Similarly,
many other microbes in the soil undertake the solubilisation of sulphur into sulphates and
phosphorous into phosphates which makes these elements accessible to a plant. The soil
microorganisms also promote plant health by making the plants own immune system stand on ‘alert’,
so you not only have a plant which is being protected and fed, it is also alert and ready for any potential
attacks. So, the range of functions completed by the soil biology is astronomical.
