Benefits of Compost Tea

Why Use Compost Tea?

Sustainable plant health and plant production depends on specialised relationships with beneficial soil microbes. With this in mind, compost tea is used for two reasons:

  • To inoculate diverse beneficial species of microbial life into the soil or onto the foliage of plants and
  • To add soluble nutrients to the soil in order to feed the organisms and the plants present.

The use of compost tea is suggested any time the organisms in the soil or on the plants are not at optimum levels. Chemical-based pesticides, fumigants, herbicides and synthetic fertilizers will kill a range of the beneficial microorganisms that encourage plant growth. Compost teas improve the life in the soil and on plant surfaces. High quality compost tea will inoculate the leaf surface and soil with beneficial microorganisms, instead of destroying them.


What Is Compost Tea?

Compost tea is a liquid inoculum produced by leaching soluble nutrients and extracting bacteria, fungi, protozoa and nematodes from compost. The compost tea brewing process can be likened to brewing beer or wine and like these same processes, requires care and the correct tea-making equipment.

When these elements are present, making compost tea that will help your plants becomes as easy as flipping a light switch. If you want to inoculate a highly beneficial group of bacteria and fungi, protozoa and possibly nematodes, you can buy or make a high quality inoculum compost that has these organisms present and make Actively Aerated Compost Tea. “Compost tea” is a soil inoculum that helps to ensure that the needs of plants are met throughout their productive life.


Benefits of using compost tea

Improved plant growth as a result of protecting plant surfaces with beneficial organisms which occupy infection sites and also prevent disease-causing organisms from attacking the plant.

Improved plant growth through improving nutrient retention within the soil and subsequent reduction in the need for fertilizer. Beneficial soil biology communites substantially reduce the loss of nutrients from the plant root zones into groundwater.

Improved plant nutrition by increasing nutrient availability in the root system.  Predator-prey interactions increase plant available nutrients in exactly the right place, time and amounts that the plant needs.

Reduce the negative impacts of chemical-based pesticides, herbicides and fertilizers on beneficial microorganisms in the ecosystem.

Improves plant nutrient by increasing foliar uptake. The beneficial micro-organisms increase the time that plant stomates stay open, while reducing evaporative loss from the leaf surface in adverse conditions.

Reduces water loss, improves water-holding in the soil, and thus reduce water use in your system.

Reduces tillage by building better soil structure. Only the biology builds soil structure, and ALL the groups in the foodweb are required to be present. You can’t have just bacteria present in soils, you must have the fungi, protozoa, nematodes and microarthropods as well!.

Please be aware that plate count methods don’t tell you about the whole foodweb.


What Is In Compost Tea (microbial inoculum)?

Tea contains all the soluble nutrients extracted from the compost, plus additional microbe foods and  the species of bacteria, fungi, protozoa and nematodes that are present in the compost. Not all the individuals in the compost, but representatives of all the species in the compost are found in the compost tea. Making sure only beneficial species(anaerobes) are present in the compost is therefore critical.

Foods extracted from the compost or added to the tea grow beneficial organisms. A large diversity of foods and organisms are extracted from compost. The beneficial bacteria and fungi growing on the compost foods, along with the added specific microbe foods result in the growth of many individuals of different species. Molecular diversity analysis is required, however, to assess even a small portion of the species present in compost tea.

Only aerobes are desired. Anaerobes make alcohols that kill plant tissues very rapidly. Putrifying organic matter, which is anaerobic, also contains organisms which are not beneficial for your plants or your soils.


The Method Is Critical In Making Tea

In order to have the organisms in the tea, brewing conditions must be correct. 
The biology that is active and performing a function will be very different, depending on:

  1. Temperature of brewing
  2. The foods added to the brew
  3. Oxygen concentrations in the brewer during production
  4. The initial compost used, and therefore which species are present to be extracted (highly diverse inoculum compost is a pre-requisite to highly diverse “compost tea”)
  5. The length of time tea is brewed


Temperature during brewing should be related to the temperature of the soil, or of the leaf surface. If tea is applied in the late autumn, when temperatures are cool, it may be wiser to apply a tea where the organisms are mostly asleep, or that are selected to grow on plant residues and active during the cooler periods. Selection for this ability would be enhanced by addition of plant material to the brew, such as oatmeal, alfalfa meal, etc.


Foods added to a brew will select for particular species that can use those foods. Do you want a bacterial tea? Add sugars, simple proteins, and simple carbohydrates. If a fungal brew is desired, add more complex foods, such as plant material (oatmeal, soybean meal, flour), humic acids, fulvic acids (which will release bacterial foods after fungi begin the process of decomposition). Predators (especially protozoa) can be enhanced by adding hay (cut green and dried), or by soaking hay for a few days and adding the water to the tea brew.


Oxygen is perhaps the parameter that has been least understood in centuries of tea-brewing. Most beneficial organisms, the organisms that promote the processes that plants need in order to be productive, grow without stress, and therefore have the greatest resistance to disease, are aerobic organisms. To enhance this community of beneficials, tea must remain aerobic.


The Biological Approach - Benefits of a Healthy Foodweb

A healthy foodweb occurs when:

  1. All the organisms the plant requires are present and functioning.
  2. Nutrients in the soil are in the proper forms for the plant to take-up. It is one of the functions of a healthy foodweb to hold nutrients in non-leachable forms so they remain in soil, until the plant requires the nutrients, and then the plant “turns-on” the right biology to convert the nutrients into forms the plant can take-up (but which are typically very leachable).
  3. The correct ratio of fungi to bacteria is present, and ratio of predator to prey is present, so soil pH, soil structure, and nutrient cycling occur at the correct rates and produce the right forms of nutrients for the plant.

The functions of a healthy foodweb are:

  1. Retention of nutrients so they do not leach or volatilize from the soil. Reduction or complete deletion of inorganic fertilizer applications is possible.
  2. Cycling nutrients into the right forms at the right rates for the plant desired. The right ratio of fungi to bacteria is needed for this to happen, as well as the right numbers and activity of the predators.
  3. Building soil structure, so oxygen, water and other nutrients can easily move into the soil and into deep, well-structured root systems. Current concepts of plant root systems as being at the surface of the soil is the result of current agricultural and urban practices, not a real condition of plants.
    Roots should go down into the soil for at least several to 10’s and perhaps 100’s of feet, but the compaction that humans impose on soil results in toxic materials being produced, preventing good root penetration. The only sustainable way to deal with this is to have the proper biology build the structure in the soil again, so oxygen and water can move into the soil. When the biology is functioning properly, water use is reduced, the need for fertilizers is reduced, and plant production is increased.
  4. Suppression of disease-causing organisms through competition with beneficials, by setting up the soil and foliar conditions to help the beneficials instead of the diseases.
  5. Protection of plant surfaces, above or below ground by making certain the foods the plant surfaces release into the soil are used by beneficial, not disease organisms, making certain that infection sites on plant surfaces are occupied by beneficial, and not disease-causing organisms. And by making certain predators that prefer disease-causing organisms are present to consume disease-causing organisms.
  6. Production of plant-growth-promoting hormones and chemicals can result in larger root systems, although whether forcing larger root systems on plants is a positive result needs to be understood.
  7. Bio-Decomposition of toxic compounds.