Worm tea is a liquid produced
by leaching soluble nutrients and extracting bacteria, fungi, protozoa and
nematodes from compost.
Why use Worm Tea?
Worm tea is used for two
reasons: To inoculate microbial life into the soil or onto the foliage of
plants, and to add soluble nutrients to the foliage or to the soil to feed the
organisms and the plants. Chemical-based pesticides, fumigants, herbicides and
some synthetic fertilizers kill a range of the beneficial microorganisms that
encourage plant growth. High quality compost tea is used to re-populate the
leaf surface and soil with beneficial microorganisms.
Why are repeated applications
important? Environmental conditions, although they vary, commonly include
numerous negative impacts that kill the microbial populations on an ongoing
basis. They include air pollution, prior pesticide and herbicide use, drift and over-spray, synthetic fertilizers, water pollution, chlorine, current building
and agricultural practices, over or under watering, compacted soils, unusual
freeze, drought, flood, etc. Repeated applications re-establish the beneficial
microbes that suffer or can be killed under the above abuses.
Improve plant growth as a
result of protecting plant surfaces with beneficial organisms which occupy
infection sites and prevent disease-causing organisms from finding the plant.
Improve plant growth as a
result of improving nutrient retention in the soil, and therefore reduce
fertilizer use, and loss of nutrients into ground- and surface waters.
Improve plant nutrition by
increasing nutrient availability in the root system as the food-web increases
plant available nutrients in exactly the right place, time and amounts that the
Reduce the negative impacts
of chemical-based pesticides, herbicides and fertilizers on beneficial
microorganisms in the ecosystem.
Improve uptake of nutrients
by increasing foliar uptake.
Reduce water loss, improve
water-holding in the soil, and thus reduce water use in your system.
Improve tillage by building
better soil structure. Only the biology builds soil structure.
A nice cup of good, hot tea has for years been enjoyed as a restorative
to the mind and body. Centuries ago human kind learned that the flavor and
beneficial essence of certain plants could be drawn from their leaves, bark and
roots by steeping them in water, sometimes fortifying the brew with a bit of
milk and honey.
How well we understand that a nip of soothing mint tea will settle the
stomach, a cup of fragrant chamomile tea will soothe frayed nerves, and a heavy
mug of vitamin rich alfalfa tea can stimulate a weak appetite. By steeping
these plant materials in water we can partake of what is best about them when
eating the plant is not an option. This concept of using water to draw
beneficial extracts from solid materials for the purpose of making a liquid
solution has applications beyond making we humans feel better, however. Our
plants and even our soils can benefit greatly from a nice cup of tea when that
tea is derived from a plant nutrition source like worm castings.
Understanding the Value of Castings
[worm poop] Castings added to the soil carry to the root zone a rich compliment of soluble
plant nutrients and growth enhancing compounds, a diverse and populous
consortium of microbial life and a substrate of organic matter harboring a
storehouse of nutrients that are not lost to rain and irrigation. The plant is
delivered an ongoing, reliable food source when bacteria and microscopic fungi
feed on the organic matter, releasing some of the nutrients to the soil and
storing others for their own energy and reproduction. When nematodes and
protozoa in turn feed upon them, the nutrients stored in the bacterial and
fungal bodies are released to the soil in a plant-available form.
Further, unlike soluble plant fertilizers, the nutrients stored in
organic matter and the bodies of the microbial life are not lost through
irrigation to contaminate ground water. When we add castings and the microbial
life they support to the soil, we aid in increasing the complexity and
diversity of organisms in the root zone, thus aiding in disease and pest
From Castings to Tea So, “why tea?” one may wonder. With compost and worm products
demonstrating such tremendous benefit to soil and plant life, why take the
extra steps to generate a liquid from this already understood and easily
applied solid material?
Leaf surfaces, like plant roots, harbor a rich microbial population that
protects the leaf, and thus the plant, from infection and attack by pathogenic
organisms. When the microbial consortium present on the leaf surface is reduced
by pesticide use or environmental damage, it exposes leaf surface, opening
infection points. We can reinoculate the leaf with the diverse communities of
microbial life found in compost and worm castings by applying a tea made from
these materials. Further, teas can be applied as soil drenches and root washes
after pesticide use, to reintroduce to the soil microbial communities that may
have been damaged by the pesticide. The microbes can then continue to provide
protection from pathogens to the plant as well as aiding in breakdown of any
pesticide residues in the soil, thereby preventing ground water contamination.
Teas also carry the soluble nutrients and beneficial growth regulators
contained in the solid matter used to make the tea. Many of these compounds can
be absorbed through the leaf surface, feeding and enriching the plant.
Steeping the finished, stable end product of a composting or
vermicomposting system in agitated, aerated water, then adding a nutrient mix
for microbial growth makes a true tea. The water is agitated to extract as many
of the organisms clinging to the solid matter as possible, and the nutrient mix
provides those microbes dislodged into the liquid with a food source on which
to grow and reproduce.
Aerating the water ensures that it is the aerobic
organisms that are supported in the liquid.
This blend of food and oxygen in the tea enables the microorganisms to
grow to numbers rivaling those found in the solid matter from which the tea is
derived. Teas must then be used within a few hours of being generated in order
to ensure aerobicity and high microbial populations.
Once the oxygen and food
are consumed, anaerobic organisms will begin to populate the system, producing
alcohols and phenols toxic to plants.
Good tea begins with good, quality compost, worm castings or
vermicompost, or a blend of these materials. Provided the solid material is
stable and supports sufficient beneficial microbial life, there is nothing in
these liquids to cause plant damage.
Using the tea
Compost and castings teas are a relatively new product in today’s
agriculture and gardening industries. Researchers are still identifying uses,
though there is considerable research demonstrating that teas can suppress
fungal disease in a variety of plant species and aid in disease prevention on
plants where disease pressure is great.
Application rates for tea will vary considerably with the type of plant
being treated, climate, and whether or not the plant is already battling a pest
or infection. Dr. Ingham suggests that in agricultural fields the application
rate begin at five gallons of undiluted tea per acre per week and adjusted as
needed based on performance. For home use, teas can be applied to flowers,
perennials, turf, roses, shrubs, trees and vegetables.
What we do not know about teas still far outweighs what we do know,
though research demonstrates an exciting future for tea use. The possibility of
finding a means of controlling certain plant diseases with a truly effective
yet benign material that simply capitalizes on nature’s own means of control is
a basic precept of sustainability and promises to help us repair the damage
already caused by conventional agriculture techniques.
we may not know everything there is to know about tea, we know that using it
harms nothing and very often brings great benefits. Indeed, there’s nothing
like a good cup of tea!
In collaboration with the people who have on-the-ground experience
with compost teas—namely the organic farmers using compost teas and the
manufacturers of compost tea brewing equipment—Dr. Ingham and Soil
Foodweb, Inc. have pioneered advancements in aerobic compost tea
brewing on the West Coast. The following characteristics of a healthy
soil foodweb, good-quality compost, and good-quality compost tea are
based on her work.
Characteristics of a Healthy Soil Foodweb,
per Gram of Soil
600 million bacterial individuals
15,000 to 20,000 bacterial species
150 to 300 meters of fungal biomass
5,000 to 10,000 fungal species
20–30 beneficial nematodes: bacterial-feeding, fungal-feeding, predatory
200,000 arthropods per square meter
Minimum Standards for Compost (for Row Crop Plants), per Gram of Compost
50-70% — moisture
2-10 µg — active bacteria
150-300 µg — total bacteria
2-10 µg — active fungi
150-300 µg — total fungi
10,000 — flagellates
10,000 — amoebas
50-100 — ciliates
10-50 — beneficial nematodes
Minimum Standards for Compost Tea, per Milli-Liter of Compost Tea
10-150 µg — active bacteria
150-300 µg — total bacteria
2-10 µg — active fungi
5-20 µg — total fungi
1,000 — flagellates
1,000 — amoebas
20-50 — ciliates
2-10 — beneficial nematodes
The Soil Biology Primer
is a landmark publication from the USDA on the living components of the
soil. It provides a graphics-rich summary of the soil foodweb and
relates foodweb health to soil health. It features individual chapters
on soil bacteria, fungi, protozoa, nematodes, arthropods, and
earthworms. Printed copies can be ordered through: Soil and Water
Conservation Service at 1-800-THE-SOIL