A liquid form of compost with concentrated active
and dormant forms of microbes plus organic plant growth promoting
substances.
Spray
it on the soil and plant surfaces or inject it into rooting areas.
It may also be used to treat seed before or during planting and to
control insects.
It
improves soil structure and the nutrient cycling
capability of the soil. Also, it improves pest and disease
resistance of plants.
Microbes
create pore spaces in soil through their ability to stick fine
particles together, aggregate larger clumps with fungal branches and
tunnel through the aggregates. As fine structure builds, larger
organisms can inhabit the soil, creating even more pore space. This
allows more oxygen to enter the soil so even more biological activity
can occur. It also allows the soil to act like a sponge and soak up
rain water, storing it for the plants to use and preventing erosion.
Soil with good structure is easier for plants to root into.
Plant
nutrition is mediated by the microbes and higher organisms in the
soil. Through their digestion of organic matter, they pass a steady
stream of mineral nutrients to the plant roots. Healthy soils,
containing high numbers of diverse microbes have the capability of
passing a full spectrum of mineral nutrients, hormones, amino acids
and vitamins to plants. By enhancing soil biology, compost tea
builds the capacity of the soil to pass nutrients to the plants.
It
is of little value when microbial biomass or diversity is low.
It
does not have the same long term ability as compost to improve soil.
It
is inexpensive.
It
has demonstrated the ability to protect plants from disease.
It
has demonstrated the ability to improve forage quality in pastures.
It
has demonstrated the ability to improve plant stress resistance.
It
can be applied directly to plant foliage, stems, limbs, etc.
Modern
compost tea “brewers” use either moving water or air to
agitate compost in a water bath to dislodge the bacteria, fungi,
protozoa, nematodes and other small soil organisms, as well as
compounds that promote plant growth. Microbial foods are then added
to cause the microbes to grow and multiply while the entire batch is
aerated to keep the oxygen level high enough to avoid fermentative
conditions (anaerobic activity). Most tea brewers are designed to
produce a finished compost tea in about 20-24 hours.
Early
work with compost teas demonstrated their effectiveness in
controlling some plant diseases if the microbial concentrations were
high enough. Many laboratories will perform direct count bio-assays
on compost tea to evaluate its quality. Laboratories usually measure
bacteria and fungi, and sometimes protozoa and nematodes in compost
tea.
There
are two controlling factors in the production of high quality compost
tea. First, extraction grade compost must be used. Secondly,
controlled conditions in the brewer are essential.
Composts made with a wide variety of materials are best for compost tea
brewing because they tend to have a greater diversity of
microorganisms. For example, manure based composts are typically low
in saprophytic fungi but high in bacteria, while wood waste compost
is usually high in fungi and comparatively lower in bacteria.
Protozoa usually do not have time enough to proliferate in a 24 hour
brewing cycle but if the brewing cycle is extended, they usually
increase in numbers. Nematodes will not increase in the brewer, so
they need to be supplied by the compost. The best compost for
compost tea production is usually a blend of bacterial compost and
fungal compost that is activated by the addition of minerals and
complex carbohydrates.
There are four parameters (other than compost quality) that control the
quality of compost tea:
- Water
temperature – higher temperatures increase the rate of
multiplication of bacteria and growth of fungi, which can speed up
the brewing process. At the same time, warmer water holds less
oxygen. Water that is too warm therefore, can cause the available
(dissolved) oxygen to be used up too fast, which will cause an
anaerobic condition. (Anaerobic conditions result in the production
of plant toxic compounds.)
- Water
quality - the optimal range of pH for compost tea production is
between 6.5 and 7.5. Also, water treated with chlorine or
chloramines should be de-chlorinated before use in the brewer.
- Amount
and types of microbial foods added to the brewer – if too much
nutrient, especially nutrients high in sucrose (sugar, molasses,
fruit syrups, etc.) are added to the brewer, microbial growth will
outstrip the supply of oxygen, again causing an anaerobic condition
in the compost tea. If too little nutrient is added, a ‘weak’
compost tea will be the result.
- Brewing
time – there is an optimum time period for brewing compost
tea. Too short a brew time will result in a weak tea containing
unused microbial foods. Too long a brewing time will usually result
in a loss of bacterial and fungal biomass, a loss in nematodes and
frequently an increase in protozoa (protozoa feed on the bacteria
and fungi).
Compost
tea is a living substance. It should be applied shortly after the
end of the brewing cycle. It may be sprayed on all above ground
parts of plants for foliar feeding and disease protection. Addition
of a sticker spreader is very useful for foliar applications. Once
applied to the foliage, the active microbes in compost tea begin to
attach themselves within 20 minutes and will not usually be dislodged
by a rain event. Compost tea may also be applied to the ground,
including turf, mulched beds or bare soil. When applied to the
ground, it is almost always beneficial to water it in well. To
improve plant rooting in poor soils, root injections can be very
beneficial.
In
agriculture, as little as 5 gallons per acre of compost tea are often
beneficial. This is of course added to enough water to evenly apply
it, and frequently added to the irrigation water. For landscape
applications however, it is not untypical to apply 10 gallons per
1,000 square foot area. Much depends on the purpose of the
application. When applying compost tea as a foliar spray to help
protect plants from disease, it is recommended that top and bottom
leaf surfaces be sprayed. About a cup of compost tea should be
enough for an average rose plant.
While
compost tea is always beneficial to soil and plants, often the
effects of one application are too subtle to notice. Occasionally,
the plants treated will receive an essential limiting nutrient or
nutrients from the action of the compost tea and very noticeable
changes are seen. The truest benefit of a program of compost tea
application are the long term building of soil quality and the
resultant hardiness of plants resulting from it. Plants well rooted
in healthy soil look better, resist diseases and withstand stress
better.
Addition
of soluble and chelated nutrients, as well as specific microbial
agents to compost tea can have a dramatic effect on plants. From
simple performance boost to plant rescue, enhanced compost tea is an
important new tool in agriculture and general land care. Addition of
enhancing products is usually done just before the application of the
compost tea. We call this enhanced compost tea BioSolutions.
