To start, the physical characteristics of coco is unique in
that it changes its physical and chemical characteristics
dramatically over time. Green or newly harvested
mulch is actually the dust (and broken fibers) generated
by removing the fibers from the husk of a coconut. This
is unusable at this point. After several months of decomposition,
it begins to take on some usable characteristics
of holding moisture better, the release of Potassium and
other salts slows to a reasonable level, and the structure
remains intact. There is a fairly short period from this point
that the coco peat is usable in container plant production.
Ideally, the coco peat has to go further to actually
work with the plant correctly, but by then much of the
structure is lost and the usable time in is severely shortened.
While later stages of coco degradation are very
acceptable as a soil amendment, it is not suitable for
directly growing in. Structural problems are, however, a
small part of the issue.
In addition, the availability
of the nutrients present
is affected on a changing
scale along with continuing
decomposition. Coconut
Palms have the rare ability
to utilize seawater solution as
its source of water. Seawater
has a high EC, or Electrical
Conductivity, which is a measure of how concentrated
the salt level is. Plant cells do not exist in this range but
much lower. For water to move into the roots of a plant,
it has to overcome the Osmotic Potential of the membranes
the water molecules pass.
In typical soils and container mixes, fertilized at
recommended levels, the EC of the root zone moisture
(which includes nutrients [salts]) is lower than the internal
EC of the root cells, allowing water to move, or diffuse,
across the barrier membranes. As root zone EC reaches
EC levels of the plant, water movement slows and eventually
halts. Unfortunately, it does not stop here and is capable
of moving the other way. In this manner, most salt
burn situations arise, but not all.
Additionally, the process of
harvesting the fibers also increase EC levels because
the coconut husks are first soaked in seawater (the most
abundant water supply close to where coconuts grow),
which imparts its salts into all the pores of the coconut
material. When decomposition occurs, these salts come
out in very high amounts, especially Potassium, the most
prevalent element found as an ion (salt).
All usable nutrients become available to the plants internal
processes as ions, or charged atoms or functional
groups like nitrate. Ions affect each other, in fact, in the
plants processes they are combined in controlled fashion.
In a solution with other ions, and no controls, they still combine or associate with other ions of opposite
charge. They also affect the availability of each
other as similar charges. This is known as antagonisms,
where one element in a large amount will
decrease availability of another where it is in a
smaller amount. In this case as the concentration
of Potassium increases, the availability of both Calcium
and Magnesium decreases. It is more commonly
known as locking out. When combined
with the effects of pH and temperature, precipitation
of these salts can occur. The effect works the
other way when Calcium increases, potassium
availability decreases. Additionally, Potassium
has the ability to almost move at will throughout a
plant, it is mostly un-regulated; a characteristic all
plants have adapted by harnessing these ions to
do work as they move around.
This is all well and good, but how does that affect
the use of coconut peat/ mulch with plants? As
the coco decomposes, it gives off salts that increase
the EC of the medium which will result in
burning and imbalances in Calcium/ Magnesium
and Potassium balances or ratios; the greener
the coco, the worse the problem. About the time
this give off slows enough to really grow a crop in,
the structure has the characteristics of muck peat
and has to have amendments like perlite, sand,
pebbles or other large particles added to it to give
the medium air. Also, the state of decomposition is
at its highest, so what is left will not last long, even
being washed easily from the container. We know
that if the level of salts AND the ratio of these salts
could be controlled at an earlier stage, we would
have the advantage of good physical structure
and proper nutrient balance.
Coconut peat has some wonderful physical properties
that greatly benefit plant growth. To begin, it
is renewable so no stripping of natures resources. It
makes use of the final product left over from cultivating
and harvesting the much prized nut. At the
right point in decomposition, the coco peat can
be used as a stand-alone medium with no need
to add perlite or other persistent amendments. The
coco peat itself is fairly pH stable and buffers the
pH well, in a very acceptable range for plant
growth. While they are fairly solid and big early
on, once the peat particles are treated and
decomposed to a certain point, they are like
sponges with micro-pores that hold water,
away from the plant root but available to replenish
the larger pores the plant root can access.
This effectively limits excess water while
holding water in a reserve status. These particles
hold onto no ions, so as long
as the medium is moist, nutrients are available.
At the proper point of decomposition,
the particles form the perfect combination
of air-to-water spaces, because of the different
fractions now present, which can actually
mean more air space to water space with the
micro-pores holding a reserve of water, giving
a nice water buffer to the grower. There is no
oil on its surface, unlike peat moss, so wetting
the particle is never an issue. The key in all this
is to decompose the particle to the perfect
point to achieve this. The problem is still that
the rate of salt given off remains high at this
perfect point.
By controlling the decomposition process,
adding the correct nutrient buffer to adjust
the ratio, feeding the plants the correct ratio
of nutrients to offset the coco give off
will produce the perfect growing conditions.
When the medium is not taken into account,
the results can be disastrous. Even when fed
correctly, and the correct buffer of nutrient
ratio sets up, just one (1) watering with plain
water will wreak the buffer sending the plant
and medium into shock, rapidly escalating the
potassium level. Consequently, plants that do
not have enough of some ions like Calcium (there
are several) from under feeding or washing out,
will show deficiency in these and other elements
while the Potassium builds up in the plant tissue ultimately
to express as margin burning on the leaf
surface, mostly at the tip. The first thing the inexperienced
grower assumes is that they are feeding
too high and have salt issues so they back up
the feed concentration and leach the medium.
This, of course, magnifies the problem and it gets
worse. The key to proper coco growing is to use
the right feed to balance the products the coco
gives off, not just availability, but ratio of one to another
mineral as well.
It is equally important to water correctly.
Coco peat holds about 33 % more moisture then similar
grades of peat based mediums if it is in good structure,
but, because a great amount of this is tucked away in
the micro-pores, the medium can look dry but still be
plenty wet. The same rules apply here as
soil or soilless mix, water when the container looses 50%
of the maximum water it will hold against gravity (immediately
after drainage of a newly watered container).
Correctly this is done by weight and yes it does change
with time, root mass, humidity, temperature and growers
temperament (thumb on scale syndrome). By controlling
closely the decomposition and particle size, there
is no need for using anything to increase drainage like
perlite, which happily removes a disposal concern. Even
more air space can be achieved by increasing the fraction
of coco fibers and husks.
This results in a totally renewable and biodegradable
medium that resists compaction.
Finally, the pH of the medium, when buffered and controlled,
remains constant pretty much throughout its useful
life. The medium sets its pH at between 5.2 and 6.2,
perfect range, and will hold it there. Unlike peat based
products that try to go back to a pH of 4.5 or less within
3 months of being planted. By using the correct age
of coco, with the right porosity, coco potting medium
should be able to work through almost a years worth
of cropping before changing. The pH stays correct and
only the structure changes limiting the useful period.
So, we see that by controlling the aging process, using
the correct ratio of nutrients, using the correct composition
of nutrients, and pre-buffering the coco peat, growers
can anticipate getting the perfect medium, correctly
balanced, correctly composed, with good porosity, a
water buffer, and a lot less headaches then peat based
soilless mix products. That is great for a start, but to complete
a crop, it is critical that the correct nutrients be used
as well.
Consider coco as needing to be fed along with
the plants. Once the medium establishes a buffer, which
it will do based on the nutrients it sees right or wrong; the
grower can wipe this out by applying plain water to the
medium. The medium hangs on to nothing and will readily
flush away its nutrients; then the plant will suffer until
the buffer is restored. Always use fertilizer when you water
coco that a plant is actively growing in, at least at about
EC=0.6 mS/cm3. This will hold the balance or ratio of the
nutrients to each other and insure that the plant gets exactly
what it needs.
I don't have to think about it, they just deliver the goods... 
Saying that I haven't had the worst results using them.
