WHAT IS FOLIAR
fertilization is any fertilizing substance applied
in a liquid form.
fertilizers are concentrated solutions using very
high grade technical elements, in which the
nitrogen, phosphorus and potassium are combined to
the desired ratio in a controlled environment.
elements in this method are true solutions, soluble,
and thus very plant available.
This is in
contrast to soil applied (solid) fertilizer, which
is applied as a powder or granules to the soil in
dry form. This then, has to be dissolved, by
moisture (rain) to be plant available via the roots.
In other words, it has to dissolve into the soil
solution to be available.
To these foliar
solutions, trace elements in the form of chelates
are added, along with other additives to give a
balanced fertilizer, supplying not only NPK, but all
the trace elements as well as growth hormones,
Many different NPK
formulation combinations can be made, depending on
the application required. The same elements that
make up foliar fertilizer are required for plant
growth and development, and are formulated to meet
quite specific plant requirements. (see Table 1.)
composed of the various elements in the proportions
indicated below on which modern foliar fertilizers
16 elements are
considered essential for plant growth,
Internal Concentrations of Essential Elements in
Higher Plants - Concentration in Dry Tissue
elements are divided into two groups: the
macronutrients; those required in relatively
large quantities including carbon, hydrogen, oxygen,
nitrogen, phosphorus, potassium, calcium, magnesium
and sulphur and the micronutrients, those
required in small quantities; including iron,
chlorine, manganese, boron, zinc, copper and
You will see that
by far the biggest proportion is hydrogen, carbon
and oxygen which makes up 96% of the plant and are
freely available from the air and water.
All of the other
elements make up the remaining 4%, of which the
major elements nitrogen, phosphorus and potassium
make up 2.7%, leaving 1.3% minor or trace elements.
and oxygen which form the actual plant structure are
readily obtainable from air and water, specifically
carbon dioxide or water. Along with chlorine, which
is found in most water sources, these elements are
generally not considered in the formulation of
The following illustrates the
amount of each nutrient in Kgs/ Hectare, in pasture
of 2000 kg DM/ Hectare:
Depending on the
application required, foliar fertilizers can be
formulated to meet very specific plant requirements.
For example a high
nitrogen formulation is used when the demand in
plants is for more nitrogen in relation to
phosphorus and potassium, but the formulation is
changed for growth periods that require higher
phosphorus and / or potassium, in relation to the
demand for nitrogen.
This often happens
when a plant is under stress, which coincides with
periods of great growth, such as when a plant is
changing from a vegetative to a reproductive stage.
At the same time,
the exact plant requirement for trace elements can
be addressed, as a result of leaf analysis.
Certain soil conditions, such as pH,
excess moisture, or cool temperatures, may render a
nutrient or nutrients unavailable to the plant root.
curves indicate that there are stages in a plant's
life-cycle when demand for some nutrients may be
greater than its physiological capacity to supply
itself, even when these soil nutrients are available
in abundant supply. This often occurs during the
development of fruit or grain.
Data from trials
on crops, show that increases in yield and/or grade
results from applications of foliar nutrients during
these periods of peak demand.
can be designed to meet a plantís specific needs for
one or more micro and macro nutrients--especially
trace minerals and enables you to correct
deficiencies, strengthen weak or damaged crops,
speed growth and grow better plants, which is of
course, the bottom line.
applications can be targeted to a particular stage
of crop development to achieve specific objectives
and is an excellent way to "fine tune" a high
EFFICIENCY OF UTILIZATION OF
Here are some striking
examples of comparisons of foliar fertilizers
versus soil applications.
Such ratios favoring foliar
applications exist only under extreme conditions
of soil fixation. Nevertheless, they single out
the effectiveness of leaves as organs for
Related to the marked
efficiency in absorption of nutritional sprays
may be indirect effects of this method of
applying fertilizer on other plant processes.
Comparative efficiency of
foliar and soil applications of fertilizer.
Approximate ratios of
amounts required for comparable
et al. (1957)
et al.(1957, 1961)
showed that it was 8 -10 times more effective to
foliar feed a plant as far as the amount of
nutrients required and the speed with which
those nutrients were utilized, the above
authorities found the figure to be between 12
and 100 times more effective.
available nutrients are more easily utilized, as
they are directly available to a plant and
because they do not have to be dissolved by
moisture before going into the soil solution and
where they may be subjected to insolubalization
by incident anions such as carbonate,
bicarbonate, hydroxide, etc, known as fixation.
in foliar fertilizers, is whether or not the
products being used are chelated. Chelation,
allows a nutrient to "maintain its own identity"
within the spray tank, and not get tied up by
other nutrients or pesticides being used with
These days we
have materials available which are ideally
suited to spray applications.
are specialized chemical substances produced by
plants. Foliar fertilization is a particularly
useful technique: and are the main internal factors
controlling growth and development.
produced in one part of a plant and transported to
others, where they are effective in very small
Depending on the
target tissue, a given hormone may have different
Auxin, one of the
most important plant hormones, is produced by
growing stem tips and transported to other areas
where it may either promote growth or inhibit it.
It also retards
the abscission (dropping off) of flowers, fruits,
synthetic auxins are used to initiate adventitous
roots from plant cuttings eg. in nurseries.
Weed control by
another synthetic auxin, 2, 4-dichlorophenoxyacetic
acid (2,4-D), is widespread as a selective herbicide
against broadleaf weeds.
Producers have been
using foliar fertilizer since the early 1950's. Even
though the subject of foliar fertilization was little
understood, 'experts' told farmers that they shouldn't
use them, because in comparison to solid type
fertilizers, foliars contained less nutrient.
Nutrient demand curves
indicate stages in a plant's life-cycle when the need
for some nutrients may be greater than its physiological
capacity to supply itself, even when these soil
nutrients are abundantly available. Highly soluble
potassium and nitrogen-based fertilizers can be easily
washed out from the soil, and phosphate fertilizers can
attach themselves to ions of potassium, magnesium,
aluminum and iron into chemically insoluble form for
Foliar nutrients on
the other hand are mobilized directly into plant leaves,
which is the goal of fertilization to begin with,
increasing the rate of photosynthesis in the leaves, and
by doing so stimulate nutrient absorption by plant
is by far the most effective way to apply micro
nutrients or trace elements, and supplement the major
elements. The readily available nutrients are more
easily utilized, because they do not have to be
dissolved by moisture and go into the soil solution.
used in conjunction with solid fertilizers, can be used
to quickly correct a nutrient imbalance and stimulate
increase in root uptake. In addition, foliar
fertilization can correct deficiencies, strengthen weak
or damaged crops, speed growth and grow better plants,
which is of course, the bottom line.
Tissue studies of
plants have found more than 60 different mineral
elements, although it has generally been accepted
that 16 -17 elements are essential for plant growth.
Many farmers are
well aware of the consequences of low levels of
copper or cobalt in pasture, and in some areas
selenium, as well as magnesium (grass staggers),
even iodine and zinc and in many cases calcium (as
in milk fever).
There are many
cases where several of the nutrients are missing or
are at such low levels that supplementation of the
animal is necessary, otherwise the animal would die
or be severely undernourished.
mineral deficiencies occur more frequently than
recognized by many livestock producers and can be a
bigger problem than acute mineral deficiencies,
because the specific symptoms that are
characteristic of a trace mineral deficiency are not
animal grows or reproduces at a reduced rate, uses
feed less efficiently and operates with a depressed
immune system. The end result is inefficient
production and lower profitability.
micro-nutrients become a limiting factor, water,
fertilizer and other high-energy production inputs
In most cases the
elements needed by the plant are also needed by the
animal which feeds on the plant.
needed by the animal are not required by the plant,
but plants takes them up and makes them available
to the animal, and therefore plays a significant
role in animal health. Selenium, iodine and cobalt
minerals, have been shown to be needed in
supplementing animal diets. They are iron, copper,
zinc, manganese, cobalt, iodine and selenium.
Soils are derived
from weathered parent material.
If the original material was low in a particular
element or non existant, so too is the resulting
Soils can become
depleted of minerals and trace elements which too
are absorbed into the likes of meat, milk, bone,
wool, vegetables and fruits, as well as the major
elements, and many soils are naturally deficient in
one or more of these elements.
Soils can be
radically different, with localized deficiencies of
trace elements like copper, cobalt or selenium.
Because our supply
of minerals comes through the food chain, from the
plants and animals we eat, and because these same
minerals are essential ingredients of these same
plants and animals, any that are missing can have
serious implications for plant, animal and
ultimately our own health.
One has to conclude then, that this
is where fertilization should start.
Even though the
major element solid type NPK fertilizer is required
in the largest amounts, if used exclusively, sooner
or later a deficiency of a minor element can occur
in soils low in that particular element, and it too
should be replaced.
can quickly correct a nutrient imbalance, and are by
far the most effective way to apply micro nutrients
or trace elements and supplement the major elements
, because foliar nutrients are readily available and
more easily utilized by the plant than soil