May 2021 - 17

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Answering the Calcium Conundrum
Balancing nutrient supply in leafy
vegetables will not only improve
color and appearance, but also
ensure maximum marketable
yield, says Dean Konieczka of
OMEX®
Agrifluids.
Few growers will have any
qualms about rolling out a
nutrition program for the basic
macronutrients such as nitrogen,
phosphorus and potassium,
but many will wish they had the
same degree of confidence in
managing calcium nutrition.
Calcium deficiency is a significant
problem in leafy vegetables and
salad leaves, tip burn the most
common symptom. A collapse
and death of the cells, causing
breakdown of the leaf tissue and
the all-too-familiar browning
effect, it can generate serious
economic losses through loss of
quality and marketability.
Testing of the affected tissues
usually reveals low levels of
calcium, but the cause of the
imbalance isn't always clear: is
it due to poor transport within
the plant? Or insufficient calcium
absorption?
It's both. Insufficient movement
of water through plant tissue can
lead to tip burn, but sometimes
the plant can't acquire sufficient
calcium in the first place.
Understand what's caused it, and
then a grower can decide how
best to manage it.
What's the crop?
On closed-head lettuce, or
brassicas, tip burn usually
appears in the center. This is a
sure sign that calcium transport
is the culprit.
Calcium isn't mobile in the plant's
phloem. Crops cannot move it
around the plant. Instead, calcium
moves with water in the xylem.
Parts of the plant with the highest
water loss also exhibit the highest
throughput of calcium. And
because calcium absorption is
controlled by the plant hormone
auxin, parts of the plant that
enjoy high levels of auxin also
absorb the most calcium.
Let's look at the closed-head
variety. Tip burn is occurring in
the newest leaves, where auxin
levels must be high. We can
deduce that this isn't a problem
of inability to absorb calcium;
instead, it suggests there's not
enough calcium reaching those
leaves.
Here, the focus should be on
insufficient water movement -
either because the surrounding
air is cool and moist (little water
loss from leaves), or thought hot
and windy conditions increasing
water loss from outer leaves.
In these circumstances, a foliar
calcium application will be
wasted, because it's not going to
reach the all-important core. The
outer leaves will absorb calcium,
but they don't need it; and the
plant won't be able to move the
excess internally.
Solving this type of tip burn needs
a dual approach: make calcium
available in the root zone, where
it can be drawn to the right part
of the plant; and try to manage
the crop to maintain a more even
flow of water through the plant.
The latter is easier to enact where
crops are protected.
Careful selection of nutritional
products is also helpful. How
many of you have experienced
the frustration of seeing no
effect from a calcium application?
OMEX®
Cell Power®
Calcium
Gold contains the unique LoCal®
technology - developed by
our British partners Levity Crop
Science - which directs the plant
to use calcium in a different way.
This allows lower rates of calcium
to be applied, while producing
greater effect.
What about loose-head
varieties?
Here, tip burn usually appears
on the outer leaves - and isn't
due to water transport. Instead,
it's because auxin levels in these
older leaves, where cell division
has stopped, have declined.
This reduces the leaf's calciumabsorbing
ability.
Again, foliar calcium applications
in these circumstances will lead to
frustration: those fresh new leaves
in the center, packed full of auxin,
will absorb it, with no effect on the
calcium-deficient outer leaves.
Thankfully, the remedy is the
same. The LoCal®
technology
within Calcium Gold uses a
calcium transport stimulant that
emulates auxin, allowing all parts
of the plant to take advantage of
enhanced calcium levels.
What's more, growers can also
choose to incorporate a valuable
dose of micronutrients at the
same time, by applying Cell
Power®
Calcium Platinum. It
adds critical micronutrients such
as copper, iron, zinc, manganese,
boron and molybdenum to the
formulation, providing growers
with a unified solution to remedy
other micronutrient deficiencies
in the same application.
Learn more at www.OMEXusa.com.
The product names and
brands referenced here are
registered and trademarks of
OMEX®
Agrifluids, Inc.
© OMEX® Agrifluids, Inc. 2021.
Call 559-661-6138
Visit www.OMEXusa.com
Email omexusa@omex.com
VGN | MAY 2021 | 17
http://www.OMEXusa.com http://www.OMEXusa.com
May 2021

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