September/October 2019 - 20

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Importance of early, mid and late season
application of Calcium
Good calcium levels in potato
tubers can reduce multiple quality
problems including Internal Rust
Spot (IRS), internal browning and
hollow heart. Calcium also plays
a role in reducing susceptibility to
bruising and post-harvest diseases.
However, despite this, farmers do
not always get a good response to
calcium fertilizers. Here we explore
why, and what can be done to
improve it.
So what exactly do plants do
with calcium?
Calcium's main function within
cell walls is to give cell wall rigidity
& strength, explains Dr. David
Marks, managing director of Levity
Crop Science. The main symptom
of calcium deficiency is the
disintegration of cell walls and the
collapse of affected tissues.
It's this tissue collapse that
contributes to IRS, internal
browning, and premature rotting
and bruising post-harvest.
Potatoes don't actually need very
much calcium, the quality problems
associated with calcium result from
tiny local deficiencies, but these
minor deficiencies (in terms of the
amount of tuber affected) can make
crops unsellable.
While tubers may have small areas
of calcium deficiency, the rest of the
plant rarely suffers any shortage at
all, and is often precipitating Ca out
from leaves as in excess.
The Math should make us Think
If a 24 tons/acre crop of potatoes
had complete loss due to internal
rust spot, the actual quantity of Cadeficient
tissue (2% of each tuber is
actually affected) is only 624 lbs/acre.
The difference between the affected
and healthy part of the potato is
typically only 4ppm.
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Therefore, the amount of calcium
required to prevent an entire 24
tons/acre crop of potato from
having internal browning is only
0.0025 lbs/acre. This should raise a
few questions for growers.
* Why are small parts of the tuber
deficient when the area right next
to them isn't?
* Why are these small areas of
tissue deficient in Ca when there's
no whole plant deficiency?
* Why doesn't applying large
amounts of calcium reverse the
deficiency?
In order to answer these questions,
it's important to understand how
calcium behaves in a plant, he
says. There are two factors to be
considered in plant Ca availability;
transport and absorption.
Ca Transport
Unlike most other mineral
nutrients, Ca isn't phloem mobile
and can only be transported
through the xylem. Ca enters the
plant with water and is transported
upwards with transpiration,
where it's either absorbed and
stored, or is precipitated from
the leaves as excess.
Ca only moves upwards. Nobody
has ever witnessed or discovered
a way to change this. This is why
targeting and correct placement
of applications of calcium is so
important. Ca applied to leaves
can't correct problems in the
roots. Therefore, foliar sprays
of Ca fertilizers will never put
the nutrients into the tuber. It's
physiologically impossible for the
plant to move calcium down.
Ca Absorption
Ca is absorbed into cells using polarauxin
transport, as auxin moves out
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of the cell, Ca enters and replaces it.
Parts of a plant that are low in auxin
can't absorb the nutrient effectively,
regardless of how much is available.
High auxin-producing areas include
new shoots, new flowers, and new
leaves. Low auxin-producing areas
include fruits, roots and tubers.
This is why applying Ca to correct
physiological disorders can be so
ineffective. It doesn't matter how
much is applied, parts of the plant
with low auxin levels such as tubers
can't absorb it properly.
Target optimum absorption
stages
Time applications to when tubers
can absorb it. Tubers produce very
little auxin once they start growing,
so to get conventional Ca sources
into a tuber it really needs to be
done during the cell division stage.
Once tubers reach 5mm in size
there's very little new cell formation,
and auxin levels decline. For Ca to be
able to get into the tuber it needs to
be available between hook and 5mm
tuber size.
Use LoCal chemistry
LoCal is a chemistry that allows
low auxin parts of plants (like
tubers) to absorb calcium. Calcium
fertilizers incorporating LoCal like
Cell Power®
Cell Power®
Calcium Gold and
Calcium Platinum
(marketed in the US by OMEX®
USA) are most effective.
Cell Power®
Cell Power®
Calcium Gold and
Platinum have
been incredibly effective on fruit
crops preventing calcium related
physiological disorders.
For more information on products
please contact OMEX®
Agrifluids
at OmexUSA@Omex.com or
call 559-661-6138.
http://www.Spudman.com
September/October 2019

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