May/June 2019 - 19

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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, " explains David Marks.
Understanding transport
" Ca only moves upwards. Nobody has ever
witnessed or discovered a way to change this.
This is why targeting and correct placement
of applications is so important. Ca applied
to leaves can't correct problems in the roots.
Therefore, foliar sprays of Ca fertilizers
will never put the nutrient into tuber. It's
physiologically impossible for the plant to
move down, " he stresses.
Understanding absorption
" Ca is absorbed into cells using polar-auxin
transport, and as auxin moves out of the cell,
Ca enters. 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, " he says.
How to improve agronomy
So how can we improve tuber Ca levels? Part
of the answer is targeting the tuber zone,
believes David Marks. " Don't apply it to foliage
and expect it to get to tubers. For best results
it must be placed near the stolon roots inside
the tuber zone.
" Use Ca in an available form, and don't confuse
it with liming agents. It's easy to think Ca status
will be improved where liming agents are used
to adjust pH, where in reality, they supply
very little (the Ca in lime is only 1 in 10,000
available).
" 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 in the tuber it needs to be
available between hook eye and 5mm tuber
size, " advises David Marks.
Finally, he advises growers who use more
advanced Ca products that have been shown
in field trials shown to lift in-tuber calcium
levels. One such technology is LoCal, known as
Cell Power®
Calcium Gold and Cell Power®
Calcium Platinum in the U.S., developed
by scientists at Levity it stimulates Calcium
transport into low auxin tissue. David explains
" Levity has done a lot of research on fruit crops
like apples, and we have had consistently good
results correcting the physiological disorder
Bitter Pit using low rates at the right timings.
We have shown that 100 fl. oz. of a product
that the fruit can absorb is far more effective
than 31 gallons of standard calcium. " So, what
does that mean for potato growers? David
adds, " to get Ca into tubers we need to hit the
tuber zone. Our approach is to use a product
that combines Ca with LoCal (in the US we
recommend Cell Power®
SizeN®
Calcium) soil
applied at tuber initiation through bulking. This
approach puts calcium in the right place, in the
right form and unlocks the ability of the tubers
to absorb it, where they would otherwise be
unable to. "
For more information on products please
contact OMEX®
Agrifluids at
OmexUSA@Omex.com or
call 559-661-6138.
May/June 2019

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