OMEX USA - 8

Calcium in Permanent Fruit Crops
By Dr. David Marks
OMEX® USA and Levity Crop Science
form partnership with Levity's LimiN
and LoCal technology. In OMEX®
Power® SizeN®
and Cell Power®
Calcium Gold and Cell Power®
Calcium Platinum.
Calcium is an important nutrient in
fruit crops, but the majority of Ca
applied by growers goes to waste.
Let's explore why.
There are three golden rules to
remember in calcium nutrition,
once learned they can form the best
practices on a crop.
1. Crops cannot store excess Ca.
2. Calcium can only move up.
3. Calcium can only be absorbed if
there is auxin
Let's look at each point and apply it to
permanent crops.
Plants can't store excess Calcium
Unlike potassium and many other
nutrients, plants have no capacity
to store reserves of Calcium. Ca
is stored in calmodulin proteins
between the cell wall and cell
membrane, once these Ca storage
sites are all occupied the plant
ejects any extra calcium as it is not
beneficial to plants to have free
calcium in cytosol. This means that
plants precipitate out large amounts
of calcium oxalate from leaves, even
when there are calcium deficiency
symptoms on fruit.
It is also the reason that tissue
tests are a poor way of assessing
need for Ca in fruit crops: A. Leaf
analysis tells us little about fruit
tissue content which is usually a
local problem and, B. the difference
between sufficient Ca and a problem
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Calcium can only move up
Calcium is not phloem mobile,
meaning that plants cannot easily
mobilize it and move it from one
Instead Calcium
place to another.
moves through the Xylem with
water transpiration. This means
Calcium follows water through
plants from the roots to the places
of highest water loss (usually the
foliage at the top of the plant). This
is why there is usually a difference
observed between the shady half
of a fruit and the sunny half). It is
also why any conditions effecting
water transport such as drought,
waterlogging and wind can lead to
worsening calcium related quality
problems.
Calcium can only be absorbed if
auxin is present
Calcium transport into cells is
directly related to auxin content in
plant tissue, as calcium transport
is governed by polar auxin
transport. This means that there
are places in crops that can not
absorb calcium properly no matter
how much is applied.
To understand how this effects
fruit crops we need to understand
when and where fruit produces
auxin. Auxin is a growth hormone
involved in cell division, so only new
tissue has a good content. When
fruits are small they are producing
lots of new cells, and have good
auxin content and good ability to
absorb applied Ca. However when
the fruit gets over 4mm in size it
Cell
like bitter pit (in apples) is only
2ppm which is outside of analytical
test method tolerances.
has all its cells and shifts to cell
expansion, whereby the ability to
absorb Ca decreases rapidly. This
means that young fruit can absorb
Ca well, but mature fruit struggle.
So what can we do to help with
fruit quality? We can work with
the crops physiology to support
better calcium nutrition
OMEX®
Cell Power®
SizeN®
Ca
combines Levity's LimiN chemistry
with calcium. The product
emphasizes root growth and a
good compact growth habit which
is vital to fruit trees ability to supply
Calcium to fruit. Remember Ca
moves up from active root tips
to vegetative growth at the top
(through transpiration stream), and
is absorbed mostly in the actively
growing parts. When trees receive
standard N sources we see reduced
root growth and too much focus
on apical shoot growth. This means
that a huge Ca sink is created at
the top of the tree which effectively
diverts Ca away from developing
flowers and fruit.
When we use OMEX®
SizeN®
Cell Power®
we encourage good root
activity, and do not create a source
sink imbalance. Good growth habit
is the first key to good fruit quality.
LoCal is another Levity technology.
Cell Power®
Cell Power®
Calcium Gold and
Calcium Platinum,
containing LoCal technology,
allows parts of plants low in auxin
to properly absorb Ca where they
would normally have a low ability
to do so. Calcium fertilizers Cell
Power®
Calcium Gold and Cell
Power® Calcium Platinum) that
use LoCal technology can supply
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