Calcium (Ca)
Form used by plants:
Ca2+
Important functions:
-
Important in cell wall
and membrane construction
-
Regulates nutrient
uptake by roots and movement in plant
-
Necessary for
development of firm fruit
Ideal foliage range for apple leaves:
1.2-1.6%
(However, do not rely on leaf analysis to identify Ca
deficiency). Vegetative
growth out competes fruit for available Ca.
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Ideal fruit concentration:
0.01-0.03% of dry weight
(fruit flesh)
Ideal soil range:
600-4000 ppm
Calcium is strongly sorbed by soil
components and thus not mobile.
Best indicators:
Fruit analysis- observe
fruit for bitter pit (see
photo below) or cork spot. May see premature shedding of blossoms and
buds.
Mobility in plant:
Not remobilized within
plant
Deficiency symptoms: 
Fruits have a low
ability to attract Ca and instead it is utilized by growing shoots and
leaves.
Fruit symptoms: bitter
pit (see photo), cork spot, senescent breakdown, watercore.
Maturity will be hastened (if not monitored, may lead to
significant drop and poor storageability).
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Increased risk of Ca deficiencies on:
-
Overfertilized plots
(excess Mg or K in soil makes it more difficult for roots to take up
Ca; too much N stimulates vegetative growth which will take Ca away
from fruit)
-
Excessively pruned
plots (due to stimulation of vegetation)
-
Areas with B
deficiencies because this may reduce calcium movement
-
Excessively large
fruit should be avoided
-
Water-stressed areas
or areas subject to wide fluctuations in moisture supply
Excess problems/Interactions with other
elements:
*see increased risk section above
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