Calcium- sources and content – forms of calcium in soils – Functions – Deficiency symptoms – corrective measures

1. Calcium- Sources and Content –
Forms of calcium in soils –
Functions – Deficiency symptoms –
corrective measures
JEEVAN NAIK. B
M. Sc, (ag)
ANGRAU
SPEAKER

2. SECONDARY NUTRIENTS (Ca)
These nutrients received little attention due to their inadvertent
application through fertilizers and irrigation water.
 (NH4)2SO4 (100 kg) supplies 20 kg N and 24 kg S
 Ca(H2PO4)2 supplies 16 kg of P2O5, 21 kg of Ca and 12 kg of S
 K2SO4 supplies 52 kg K2O and 18 kg of S
 Lime (CaO) which contains Ca and Mg is applied to raise the pH
 Sulphur compounds are used to lower the pH of soil
 Irrigation water may contain on an average 25 ppm of SO4 , 50 ppm
of Ca and 5 ppm of Mg.

3. Content and sources of soil calcium :
 The Ca concentration of the earth’s crust is about 3.20 %,
 It may be as low as 0.015 % in humid region to as high as 5 %
in arid region…???
 The major sources of Ca are the weathered products of rocks
and minerals

4. Mineral Chemical formula Total CaO (%)
Calcite CaCO3 56.0
Apatite Ca10(PO4)6 50.0 – 53.2
Dolomite CaCO3.MgCO3 33.2
Gypsum CaSO4.2H2O 32.2
Sources of Ca (secondary minerals)

5. Besides these secondary minerals, primary minerals like
 Augite (18.7%),
 Hornblende (4.6%),
 Anorthite (10.0 – 20.0 %)
 Epidote (22.0-25.0%) etc., are the sources of calcium in
the soil.

6. Forms of calcium in soils
Mineral particles : Calcium is mostly present as primary minerals
such as anorthite, and basic rocks like basalt, gabbro. They all
release Ca on weathering.
Calcium carbonate : Calcite mineral is very common. The nodular
form of calcium carbonate and amorphous calcium carbonate
exist.

7. Nodular form of calcium Amorphous calcium

8.  Simple salt : it is present in many simple salts such as
 Calcium chloride(CaCl2),
 Calcium sulphate(CaSO3),
 Calcium nitrate and (Ca(NO3)2)
 Calcium bicarbonate(Ca(HCO3)2).
Exchangeable calcium : Of all the cations on the exchange
complex of soils Ca2+ is the most dominant cation.

9. 1. Absorbed by organisms :
 Legumes use much more calcium than grasses.
 Prolonged cropping like alfalfa on sandy soils depletes
Ca resource.
2. Losses due to leaching :
 Due to rainfall , irrigation and permeability of the soil
 Greater loss of calcium in Light textured soil
 Leaching losses range between 84 to 224 kg ha-1
The fate of released calcium

10. 3. Adsorbed by clay colloids :
 If the activity of calcium suddenly increases, there will be a shift
in equilibrium with subsequent adsorption of some Ca2+ by
exchange complex
 If the activity of calcium decreases the adsorbed calcium releases
into soil solution
4. Reprecipated calcium (precipitating a substance from a solution)
 Calcium is reprecipitated as secondary calcium compounds in arid
climate
 In arid region, due to low rainfall, Ca in soil solution will be
precipitated as least soluble calcium compounds

11. Factors affecting the availability of “Ca” to plants
 Calcium that is in the form of an insoluble compound is not
available to plants.
 Since calcium is a positively charged ion,
 Clay and organic particles which are negatively charged.
 Positively charged ions adsorbed to soil particles are termed
"exchangeable ions“
 Soil analysis determines the level of exchangeable calcium ions,

12.  Soil pH
 Usually soils with a higher pH level contain more available calcium.
 CEC
 A higher CEC indicates a higher capacity of the soil to adsorb and hold
calcium, and therefore higher calcium availability.
 Presence of competing ions
 Such as sodium (Na+), potassium (K+), and magnesium (Mg+2).
 Decrease calcium uptake by plants.
 Sodium ions can replace the adsorbed calcium, damage soil structure and
decreases calcium availability.

13. Mobility and uptake of calcium by plants
 Ca uptake by the plant is passive.
 Ca mobility in the plant takes places mainly in the xylem,
together with water.
 Therefore calcium uptake is directly related to the plant
transpiration rate.
Conditions of
 high humidity, cold, low transpiration rates, and Salinity
buildup may result in calcium deficiency. because it
decreases the water uptake by the plant.

14.  The sufficiency Ca range is between 0.2 – 1.0 %.
 Calcium is absorbed by the plant as Cationic form (Ca 2+),
 Calcium deficiency will appear (<0.2% Ca) Though calcium is highly
mobile in soil, in the plant system it is the immobile nutrient
 in younger leaves (die back or burns) and
 in fruits (blossom end rot, bitter pit), because they have a very
low transpiration rate.

15.  Participates in metabolic processes of other nutrients
uptake.
 Promotes proper plant cell elongation.
 Strengthen cell wall structure
 Participates in enzymatic and hormonal processes.
 Helps in protecting the plant against heat stress
 Helps in protecting the plant against diseases
Functions of calcium in plants

16. Affects fruit quality.
 It plays a role in mitosis (cell division) and helps to maintain the
chromosome structure.
 Has a role in the regulation of the stomata.
Essential co-factor or an activator of a number of enzymes like
hydrolases.
 It activates phospholipase, arginine kinase, amylase and ATPase
enzymes.

17.  Failure or desiccation of terminal bud development.
 No unfolding of new leaves in corn, whose tips are colourless
 Chlorosis of young leaves followed by distortion of the growing
points of the stem.
 In fruit trees, the death of growing points followed by die back.
 In guava, the old leaves are chlorotic with red brown spots.
 In apple, the discoloration of the fruit meat, the condition
generally referred to as “bitter pit”.
Deficiency symptoms

18.  In Brassica, severe loss of color in young leaves, terminal bud
leaves are hooked, leaves below become cup shaped. Old leaves
collapse due to terminal bud disintegration.
 Blossom end rot in tomato is due to Ca deficiency

19. blossom
end rot

20. Die back

21. Chlorotic with red brown spots

22. Bitter pit
Discoloration

23. Correction measures Calcium as a plant nutrient is more
important in calcium deficient acid soils.
 The application of carbonate or sulphate salts of calcium @ 2 –
4 q ha-1 in furrows could increase the yield by 48 %.