Zn: An indispensable micro nutrient for plant growth_Amlan_IARI_New Delhi

2
A seminar on
Zinc: An Indispensable Micronutrient for Plant
Nutrition
AMLAN NATH
ROLL NO. 21249
M.SC. 1ST YEAR
Division of Agronomy
ICAR-Indian Agricultural Research Institute
New Delhi 110 012

OutlineDIVISIONOFAGRONOMY,ICAR-IARI
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 Introduction
 Role of Zn in plant
 Forms of Zn in soil
 Factors affecting availability
 Interactions with other nutrients
 Zn deficiency & Causes
 Management
 Case studies
 Conclusion

Why Zinc ?
 An indispensable element for plants, animals and
humans.
 An essential mineral vis-à-vis essence to life having
“exceptional biological and public health importance”.
 “Life saving commodity” (United Nations).
 Could play pertinent role in mitigating COVID-19.
 Zinc inhibits Coronavirus and Arterivirus RNA Polymerase
activity in vitro (Aartjan J. et al., 2010).
 Zinc ionophores block the replication of these viruses in
cell culture (Aartjan J. et al., 2010).
DIVISIONOFAGRONOMY,ICAR-IARI
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Zinc (Zn)
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 23rd most abundant element on earth.
 Transitional metal of atomic no. 30 & molecular wt. 65
 Major form of uptake- Zn2+
 Essentiality by- A.L. Sommer and C.P. Lipman (1926).
 Average total Zn concentration in cultivated soils ~65 mg
kg-1 (Alloway, 2009).
 Zinc is partially mobile in plants.

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Role of Zn in Plant system

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1. Low Molecular Weight Complexes of Zinc: In plant leaves,
soluble zinc occurs as an anionic compound, associated
with amino acids.
2. Protein Metabolism: Co-factor of a large no. of enzymes
involved in protein synthesis & also involved in stability and
functioning of genetic material.
3. Carbohydrate Metabolism:
a. Photosynthesis- Constituent of Carbonic anhydrase
(CA) enzyme, which have role in CO2 fixation. CA
contains a single Zn atom which catalyses the
hydration of CO2.
b. Sucrose and Starch Formation- Component of aldolase
which involved in sucrose formation coupled with
important role in starch metabolism.
Continued…

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4. Detoxification of superoxide radicals: Zn involved in the
enzyme Cu-Zn-SOD (most abundant SOD in plant).
5.Anaerobic root respiration: Carbonic anhydrase is involved in
root respiration & Zn is a part of it.
6. Membrane Integrity: Structural orientation of
macromolecules and maintenance of ion transport systems.
7. Auxin Metabolism: Required for synthesis of Auxin, while
lack of Zn reduces the level of auxins in plants.
8. Uptake and Stress: Water uptake and transport in plants,
and alleviate short periods of heat and salt stress.
9. Zn imparts disease resistance in plant.
Continued…

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5 Pools
2.Water soluble
4.Exchangeable 3.Organically bound
5.Sorbed and
insoluble
metallic oxides
1.Primary minerals
Forms of Zinc in Soil

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1. Soil pH and liming
 Availability ( ) with ( ) pH.
 Solubility is pH dependent.
 Each unit ( ) in pH= 100 fold ( ) in solubility.
 Deficiency usually occurs on soil pH 6.0 or above.
 pH < 7.7= Zn2+ , pH >7.7= Zn(OH)+, pH > 9.1= Zn(OH)2
 Lime causes more fixation than that caused by P fertilizers.
Factors affecting zinc availability

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2. Soils of Low Zinc Content
Sandy soils, Peats & mucks
(Histosols),High rainfall areas
3. Restricted Root Zones
Hardpans, high water tables &
soil compaction by tractor
Continued…

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4. Calcareous Soils
 pH is generally 7.4 or higher.
 Deficiency most prevalent .
 Directly sorbed into carbonates.
 Forms insoluble calcium zincate.
 Effects of CaCO3 on Zn availability is 3
fold.
5. Low Organic Matter
 Incorporation of rapidly decomposable
organic matter.
 Root exudates can chelate Zn.
 Alkaline soil- Zn is strongly adsorbed by
insoluble organic matter.
 Some micro organisms release zinc from
insoluble sources.
Continued…

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6. Cool Soil Temperatures &
Reduced Microbial activity
 Temporary Zn deficiency.
 Root system are not well
established.
 Reduced microbial activity.
7. Plant Species and Varieties
 Plants differ widely in their ability
to obtain zinc from soils.
 Availability differs among the
varieties .
Continued…

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8. High Levels of Phosphorus
 High level of available P induces
Zn deficiency.
 Application of superphosphate
with zinc fertilizer reduced the
effectiveness of the zinc.
9. Effect of Stress
 Plants are more susceptible to low
Zn supply when exposed to heat
and drought stress.
Continued…

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Nutrient Interactions
 Antagonistic reaction.
 High soil P= Zn deficiency.
 Application of P fertilizers accompanied by liming- increases
risk of P induced Zn deficiency.
 P inhibits the translocation of zinc from roots to shoots.
 High soil P may reduce AM development and infection on
roots that may decrease Zn absorption and utilization.
Zn-P Interaction
Zn-N Interaction
 Zn x N= Positive interaction
 Application of N without applying Zn leads to Zn deficiency
through dilution effect.
 Nitrogen fertilisers such as ammonium sulphate ((NH4)2SO4)
acidifies the soil and enhances the Zn availability contrasting
to high soil pH.

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 High Ca, Mg inhibits the absorption & translocation in plants.
 Zn x Cu = Competitive inhibition of absorption.
 Zn x Fe = Negative interaction.
 Zinc def. = increased Fe conc. in the shoots (acidification of the
rhizosphere & release of reductants and phytosiderophores).
Zn interaction with other nutrients
Continued…
Zn-K interaction
 Zn x K= Positive interaction.

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Zn deficiency status: World Scenario
“One of the widest ranging abiotic stresses in world agriculture arises from low
zinc availability in calcareous soils, particularly in cereals.”- Singh et al., 2005
Alloway, 2008

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Zn deficiency status in Indian Sub-continent
Shukla and Tiwari, 2016

Zinc conc. in different soil ordersDIVISIONOFAGRONOMY,ICAR-IARI
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Soil Order Total Zn
(mg/kg)
Entisol 47
Inceptisol 60
Aridisol 61
Vertisol 63
Alfisol 44
Ultisol 43
Mollisol 30
Oxisol 72
Katyal and Sharma, 1991
 >90% Zn- insoluble in soil.
 Soluble Zn conc. in soil solution- 4 x 10−10 to 4 x 10−6 M
 Conc. of exchangeable Zn- 0.1-2 mg/kg of soil.

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Causes of Zinc Deficiency in Crops
Zinc-deficient
crop
(reduced yield
/impaired
quality)
Low total zinc
content in soils
(i.e.sandy soils) High soil pH
(e.g. calcareous
soils, heavily
limed soils)
High phosphate
applications
High salt
concentrations
(salinity)
Waterlogging /
flooding of soil
(e.g. rice paddy)
High soil organic
matter content
(e.g. histosols)
Zinc
inefficient
crop varieties
Low manure
applications

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Zn Deficiency
Soils in which Zn deficiency may occur
 Alkaline soils, Calcareous soils, Leached acidic coarse textured
sandy soils, Peat or Muck Soils (Organic Soils), Red/ Laterite soils.
Farming practices that may cause Zn deficiency
 Application of High does of
phosphatic fertilizer
 over liming of acid soils

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Zinc deficiency symptoms
 Zn def. symptoms are found in both new & older leaves.
 The most characteristic visible symptoms-resetting and little
leaf (in dicotyledonous).
 Interveinal chlorosis.
 Acute deficiency- necrosis and dead spots in younger leaves.
 Premature leaves drop.
 Bud fall off.
 Lesser seed formation.
 Deformed fruits associated with yield reduction.
Zinc deficiency symptoms in different crops
 Khaira disease in Rice
 White bud of maize
 Little leaf of cotton
 Mottled leaf of citrus or frenching of citrus

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Khaira Disease
 First reported Zn deficiency in India.
 By Y.L Nene in 1966 in paddy soil at Pantnagar.
 Also known as Akagare type II (Japan), Taya-Taya and
Apulapaya (Philippines) and Hadda (Pakistan), suffocating
disease in Taiwan.
Fig: Khaira Disease of Rice

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Fig: Interveinal chlorosis in rice
Fig: Chlorosis and necrotic spots on wheat
Fig: Interveinal chlorosis and “white
bud” in Maize

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Barley Sugarcane Cotton
CitrusSoybeanRape

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Relative sensitivity of crops to Zn deficiency
High Medium Low
Bean Barley Alfaalfa
Citrus Cotton Asparagus
Flax Lettuce Carrot
Fruit Trees Potato Clover
Grapes Soybean Grass
Hops Sudan Grass Oat
Maize Sugarbeet Pea
Onions Table Beet Rye
Pecan nuts Tomato Wheat
Rice
Sorghum
Sweetcorn
Martens and Westerman, 1991

28
Management of Zn deficiency
A. Soil application of Zinc fertilizer
 Broadcasting or Band placement.
Band placement is superior over
broadcasting.
 Efficiency increases when applied
with physiological acidic
fertilizers (Ammonium Sulphate)
and placed in band.
 Most common recommendation-
soil appl. of 10-25 kg/ha of
ZnSO4
 Zincated Urea- Urea fertilizer
granule coated with ZnSO4
(42%N, 1-2% Zn). It is used in
India & some other places in rice.

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Continued…
 Feeding plants by directly
applying liquid fertilizer to the
plant.
 Rates lower than soil application.
 Uniform distribution.
 Almost immediate response.
 ZnSO4 or Zn-EDTA (0.1 to 1.5 %).
 General recommendation- 0.5%
sol. of ZnSO4 mixed with a small
amt. of lime.
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
B. Foliar Feeding

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Continued…

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Types of Zinc Fertiliser
 Include ZnO, ZnCO3, ZnSO4,
Zn(NO3)2 and ZnCl2.
 ZnO: nearly insoluble in water
but soluble in acids.
 ZnSO4·xH2O: heptahydrate
form most commonly used.
A. Inorganic Compounds
 Chelating agent (EDTA/DTPA) +metal ion.
 Lesser chances of retention by soil colloids, higher
transportation from soil to roots.
 Na2Zn-EDTA-most commonly used.
 Suitable for mixing with conc. fertilizer solutions for soil,
fertigation & hydroponic application.
B. Synthetic Chelates
C. Natural organic complexes
 Zn salts +
citrates/lignosulphonates/
phenols /polyflavonoids.
 Cheaper and environment
friendly.
 Less effective.

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Commonly used zinc fertilizers
Mortvedt and Gilkes, 1993

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Bio-fortification
Genetic Bio-fortification Agronomic Bio-fortification

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Bio-fortification
Agronomic Bio-fortification

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Agronomic Bio-fortification
 Application of fertilizers to seeds, soil and/or foliage.
 Cheaper, Faster & Safer.
 Can be applied to a number of crops
 Ferti-fortification: Agronomic bio-fortification through Zn
fertilization (Prasad, 2009)
 Seed plus foliar application is most appropriate for
agronomic bio-fortification (Cakmak, 2007).

Crop response to zinc fertilization
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Affect of Soil & Foliar Zn application on
Shoot & Root Growth of Rice Seedlings
Journal Of Plant Nutrition Phuphong et al., 2020
Shoot and root characteristics of rice seedlings grown in different soil Zn treatments by supplying of 0,
0.02, 0.1, 0.5 and 5.0 mg Zn kg-1 soil in form of ZnSO4 .7H2O with and without foliar Zn application at the
rate of 0.5% ZnSO4 7H2O in deionized water.

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Affect of Soil & Foliar Zn application on
Shoot & Root Growth of Rice Seedlings
Journal Of Plant Nutrition Phuphong et al., 2020
Soil Zn treatment (mg kg-1 soil)
ShootDryWeight(gpot-1)
Soil Zn treatment (mg kg-1 soil)
RootDryWeight(gpot-1)
Dry weight of shoots (A) and roots (B) of rice seedlings grown in different soil Zn treatments with and
without foliar zinc fertilizer at 0.5% ZnSO4. P<0.05

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Effects of zinc fertilizer on maize yield and water-
use efficiency under different soil water conditions
Zhang et al., 2020Field Crops Research
Water Zn Treatment
(Kg 𝐡𝐚−𝟏)
Grain Yield
(Mg 𝐡𝐚−𝟏)
WUE
(kg 𝐡𝐚−𝟏 𝒎𝒎−𝟏)
2017 2018 2017 2018
Draught
Situation
0 5.98 3.88 30.14 26.81
20 6.72 4.08 33.76 27.95
50 6.87 4.21 34.76 28.61
80 6.37 4.12 32.41 27.94
Water
Condition
0 15.13 13.16 31.83 44.73
20 16.28 14.21 34.48 47.90
50 15.29 12.88 32.23 43.44
80 15.33 11.71 32.20 39.91
P < 0.001

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Impact of Zn fertilization on water
productivity and grain yield of Basmati Rice
Zinc Fertilization Total water productivity
(kg ha−1 mm−1)
Grain yield
(t ha−1)
2015 2016 2015 2016
Control 1.75 2.58 3.68 3.71
5 kg Zn as SA 1.97 2.93 4.15 4.21
2.5 kg Zn as SA + 1 aFA
at flowering
2.03 3.01 4.26 4.32
aFA of Zn at AT +
flowering + GF
2.31 3.42 4.85 4.91
aFA of Zn at 20, 40, 60
and 80 DAT
2.37 3.51 4.98 5.04
SEm± 0.006 0.029 0.012 0.042
LSD (P = 0.05) 0.017 0.086 0.035 0.123
a0.5% solution of chelated Zn-EDTA @ 500 L ha–1, SA – Soil Application, AT- Active Tillering, FA–Foliar Application,
DAT- Days After Transplanting
Communications in Soil Science and Plant Analysis Yadav et al., 2019

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Effect of zinc fertilization on wheat yield
under sandy loam soil
Journal of Pharmacognosy and Phytochemistry Vora et al., 2019

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Effects of foliar application of zinc sulphate
and zinc nanoparticles in coffee plants
Plant Physiology and Biochemistry Rossi et al., 2019
Fresh and dry weight of root, stem and leaves of Coffee foliar fertilized with ZnSO4 and ZnO NPs.
Root FW Stem FW Leaves FW
Root DW Stem DW Leaves DW
P< 0.05

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FS: Foliar spray; SA: soil application; V: varieties; MT: maximum tillering; BS: booting stage.
Influence of varieties and Zn fertilization on
Grain and straw yield of wheat
Ghasal et al., 2017ARCHIVES OFAGRONOMY AND SOIL SCIENCE
P = 0.05

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Effect of Green Manuring and Zinc Fertilization on
Quality Parameters of Basmati Rice
Communications in Soil Science and Plant Analysis Pooniya et al., 2015

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Effect of Zn treatments on Zn & Fe concentrations
in aromatic rice
Indian Journal of Agricultural Science Shivay et al., 2015
Treatments Zn concentrations
(mg kg-1 )
Fe concentrations
(mg kg-1)
Rice
kernel
Rice
husk
Rice straw Rice kernel Rice
husk
Rice
straw
Check 20.0 125.0 91.0 8.2 12.3 42.0
5 kg Zn ha-1 (soil) 21.3 130.0 100.0 9.0 13.4 48.0
1 kg Zn ha-1 (foliar) 22.0 147.0 102.0 8.4 12.8 45.0
5 kg Zn ha-1 (soil) + 1 kg Zn ha-1
(foliar)
25.0 175.0 107.0 9.3 14.1 55.0
2.83 kg Zn ha-1 through Zn-
coated urea (soil)
23.8 170.0 105.0 9.1 13.8 56.0
SEm± 0.30 1.46 0.98 0.15 0.39 0.58
LSD (p = 0.05) 0.86 4.13 2.78 0.44 1.10 1.66

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Effect of Zn-coated urea on productivity of
Basmati Rice
Shivay et al., 2012
Journal of Plant Nutrition

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Conclusion
 Zn-an important element to accelerate crop yield.
 Widespread deficiency arises as a major threat to crop
production vis-à-vis nutrition.
 Zn availability suffers a major set back in the populations
mainly dependent on cereal grains for their major food
requirements.
 It is important that farmers, agronomists and extension
workers should ensure that the zinc status of their soils and
crops are adequate to satisfy both the yield and quality
criteria.
 Increased use of Zn fertilizers to crop is a sustainable way of
addressing Zn deficiency in soil, crops, animals & human in
continuum.

Zn: An indispensable micro nutrient for plant growth_Amlan_IARI_New Delhi

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