Speaker: Dibakar RoyM.Sc. (Ag.), 4th Semester

Chairman: Professor Biswapati Mandal

DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCE

FACULTY OF AGRICULTUREBIDHAN CHANDRA KRISHI VISWAVIDYALAYA

Course No. ACSS-592 Date: 11.05.2016 SEMINAR-II

1

Role of Zinc in Crop Production

Introduction

Zn is an important micronutrient for plant growth.

Essentiality of Zn was discovered by- A.L. Sommer and C.P. Lipman

In plant Zn content varies from- 27 ppm to 100 ppm

In Soil Zn content in indian soils varies from- Arid/semi-arid climate - 20-89 mg/kgHumid/sub-humid tropics – 22-74 mg/kg Vertisols - 69-76 mg/kgOxisols (coarse textured)- 24-30 mg/kg

Essential NutrientsMacro Nutrients

Micro Nutrients

Katyal and Vlek, 1985

Role of Zinc in Plant systemLow Molecular weight complexes of Zinc- In plant leaves soluble Zinc occurs mainly as anionic compound possibly associated with amino acid.

Carbohydrate metabolism- Photosynthesis- Zinc is a constituent of Carbonic anhydrase enzyme, which have

role in co2 fixation.

Protein metabolism- Zinc is necessary for the activity of RNA polymerase enzyme and it protects ribosomal RNA from attack by the enzyme ribonuclease.

Membrane integrity- The role of Zinc in maintaining the integrity of cellular membranes involving structural orientation of macromolecules and maintenance of ion transport systems.

Auxin metabolism- Zinc is required for synthesis of Auxin, zinc is required for synthesis of tryptophan which is precursor of Auxin.

Forms of Zinc in Soil Mineral form- Zinc exist as Zinc sulphides, Zinc carbonates, and

Zinc silicates. On weathring Zn ion released. Sphalarite- ZnS Smithsonite- ZnCO3 Willemite- ZnSiO4 Franklinite- ZnFe2O4

Adorbed form- Zn is adsorbed on the surface of clays, oxide minerals, carbonates and organic matters.

Solution form- In soil solution Zn exists as Zn ion and Zn(OH)+.

Organic complex form-Zn form stable complex with organic colloids. This form is not readily available to plants.

Soil pH and Liming

Hydrous oxides of iron and aluminium

Carbonates of calcium and magnesium

Organic matter

Soil submergence

Nutrients other than Zinc

Seasons

Factors affecting Zinc availability

Soil pH and Liming

At pH values below 7.7, Zn2+ predominates, but above pH 7.7, ZnOH+ is the main species, and above pH 9.11 the neutral species Zn(OH)2 is dominant.

Adsorption strength - Magnesite (MgCO3) > Dolomite ( CaCO3. MgCO3) > Calcite (CaCO3 )

Carbonates of Calcium and Magnesium

Fe

Fe

OH

OH

O

OH

OH

+ Zn 2+ O

Fe

Fe

OH

OH

OH

OHH

H

Zn + 2H+

Hydrous oxides of iron and aluminium Zinc is

adsorbed on

hydrous oxides

Specifically

Carbonates of calcium and Magnesium reduces availability of Zinc.

• Zn- organic complexes

• Some root exudates can chelate Zn, increases availability.• Zinc strongly adsorbed by insoluble organic matter, specially

in alkaline soil.• Some micro organisms release zinc from insoluble sources.

Soil submergence reduces availability of Zinc in acid soils, due to high pH and formation of Franklinite ( ZnFe2O4) , Zinc sulphide (ZnS).In alkaline soils on submergence pH decreases, zinc availability increases. Over all effect- submergence reduces zinc availability.

Organic matterSoluble

Insoluble

Soil Submergence

Phosphorus is the most important nutrient which interferes Zn uptake by plants.

Causes- Increased plant growth caused by P addition dilutes

Zn concentration in plants ( Dilution effect). High P hinders Zn translocation from root to Shoot. Disproportionate distribution of Zinc in roots and tops

due to lower mobility of Zinc with in plant system compared to Phosphorus.

High soil P may reduce VAM development and infection on roots that may decrease Zn absorption and utilization.

Other cationic micronutrients , Fe2+ , Mn2+ , Cu2+ may suppress Zn2+ uptake, due to ionic competition in soil, competition for same carrier protein in plants.

Nutrient Interaction

Minerals Fertilizers

Gains of Zinc in soils

Losses of Zinc from soil

Plant removal

Soil erosion

leaching

Zinc Deficiency

Alloway, 2008

Zinc Deficiency in India

M.V. Singh, 2000

The average level of Zn deficiency in Indian soils is 50% and is projected to increase to 63% by 2025.

Alkaline soils Calcareous soils Leached acidic coarse textured sandy soils Peat or Muck Soils ( Organic Soils) Red/ Laterite soils

Application of High does of Phosphatic fertilizer

over liming of acid soils

Soils in which Zinc deficiency may occur

Farming practices that may cause Zinc deficiency

Interveinal chlorosis and reduction in the size of the young leaves In acute deficiency, younger leaves show necrosis and dead spots Dicot plants show, short internodes ( rossetting) and decrease in leaf expansion ( Little leaf) Premature leaves drop Bud fall off Seed formation is less Fruits are deformed associated with yield reduction.

Khaira disease in Rice White bud of maize Little leaf of cotton Mottled leaf of citrus or frenching of citrus

Zinc deficiency symptoms

zinc deficiency symptoms in different crops

Zinc deficiency symptoms

Relative sensitivity of crops to Zinc deficiency

High Medium Low

Bean Barley Alfalfa

Citrus Cotton Asparagrass

Flax Lettuce Carrot

Fruit Trees ( deciduous) Potato Clover

Grapes Soybean Grass

Hops Sudan Grass Oat

Maize ( Corn) Sugar Beat Pea

Pecan nuts Table beet Rye

Rice Tomato Wheat

Sorghum

Zinc in Soils and Crop Nutrition by- Brian J. AllowayI

Soil application of Zinc fertilizer

Foliar Spray

Managing Zinc deficiency

Zinc fertilizer applied in soil by Broadcasting or Band placement.

If broadcasted in soils, then zinc fertilizers should be thoroughly mixed.

For soils, having low zinc content band placement is beneficial.

Band placement of Zinc fertilizers is superior over broadcasting.

Efficiency of zinc fertilizer increases when it is applied with physiological acidic fertilizers ( Ammonium Sulphate) and placed in band.

Soil application of Zinc fertilizer

Sources Zinc contentZinc sulphate heptahydrate

21-23 %

Zinc sulphate monohyadrate

33-36%

Zinc oxysulphate 40-55%

Zinc oxide 55-70 %

Zinc nitrate 22%

Zn-EDTA 12-14 %

Zn- HEDTA

9 %

Commonly used zinc fertilizers

Rates lower than soil application

Uniform distribution

Almost immediate response

Foliar spray

For soil application, dose of Zinc sulphate varies from 10-50 kg/ha depending on crops to be grown.

For fruit tree, Zinc sulphate applied 100 g- 1000 g per tree.

For, plantation crops like Tea, zinc sulphate applied 20 kg/ha per year.

For foliar spray, dose is varied from (0.1 to 1.5) % ZnSO4 or

Zn-EDTA along with lime.

Application rate

Fertilizers – A text book by R.K.Basak

Crop response to zinc fertilization

Muthukumararaja and Sriramachandrasekhharan, 2012

Effect of Zinc application on Dry matter production (DMP) and yield of Rice Zn levels

DMP( Tillering stage)

DMP( Panicle initiation)

Grain yield( g/pot)

Straw Yield(g/pot)

mg/kg

S1 S2 Mean

S1 S2 Mean S1 S2 Mean S1 S2 Mean

0.0 1.59 2.54 2.06 20.44 28.62 24.53 13.68 23.73 18.70 18.01 34.23 26.12

2.5 2.28 3.23 2.75 30.00 38.72 34.72 25.68 25.66 31.17 30.67 53.06 41.86

5.0 2.51 3.46

2.98 36.00 45.87

40.93

32.04

43.02

37.53 35.35 59.74

48.54

7.5 2.45 3.17 2.92 35.50 45.35 40.42 31.36 42.34 36.85 37.03 59.42 48.22

Muthukumararaja and Sriramachandrasekhharan, 2012

( t ha-

1 )

Zn rates ( kg/ha)

Harvest index

Length of cob

Number of rows per cob

Number of

Kernels per row

Number of

Kernels per cob

Thousand grain weight

( g)

0 47.9 138.8 14.66 27.8 407.0 253.4

0.5 41.9 153.7 15.00 29.2 438 266.1

1.0 42.9 157.2 15.13 31.7 479.5 264.3

1.5 43.2 151.9 15.04 29.4 441.7 275.0

Effect of foliar zinc application to maize leaves at 5-6 leaf stage on grain yield

Crops Treatments

Zn0

( mg/kg)

Zn1

(mg/kg)Shoot to grain transfer coefficient

%Changes over control

%Changes over control

Grain Straw/ stalk

Grain

Straw/ stalk

Zn0 Zn1 Grain Straw/ Stalk

Rice Local 16.1 35.2 22.

3 55.7 0.46 0.43 38.5 58.2

High yielding

29.1 34.1 40.7

46.4 0.85 0.88 39.9 36.1

Hybrid 20.7 41.9 31.9

75.5 0.49 0.47 54.1 80.2

Wheat

Timely sown

25.0 22.1 36.1

35.0 1.13 1.03 44.4 58.4

Late sown 27.9 22.7 37.4

33.5 1.14 1.12 44.4 47.6

Influence of Zn application on Zinc sequestration potential in grains & straw/stalk with their shoot to grain transfer coefficients in different cultivars of cereals

Saha et al., (2015)

ConclusionZinc is a important nutrient element to boost up crop yield.

Widespread deficiency of zinc throughout the world arising as a big threat to crop production.

Zinc deficiency can lead to several physiological disorders and ultimately decrease in yield in major food crops like rice, maize and wheat.

Judicious application of zinc along with suitable crop varieties can show remarkable increase in economic yield and zinc content in crops.

Thank You