Gaurav Kumar Singh

Definition CHELATION: A process in which bivalent metals make a stable soluble complex with an organic acid or Chelator to become an inert, water soluble organic compound is called Chelation.For example: Zn + EDTA = ZnEDTA (Chelate)CHELATOR: Those organic acids which form a soluble complex with bivalent cations especially with metals like Zinc called Chelator

CLASSIFICATION OF CHELATORS1) STRONGEST (Synthetic): These make a stable

chelated compound with bivalent metals (pH non sensitive).

2) INTERMEDIATE (Long Chain Natural Organics): These make a lose chelated complex with cations (pH sensitive).

3) WEAKEST (Short Chain Organics): These make weakest chelated complex with cations (pH Sensitive).

Chelation

Organic Chelating Agent Include:

EDTA DTPA HEEDTA Citric Acid Glucoheptonate Mannitol

Uses of Chelates & Complexes Soil: –EDTA –Citric Acids –Glucoheptonates –Ammonium ComplexesFoliar –EDTA –Citric Acid (diluted) –Glucohptonates –Lignin Sufonates

BEST CHELATOR:-EDTAWHY?1) It is a strong Chelator and makes a stable soluble complex

with cations.2) It is stable in acidic and alkaline conditions.3) It easily releases the cations to Metallo-enzymes.4) It has high affinity with lead and plays a vital role in

detoxification of lead in plants and thus prevent plant from its toxic effects.

5) Its degradation produces raw material for Indole Acetic Acid (PGR).

6) Cheaper and easily available than other strong Chelator.

CHELATED FORMS VS. INORGANIC FORMS

Chelates Non ChelateRemaining inert in soil thus remain in available form to plant

Fixed in soil and convert in unavailable form for plants in alkaline soils.

Can not bond to anions in soils and also increase its availability.

Precipitate with anions (like phosphate) and also make these anions unavailable along with soil calcium to plants and decrease yield badly.

Cont……

Chelates Non Chelate ExampleThere is no interaction in between the nutrient

Due to excess quantity used of one micronutrient disturbed the uptake of another micronutrient.

Excess Zinc quantity in soil disturbed uptake of Copper thus instead of increase in crop yield, crop yield reduce due to Copper deficiency.Chelated nutrients

can be sprayed with any type of Pesticide or Herbicide or any other Chelated product

It can not spray these nutrients with phosphorus products

Cont……

CHELATED FORMS VS. INORGANIC FORMS

Cont……

Chelates Non ChelateNeutral condition of Chelated products promotes nutrient absorption in plant through cuticle.

Plant leaves cuticle is negatively charged and adsorb cations when spray in inorganic form (charged form) cause necrotic spots on leaves, most common in rice field after application of zinc sulphate (In spray).

Chelated product not only provide essential nutrient to plant but also inactivate toxic metals in plants like Lead and decrease chlorosis and necrosis problem in crops due to Lead accumulation.

No such property found in inorganic forms.

CHELATED FORMS VS. INORGANIC FORMS

Cont……

Chelates Non ChelateEDTA also promotes the auxin (PGR) formation thus enhance plant growth rate.

No such property found in inorganic form.

EDTA acts as metal carrier in plants translocation system thus enhance necessary metal availability at site of utilization.

No such property found in inorganic forms.

When EDTA carrying crops or fruits go in human beingsEDTA does EDTA therapy.

No such property found in inorganic forms.

Chelated micronutrients especially Chelated copper and Zinc suppress the growth of plant pathogen and fungus, thus increase agricultural growth.

No such property found in inorganic forms.

CHELATED FORMS VS. INORGANIC FORMS

Efficiency Ratios

Efficiency ratio is the comparison of chelates to sulfates (dry). Because of chelation and the “protection" of the metal ion from tie-up and metal precipitation, it is possible to apply a chelated product from 1/8 to ½ the rate of a sulfate product.

EDTA 8:1 Citric Acid 6:1 Glucoheptonate 6:1 Lignin Sulfonate 2:1

Rate of applicationChelates Non ChelateFor band placement @ 0.5-1.0 and broadcast @ 0.5-4 kg Zn ha-1

Soil application of Zn through broadcast and band placement at 5-20 and 3 -5 kg Zn ha-1, respectively

(Katyal and Rattan 1990).

Price comparison between ZnSO4 and ZnEDTA

Zinc sources FormsRate of application

(kg/ha)Application Cost

(Rs./Ha)

Sulphate Mono 15-60 900-3600

  Hepta 25-100 750-3000

ZnEDTA   0.5-1.00 300-600 

(Katyal and Rattan 1990).

Effectiveness of the Zn sources as foliar spray in wheat

1. Zinc chelates applied at the earlier growth stage of wheat, has larger effect than the Zn suphate i.e. before tillering stage

2. Zinc chelates & Zn suphate are equally effective in later growth stages i.e. mid tillering stage.

Effect of different Zinc sources on yield of wheat

1.The symbol shows the effect of Chelated form and shows the effect of sulphate form of Zinc2. In GS 14, Zinc applied at early stage and in GS 22-24, Zn applied at late stage

Ross, F. Brennan (2005)

Relative effectiveness (RE) of two sources of Zinc

Effect of different sources of zinc on growth and yield of Maize

Zinc source

Rate of applicatio

n (l/ha)

Plant height

(cm)

No. of cobs/pl

ant

Cob length(cm)

Grain yield

(t/ha)

Oil content(%)

Protein

content(%)

No Zinc 0 133.3 1 15.93 7.16 4.29 9.8

ZnSo4-DTPA 7.5 180.3 1.66 22.83 9.14 4.31 11.4

ZnSo4-EDTA 7.5 162 1.33 20.03 8.41 4.28 10.33

ZnSO4-Lignosulphate 7.5 155 1 19.77 8.12 4.3 10.56

ZnSO4-fulvate 7.5 142 1 21.13 8.36 4.29 10

ZnSO4.H2O 7.5 141 1.33 21.23 7.8 4.3 10.44

F value   S NS S S NS S

(Tahir et al, 2009).

Zinc sourceZn applied per tree (g)

No. of application

Summer flush

Zn content in leaves of pineapple orange leaves (ppm)

Avg.Spring flush Avg.

ZnSo4.H2O 100 1 33   28    164 1 29   28    328 1 44   44    100 3 35   30    164 3 42 38.5 42 34.17

  328 3 48   33  ZnSo4-EDTA 12.5 1 28   21  

  25 1 29   21    50 1 33 31.67 25 27

  100 1 33   26    12.5 3 34   31    25 3 33   38  

Effect of different sources of Zinc on Zn content in leaves