Chelate Benefits

Quick absorption

When they are chelated, micronutrients are absorbed by plant leaves more quickly than when applied as crystalline salts, becoming available to plants rapidly.

Tolerance

Plant leaves are normally very tolerant of chelates. In contrast, mineral salts often cause leaf burning after foliar application.

Good solubility

Mineral chelates normally dissolve very easily in water. They form clear solutions, without sediments or precipitates. This guarantees a high level of effectiveness and stops the nozzle becoming blocked.

Good miscibility

Chelated fertilisers mix well with many crop protection products, as well as with other foliar fertilisers. They can therefore be used in various tank mixes, saving on field manoeuvres. The grower should always check the manufacturer’s label before preparing tank mixes.

High stability

Chelated fertilisers are stable, even under adverse soil conditions. For example, HBED chelated Fe(III) remains stable even in calcareous soils with a pH of up to 12.

High cost-effectiveness

As chelated fertilisers are normally more effective than crystalline salts composed of the same nutrients at the same molar concentration, a lower rate of chelated fertiliser is needed. This markedly reduces the final expenditure required for peak performance.

Zn sulphate compared with Zn chelate

ZnSO₄ · 7H₂O (0.3% w/w aqueous solution)
Solubility is pH-dependent. Even neutral or slightly basic pH prevents the production of a homogeneous solution. The photos were taken immediately after preparation.

ADOB® 2.0 Zn IDHA (0.3% w/w aqueous solution)
The Zn-chelate solution remains clear regardless of the solution pH, even 5 hours after preparation.

Plants absorb the nutrients contained in the fertilisers in their ionic form only. If a fertiliser does not fully dissolve in water, its dissolution process is slow and precipitates and sediments are produced. This means that a considerable number of its nutrients do not convert into plant-available ions. Its nutritional potential and effectivity are low and its contribution to the plant is limited.

A comparison between chelated and non-chelated micronutrients in high pH solutions

Chelated micronutrients

Chelated Zn, e.g. Zn-HBED
In high pH solution, chelated zinc is fully protected against the reactive hydroxyl anions (OH^–). All the Zn²⁺ contents will be taken up by the plant.

Non-chelated micronutrients

Crystalline Zn salt, e.g. ZnSo₄
In high pH solutions, zinc cations are not protected, so under the attack of hydroxyl anions (OH^–) they will rapidly precipitate in the form of zinc hydroxide Zn(OH)₂, resulting in Zn unavailability to plant roots or leaves.

A comparison between chelated and non-chelated micronutrients under tank mixing with phosphate fertilisers such as NPK, MAP or MKP

Chelated micronutrients

Chelated Mn, e.g. Mn-DTPA
Manganese cations in the manganese chelate are fully protected against the reactive phosphate anions (PO₄^3–). All the Mn²⁺ contents will be taken up by the plant.

Non-chelated micronutrients

Crystalline Mn salt, e.g. MnSO₄
Manganese cations are not protected, so under the attack of phosphate anions (PO₄^3–), all the Mn²⁺ contents will leave the solution in the form of manganese phosphate Mn₃(PO₄)₂ precipitate, resulting in Mn unavailability to plant roots or leaves.

Application recommendations

Preferences of ADOB®’s chelated products, based on soil pH, chelate type and deficient nutrient

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Soil pH	IDHA		EDTA		DTPA		HBED
Soil pH	Fe	Cu, Zn, Mn	Fe	Cu, Zn, Mn	Fe	Cu, Zn, Mn	HBED
<6.5	+++	+++	+++	+++	+	+	–
6.5-7.5	–	++	–	++	+++	+++	+
>7.5	–	+	–	+	–	–	+++

Preferences of ADOB®’s chelated products, based on application method

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Method of fertilisation	IDHA	EDTA	DTPA	HBED
Foliar	+++	+++	–	–
Soil	++	++	+++	+++
Fertigation	++	++	+++	+++
Hydroponics	++	++	+++	++

Recommendation

+++ Very highly recommended

++ Highly recommended

+ Moderately recommended

– Not applicable