Sentinel WG MC

Wilchem Sentinel – Wettable Micro Granule

In 2020 Wilchem released a range of wettable micro granule EDTA’s.

At Wilchem we are always looking to improve the range of nutritional products available to meet the changing needs in the market, not only new products but improved versions.

Wilchem’s new range of EDTA’s are Sodium Free, utilising potassium through a new formulation that will provide a significant plant benefit. The Potassium in the new range is plant available, giving not only a plant benefit but also a commercial advantage.

A comparison of product analysis can be seen below.

• Sentinel Zinc – 10.5% Sodium has been replaced by 17.3% plant available Potassium.
• Sentinel Manganese – 10.9% Sodium has been replaced with 17.7% plant available Potassium.
• Sentinel Copper – 10.1% Sodium has been replaced with 6.8% Nitrogen.

Wilchem Sentinel is a range of Ethylenediaminetetraacetic acid (EDTA) chelates. EDTA forms sexadentate chelates – they form six bonds to the nutrient to form a “chelate ring”. As can be seen in the diagram below showing the octahedral structure of EDTA chelating a metal ion. The chelate ring is stronger than a single ionic bond and protects the nutrient and maintains it in solution. EDTA chelates protect the nutrient from interaction with other crop protection products making it the most compatible product on the market.

Metal Chelates Definition

IUPAC (International Union of Pure and Applied Chemistry)

“Chelation is the formation of bonds between two or more binding sites within the same molecule and a single central metal atom.”

Wilchem Sentinel range covers the three most commonly used micronutrients for broad acre agricultural use. They are –

• Zinc
• Manganese
• Copper
• Blends

A full list of products can be found on the product information PDF.

Compatibility Function

Increased compatibility
The EDTA molecule (ethylenediaminetetraacetic acid) is the strongest chelation agent currently available. The benefit of strong chelate bonds is that it makes this range of products the most compatible micronutrient products for tank mixing and for soil applications. This is very important for furrow injection in alkaline soils and tank mixes that contain soluble phosphates.
The synthetic EDTA molecule does not provide any additional nutritional benefit, it purely acts as a stable transporter of the micronutrients in solution.

Uptake Mechanism

Foliar micronutrient applications can enter the plant two ways. Via the stoma which is used by the plant for respiration or by direct absorption through the leaf cuticle. The leaf cuticle is highly negatively charged making it difficult for positively charged ions to be absorbed. Chelating the positive ions to a highly negatively charged EDTA molecule creates a molecule that remains negatively charged that can pass through with no interaction. The nanopores that allow passage through the cuticle are very small. EDTA chelates have a low molecular weight and can pass through these pores.

EDTA chelates cannot be absorbed directly through the cell membrane. The micronutrient must first be uncoupled from the EDTA molecule either in the rhizosphere (soil applications) or epidermis or palisade cells (foliar applications). It can then be absorbed through the cell exchange process as pictured to the right.
EDTA chelate structure

Sentinel EDTA Chelates Physical Compatibility

Wilchem’s Sentinel Range of EDTA chelates is the most compatible of our offering of liquid micronutrient product lines. Key areas where there is benefit in using this product line over amino acid chelates or liquid sulfates are in tank mixes with one of the following products or applications –

• Highly alkaline soils
• Soluble phosphates
• Polyphosphate
• Orthophosphate
• 24D Amine
• MCPA Amine (when zinc is required)
• Glyphosate

The Sentinel Range should not be used in tank mixes in the presence of free calcium or potassium.