Why are chelation mechanisms so important?

In many soil systems, nutrient availability is not a matter of dosage but of chemical form. At high pH, iron and manganese quickly precipitate. In clay soils, zinc and copper are strongly bound. Chelation prevents these losses and increases effective availability.

For formulators, this means: chelation is often the difference between “nutrient present” and “nutrient utilized”.

How does chelation work on a molecular level?

Chelators contain functional groups that can grasp metal ions, such as carboxyl, hydroxyl, or amino groups. The chelator-ion complex is stable but reversible: the ion remains protected but can be released when the plant absorbs it.

This makes chelation a controlled transport mechanism rather than a permanent bond.

Chelation in the soil: mobilization and protection

In the soil, chelation prevents micronutrients from:

• precipitating as insoluble hydroxides
• being fixed by clay minerals
• becoming inactive due to ion competition

This keeps nutrients available in the rhizosphere and allows them to be actively absorbed. Chelation thus directly supports nutrient mobilization.

Rhizosphere interaction and natural chelators

Chelation occurs not only in formulations but also biologically in the rhizosphere. Plant roots excrete organic acids and amino acids that form natural chelators. Microorganisms also produce chelating metabolites that release phosphate and micronutrients.

This underscores the importance of chelation as a fundamental mechanism within rhizosphere interaction.

Fulvic chelation: a biostimulant-specific mechanism

One of the most relevant chelation mechanisms in biostimulants is fulvic chelation. Fulvic acid is low molecular weight, highly soluble, and forms stable complexes with micronutrients over a wide pH range.

Fulvic chelation combines chelation with bioactivity: it not only improves availability but also supports uptake processes and metabolic efficiency.

Chelation and internal nutrient transport

After uptake, micronutrients need to be transported to leaves, growth points, and fruits. Chelation also plays a role internally by keeping nutrients in mobile transport within xylem and phloem.

This is essential during critical phases such as flowering and fruit setting, when the redistribution of nutrients is yield-determining.

Chelation under stress conditions

Under abiotic stress, uptake efficiency often decreases. Root activity diminishes, water flows decline, and transport proteins function less effectively.

Chelation mechanisms help mitigate stress by keeping micronutrients available for antioxidant enzymes and photosynthesis, even when uptake is under pressure.

Plant Stress Mitigation: chelation as a protective layer

Within plant stress mitigation, chelation is an indirect but powerful intervention. By keeping nutrient flows intact, chelation supports:

• chlorophyll formation and photosynthesis
• ROS neutralization via enzyme cofactors
• root continuity under stress

Biostimulant raw materials with chelating action

Various raw material clusters contribute to chelation and nutrient mobilization:

Fulvic acid and humic acids

Important for solubility, mobility, and synergy with micronutrients.

Amino acids and protein hydrolysates

Amino acids can form mild natural chelators and support transport processes.

Organic acids

Citrate, malate, and other organic acids mobilize nutrients in the rhizosphere.

Microbial metabolites

Microorganisms produce chelator-like substances that release nutrients and support stress adaptation.

Synergy: chelation as the basis for other biostimulant actions

Chelation mechanisms enhance the action of many other biostimulant components. Without available micronutrients, priming, antioxidant activity, and root growth are less effective.

Chelation is therefore often the “enabling technology” within synergistic formulations.

From chelation to yield stability

When nutrients are stably available, growth and yield formation are less sensitive to stress moments. This results in:

• higher nutrient efficiency
• better photosynthesis under stress
• more uniform fruit setting
• more stable yield and quality

Overview: chelation mechanisms in biostimulation