Application of chelated micronutrients has proven to be a highly effective way to increase crop yields and their quality.
The word ‘chelate’ stems from the Greek word ‘chele’, meaning ‘pincers’ or ‘crab claws’.
A chelate can be described as a cation surrounded by a chelating compound (a ligand). This complex molecule is stabilised by strong chemical bonds. There are approximately 450 well-defined different chelating compounds. The most effective fertilisation takes place when the nutrients are chelated; chelation protects nutrients from being adsorbed or oxidised by different soil particles and reagents. This is especially true when dealing with micronutrients, but also when dealing with cations such as calcium and magnesium.
A micronutrient chelate is produced by a chemical process, in which a chelating compound is reacted with micronutrient cations (e.g. Fe, Mn, Zn or Cu) under very specific reaction conditions.
Chelates are formed in the process of chelation
Chelate products are most effective when 100% of the cations are actually chelated (complete chelation). However, since it is a technical challenge, the current fertiliser registration acts permits that a product can be termed a ‘chelate’ even if only 80% of the micronutrient cations are really complexed (partial chelation). This means that when the product is applied under unfavourable conditions (e.g. high soil pH), the non-chelated cations may quickly become unavailable to plants. This is why it is worth reading the product label carefully. In contrasts, chelates produced by ADOB® are comprised of 100% chelated nutrients, which ensures complete effectiveness of the applied fertiliser.
Chelation can only take place when the nutrient is a cation. However, boron and molybdenum do not form cations; as a result they cannot be reacted with chelating compounds. Therefore, these micronutrients occur in fertilisers as inorganic salts exclusively.