Fertilisers with micronutrients and microfertilisers are used in practice. The latter have recently been promoted in the form of preparations for foliar application.
The production of these fertilisers has developed intensively over the last 20 years, especially in Poland, with a focus on the use of micronutrients. A novelty of recent years is the definition of chelating compounds that may be applied and declared by fertiliser manufacturers.
Micronutrients, which are technical salts or micronutrient chalates, are commercially available as single or mixed micronutrients in solid or liquid form.
Single microfertilisers in the form of technical salts require a declaration of the water-soluble micro-nutrient content.
The producer declaring the fertiliser type as “metal chelate” or declaring the chelating compound for micro-nutrients in compound liquid fertilisers shall specify the name of the chelating agent, the content of the water-soluble component, the content of the chelated form, and the pH range that guarantees the acceptable stability of the chelated fraction.
The content of chelated form of the micro-nutrient in single micro-nutrients shall not be less than 80%. Minimum values for mixtures of microfertilisers apply to the sum of the microelements. The minimum content in solid fertilisers shall be 5% and in liquid fertilisers 2% .