The combination of chelator with EDTA structure and iron salt is sensitive to light not only in solution but also in form (even if considerably less so). The energy consumption through light absorption destroys the EDTA structure with a loss of chelator properties (this process is known as photochemical decarboxylation).

In short, the powder must always be protected from light and also from moisture, so that it does not cause problems due to caking when dissolved later.

If stored in such a way, the fertilization powders can be kept for many years.

Slight caking and a change in colour of the fertilizer powder is not a sign of spoilage but a completely normal ageing process of the mixture, so to speak, which has no influence on the later effect of the solution.