Most micronutrients in plants are involved in enzymatic reactions like photosynthesis and respiration. We need micronutrients in minimal amounts. The essential micronutrients are iron [Fe], manganese [Mn], boron [B], chlorine [Cl], copper [Cu], zinc [Zn], molybdenum [Mo], nickel [Ni] , cobalt [Co], vanadium [V], sodium [Na], and silicon [Si]. Deficiencies of the last four minerals are very rare.
Soil chemistry wreaks havoc on nutrient availability. For example, we need iron in relatively large amounts, but it is the most difficult to make available because soil chemical processes sometimes quickly make it unavailable. Low soil pH can cause excessive amounts of micronutrients to become available in solution causing toxic effects. Too high a soil pH can make them unavailable for plant needs. Providing these nutrients in chelated form is essential. However, not all chelates are equal.