Microbes  produce organic Chelates that are used to complex nutrient in the soil to make then ex tractable. Levesol is a EDDHA chemical chelate that is use for primarily for iron in high pH soils. Biodegradability of the chemical chelator has been disputed for along time. I would rather mimic nature and use a organic compound as much as possible.  When chelators combine with a micro nutrients, they form a chelated fertilizer. Chelated micronutrients are protected from oxidation, precipitation, and immobilization in certain conditions because the chelator  forms a ring around the micro nutrient. If the chelator is too powerful the plant will not beable to extract it especially in foliar applications.