The Q&A Archives: What does chelated mean?

Question: I often hear about chelated forms of fertilizers such as chelated iron. What does chelated mean and how is it different from regular fertilizers? Larry Andrews Lindrith, NM

Answer: Chelated fertilizers are elements that have been treated with organic (carbon based) compounds to enhance their availability to plants, says Bob McCaslin, soil specialist at New Mexico State University in Las Cruces. In our area, the most common chelated elements are zinc and iron, he says. Nitrogen, phosphorus and potassium are rarely chelated because they're more readily available. However, minor elements such as iron and zinc are easily bound by compounds in our highly alkaline soils. Chelates prevent these elements from being bound up in the soil and allow them to be taken up by the plants, says McCaslin. Where the soil pH is slightly acidic, expensive amendments like chelated iron aren't necessary. A fertilizer such as iron sulfate would work just as well, McCaslin adds.

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