Anyone who has worked in a garden for a season or two is familiar with the major soil nutrients – nitrogen, phosphorus, and potassium – or NPK. Fertilizer bags and bottles have the content of these nutrients written in numbers, such as 10-10-10 or 5-2-6. Many of us are also familiar with the secondary nutrients necessary for plant growth – calcium, magnesium, and sulfur. (See my post on Epsom Salt in the Garden for supplementing magnesium and sulfur organically.) Yet, few gardeners are aware that plants must also have eight micronutrients to grow and produce well, and most soil in the U.S. is deficient in many micronutrients. What are they?!