Examine the Essentials: Nickel
Depending on who you ask, nickel may or may not make it into the essential list for plants. It wasn’t until the late 1980s that researchers identified nickel as a possible essential nutrient, and it took until 2004 for its status to be recognized by the American Association of Plant Food Control. But given its role in nitrogen availability, we consider it pretty essential.
Nickel is a component of the enzyme that metabolizes urea into ammonia, making the nitrogen available to plants. Legumes, with their nitrogen-fixing capabilities, have the highest nickel needs. A deficiency will cause urea to build up in leaves, causing burns to the tips of the plant’s leaves. However, plants’ nickel needs are lower than any other nutrient, so deficiency is rare. Toxicity is actually more common, which can inhibit root growth and make leaves blotchy.
Rocks of many types contain nickel, so as the rocks weather, the element is released into the soil. High pH can limit the availability of nickel to plants, however, and it is fairly immobile in soil. Pecan growers in the southeast may see “mouse ear” if they fertilize with urea and there is not ample nickel in the soil to metabolize it. Without nickel, that urea fertilizer “ain’t worth a plugged nickel”!