Researchers with the U.S. Department of Agriculture, Agriculture Research Service at Cornell University published as series of research papers on nickel nutrition. The culmination of this research, published in 1987, established nickel as an essential mineral element for all plants. Nickel is an essential component of urease, an enzyme that enables plants to metabolize and use nitrogen in the form of urea. Deficient levels of nickel not only impairs the utilization of urea but also is expressed as urea toxicity, particularly when urea is applied foliarly. The greater the Ni deficiency, the greater the symptoms of urea toxicity which is expressed as necrosis (burning) of leaf tips. When plants are supplied with nickel, the urease enzyme function increases and necrosis is reduced.
Seeds that have no nickel will not germinate. Seeds with deficient levels of Ni can often produce plants with severe necrosis. Nickel is also essential for iron uptake in plants. Nickel can be toxic to plants in levels greater than 10 – 50 micrograms/gram depending upon the plant’s sensitivity to nickel.