Technical Abstract: The nutritional physiology of essential micronutrients in pecan, especially that of nickel, is a limiting factor in optimization of physiological efficiency of orchard enterprises. Knowledge by farmers and extension specialists about the role of nickel, a newly recognized micronutrient, is meager. This review summarizes situations where nickel influences key metabolic and physiological characteristics that influence tree and orchard yields and profitability. This information assists in recognition and correction of subtle forms of nickel deficiency in orchards, thus, helping to maximize profitability.