ABSTRACT
The importance of copper (Cu) for the growth of higher plants was first discovered in 1931 by Lipman and MacKinney (Fageria Baligar, and Jones 2011). Copper deficiency has been observed in an ever-increasing range of crops and environments, and the use of copper fertilizers has increased accordingly (Graham and Nambiar 1981). In the twenty-first century, Cu deficiency in annual crops, including rice, has been reported in many regions (Fageria, Baligar, and Clark 2002). However, variations in soil conditions, climate, crop genotypes, and management result in marked variations in the deficiency problem (Alloway 2008; Fageria and Stone 2008; Graham 2008). Alloway (2008) found that copper deficiency is more predominant in Europe and Australia, where cereals are most affected. Fageria and colleagues reported that micronutrient deficiency in food crops is very common in different parts of the world due to low natural levels of micronutrients in the soils; the use of high-yielding cultivars; liming of acidic soils; interactions among macro-and micronutrients, sandy and calcareous soils; the increased use of high analysis fertilizers having low amounts of micronutrients; and the decreased use of animal manures, composts, and crop residues (Fageria, Baligar, and Clark 2002; Fageria, Slaton, and Baligar 2003; Fageria, Baligar, and Jones 2011; Fageria et al. 2012). Copper deficiencies in the United States have been reported in Florida, Wisconsin, Michigan, and New York, where high value crops are intensively grown on Histosols (Tisdale, Nelson, and Beaton 1985). Graham and Nambiar (1981) noted that copper deficiency is usually best demonstrated in the field by measuring the increase in grain yield following copper application.
