Zinc

Essentiality of zinc (Zn) for higher plants was discovered by A. L. Sommer and C. B. Lipman in 1926 (Marschner, 1983; Fageria et al., 1997). Zinc is a micronutrient needed in small amounts by crop plants, but its importance in crop production has increased in recent years. It is considered to be the most yield-limiting micronutrient in crop production in various parts of the world (Sims and Johnson, 1991; Cakmak et al., 1996; Cakmak et al., 1998; Mandal et al., 2000; Fageria, 2001; Grewal, 2001; Fageria et al., 2002; Fageria et al., 2003ab; Fageria and Baligar, 2005). Duffy (2007) reported that yield losses in wheat, rice, corn, and other staple crops of up to 30% is common even in mildly zinc-deficient soils. Approximately, 50% of the soils used worldwide for cereal production contain low levels of plant-available zinc (Graham et al., 1992; Welch, 1993).