Zinc occurs in the soil in the form of ferromagnesian minerals like magnetite, biotite and hornblende. Increase in soil pH decreases the availability of zinc. Bivalent form of zinc (Zn2+) is exchangeable and is readily available in the soil. Plants require this mineral only in traces and its higher concentrations are highly toxic. Due to deficiency of zinc, the leaves become distored, sickle shaped and get clustered to form rosette. This effect is known as little leaf disease.