Avoid applying granular zinc oxide on calcareous soils due to its low solubility. Some of these materials have been shown to be three to five times as effective as the inorganic sources. Effective zinc chelates may be used at about one-third the rate of inorganic products. Manure applications are quite effective in eliminating zinc deficiency problems when applied at the rate of 15 to 20 tons per acre. Areas frequently have had the topsoil removed by erosion or leveling.
Iron deficiencies are worse in cool, damp springs.
Deficiency symptoms are frequently most severe on young seedlings. Sorghum, corn, potatoes and pinto beans are the most severely affected Crops, with corn intermediate in susceptibility. Wheat and alfalfa are the least sensitive. Varietal differences in susceptibility have been recognized within each species. Because iron is not translocated in the plant, deficiency symptoms appear on the new growth first.