Secondary and Micronutrients for Vegetables and Field Crops Extension Bulletin E-486, Revised August 1994 By M.L. Vitosh, D.D. Warncke and R.E. Lucas Department of Crop and Soil Sciences Michigan State University Extension Zinc is essential for plant growth because it controls the synthesis of indoleacetic acid, which dramatically regulates plant growth. Zinc is also active in many enzymatic reactions and is necessary for chlorophyll synthesis and carbohydrate formation. Because zinc is not readily translocated within the plant, deficiency symptoms first appear on younger leaves. Research shows a need for zinc in many areas where dry edible beans are grown. Corn, onions, soybeans and barley have also shown benefits from zinc applications at some locations. Several other states report that Sudangrass, sorghum, tomatoes and potatoes have been responsive.Soils associated with zinc deficiency are usually neutral to alkaline in reaction. The more alkaline the soil, the greater the need for zinc. Deficiency is particularly noticeable on crops growing where calcareous subsoils have been exposed by land leveling or erosion, or where subsoil is mixed with topsoil, such as after tiling and spoil-bank leveling. Lake bed soils and organic peats show the greatest zinc deficiencies in Michigan. Observations and field tests show that dry edible beans following sugar beets often need zinc. The large quantities of phosphorus fertilizer used for sugar beets and the high zinc requirement of dry edible beans are believed to cause the problem. A recent reduction in phosphorus use on ugar beets and the long-term use of zinc fertilizers have reduced the incidence of zinc deficiency. Zinc deficiency varies from year to year. Wet, cool, cloudy weather during the early growth season increases the deficiency. Zinc deficiency in corn is occasionally noted in June, but the deficiency disappears after the soils dry out and warm up. Crops on poorly drained organic soils show a deficiency probably because of restricted root growth. Field and vegetable crops often show differences in response to zinc fertilizer. The relative crop response to fertilizer zinc is given in (Vis. 6). Dry edible beans, corn, onions, sorghum, snap beans, spinach and sweet corn are the most responsive crops.
