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Northern Illinois Agriculture

University of Illinois Extension

Are micronutrients needed?

Last week Illinois Extension hosted the two-day Northern Illinois Crop Management Conference in Malta. Over 100 individuals from three states traveled to DeKalb County to participate. The Northern Illinois Crop Management Conference is one of four like conferences held across the state. Individuals from 18 Illinois counties heard campus specialists and researchers share summaries and information on current issues.

Dr. Fabian Fernandez, Assistant Professor of Soil Sciences in the Department of Crop Sciences at the University of Illinois shared information on secondary macronutrients and micronutrients for corn and soybean production. The following information is a summary of Dr. Fernandez's presentation.

There are 16 essential nutrients of higher plants. An element is deemed essential if

  • In its absence the plant cannot complete its life cycle (produce viable seed)
  • Its deficiency cannot be corrected by another element
  • Deficiency symptoms may develop

The 16 essential nutrients are divided into macro and micro nutrients based upon the concentration of the nutrient required by the plant. Farmers are familiar with the Macro nutrients N-nitrogen, P-phosphorus and K-potassium. The remaining macronutrients, referred to as secondary macronutrients include Ca-calcium, Mg- magnesium and S-sulfur. The micronutrients include B-boron, Cl-chlorine, Cu-copper, Fe-iron, Mn-manganese, Mo-molybdenum and Zn-zinc. Unfortunately, soil tests are an unreliable indicator of the presence or absence of the secondary macro or micronutrients. A medium or low test does not necessarily guarantee a crop response if that product is added. Tissue testing, if done mid to late season can be beneficial for future crops, but rarely allows you the opportunity to remedy deficiencies that season when plants have neared maturity. Concerns for corn production include zinc and possibly sulfur. Manganese (most common) and iron deficiency have been found in Illinois soybean. Dr. Fernandez reminded producers that maintaining a pH of 6-7 in your production fields could be some of the best fertility dedicated dollars spent because the proper soil pH influences nutrient availability. If growers have experienced deficiency symptoms in the same field in repeated years, further testing is recommended. If a deficiency is identified, remember that deficiencies are often localized in areas of the field. Often the entire field does not need to be treated.

Dr. Fernandez's general rule is as follows "If the pH is 6-7 on soils of average or greater productivity there is little chance that addition of micronutrients will produce a consistent response in corn, soybean or wheat yields"

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