Manganese (Mn) Deficiency of Soybean
Manganese (Mn) deficiency is the most common micronutrient deficiency in soybean. Mn deficiency causes interveinal chlorosis on newly formed leaves. Chlorotic tissue may die if the deficiency continues. Symptoms can be confused with those caused by iron deficiency chlorosis (IDC) or soybean cyst nematode (SCN).
Foliar symptoms of manganese (Mn) deficiency.
Mike Staton
Field with symptoms of manganese (Mn) deficiency.
Mike Staton
Mn levels are adequate in most soils. Mn deficiency occurs most commonly in areas of fields with high pH because availability decreases as pH increases above 6.5. Generally, Mn is most available when pH is between 5.0-7.0. Dry conditions reduce Mn availability; yellow flash can occur when rainfall causes the nutrient to become available again. Mn deficiency is more common if soil is high in organic matter or is coarse-textured with high sand content. Deficiency symptoms occur in the same patches over time and often occur in low areas or depressions of a field.
Management includes avoiding increasing pH over 7.0 by grid soil sampling and variable rate application of lime. Tissue testing soybeans with suspected deficiency and using locally developed sufficiency levels is preferred over soil testing. If a deficiency is identified, foliar applications of chelated Mn are suggested over broadcasting because nutrients applied to the soil become unavailable to plants quickly. Suggested rates are often higher than products recommended for maintenance levels and are between 0.5 lbs. applied multiple times or 0.7-1.0 lbs. applied once. These rates are based on Mn sulfate, not chelated rates.
Prepared and reviewed by the Science for Success team and the Integrated Pest Management Program at Iowa State University.
Field with symptoms of manganese (Mn) deficiency. Mike Staon
Field with symptoms of manganese (Mn) deficiency. Mike Staton
Foliar symptoms of manganese (Mn) deficiency. Mike Staton
Foliar symptoms of manganese (Mn) deficiency. Mike Staton
Gallery images courtesy Mike Staton.
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