Manganese management in field crops

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.    

Manganese (Mn) is one of the more challenging micronutrients to manage and is the one most likely to be deficient on many field crops. MSU Extension bulletin E-486 is an excellent resource for information on manganese and the other secondary and micronutrients. The field crops most likely to show Mn deficiency are dry beans, soybeans, sugarbeet, wheat and oats. Manganese is characterized by a drab olive-green appearance of the crop with leaves of broadleaves showing yellowing between the green veins. Leaves of corn and the cereal grains show a yellowish striping. With more severe deficiency on wheat and oats, the yellow strips become more diffuse and the leaves more yellow. Deficiencies are most likely to occur on old lake bed soils, high organic matter soils, soils with pH above 6.5 and acid soils that have been limed up to near 6.5.

Manganese deficiency is also more likely to occur under dry soil conditions than moist soil conditions. Soil application of Mn is of limited benefit because it readily reacts with the soil and is bound in slowly available forms. Broadcasting Mn is a waste of money. Including Mn in band fertilizer (1-2 lbs/a) does provide Mn during the early growth stages. However, sometimes even when Mn is supplied in the starter fertilizer, it is necessary to spray the foliage with Mn to fully prevent or correct a deficiency. Application rate is very important. When spraying Mn, be sure to supply near 1 lb actual Mn per acre. Last year in one Mn deficient soybean field only 0.5 lb Mn per acre was applied and the soybeans still showed Mn deficiency except where there was spray overlap. There the soybeans were a good, green color. Since Mn has limited mobility in the plant, a second application may sometimes be necessary to cover new growth and fully correct a deficiency.

Recently, there have been some reports of possible Mn deficiency in wheat. This may be partially due to the somewhat dry soil conditions that have existed during April in some areas. When spraying Mn to correct a deficiency, apply 1 lb actual Mn per acre. Spraying Mn during the early growth stages will be more likely to improve subsequent growth and yield. Including some Mn with fungicide sprays may help, but is probably too late to be of major benefit.

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