Identifying and correcting manganese deficiency in soybean

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 deficiency is common in Michigan and can cause yield reductions if not corrected. Because of this, soybean growers need to be able to identify manganese deficiency symptoms and know the best strategy for correcting them. Manganese deficiency typically occurs in muck soils or dark-colored sands with pH levels above 5.8. Lakebed and out-wash soils having soil pH levels above 6.5 are also likely to produce manganese deficiency symptoms. Deficiency symptoms include yellowing between the veins on the newer leafs and stunting in severe cases. Early detection is critical to preventing yield losses due to reduced photosynthesis and nitrogen fixation. Since increasing the available manganese levels in the soil is difficult, deficiency symptoms will reoccur in the same areas each year that soybeans are grown.

Foliar application of one pound of actual manganese (Mn) applied in 30 gallons of water per acre will alleviate deficiency symptoms. Applying a lower rate, regardless of source, frequently requires a second application to fully correct the deficiency. When deficiency symptoms are quite severe, apply 1.5 to 2 lb Mn/a or make a second application two weeks after the first. Manganese sulfate is the preferred choice except when tank mixing with glyphosate. It is quite soluble and provides greater crop safety than the chelated forms of manganese at the same rate. Always apply the glyphosate at least two days before the manganese.

If care is not taken when tank mixing, the performance of both the manganese and the glyphosate may be reduced. If you must tank mix manganese and glyphosate, use the chelated manganese carrier (Mn-EDTA). Add the manganese to the tank after the ammonium sulfate has been added. One of the down sides of tank mixing is that Mn-EDTA must be applied at lower rates (less than 1 lb Mn/a) to avoid burning leaf tissue so more than one application may be required.

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