Of all micronutrients, manganese tends to be the most common deficiency noted in soybean production.

These deficiencies, however, usually respond positively to remedial treatments of manganese (when they are timely). As with all nutrients, yield responses are only attainable when manganese is deficient and therefore limiting yield.

This Crop Insights describes manganese requirements, deficiency symptoms, soil and plant sampling, and fertilization practices in soybean production.

Summary

• Soybeans more often are deficient in manganese than other micronutrients and respond well to manganese fertilizers when deficient.

• Manganese is more likely to be deficient in sandy soils, dry soils, high organic matter soils, and soils with high pH levels.

• Fields with manganese deficiency seldom are affected uniformly. Manganese deficiency symptoms also may vary from field to field and are strongly tied to soil properties.

• Plant tissue analysis is the best tool to confirm a manganese deficiency. Randomly select a number of plants, picking the youngest fully opened trifoliate from each.

• To correct manganese deficiencies, a number of manganese sources may be used with preference to chelated forms of manganese (as opposed to salt forms) supplied by foliar application.

• To avoid weed control efficacy and nutrient absorption issues when tankmixing with glyphosate:

− Use the label-recommended rate of spray-grade ammonium sulfate (usually 8.5 to 17 pounds per 100 gallons) in the carrier, and;

− Add the products in the correct order: 1) water, 2) AMS, 3) glyphosate, 4) chelated manganese (EDTA preferred).