Soybean South


Why Use Seed Treatments?

Seed treatments, such as fungicide, inoculants and molybdenum offer
benefits and add value to soybeans under different scenarios.


Although soybean seed can be treated with fungicide, inoculant and molybdenum, farmers sometimes question if the treatments add value. Often it depends on environmental conditions and other factors.

LSU AgCenter soybean specialist Ron Levy says there is a definite advantage to treating soybean seed with fungicide if farmers are going to plant early, especially in some of the heavier soils.

“A fungicide seed treatment provides an advantage, especially in the South where we get those early, cool spells when the soil is still damp and wet,” he says. “For the cost, it’s good insurance and can contribute to achieving a good stand. If you start out with a good stand, your yield potential is much better.”

Inoculants fix nitrogen
Soybean inoculants, which are applied at plant-ing, are nitrogen-fixing bacteria that can take nitrogen from the soil and make it available to the soybean plant.

“Typically, we recommend that an inoculant be used if a field has not been planted in soybeans for three to five years,” Levy says.

The University of Georgia Extension Service notes, “Nitrogen-fixing bacteria are living organisms. They can be destroyed if the inoculant is exposed to high temperatures or chemicals, such as seed fungicide or molybdenum.”

Inoculants are sensitive and should be stored in a cool place and kept separate from seed treatment until it’s time to plant. It’s also important to check the expiration date on the inoculant.

Molybdenum’s role
Molybdenum, a micronutrient, also can be used as a seed treatment. It improves efficiency of nitrogen fixation in the soybean root nodule.

“Molybdenum is usually recommended when the soil pH is slightly low,” Levy says. “The better option is to apply lime to correct the pH prior to planting. However, if a farmer can’t afford to apply lime at the time, then we recommend that he use some molybdenum.”

Improving soybean stands
Can good soybean stands be obtained with sub-standard planting seed? According to the University of Georgia Extension Service, they can, but the risks of stand failure are much increased. A seed fungicide will help improve seedling emergence for many soil environments, but low vigor soybean seed may emerge poorly if soil temperature is low (below 70 degrees F) or high (above 90 degrees F), if soil crusting occurs, if soil moisture is marginal, or if plant residue is present in the seed furrow.

If adverse soil environments and/or planting conditions are an issue, following are some things that UGA says can help improve soybean stands:

1. Use a good seed fungicide. Most seed companies marketing marginal quality soybean seed will likely pretreat the seed with fungicide. This effort should be of benefit, especially if germination is below 80 percent. The value of fungicide on seed with above 80 percent germination is negligible.

2. Increase seeding rate to compensate for low germ. Normal seeding rates for 36-inch row spacing are in the range of 8 to 10 seed per foot. For marginal quality seed, this rate should be increased to 10 to 12 seed per foot.

3. Plant only in moist soil. Georgia soils often get hot and dry in late May and June. With double-cropping, there is an urgency to get soybeans planted as quickly as possible after winter crop harvest. Timely soybean planting is important but should not be done if/when the soil is hot and dry. Waiting until a good rain comes along will be especially important for getting an acceptable soybean stand with marginal quality seed.

4. Avoid placing soybean seed in or near old crop litter. Decaying crop residue increases populations of soil microorganisms, some of which are seed decay organisms. Planter units that sweep old crop residues away from the seed bed can help improve soybean stands.