Biologicals have taken the agriculture industry by storm in the last decade, but confusion still exists about what they are and what they do.

“A biological is an umbrella term referring to a much broader array of products and opportunities for the farm,” says Connor Sible, postdoctoral research associate at the University of Illinois.

Biologicals can be classified into three different categories: plant growth regulators, beneficial microbes and biostimulants.

“If we were really to over-simplify this, beneficial microbes are the living and the biostimulants are the dead,” Sible explains. “One of the important things as growers that you need to remember is, if you’re working with the living, you have to keep them living.”

Sible says that 85% of biological products on the market fit into one of the following eight subcategories:

1. Nitrogen-fixing bacteria. Biologicals that increase plant-available nitrogen.

2. Phosphorus-solubilizing microbes. Biologicals that increase availability of mineral phosphorus.

3. Mycorrhizal fungi. Biologicals that extend the plant’s root system.

4. Residue degradation. Biologicals that enhance the release of organic nutrients.

5. Enzymes or phosphatases. Biologicals that release organic phosphorus.

6. Humic or fulvic acids. Biologicals that chelate soil cations and feed microbes.

7. Marine extract. Biologicals that mitigate stress in foliar application and enhance root zones in soil application.

8. Sugars. Biologicals that stimulate microbes and roots in soil application and stimulate growth to a point in foliar application.

The first four subcategories are classified as beneficial microbes; the last four are biostimulants.

Breakdown of biologicals

Sible says nitrogen-fixing bacteria, phosphorus-solubilizing microbes and residue degradation have been receiving the most attention in the crop science world. It’s important to understand how each type can be applied most effectively and efficiently to increase yield and return on investment.

Nitrogen-fixing bacteria fix atmospheric nitrogen into a form that is usable by plants and microbes through a symbiotic relationship where bacteria supply the plant nitrogen in exchange for sugars.

In University of Illinois studies, Sible found that biologically fixed nitrogen from an applied biological product improved corn grain yields, with the greatest responses in fields where preplant nitrogen was at or over 160 pounds per acre.

“N-fixing bacteria can be a new source of nitrogen from the atmosphere, but they will not replace all nitrogen,” Sible says. “Balanced management is key.”

Examples include Pivot Bio Proven, TerraMax, Envita and Corteva Utrisha.

Phosphorus-solubilizing microbes increase the plant’s availability to uptake mineral phosphorus.

“Soils are loaded with good phosphorus, but it’s tied up in cations,” Sible explains. “When we add these microbes, they secrete some weak organic acids that release the phosphate to make it plant available.”

In studies, Sible found the greatest yield increase from in-furrow application because soil contact near the root system is needed.

“When we add these solubilizing microbes, they’re actually working really well with fertilizer because it keeps the fertilizer available,” he says. “It’s a different approach and different concepts. We’re just going to protect the fertilizer, not mine the soil.”

Examples include Bayer BioRise and Invigorate.

Residue degradation enhances the release of organic nutrients, and most are Bacillus species. Sible expects the market for this subcategory to increase in the coming year. They’re naturally occurring soil microbes that stimulate plant growth and other beneficial soil microbes. Bacillus species produce extracellular proteins and enzymes related to residue decomposition, nutrient cycling and symbiotic plant interactions.

“What I really like about this is, not many consider the organic phosphorus pool as a tool for your phosphorus nutrient management,” Sible says. “About 50% of soil phosphorus is in the organic form. Access your organic phosphorus in your soils, and just a little bit can go a long way in improving phosphorus efficiency.”

Market examples include Bacillus megaterium, Bacillus amyloliquefaciens, Bacillus licheniformis and Bacillus pumilus.

Regardless of the biological, Sible says nothing will replace good management.

“It’s important to understand what these products are and what they do before trying them,” he says. “It will take good management of inputs and fertility; then with a biological, there might be an opportunity to increase grain yields.”

But in the end, it’s about return on investment.

“If you reduce phosphorus inputs and maintain yield, you’ve now increased ROI,” Sible says. “So it’s not always about the yield number.”