Biologicals are like the Wild West of agriculture — products with big potential but little regulation. As a result, it can be difficult to determine what’s a worthy investment.

“Industry has taken on the role of defining biologicals,” says Drew Clemmensen, field services program manager at the Iowa Soybean Association (ISA). “It’s quite a mess as to what gets designated as a biological — with no committee or agency regulation.”

ISA surveyed growers in February and found 75% of farmers used a biological product. Respondents were most interested in biofertilizers — a classification that includes nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and mycorrhizal fungi. 

Inconsistent Results

Over the years, ISA has tested these six biofertilizers with the help of Iowa farmers: 

• Source by Sound Ag, a foliar-applied, nitrogen-fixing and phosphorus-solubilizing bacteria for corn and soybeans;
• Proven 40 by Pivot Bio, an in-furrow N-fixing bacteria for corn;
• EndoPrime by Valent BioSciences, an in-furrow mycorrhizal fungi for corn and soybeans;
• Vertex-IF by TerraMax, an in-furrow N-fixing and P-solubilizing bacteria that adheres to corn roots;
• Envita by Azotic North America, an in-furrow N-fixing bacteria for corn; 
• Utrisha N by Corteva, a foliar-applied N-fixing bacteria for corn and soybeans. 

Replicated strip trials were conducted in a variety of tillage systems and in fields with a range of yield environments. Clemmensen says the tested biologicals have not produced consistent results and have not proven their value, based on ISA’s trials. It should be noted, however, that the results came from single-year trials. 

For example, ISA tested Source by Sound Ag in soybeans and corn in 2021. The product was sprayed at R1-R3 on soybeans following corn in 9 no-till and conventional tillage fields, in addition to the regular nutrient program. Some of the test plots were lower-yield environments in the 50-55 bushel range, while others were high-yielding fields pushing 85 bushels per acre. On average, Source provided a 1 bushel-per-acre increase. One trial resulted in a 2.7 bushel advantage with Source, but Clemmensen says the rest of the plots were not significantly different.

In corn trials, Source was sprayed at V4-V6 in 10 no-till and conventional fields. Yields in those fields ranged from 160 bushels per acre to 250 bushels per acre historically. Two of the trials showed yield increases of 5.6 bushels and 3.8 bushels, but overall none of the trials was significantly different.

“We have not seen biologicals perform where they’re improving yields or returning investment,” Clemmensen says.

Clemmensen says he didn’t see major differences among trials under conventional tillage, strip-till, no-till and cover crops. All trials were not significantly different, according to Clemmensen, and the data didn’t support one practice being better than another when analyzing the impact of biological fertilizers. 

More Testing Needed

There is hope for biologicals, but finding success may require more time and management. Clemmensen recommends using biologicals as part of an integrated system. 

“If those core nutrients aren’t there, don’t expect these products to bail you out,” Clemmensen says. “Biologicals are complementing our fertilizer programs and may start to reduce some rates, but we still need to have that well-managed system in place before we start.”

Here are three tips to get started with your own on-farm trials:

1 To ensure an accurate assessment of the biological’s performance, leave check strips in the field where the biological is applied. ISA uses 4 check strips at a minimum of 700 feet long for its trials. 

“The longer the strip, the more accurate and reliable the data is,” Clemmensen says. 

2 For products that claim to reduce fertilizer rates, try reducing rates in check strips to compare to the rest of the field with the full applied rate. Increasing the rate could also help assess the effectiveness of the products. 

3 Finally, be prepared to test biologicals over several years. If soils already have nutrients built up in excess of what the crop is using, it’s difficult to determine if the biological is making nutrients more available. It also may take multiple years for biologicals to build up microorganisms in the soil. Clemmensen advises using the products for 2-3 years and adjusting nutrient rates as you go. 

“Maybe you can cut back on some of your macro inputs and combine them with biological products to see if they can complement each other,” Clemmensen says.