Crop scientists and extension specialists at the University of Illinois Urbana-Champaign, including Fred Below and Connor Sible, are frequently asked by Illinois farmers about "what biostimulants do and whether they work." Although they are happy to share their knowledge of natural growth stimulants based on dozens of trials and published studies, the constant influx of new products and the confusing regulatory environment make farmers' needs unclear.
Below noted that during extension talks, they found that farmers and companies refer to these products as biologicals, while scientific literature and regulatory agencies call them biostimulants. Different products are subject to the same (or no) regulation, and the terminology is confusing. This realization prompted Below, Sible, and their colleague Juliann Seebauer to conduct an in-depth study. Their review article, titled "Biostimulants or Biologicals? The Complexity of Defining, Classifying, and Regulating Microbial Inoculants," has been published in Agricultural & Environmental Letters.
In basic terms, biologicals and biostimulants are active microbial inoculants and non-living natural chemicals or extracts applied to soil, seeds, and plants to promote growth. They work through mechanisms such as improving fertilizer efficiency, alleviating crop stress, and enhancing soil health. Sible explained that biologicals originally referred to soybean inoculants, which have existed for decades or even a century. Later, products such as humic acids, fulvic acids, hydrolysates, and alginates were mainly used for specialty crops, where measures to improve crop quality have a significant effect.
After these products gained a foothold in specialty crops, the industry shifted toward row crops such as corn and soybeans, leading to explosive market growth and the emergence of hundreds of products with different active ingredients promising various benefits. Below noted that in many cases, marketing exceeds actual research, and the lack of unified terminology and inconsistent regulation makes oversight difficult. Many live microbial products are currently regulated at the state level as fertilizers, with essentially no dedicated regulatory procedures for them.
As part of the university's land-grant mission, Below, Sible, and others are tasked with providing research-based, impartial solutions to the public and policymakers. They delve into the products to help farmers understand what is available on the market and make it easier for policymakers to apply reasonable regulations.
Although products can be divided into more than a dozen categories based on active ingredients, the researchers call for simplification. Sible stated that the market is too large to be simply categorized, and the ultimate customers are farmers, who need to be addressed in language they understand. The team suggests linking "biologicals" with microbial products and "biostimulants" with non-microbial products to clarify the terminology.
The researchers believe that this terminological distinction is crucial for appropriate industry regulation. Currently, the U.S. federal Insecticide, Fungicide, and Rodenticide Act only defines live microbial inoculants. Products that qualify as plant inoculants are not regulated under this act, and there is no policy to confirm whether the microbes listed on the label are alive and present at the claimed concentrations. Label approval is handled at the state level. Although there are labeling guarantees and expiration date requirements, there is no mature third-party testing program to enforce company claims, and each state has its own unique process, resulting in the same product being classified differently across states.
Sible also pointed out that from a risk perspective, placing biologicals and biostimulants under the same regulatory framework makes no sense. Microbes can mutate, and if they are closely related to pathogenic strains, additional regulatory considerations are needed.
