ROOTED INRESEARCH
A CLASSIFICATION SYSTEM FOR TURFGRASS BIOSTIMULANTS
By Mike Fidanza, PhD
Te term “biostimulant” has been misunderstood or misused as a potential “miracle cure” in the turfgrass industry, and therefore biostimulant products were often dismissed as “snake oils.” Some biostimulant products make performance claims substantiated with scientific research, while other products lack direct evidence of their actual benefit.
Dr. Richard Schmidt (Emeritus Professor at Virginia Tech) is considered the pioneer of biostimulant research in turfgrass science. Dr. Schmidt defined biostimulants as follows:
“Biostimulants are organic materials that when applied in small or minute quantities enhance plant growth and development.”
Te use of the word “minute” is intended to differentiate the fact that these substances, compared to traditional fertilizer nutrients and/or soil amendments, elicit a measurable and beneficial response at much lower application rates.
In his early work, Dr. Schmidt considered the plant biostimulant effect was attributed to a hormonal response and the plant protection response against abiotic stress was attributed to antioxidant production, and both of those effects were achieved from low concentrations of biostimulant materials from foliar applications. Dr. Schmidt also used the term “metabolic enhancers,” but the important distinction was that something positive was happening to the plant beyond what mineral nutrition supplied.
More recently, plant biostimulant is defined as: “…any substance or microorganism applied to plants
with the aim to enhance nutrition efficiency, abiotic stress tolerance, and/or crop quality traits, regardless of nutrient content.”
Te term “plant biostimulant” often is used to describe the various categories of compounds and substances used in these products: plant growth hormones (e.g., abscisic acid, auxins, cytokinins, gibberellic acid, etc.), microorganisms (e.g., Bacillus spp., Trichoderma spp.., mycorrhizae, etc.), amino acids, humic and fulvic acids, plant defense-activating substances, plant growth-promoting compounds, vitamins, pigments and oils, soil amendments and soil conditioners, composts and compost teas, and more.
66 TPI Turf News July/August 2024
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