Commercial biostimulant seed treatments showed minimal impact on soybean seed yield across the United States

Context

The use of biostimulant seed treatments (BST) in soybean (Glycine max (L.) Merr.) is a growing market, with many different products and active ingredients (microorganisms) available. Companies promote the use of biostimulant seed treatment products by claiming several potential benefits to crop production, including seed yield increase. There are limited field evaluations on the efficacy of biostimulant seed treatments to increase soybean seed yield in the USA, and many of the microorganisms included in biostimulant products that are marketed to soybean farmers have never been documented in the peer-reviewed literature.

Objective

Here, we evaluated the effect of several commercially available biostimulant seed treatment products on soybean seed yield.

Methods

Field trials were established using a standard protocol during the 2022 and 2023 growing seasons across 22 states (103 site-years) in the USA. The 103 site-years were separated into four environmental clusters based on weather and soil properties.

Results

No significant yield differences were observed due to biostimulant seed treatment across and within clusters in both years. We believe that the lack of yield response may have been due to factors such as competition of active ingredients with native soil microorganisms or lack of favorable conditions for plant-microbe interactions. Overall results suggest that management practices, such as row spacing, seeding rate, foliar insecticide, and tillage affect yield more than any of the examined biostimulant seed treatments.

Conclusion

We argue that there is a need for further evaluations and standard requirements on the registration, production, commercialization, handling, and viability testing of biostimulants in the USA.