Are plant biostimulant products providing a return on investment on-farm?
BY: Christopher Forsythe, On-Farm Network Agronomist, Manitoba Pulse & Soybean Growers
At the end of the day, farmers want to know if plant biostimulant products increase yield and provide a return on investment on their farms.
“Plant biological” is a blanket term for naturally derived products that can serve as biostimulants, biocontrol agents, resistance inducers or biofertilizers.
Biostimulants can be defined in many ways, but perhaps biostimulants should be defined by what they are not. They are not nutrients, pesticides or soil improvers.
Without going too deep into how they work, biostimulants claim to enhance crop production, improve crop quality and increase plant stress tolerance to things such as excess heat, cold events and drought. Biostimulants are usually applied to the crop foliage but can also be applied to the seed or as a soil amendment at seeding.
Biostimulants encompass a diverse group of product technologies with many different types and formulations. Most biostimulant products are based on bacteria, humic and fluvic acids and seaweed extracts. Some products are promoted as nitrogen fixers with an active ingredient derived from bacteria. Some products are a combination of active ingredients with of humic acids, seaweed extracts and other compounds.
Generally, farmers are leery about changing production practices by completely removing inputs such as inorganic fertilizer and fungicides and replacing them with biostimulants. As a result, they keep all other inputs the same and add biostimulants as a tank mix with herbicide or fungicide passes, adding a significant cost per acre.
Biostimulants can play an important role in crop production systems – if they can effectively reduce pesticide and fertilizer use while maintaining yields. This climate-smart production technology potential was recognized by Baljeet Singh, faculty researcher for the Russ Edwards School of Agriculture and Environment at Assiniboine College in Brandon, M.B. Singh’s team is currently conducting small plot field experiments with agricultural biostimulants, and they will examine the impacts of five commercially available biostimulants on growth, yield and seed quality of soybean crops. The project, funded by Manitoba Pulse & Soybean Growers, began in 2025 and will run until 2027. It has sites in Melita, M.B., Portage la Prairie, M.B., and Carberry, M.B.
There is also a need to take those small-plot results and other private company published results and verify the same product’s effectiveness for yield and economics at field-scale.
Every year since 2019, the On-Farm Network (OFN) has been evaluating biostimulant products for yield and return on investment, with treated and untreated strips or plots the width of a combine header running the length of the field. With seven years of data, the results have encompassed extreme and variable weather conditions.
Generally, OFN has tested biostimulant products applied to crop foliage after emergence. We look primarily at yield, plant stands and economic impact. To date, OFN hasn’t researched the benefits of these products for impact on soil health and benefits to a cropping system over the long-term.
From 2019 to 2024, there have been 33 soybean trials comparing an application of a biostimulant product to no use of biostimulants. In 2019 and in 2025, a total of four trials compared plant biostimulant products in peas, and one dry bean site in 2024 compared a biostimulant to untreated. (Note: Four more soybean and two more dry bean trials were harvested in fall 2025, but the data wasn’t available in time for publication.)
Totalling up all plant biostimulant on-farm trials across the three crops works out to be 38 site years. Across those 38 site years, biostimulant use has not shown a significant yield increase when compared to untreated plots. With products costing anywhere from $5 per acre to $28 per acre, the loss in profits is equal to cost of the biostimulant product, not including application cost. (Note: Applications are often tank mixed with herbicide passes, thereby reducing application costs.)
For plant biostimulants to be considered a good investment, do they need to be profitable in the application year by increased yields high enough to pay for the product and application costs? Many products claim to improve soil quality and crop production for the next cropping cycle. To know if these products will improve soil health and increase yields over time will take a longer research commitment.
Another potential savings benefit from using biostimulant inputs could be reduced fertilizer costs. Perhaps savings are made when certain biostimulant products are applied in conjunction with reduced fertilizer rates and the yields are found to be equivalent.
EcoTea, a plant biostimulant product marketed from a company headquartered in Winnipeg, M.B. promotes improved nutrient use efficiency. For example, EcoTea claims that over three years of replicated spring wheat field trials, when the applied nitrogen was reduced by 20 per cent and phosphorus by 10 per cent in combination with EcoTea, yields were within plus or minus 1.7 per cent of the grower’s full or 100 per cent fertilizer rate.
These fertilizer savings with maintained yields are significant, but does this happen at field scale? To date, OFN has only looked at whether plant biostimulants have statistically improved yields over no biostimulant use enough to be economically beneficial.
OFN generally conducts field-scale testing of a plant biostimulant treatment comparing it to untreated plots with the farmers standard practices for all treatments, but perhaps this isn’t doing a service to the product claims of maintaining yields with less fertilizer. Perhaps OFN should consider testing whether a biostimulant can maintain profits with reduced fertilizer use.
The bottom line is, these products haven’t provided a return on investment for Manitoba farmers by increasing yields to date, but that doesn’t mean OFN will stop conducting field-scale research with biostimulant products as long as farmers are interested.