The biostimulant market has been on a steady growth curve and doesn’t seem to be slowing down anytime soon.  The global market for these products was estimated at $2.6 billion in 2019 with a projected value in 2025 at over $4 billion³.  Most likely, when you see the word “biostimulant” in the news or on the internet, you see “sustainable agriculture” in the same sentence.  This has many growers asking, what are biostimulants and how do they work?  How are they sustainable and should I be using them on my farm?

What are biostimulants and how do they work?
Biostimulants were originally defined in the United States in the 2018 Farm Bill as “a substance or microorganism that, when applied to seeds, plants, or on the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient use efficiency, tolerance to abiotic stress, or crop quality and yield¹”. This is a broad definition that encompasses several types of biostimulants. The most common of these are:

1. Humic and fulvic acids. These acids occur naturally in soils because of the breakdown of organic matter. These compounds have been shown to stimulate the soil microbiome and as a result increase root biomass and nutrient uptake^2,3.
2. Seaweed extracts. Seaweed extracts represent a large group of biostimulants that come from processing various algae species.  They contain carbohydrates, plant hormones and a complex combination of other compounds that can result in improved plant growth, tolerance to biotic and abiotic stresses, and enhanced crop quality through better nutrient uptake^2,3.  
3. Protein hydrolysates. These products are created from hydrolysis of plant or animal residue and waste. They have shown to increase nitrogen metabolism and uptake due to the regulation of enzymes involved in nitrogen assimilation.  This can translate into higher stress tolerance and crop yields^2,4.
4. Beneficial bacteria. Bacteria interact with plants and soils in many ways, depending on the type of bacteria. Some of the most common modes of action for beneficial bacterial biostimulants are nitrogen fixation, increased production of phytohormones and enhanced production of phenols, flavonoids, carotenoids and antioxidants. The benefits of these can range from increased germination and vigor, increased nutrient uptake, to increased crop yield and quality⁵. 
5. Beneficial fungi. Similar to bacteria, fungi interact with plants and soil in many ways. Fungal-based products applied to plants can promote nutrient efficiency, tolerance to stress, crop yield and product quality³.

How are biostimulants related to sustainable agriculture?
At Truterra, we believe farmers have the greatest potential to protect and restore the environment and thus define sustainability in two parts - it must be profitable for the farmer, and protect our natural resources.  With this definition in mind, biostimulants can play a role in both improving profitability and protecting the environment. As discussed above, biostimulants can:

1. Provide a yield boost, which improves land use (bu or lb/A). 
2. Improve plant tolerance to abiotic stress, benefiting the farmer by possibly saving a re-plant scenario or helping the plant recover faster from the stress and avoiding a yield loss.
3. Help with nutrient uptake, which can help a grower improve fertilizer use efficiency.
4. Improve crop quality in turn helping farmers manage their risk when delivering their commodity. Many commodities get a premium for higher quality product, or a deduction if the quality is poor.
5. Support the development of beneficial soil microorganisms which improves soil health. Healthy soil can retain water more effectively, decreases soil erosion and can improve yield⁶.

 
Should I be using biostimulants on my farm?
Biostimulants can have a positive impact on your farm.  However, responses are highly variable. They are dependent on weather, soil type, organic matter content, tillage system, and the type of crop rotation. When thinking about using a biostimulant, look at the product claims and data.  Understand the “watch outs” of the product (temperature or soil type dependent, etc.).  Start small, treat a few acres, and leave an untreated check to see if it works on your farm.  As always, to gain a local perspective on whether or not these products make a difference in your area and pay for themselves, reach out to your trusted crop advisor or local extension agent for advice.   
 

Sources

¹Biostimulants in Farm Bill | Biological Products Industry Alliance (bpia.org)
²P. du Jardin; Plant biostimulants:  Definition, concept, main categories and regulation. Scientia Horticulturae 196 (2015) 3–14
³Sible, C.N.; Seebauer, J.R.; Below, F.E. Plant Biostimulants: A Categorical Review, Their Implications for Row Crop Production, and Relation to Soil Health Indicators. Agronomy 2021, 11, 1297. https://doi.org/10.3390/ agronomy11071297
⁴https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5744479/
⁵Hamid, B.; Zaman, M.; Farooq, S.; Fatima, S.; Sayyed, R.Z.; Baba, Z.A.; Sheikh, T.A.; Reddy, M.S.; El Enshasy, H.; Gafur, A.; et al. Bacterial Plant Biostimulants: A Sustainable Way towards Improving Growth, Productivity, and Health of Crops. Sustainability 2021, 13, 2856. https://doi.org/10.3390/su130528
⁶5 Ways Biostimulants Contribute to Sustainable Agriculture - CropLife