Soil inoculants for beans and corn can provide positive improvements for the health of your row crops. You can determine which corn and soybean inoculant is best suited to your needs by learning more about how they function, what benefits they provide and which management practices to use for best results.
What are inoculants for corn and soybeans?
Soil inoculants consist of a variety of helpful microorganisms that can support plant growth and improve soil nutrient availability and uptake by plants. When you use a soybean or corn inoculant, you are providing additional targeted resources that can help you optimize crop health for the next growing season.
Your crop can benefit in several ways from inoculants, including:
- Strengthened crop resilience amid environmental stressors
- Optimized yields on every acre
- Increased plant vigor
Next, we’ll look at three specific types of soil inoculants and the unique properties of each as you make your management decisions for the upcoming growing season.
Rhizobia inoculant
There are a variety of bacteria in this category, including Azorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium. Collectively, they’re simply known as Rhizobia.
Crops that Rhizobia inoculant helps
Soybeans
How and when Rhizobia inoculant is used
Although this bacteria builds up in the soil with time, it’s important to note that unlike some inoculants, Rhizobia is generally applied as a seed treatment.
Rhizobia inoculant is especially effective in fields where:
- Soybeans have never been grown
- Soybeans haven’t been planted for three to five years
- Soil pH is less than 6.0
- Soil is very sandy
- Flooding for over a week has produced anaerobic conditions, meaning existing bacteria have been starved of the oxygen they need to function1
Benefits of Rhizobia
Rhizobia applied primarily as a seed treatment or occasionally as a liquid in-furrow can have several benefits. The bacteria supports healthy nodulation of soybean roots, improves nitrogen fixation and also helps stabilize yields. The magic of Rhizobia inoculant is its ability to help soybeans fix their own nitrogen — a critical biological process that can’t happen without the symbiotic relationship between soybean roots and Rhizobia.
Mycorrhizae fungi inoculant
This Swiss army knife of a microorganism brings numerous row-crop benefits.
Crops that mycorrhizae fungi inoculant helps
Corn and soybeans
How and when mycorrhizae fungi inoculant is used
Mycorrhizae soil inoculant can be introduced in-furrow at planting and helps plants boost uptake of nutrients, including phosphorus as well as water.
Mycorrhizae inoculant is particularly helpful in fields where:
- Nutrient deficiency has occurred
- Soils dry rapidly during a drought
- Fumigation of soil has taken place
- Vast amounts of topsoil have been removed
- Trees haven’t previously been grown
- Nitrogen, phosphorus, complete fertilizers or a combination of those inputs have been applied regularly
Any of the above conditions can increase the risk of mycorrhizal deficiency. If your soil tests show adequate fertility, yet crops appear to be nutrient deficient, this might signal that a mycorrhizae fungi inoculant is needed for optimal production.
Benefits of mycorrhizae fungi inoculant
In addition to the helpful attributes outlined here, mycorrhizae fungi inoculant offers added crop protection against soil-borne disease. Mycorrhizae inoculant can also help plants persist through drought and heat. The same goes for plants grown in soils that are high in salinity, acidity or toxic elements. Note: Research supports the benefits of combining mycorrhizae fungi inoculant with Rhizobia inoculant — a practice known as co-inoculation — to boost crop growth, yield and tolerance to stress, especially in difficult production environments.
Bacillus subtilis soil inoculant
Bacillus root inoculant offers a real boost if you are searching for an optimal soil inoculant for beans.
Crops that bacillus subtilis inoculant helps
Soybeans
How and when bacillus subtilis is used
This soybean inoculant can increase root nodulation, signaling a healthy relationship between your plant roots and helpful bacteria in the soil.
Bacillus subtilis soil inoculant performs best in fields with:
- Soybean root rot diseases such as Fusarium oxysporum or F. graminearum
- Drought conditions or high salinity from 50 mM NaCl to 150 mM NaCl
- Limited availability of nitrogen, organic matter or phosphorus2
Benefits of bacillus subtilis inoculant
Several advantages of this bacteria include increased soybean plant biomass, nitrogen content and nodulation.
Vault ® NP and Vault ®IP are two examples of seed treatments available for soybeans. Vault NP is a concentrated liquid rhizobium strain used as a treater or planter box treatment, while Vault IP contains rhizobium as well as two bacillus biofungicides that aid to suppress rhizoctonia and fusarium.
Experts are available to help you make your soil inoculant decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.
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Endnotes
- Sawyer, John E., and Lori Abendroth. “Seed Inoculation.” Iowa State University Extension and Outreach: Integrated Crop Management, Iowa State University, https://crops.extension.iastate.edu/encyclopedia/seed-inoculation. Accessed 12 May 2025.
- Yuan, Haoran, et al. “Soybean Inoculation: Applying the Expanded Concept of the Host as a Niche for Rhizobial Species Selection.” Frontiers in Microbiology, vol. 13, 2022, p. 9598349, https://pmc.ncbi.nlm.nih.gov/articles/PMC9598349/. Accessed 12 May 2025.
