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Depending on the context of your cover crop mix and the health of your soil, you may want to consider applying inoculants to the seed or soil. Healthy soils have an abundance of biology working to move water and nutrients to the plants—the biology and plants work together to help each other out. Plants bring in carbon from the sun in the process of photosynthesis and feed the biology which in turn supplies the plants with water and nutrients. If your soil is extraordinarily healthy, adding inoculants may not give you the same bump in yield or growth as it would for a soil that is less healthy. As always, context is key—different situations will call for different types of inoculants.


When planting legumes as either a monoculture or polyculture mix it is important to inoculate these species with the appropriate bacteria to help them nodulate properly. These nodules are where the legumes store the nitrogen that they capture from the atmospheric nitrogen above. Most soils lack the proper bacteria for specific legumes. Different legumes require different bacteria to nodulate so it is important to know which strain of bacteria you need. Some inoculants that contain only a specific strain of bacteria for a particular legume. Other products contain multiple strains of bacteria which is key for inoculating a diverse mix. Our Rhizo-fixer inoculant by Terramax has several strains of bacteria, making it useful for inoculating several species of legumes. Along with that, it contains Azotobacter which is a free living nitrogen bacteria that helps non-legume species fixate nitrogen. It also contains bacteria strains that help solubilize phosphorus, which is generally tied up in the soil. Now, what about other types of inoculants?

Seed Inoculants

When a seed is planted or a seedling is beginning to emerge this is some of the most vulnerable times of a young plant’s life. If you lack the biology in the soil this can make the plant susceptible to disease and insect pressure. To help with seed germination and early root development, we look to the Hyprgerm product made by our partner Elevate Ag. Hyprgerm contains several ingredients to help the plant out when it is most vulnerable at early life stages. Chitosan triggers an immune response in plants that helps to fight off disease and insect pressure. Hyprgerm provides a home for microbes with the humates and humic acid it contains. To put it simply, this product attracts the microbes in the soil to the seed in order to create an environment for these microbes to feed the plant. To increase minerals and nutrients, Hyprgerm contains a soluble seaweed solution full of 70 trace minerals that increase root growth and plant vigor. The final ingredient is yucca, which is a microbial stimulant and natural surfactant for increasing water infiltration and nutrients to the root zone. Yucca can also offer protection against seed pathogens. 

Biological Soil Amendments

Seed is not the only place to increase biology. Biological soil amendments can offer a great increase in biodiversity and health to the soil and plants.One of the best ways to accomplish this is by adding mycorrhizal fungi spores to allow plants to colonize as they grow. When there are no growing plants or mycorrhizal fungi friendly plants these biologic species stay dormant in spore until conditions are right for them to colonize. As plants grow these mycorrhizal fungi spores colonize and become an extension of the root hairs. This gives the plant the ability to find water and nutrients that otherwise would not be available to the plant. Mycorrhizal fungi is able to penetrate solid rock that root hairs can’t access minerals and nutrients. Mycogreen NPK is a soil amendment that has 10 species of mycorrhizal fungi. Mycorrhizal fungi are tiny strands that are extensions of the root hairs on plants. Some plants are naturally mycorrhizal-friendly, such as oats and peas. For those plants that are not, this product is a great addition to introduce those mycorrhizal networks. Mycorrhizal fungi will help reach water and nutrients that the plant’s roots can not normally access. This fungi can bore through rock to retrieve tied up nutrients that are otherwise inaccessible. Including MycoGreen NPK in a cover crop mix is a great way to keep the mycorrhizal fungi alive and thriving, especially  if your context allows you to plant green. The good news if you aren’t able to plant green is that most fungi without a living root will go dormant into a spore and “wake up” again once a living root is present. It may be a slower process when there is this gap, but the colonies are there. This product also contains free living nitrogen bacteria, phosphorus and potassium solubilizing bacteria, and bacteria to help with root disease suppression. 

Soil Tests

Other things to consider when thinking about biological products are soil tests that test for biology in the soil. We recommend a Haney test, PLFA, and a TND test to show how biologically active your soil is and how much of each nutrient you have. Utilize these soil tests along with other educational resources in order to make the appropriate decision about which biologicals and inoculants are right for your context. 

There are many biologicals and inoculants on the market today, so be sure that you are sourcing a quality biological product. When using these products be sure to follow the principles of soil health. This will help build upon what you are adding to the seed and soil. The right biological products can increase the speed of soil health improvement by encouraging the processes that naturally occur in the soil.

This article first appeared in our “Keepin’ You Covered” email newsletter where we share 1 soil health topic, 2 success stories and 3 learning opportunities.

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