Seed Inoculants

Match living rhizobia to the exact legume group and seed quantity.

Dense mass of inoculated plant roots

Seed Inoculants for Legumes

Seed inoculants contain live rhizobia selected for compatible legume groups. When the correct bacteria form nodules on legume roots, they can fix atmospheric nitrogen. Inoculants are crop-specific: one product is not automatically suitable for every clover, pea, bean, vetch, alfalfa, cowpea, or soybean.

Not sure which cover crop and inoculant fit your garden? Use the Cover Crop Selector for Home Gardens. It recommends an inoculant only when the selected raw legume seed needs one and calculates how many packages cover the seed amount.

Choose the Inoculant That Matches Your Seed

  • Alfalfa and clover inoculant: Use only for the alfalfa and clover groups listed on the product directions.
  • Pea, vetch, and lentil inoculant: Select the package size appropriate for the amount of compatible seed being planted.
  • Cowpea, peanut, and lespedeza inoculant: Intended for the crop group named in the product directions, which may include specific warm-season legumes.
  • Bean or soybean inoculant: Match ordinary beans and soybeans to their respective inoculant groups.
  • Garden combination inoculant: Covers several listed garden-legume groups but should still be checked against the exact seed being planted.

Check Whether Your Seed Is Already Inoculated

Raw legume seed may require inoculation. Nitrocoated seed already includes an inoculant coating and generally should not be inoculated again unless its directions say otherwise. Coating, inoculation, and certified-organic status are separate characteristics, so verify each one on the seed product page.

Application and Storage

Rhizobia are living organisms. Follow the selected product directions for crop compatibility, application rate, sticking agent or moisture instructions, storage temperature, expiration date, sunlight precautions, and the time allowed between treating seed and planting.

Plan by Seed Quantity

Choose a package that treats the amount of seed you intend to plant without greatly exceeding the stated coverage. Larger farm packages may treat hundreds or thousands of pounds, while garden packages are designed for smaller plantings.

Return to legume cover crop seed, use the Cover Crop Solution Chart, or read how rhizobia and root nodules support nitrogen fixation. For fungi applied at the root zone rather than bacteria applied to legume seed, compare mycorrhizal inoculants.

Use the Legume Inoculation Guides

Before treating raw seed, use the Legume Inoculant Compatibility Chart to identify the likely crop group, then follow Legume Inoculants: Rhizobia, Nitrogen Fixation and Application for storage, coating, planting, nodulation, and troubleshooting. The current seed description and inoculant label remain controlling.

For mycorrhizal fungi and other root-zone microbial products, use Microbial Inoculants: Types, Uses and How to Choose.