Written By Lara Wadsworth

It is common knowledge these days that healthy soil is critical for healthy plants. While Mother Nature is very good at taking care of her own, yet if you have gardened or farmed for any length of time, you know that sometimes we need to intervene to nudge things in the direction we are hoping for. Soil inoculant is a great way to kickstart the natural soil microbiome to give the maximum benefits of legume covercropping to your soil in the long term. Gardeners, farmers, and anyone growing any kind of legume will find inoculants helpful. Let’s dig into the details.

What Is a Soil Inoculant?

Soil inoculant is a soil amendment made with a specific kind of beneficial bacteria called Rhizobium. This bacteria is already present in healthy soils but some plants (legumes) need a lot of it present in the soil for them to do their jobs right. Rhizobium bacteria and legume plants have a symbiotic relationship where they work together to pull nitrogen from the air and fix it into the soil in a plant-available form. The result is stronger plants, healthier roots, and improved long-term health of the soil.

Which Seeds Need Inoculant? (Peas, Beans, and More)

Inoculants are almost exclusively used for plants in the legume family. This includes but is not limited to peas, beans, clover, alfalfa, vetch, lentils, and soybeans. All of these plants need rhizobium bacteria to pull nitrogen from the air and put it into the soil for themselves and subsequent crops to use effectively. Keep in mind that not all plants need an inoculant to be applied at the time of planting. Crops such as grains, brassicas, and other non-legume plants do NOT need inoculant. However, they will benefit by being planted in the same soil in subsequent seasons to an inoculated crop. Inoculation can be used in spring or fall cover crop plantings.

Benefits of Seed Inoculants for Soil and Plants

There are numerous benefits to using inoculants with legume crops. Some of these benefits include:

• Increased nitrogen availability in the soil
• Reduced need for synthetic fertilizers
• Stronger, healther plants with more robust roots
• Better yields overall
• Long term soil improvement
• Increase presence of rhizobium in soil for improved nitrogen fixation ability

How to Inoculate Seeds Step by Step

You can find our full, in-depth guide on how to use inoculant in the back of our Cover Crop Growing Guide (page 57) with specific ratios and amounts. It is very simple and can be broken down into three main steps.

• 1. Moisten the seeds in a large bucket or mixing vat. Use a very small amount of water (a quarter tablespoon of water per pound of seeds).
• 2. Sprinkle the specified amount of inoculant powder into the container and mix well until all the seeds are evenly coated.
• 3. Plant! Once coated with inoculant, you must plant the seeds within twelve hours; otherwise, the bacteria will not be effective anymore.

Inoculant Application Video Tutorial

Want to see how easy inoculation really is? Watch this quick video where Jordan demonstrates the process step by step. You’ll be wondering why you’ve never done this before!

So remember, inoculant is made of living bacteria designed to work together with legume-family plants to put more nitrogen into the soil over the season. It benefits the current legume crop as well as subsequent crops and ultimately the soil in a long-term sense. This one simple tool can create big results for healthier plants and higher yields on your farm or garden.

Lara Wadsworth, True Leaf Market Writer

I am a native of Southwestern Michigan, where I currently reside. I love all things plants! After completing a Bachelor's Degree in Horticulture, I found a dream work-from-home job that allows me to share my passion. Now, I spend my days writing for TLM, playing with my dog, eating delicious food with my husband, and plotting my next landscape or gardening move. I believe everyone should get down and dirty in the soil now and then. Happy Gardening!