Crop-specific inoculants are microbial products that enhance the growth and help of particular crops. They contain beneficial microorganisms, such as bacteria or fungi and establish a symbiotic relationship with plants. This relationship can improve nutrient availability, disease resistance, and overall plant health. Legumes, like peas, peanuts, vetch, lentil, dry beans, alfalfa and clover are all crops that could potentially benefit from the addition of Rhizobium inoculants. There are different types of inoculants based on their function and type of microorganisms they contain. Choose the inoculant that best fits the type of crop you are planting. Information for which inoculant to choose will be found on the product label or reaching out to your local extension agent.
Rhizobium inoculants tend to improve nitrogen fixation (capturing nitrogen from the atmosphere and turning it into a plant available form) and enhance plant growth. These bacteria enter the roots of the legume plants through the root hairs and in return, the plant supplies the bacteria with carbohydrates produced through photosynthesis. However, the only way this symbiosis can occur is if the roots are infected by the bacteria that was already in the soil or you applied through inoculation.
Inoculants come in different forms. There are powders, granular, and liquids. Each having their own advantage and disadvantage. Powders are prepared as a slurry and added to the seed in the planter box. The disadvantage of powder type inoculants is they contain less bacteria. Granular inoculants are dropped alongside the planted legume seed. Liquid inoculant can be applied as the seed is being planted by attaching equipment to the planter and applying the liquid beside the seed as it drops into the furrow which ensures better contact between the bacteria and the roots. Care and handling of liquid type inoculants can be a disadvantage as live bacteria are sensitive to fluctuating temperatures.
Soil type, soil moisture, temperatures and types of other microbials present in the soil will all determine how successful inoculants will be. So how do you know if it’s working? Beginning about 14 days after emergence, dig around a few plants throughout the field and check for nodules around the crown and lateral roots. Once found, you’ll want to use a sharp knife to cut the nodule in half to expose the inside. If the inside is pink to red, rest assured the bacteria is active and fixing nitrogen allowing for increased nitrogen availability to plants potentially reducing the reliance on chemical fertilizers for subsequent crops. The best way to know what is available in your soil is by having your soil tested.