Seed inoculation is a simple pre-planting process that involves coating seeds with beneficial microorganisms. This technique introduces helpful bacteria directly to the seed before planting. For clover, inoculation ensures the presence of specific microbes necessary for the plant’s unique nutritional needs and maximizes its ability to capture atmospheric nitrogen.
Understanding the Biological Necessity
Clover, a legume, cannot independently use atmospheric nitrogen gas. It relies on a partnership with specialized soil bacteria known as Rhizobium to thrive. Inoculation introduces these specific bacteria to the seed surface, ensuring they are immediately available upon germination.
Once the seed sprouts, Rhizobium bacteria invade the root hairs and stimulate the formation of root nodules. Inside these nodules, the bacteria perform biological nitrogen fixation, converting atmospheric nitrogen (N2) into ammonia (NH3), a form the clover can readily absorb. This naturally supplied nitrogen supports the clover’s growth and enhances soil fertility. The strain required for true clovers, such as red and white clover, is Rhizobium leguminosarum biovar trifolii.
Sourcing the Specific Materials
Successful inoculation requires securing the correct, fresh materials. The most important component is the inoculant itself, which must be strain-specific for clover (Group A or Group B). These inoculants are typically sold as a finely ground peat moss powder that carries the living Rhizobium bacteria. Always check the expiration date, as the bacterial population declines rapidly afterward, reducing effectiveness.
A sticking agent is necessary to adhere the powdered inoculant to the clover seed coat. Commercial sticking agents containing gum arabic are ideal for maximum bacterial survival, but simple household alternatives work well. A solution of one part corn syrup or molasses mixed with nine parts non-chlorinated water makes an effective substitute. You will also need a clean, smooth container (such as a plastic bucket or tub) for mixing, along with a measuring cup and a wooden paddle for gentle agitation.
Step-by-Step Application of the Inoculant
The application process requires careful attention to ensure the survival of the living bacteria. Begin by placing the clover seed in the clean mixing container. Prepare the sticking agent solution using only non-chlorinated water, as chlorine can be lethal to the Rhizobium bacteria. Add just enough sticking agent to slightly moisten the seeds, ensuring every seed has a thin, tacky coating without becoming excessively wet or clumping together.
Once the seeds are uniformly moist, sprinkle the correct amount of powdered inoculant over them, following the rate specified on the package. Gently mix the seeds until every seed is completely coated with the dark powder. The goal is a uniform coating that allows the seeds to flow freely, preventing clogs in planting equipment. Immediately after coating, spread the inoculated seeds thinly on a tarp or sheet in a cool, shaded area to dry for about an hour. Direct sunlight and heat must be avoided, as UV light rapidly kills the exposed bacteria, destroying the inoculation.
Post-Inoculation Handling and Sowing
The time between inoculation and planting is critical, and handling must prioritize bacterial survival. Inoculated seed has a limited shelf life and should be planted as quickly as possible, ideally within 24 hours of coating. Seed not used immediately must be stored in a cool, dark location to maintain the viability of the microbial coating. If planting is delayed beyond a day or two, or if the seed was subjected to warm conditions, re-inoculate the batch before planting.
When sowing, place the inoculated seed into moist soil to provide a favorable environment for the bacteria. Avoid planting too deeply; clover seed should be pressed into the soil surface or lightly covered, typically no more than a quarter-inch deep. Sowing should be done on a cloudy day or late in the afternoon to minimize exposure to direct sunlight before the seed is covered. Ensuring the seeds are placed in a cool, moist seedbed gives the Rhizobium the best chance to begin nitrogen fixation.