In many areas where crimson clover has been grown successfully for several years it is not necessary to inoculate the seed with bacterial cultures for the production of nodules. But either the seed or the soil must be inoculated if crimson clover has not been grown. If the plants are not inoculated they will develop slowly, become yellow, and die. Inoculated plants are able to obtain about two-thirds of then nitrogen from the air through then root nodules. The plants may be artificially inoculated by applying cultures of the bacteria to the seed or by scattering soil from a field where inoculated crimson clover has been grown. Two hundred to three hundred pounds per acre of such soil evenly distributed at seeding time is usually sufficient.

When crimson clover is grown for the first time an additional inoculation treatment is recommended if weather conditions are dry and hot after seeding. This supplemental inoculation consists in mixing commercial cultures with sand, soil, or cottonseed meal and broadcasting the mixture over the soil surface during cloudy, rainy weather as the young seedlings are emerging. A bushel-size culture mixed with 60 pounds of the above-mentioned material is sufficient for an acre if distributed evenly. Soil from a field where inoculated crimson clover has been grown may also be used for the supplemental treatment.