http://foragesoftexas.tamu.edu/ad/fixation.html
II. Clover Group
A. Type B Inoculant Ball, red, and white clovers
B. Type O Inoculant Arrowleaf clover
C. Type R Inoculant Berseem, crimson, and Persian clovers
D. Type WR Inoculants Rose and subterranean clovers
When purchasing inoculant be sure the legume species you want to plant is listed on the package and that the expiration date has not passed. The inoculant should be purchased when buying the legume seed several weeks in advance of the estimated planting date. This allows time for the retailer to order the seed and/or inoculant if not kept in stock. Ground peat moss is used as a carrier for the bacteria by inoculant companies. There are several brands of inoculant. The most effective ones are those which have a large number of rhizobia per gram of inoculant and contain a sticker that helps hold the inoculant to the seed such as HiStick and Pelinoc-Pelgel. Rhizobia bacteria are very susceptible to high temperatures. Be sure the inoculant is kept in a cool dry location away from direct sunlight. Most inoculant companies recommend their products be kept in a refrigerator until used except for HiStick, which can be kept at room temperature. It is desirable to drill the inoculated seed in the soil to help protect the bacteria from the sun and high temperatures.