An inoculant is spores (I believe) from a bacteria that is added to legume seeds. The bacteria lives in the legume roots in a symbiotic relationship and it is what " fixes" nitrogen for the legume plant. The term " fix" means that it take atmospheric nitrogen in the soil and transfer it to a form that can be utilize by the legume plant and other plants as well (hopefully I am remembering this correctly from some of my classes many years ago). The bacteria is naturally found in the soil, but is generally added to legume seeds for extra insurance, since the cost of it is relatively cheap compare to the cost of nitrogen if it had to be purchase in a fertilizer form. There are different strains of inoculants for different species of legumes. These generally can be purchase where legume seeds are purchased. Some of the blends of seeds (like imperial clover) for foodplots already has the inoculants added to the seed. Generally, the inoculant is added to the seed by apply a small amount of some adhesive type substance (it can be a sticky soda like a coke or even sugar water) to the seed and then mixing in the inoculant. Class is over.