Clays are used in commercial biological formulations for agricultural purposes. There are different types of clays, each of which has its own unique properties. As a class, clays have several useful properties that can be exploited. The most common formulation uses are as a diluent, carrier, moisture regulator, and absorbent. As a diluent, clay is used to modify the concentration (microbial count) of a biological formulation concentration. As a carrier, clay is used to provide the appropriate particle size for application. As a moisture regulator, clay can provide a suitable moisture environment for biological activity (or lack thereof) during storage. As an absorbent, clay can absorb material such as a fermentation broth. It can then be dried and used as is or as an ingredient in a downstream process. Commercial examples of clay use are with mychorrizae, pseudomads, Trichoderma, Rhizobium, and Penicillium.