Inoculant Preparation and Formulations for Azospirillum spp.

In general, shortly after suspensions of Azospirillum spp. are inoculated into soil, seed surface, or root surfaces without a proper carrier, the bacteria population declines rapidly. This phenomenon, combined with poor production of bacterial biomass, makes difficult to sustain activity in the rhizosphere, and the physiological state of Azospirillum spp. at application time can prevent the buildup of a sufficiently large bacterial population in the rhizosphere. Consequently, a major role of formulation of inoculants is to provide a more suitable microenvironment, combined with physical protection for a prolonged period to prevent a rapid decline of introduced Azospirillum spp. Inoculants for field use have to be designed to provide a dependable source of bacteria that survives in the soil and become available to crops, when needed. This chapter provides technical details on production of several formulations proven useful for Azospirillum spp. from propagation of the bacterium in culture medium to final formulation for the field, and the industrial considerations involved in the entire process of inoculant production. These include: media for massive propagation, techniques for useful formulation, mode of application out of the laboratory setting, and industrial consideration regarding production of commercial inoculants.