ABSTRACT
Microbial inocula, involving indigenous or nonindigenous organisms, may be added to soils or agricultural soil—plant systems for several purposes. Inasmuch as sorptive interactions between microbial cells and soil particles are likely to limit microbial movement through soil, this chapter begins with a discussion of the factors affecting such interactions. The effects of soil physical properties, such as particle size distribution and pore size distribution, on the potential pathways available for microbial movement are reviewed. When chemical gradients are imposed in vitro on a population of motile bacteria, the cells migrate to, and accumulate in, that part of the gradient that provides an optimum concentration of the chemical. Soils are characterized in terms of the contribution to total mass of particles in selected size ranges, known as the sand, silt, and clay fractions.
