ABSTRACT
The soil environment is both highly buffered and heterogeneous in space and time. It consists of a continuum of a largely microscopic matrix of solid particles, air, and water covering virtually the entire land surface of the world. Many factors directly affect the growth, reproduction, and survival of organisms that live in the soil or simply use the soil as a refuge from the aboveground environment. This chapter deals exclusively with soil factors that affect plant pests of various types ranging from bacteria through fungi to insects and weeds. Yet, despite the biological diversity of these pests, the impact of various soil factors on each of them is remarkably similar, facilitating a synthesized, comprehensive view of the effects of the soil on pest populations. All soil-inhabiting organisms must operate within certain limits of temperature and water activity, pH, and salinity and must live in the void space between soil particles. Therefore, it is how the soil mediates variation in these factors and how the soil as a habitat differs from other terrestrial habitats that is the focus of this chapter.
