Strahler Companion Ch. This chapter examines the characteristics, the processes of formation and the global pattern of distribution of soil that develops at the interface between the lithosphere, the biosphere and the atmosphere. Soil is a complex mixture of solids, liquids and gases. It contains mineral material derived from the parent material and organic matter derived from living plants and other organisms in the soil. The major soil-forming factors are parent material, climate, vegetation, and time.
Soil colloids are the smallest particles in soils.
They are important because they hold plant nutrients in the soil in the form of ions. Soil pH can range from acid to alkaline. Soil structure refers to the way in which the soil grains are bound together by colloids into peds. Chemical and organic processes in soils change primary minerals into secondary minerals such as oxides and clay minerals. The nature of the clay minerals determines a soil's base status which, in turn, affects its fertility or ability to retain nutrients.