The four essential processes of soil: additions, losses, translocations, and transformations.

That same handful of soil is dynamic and responds to its environment. A great number of processes take place in the soil, but they can be grouped together under four major categories: additions, losses, transformations, and translocations. Each of these is briefly defined in the following paragraphs.
Additions are easy to understand. They consist of materials deposited on the soil from above, as well as materials moved in with groundwater, such as salts. Obvious examples are additions of leaf litter as trees shed their leaves, or additions of organic material as plants and plant roots die. Also obvious are additions of mineral material from flooding, landslides, and other geologic events. Perhaps not so obvious is the nearly constant addition of atmospheric dust to the soil surface. Some of this dust can travel long distances and is important to the overall fertility of a region. Rainfall is also an addition.
Losses are also rather obvious. Erosion is a major form of soil loss. Loss can also occur as nutrients are taken up by plants, and plants are harvested and removed. As minerals and nutrients move through soil into groundwater or out of the plants’ rooting zone, this too is considered a loss.
Translocations are similar to losses in that they involve movement of materials. Translocation differs in that the material is not removed from the soil; instead, it moves from one location to another. This internal movement is referred to as illuviation and eluviation. Eluviation removes material from a zone. Illuviation moves material into a zone. In other words, eluviation is material exiting, while illuviation is material entering.
Understanding transformations takes a little more thought. Soils are dynamic—that means they are constantly changing, and biological, chemical, and physical transformations are part of this. For example, leaf litter falling on soil eventually decomposes. This decomposition is a transformation process. Likewise as rocks weather to soil, this too is a transformation process. The initial minerals in the rock are transformed to clays in the soils over time. One mineral can be transformed to another without additions of materials.
The cumulative processes that act on a soil depend on a range of environmental factors, which in turn shape the world’s different biomes.