The kind of soil found at any point on the landscape depends on the forces exerted by the five soil-forming factors — climate, parent materials, topography, living organisms, and time. Any one of these factors may have a predominating effect on the kind of soil eventually formed. Any change in one or more factors is reflected by changes in the soil’s horizons and associated properties and in the soil series.
The weathering of soil is modified by the soil-forming factors. Therefore, soils adjacent to one another may vary greatly in horizon differentiation; whereas, soils many miles apart may be quite similar. Soil classification is based on the differences found in the soil profile.
Soils are dynamic, not static. They are constantly being weathered, though very slowly. The most fertile soils are generally those which are younger, have endured less weathering, and are still weathering rapidly enough to release an abundance of nutrients each year for plant use. Whether soils are young or old, productive or unproductive, they can usually be made more useful by applying what has been learned about soil and plant relationships.