After the soil scientists identify and describe the properties of landscape components, or natural bodies of soils, the components are correlated to an appropriate taxonomic class, which is used for naming map units. They describe plant species present (their combinations, productivity, and condition) to classify plant communities, correlate them to the soils with which they are typically associated, and predict their response to management and change. They describe the kind and arrangement of soil horizons and their color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to classify and identify soils (see chapters 2 and 3 for details). Soil scientists record the characteristics of the pedons, associated plant communities, geology, landforms, and other features that they study. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil and to determine their boundaries.

Soil scientists can observe only a limited number of pedons. Some boundaries are sharp, where soils change over a few meters, while others are more gradual. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. Hierarchical systems of classes and subclasses are established to produce groupings at the different scales.Д¬ommonly, individual soils on the landscape merge into one another as their characteristics gradually change. A system of terminology, definitions, and operations can be ascribed to the various scales. These patterns are the basis for soil identification and mapping at different scales. The repetitive patterns imprinted in soils by the soil-forming factors can be observed at scales ranging from continental to microscopic. Thus, during mapping, these models enable the soil scientist to predict with considerable accuracy the kind of soil or miscellaneous area on the landscape (Hudson, 1992). By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they formed.

Soil scientists delineate these repeating patterns of landform segments, or natural bodies, on a map. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform.

The soils and miscellaneous areas (e.g., Rock outcrop) in a survey area are in an orderly pattern that is related to the geology, landforms, topography, climate, and natural vegetation. Soil mapping is the process of delineating natural bodies of soils, classifying and grouping the delineated soils into map units, and capturing soil property information for interpreting and depicting soil spatial distribution on a map. Revised by Kenneth Scheffe and Shawn McVey, USDA-NRCS.

Scientific method map