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I 1 1 How Soil Surveys Are Made 1 ......-----... Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area.They include a description of the soils and miscellaneous areas and I their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes;the general pattern of drainage;the kinds of crops and native plants; and I the kinds of bedrock.They observed and described many soil profiles.A soil profile is the sequence of natural layers, or horizons, in a soil.The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock.The unconsolidated material is devoid of roots and other Iliving organisms and has not been changed by other biological activity. Currently,soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate,water resources, soils, biological resources, and land uses(USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. I The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of I landform or with a segment of the landform. 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 were formed.Thus, during mapping, this model enables the soil scientist to predict with a considerable I degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their I characteristics gradually change.To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless,these observations, supplemented by an understanding of the soil-vegetation-landscape relationship,are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied.They I noted soil 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 identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes(units). I Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic I classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile.After the soil scientists classified and named the soils in the survey area, they compared the I