Soil Survey Manual - Chapter Two (Part 3 of 3)

Soil Systematics

Table of Contents

Page 1
Introduction
Pedon and Polypedon
Soil Series
    New Series, Variants, and Taxadjuncts
    Phases
    Miscellaneous Areas

Page 2
Map Units
    Designing Map Units
    Kinds of Map Units
    Inclusions within Map Units
    Naming Map Units

Page 3
Miscellaneous Areas
Records and Definitions of Soil Taxa
    Soil Series Definitions
    Other Taxa
Orders of Soil Surveys
    Two Orders of Soil Survey in the Same Project
Soil Maps Made by Other Methods
    Generalized Soil Maps
    Schematic Soil Maps

Miscellaneous Areas

Miscellaneous areas have essentially no soil and support little or no vegetation. This can be a result of active erosion, washing by water, unfavorable soil conditions, or man's activities. Some miscellaneous areas can be made productive but only after major reclamation efforts. Map units are designed to accommodate miscellaneous areas, and most map units named for miscellaneous areas have inclusions of soil. If the amount of soil exceeds the standards for inclusions defined in this chapter, the map unit is named as a complex or association of miscellaneous area and soil.

Following are discussions of recognized kinds of miscellaneous areas.

Badland is moderately steep to very steep barren land dissected by many intermittent drainage channels. Ordinarily, the areas are not stony. Badland is most common in semiarid and arid regions where streams cut into soft geologic material. Local relief generally ranges between 10 and 200 meters. Potential runoff is very high, and erosion is active.

Beaches are sandy, gravelly, or cobbly shores washed and rewashed by waves. The areas may be partly covered with water during high tides or storms.

Blown-out land consists of areas from which all or most of the soil material has been removed by extreme wind erosion. The areas are generally shallow depressions that have flat or irregular floors. In some places the floor is a layer of material that is more resistant to wind than the removed material or is a layer of pebbles or cobbles; or, the floor may have been formed by exposure of the water table. Areas covered by water most of the year are mapped as Water. Some areas have a few hummocks or small dunes. Few areas of blown-out land are large enough to be delineated; small areas can be shown by spot symbols.

Cinder land is composed of loose cinders and other scoriaceous magmatic ejecta. Water-holding capacity is very low, and trafficability is poor.

Cirque land consists of areas of rock and rubble in characteristically cirque shape. The shape is caused by glacial erosion.

Dumps are areas of smoothed or uneven accumulations or piles of waste rock and general refuse. Dumps, mine consist of areas of waste rock from mines, quarries, and smelters. Some dumps with closely associated pits are mapped as Dumps-Pits complex.

Dune land consists of sand in ridges and intervening troughs that shift with the wind.

Glaciers are large masses of ice formed, at least in part, on land by the compaction and recrystallization of snow. They may be moving slowly downslope or outward in all directions because of the stress of their own weight; or, they may be retreating or be stagnant. A little earthy material may be on or in the ice.

Gullied land consists of areas where erosion has cut a network of V-shaped or U-shaped channels. The areas resemble miniature badlands. Generally, gullies are so deep that extensive reshaping is necessary for most uses. Small areas can be shown by spot symbols. Phases indicating the kind of material remaining may be useful in some places.

Gypsum land consists of exposures of nearly pure soft gypsum. The surface is generally very unstable and erodes easily. Trafficability is very poor. Areas of hard gypsum are mapped as Rock outcrop.

Lava flows are areas covered with lava. In most humid regions, the flows are of Holocene age, but in arid and very cold regions they may be older. Most flows have sharp, jagged surfaces, crevices, and angular blocks characteristic of lava. Others are relatively smooth and have a ropy glazed surface. A little earthy material may be in a few rocks and sheltered pockets, but the flows are virtually devoid of plants other than lichens.¹

Oil-waste land consists of areas where liquid oily wastes, principally saltwater and oil, have accumulated. It includes slush pits and adjacent areas affected by the liquid wastes. The land is barren, although some of it can be reclaimed at high cost.

Pits are open excavations from which soil and commonly underlying material have been removed, exposing either rock or other material. Kinds include Pits, mine; Pits, gravel; and Pits, quarry. Commonly, pits are closely associated with Dumps.

Playas are barren flats in closed basins in arid regions. Many areas are subject to wind erosion and many are saline, sodic, or both. The water table may be near the surface at times.

Quarries (see Pits).

Riverwash is unstabilized sandy, silty, clayey, or gravelly sediment that is flooded, washed, and reworked frequently by rivers.

Rock outcrop consists of exposures of bare bedrock other than lava flows and rock-lined pits. If needed, map units can be named according to the kind of rock: Rock outcrop, chalk; Rock outcrop, limestone; Rock outcrop, gypsum. Many rock outcrops are too small to be delineated as areas on soil maps but can be shown by spot symbols. Some areas are large, broken by only small areas of soil. Most rock outcrops are hard rock, but some are soft.

Rubble land consists of areas of cobbles, stones, and boulders. Rubble land is commonly at the base of mountains but some areas are deposits of cobbles, stones, and boulders left on mountainsides by glaciation or by periglacial processes.

Salt flats are undrained flats that have surface deposits of crystalline salt overlying stratified very strongly saline sediment. These areas are closed basins in arid regions. The water table may be near the surface at times.

Scoria land consists of areas of slag like clinkers, burned shale, and fine-grained sandstone remaining after coal beds burn out.(Scoria land should not be confused with volcanic slag.)

Slickens are accumulations of fine-textured material, such as that separated in placer-mine and ore-mill operations. Slickens from ore mills consist largely of freshly ground rock that commonly has undergone chemical treatment during the milling process. Slickens are usually confined in specially constructed basins.

Slick spots are areas having a puddled or crusted, very smooth, nearly impervious surface. The underlying material is dense and massive. The material ranges from extremely acid to very strongly alkaline and from sand to clay.

Urban land is land mostly covered by streets, parking lots, buildings, and other structures of urban areas.

Water includes streams, lakes, ponds, and estuaries that in most years are covered with water at least during the period warm enough for plants to grow; many areas are covered throughout the year. Pits, blowouts, and playas that contain water most of the time are mapped as Water.

Records and Definitions of Soil Taxa

Keeping definitions and names of soil taxa up to date is essential for identification of map units, for correlation of soils nationwide, and for transfer of information about soils at one place to similar kinds of soil elsewhere.

Definitions and names of soil taxa can be kept by different methods. The methods used are modified from time to time. Some kind of centralized system is needed to obtain a nationwide perspective, to maintain standards for defining soil taxa, to assemble field and laboratory data, and to disseminate information to the field.

Soil Series Definitions

Soil series are used for naming most map units of soil surveys in the United States. Over time, the concepts of the series category and of individual series have changed, but more than 16,000 series are now defined and named. These definitions are the framework within which most of the detailed information about soils of the United States is identified with soils at specific places. These definitions also provide the principal medium through which detailed information about the soil and its behavior at one place is projected to similar soils at other places.

Rigorous standards for definitions of soil series ensure that names and descriptions for the same kinds of soils are consistent from survey to survey. Consistency is a major objective of the correlation process. The classes of the soil series category are not static. As new knowledge is acquired, definitions of some established series must be modified. New series are defined for newly recognized kinds of soils. Changes in criteria or limits of taxa in higher categories often require modification of definitions of member series.

Keeping records of series names and updating definitions of series is a continuing process. The changes should be accomplished in ways that detract the least from the predictive value associated with the earlier definitions and names. A centralized system for keeping records of soil series names and definitions ensures that names and definitions of soil series meet the rigorous standards needed in a national soil survey program.

Link to Official Soil Series Descriptions

Official soil series descriptions.—Each soil series must be defined as fully and accurately as existing knowledge permits. This applies to proposed soil series used in an individual survey as well as to established series. To ensure the inclusion of essential information and to permit comparison of series definitions, a standard format for recording specific kinds of information is used.

Official soil series descriptions record definitions of soil series and other relevant information about each series. The format, the kind, and the amount of detail may change from time to time, but detailed definition and a series interpretation record are essential. General, descriptive information is also needed to aid the reader in identifying the soil in the landscape and relating it to other kinds of soil.

An official soil series description should include at least the following:

1. Full taxonomic name of the family taxon for which it is a member. This indicates the classes that provide limits of properties that are diagnostic for the series at all categorical levels, except for those between series of the same family.
2. A description of a typical pedon and its horizons, describing each in as much detail as necessary to recognize its taxonomic class. Horizons that are diagnostic for the pedon must be described.
3. A statement of the ranges of properties of the series. This section also contains statements about the relationship of the series control section and diagnostic horizons to vertical subdivisions of the typical pedon.
4. A statement distinguishing the series from "competing series" with which it might be confused. Competing series are mainly those that share common limits with the series described or are members of the same family.
5. A statement that identifies at least one specific place that represents a norm for the series—a "type location." A type location should be described accurately enough so that it can be located in the field.

Descriptive parts of an official soil series description are not required to define the series, but they aid the reader. All parts are not equally important for all soils. Many descriptions include the following:

1. Landform and physiographic position of the series, including its position relative to other landscape elements with which it is associated.
2. Evolution of the landscape. Influences of the soil-forming factors on the genesis of the series should be identified.
3. Parent-material: The kind of mineral or organic material in which the soil formed, including kinds of rock from which the regolith was derived if that can be determined.
4. Drainage of the soil by drainage class or other means of description relative to soil moisture regimes. Seasonal wetness or dryness may be important.
5. Other kinds of soil with which the series is closely associated geographically.
6. Major uses of the soil and dominant kinds of vegetation that grow on it. Native plants are identified, if known.
7. Rationale for classification. Implicit assumptions related to family classification may be described when laboratory data are not available.
8. Distribution and extent: the known geographic distribution and whether the soil occupies a large, small, or intermediate aggregate area.
9. Year and the survey area where the series was proposed or established.
10. Name of the person who prepared and approved the series description and the date it was prepared or approved.
11. References to available laboratory data.
12. Interpretations for common uses of the soil.²

Other Taxa

Soil series identified in individual surveys are classified in specific taxa of higher categories. The limits of most properties of soil series are set by the limits of the higher taxa in which they are classified. Soil Taxonomy (Soil Survey Staff, 1975) is the basic reference book for identification, classification, nomenclature, and correlation of kinds of soils for categories above the series.

During a survey, the taxonomic system is tested and retested many times. The results of these tests are reported at field reviews and at the field correlation. Problems in mapping or identifying soils and inconsistencies between the system and observed properties of the soils are recorded in field review reports and correlation memoranda. After appraising these reports, supervisory soil scientists call any inadequacies to the attention of the office responsible for keeping the system up to date.

Orders of Soil Surveys

All soil surveys are made by examining, describing, and classifying soils in the field and delineating their areas on maps. Some surveys are made to serve users who need precise information about the soil resources of areas a few hectares or less in size. These surveys require refined distinctions among small, homogeneous areas of soil. Others are made for users who need a broad perspective of heterogeneous, but distinctive, areas of thousands of hectares. A soil survey made for one group of users may not serve the other group well.

The elements of a soil survey can be adjusted to provide the most useful product for the intended purposes. Different intensities of field study, different degrees of detail in mapping, different phases or levels of abstraction in defining and naming map units, and different map unit designs produce a wide range of soil surveys. Adjustments in these elements form the basis for differentiating five orders of soil surveys (table 2-1).

Recognition of these different levels of detail is helpful for communicating about soil surveys and maps, even though the levels cannot be sharply separated from each other. The orders are intended to aid in the identification of the operational procedures used to conduct a soil survey. They also indicate general levels of the quality control that is applied during the survey. These levels affect the kind and precision of subsequent interpretations and predictions. The orders differ in the following elements:³

1. The soil survey legend, including
   • the kinds of map units: consociations, complexes, associations, and undifferentiated groups, and
   • the kinds of soil taxa for identifying the map units: soil series, families, subgroups, great groups, suborders, orders, and phases of them;
2. The standard for purity of delineated soil areas, including
   • the minimum area of a limiting dissimilar soil that must be delineated separately and thus excluded from areas identified as another kind of soil, and
   • the maximum percentage of limiting dissimilar inclusions that is permissible in a map unit;
3. The field operations necessary to identify and delineate areas of the map units within prescribed standards of purity; and
4. The minimum map scale required to accommodate the map units of the legend, the standards of purity, and the map detail justified by field methods.

Table 2-1. Key for Identifying Kinds of Soil Surveys

Mapping legends are designed to provide the degree of refinement of map units required by the objectives of the survey. A map unit can be identified as a consociation (an area dominated by a soil of a single taxon such as a series or a suborder) or as a group (geographic mixture) of taxa, such as associations or complexes. A group may be more heterogeneous, and less refined, than a consociation at the same level of classification. A soil series has a much more narrowly defined set of soil properties than a suborder; and, therefore, it is a more refined distinction. Thus, phases of soil series are used as map units if users need more precise information about small areas of soils. Phases of any category in Soil Taxonomy might be used as soil map units if a very broad perspective of the soil resources of very large areas is needed.

Standards of purity are adjusted according to the precision required by the survey objectives. Probably all delineations contain some kinds of soil besides that identified in the map unit name. These inclusions reduce purity. Different kinds of inclusions, however, have different effects on the value of the map for use. The inclusions that most detract from purity are those that are distinctly more limiting for use than the named soil. These are called limiting dissimilar soils. Not only the amount of such limiting soils but also the size of their individual areas is important. Soil survey standards for both are set at levels that do not seriously detract from the validity of interpretations based on the named soil.

Standards of purity are attained by adjusting the field operations. If the standards require that areas of limiting dissimilar soils as small as 0.1 ha be delineated, for example, the area must be traversed at intervals close enough to find areas that small and the soil must be examined at enough places along each traverse to detect them.

The map scale must be large enough to allow areas of minimum size to be delineated legibly. Figure 2-4 illustrates the effect of scale on legibility of maps.

The choice of map scale also depends on the perspective of the user. Users who need precise information about small areas focus their attention on a small part of the map and on a relatively few delineations. They are not distracted by boundaries and symbols on other parts of the map. Consequently, the map scale can be the smallest that will permit legible delineation of the pertinent areas.

Map users who want a broad perspective of large areas, however, are usually concerned with comparisons among delineations of all, or a large part, of the map. Consequently, delineations on maps for such uses are generally larger and fewer in number.

Table 2-2 shows the relationships between map scales and the smallest delineations that can be made legibly at those scales. The difference between the smallest delineation that could be made and the smallest that is commonly made increases as map scale decreases.

The order of a survey is a consequence of field procedures, the minimum size of delineation, and the kinds of map units that are used. Table 2-1 is a key for identifying orders of soil surveys.

First-order surveys are made for very intensive land uses requiring very detailed information about soils, generally in small areas. The information can be used in planning for irrigation, drainage, truck crops, citrus or other specialty crops, experimental plots, individual building sites, and other uses that require a detailed and very precise knowledge of the soils and their variability.

Figure 2-4 (Click here or on picture for high resolution 234 KB image)

Copies of the same map at different scales: A, 1:21,120; B, 1:31,680; C, 1:63,360 (equivalent to 3, 2, and 1 inch equals one mile, respectively). The numbers within individual delineations are the acreages of the areas represented (1 acre equals 0.40 hectares).

Field procedures permit observation of soil boundaries throughout their length. The soils in each delineation are identified by traversing and transecting. Remotely sensed data are used as an aid in boundary delineation. Map units are mostly consociations with few complexes and are phases of soil series or are miscellaneous areas. Some map units named at a categorical level above the series may be appropriate. Delineations have a minimum size of about 1 hectare (2.5 acres) or less, depending on scale, and contain a minimum amount of contrasting inclusions within the limits permitted by the kind of map unit used. Base map scale is generally 1:15,840 or larger.

Second-order surveys are made for intensive land uses that require detailed information about soil resources for making predictions of suitability for use and of treatment needs. The information can be used in planning for general agriculture, construction, urban development, and similar uses that require precise knowledge of the soils and their variability.

Table 2-2. Guide to Map Scale and Minimum Delineation Size

Field procedures permit plotting of soil boundaries by observation and by interpretation of remotely sensed data. Boundaries are verified at closely spaced intervals, and the soils in each delineation are identified by traversing and in some map units by transecting. Map units are mostly consociations and complexes. Occasionally undifferentiated groups or associations are also used. Components of map units are phases of soil series or phases of miscellaneous areas; map units named at a categorical level above the series can be used. Delineations are variable in size with a minimum of 0.6 to 4 hectares (1.5 to 10 acres), depending on landscape complexity and survey objectives. Contrasting inclusions vary in size and amount within the limits permitted by the kind of map unit used. Base map scale is generally 1:12,000 to 1:31,680, depending on the complexity of the soil pattern within the area.

Third-order surveys are made for land uses that do not require precise knowledge of small areas or detailed soils information. Such survey areas are usually dominated by a single land use and have few subordinate uses. The information can be used in planning for range, forest, recreational areas, and in community planning.

Field procedures permit plotting of most soil boundaries by observation and interpretation of remotely sensed data. Boundaries are verified by some field observations. The soils are identified by traversing representative areas and applying the information to like areas. Some additional observations and transects are made for verification. Map units include associations, complexes, consociations, and undifferentiated groups. Components of map units are phases of soil series, taxa above the series, or they are miscellaneous areas. Delineations have a minimum size of about 1.6 to 16 hectares (4 to 40 acres), depending on the survey objectives and complexity of the landscapes. Contrasting inclusions vary in size and amount within the limits permitted by the kind of map unit used. Base map scale is generally 1:20,000 to 1:63,360, depending on the complexity of the soil pattern and intended use of the maps.

Fourth-order surveys are made for extensive land uses that need general soil information for broad statements concerning land-use potential and general land management. The information can be used in locating, comparing, and selecting suitable areas for major kinds of land use, in regional land-use planning, and in selecting areas for more intensive study and investigation.

Field procedures permit plotting of soil boundaries by interpretation of remotely sensed data. The soils are identified by traversing representative areas to determine soil patterns and composition of map units and applying the information to like areas. Transects are made in selected delineations for verification. Most map units are associations, but some consociations and undifferentiated groups may be used in some surveys. Components of map units are phases of soil series, of taxa above the series, or are miscellaneous areas. Minimum size of delineations is at least 16 to 252 hectares (40 to 640 acres). Contrasting inclusions vary in size and amount within the limits permitted by the kind of map unit used. Base map scale is generally 1:63,360 to 1:250,000.

Fifth-order surveys are made to collect soils information in very large areas at a level of detail suitable for planning regional land use and interpreting information at a high level of generalization. The primary use of this information is selection of areas for more intensive study.

Field procedures consist of mapping representative areas of 39 to 65 square kilometers (15 to 25 square miles) to determine soil patterns and composition of map units. This information is then applied to like areas by interpretation of remotely sensed data. Soils are identified by a few onsite observations or by traversing. Most map units are associations, but some consociations and undifferentiated groups may be used. Components of map units are phases of taxa at categorical levels above the series and miscellaneous areas. Minimum size of delineations is about 252 to 4,000 hectares (640 to 10,000 acres). Contrasting inclusions vary in size and amount within the limits permitted by the kind of map unit used. Base-map scale ranges from about 1:250,000 to 1:1,000,000 or smaller.

Two Orders of Soil Survey in the Same Project

Some soil survey areas have two or more separate and distinct parts that have different needs. For example, one part may be mapped to make predictions that pertain to irrigation, but the other may be mapped to make predictions that relate to range management. The irrigated part should be mapped at the intensity required for a second-order soil survey, and map units are mostly consociations of narrowly defined phases of soil series. The part used for grazing, however, can be mapped as a third-order survey and uses associations, complexes, and some consociations of more broadly defined phases of soil series or of taxa above the series. Some map units of the two parts will consist of the same kinds of soil, but great care is exercised to ensure that map units for the two different orders of soil survey maps do not have the same names or symbols.

Large, separate, and distinct areas that are within the same project but surveyed by different methods should be distinguished clearly by boundaries on the published soil map or on a small-scale inset map. Each part is identified by a note printed parallel to the line separating the areas of each survey order. The two parts have separate legends. The parts are considered as distinctly different orders of soil survey, but the results are reported in the same publication. The same or different map scales may be used for the different survey orders, depending on the intended uses.

Many 2nd-order surveys delineate some map units by methods that are less intensive, even though the areas mapped at different intensities are intermingled on the map. For example, within an otherwise detailed soil map, the delineations of very steep or very stony soils are commonly investigated at the intensity normally used in a third-order survey. This is discussed in soil survey procedures.

Still other soil surveys include areas consisting of two or more distinctive soils that could be mapped separately by detailed soil survey methods; however, the cost of making the separation cannot be justified. For example, a survey area that is mostly productive soils suitable for general farming may contain large areas of unproductive sandy soils covered with thick brush. Although the sandy areas contain contrasting kinds of soil that could be delineated separately, the cost of detailed mapping to separate the two kinds of soils may exceed the expected return. The outer boundaries of the sandy areas are plotted in as much detail and with as careful investigations as any other boundaries of the soil survey, but the sandy areas themselves are mapped by third- or fourth-order methods. Traverses are made, and the composition of the areas is defined in terms of the kinds, proportions, and patterns of the individual soils. The delineations are described in the text of the published soil survey as soil associations mapped by methods of the appropriate survey order.

Soil Maps Made by Other Methods

Although most soil maps published in the United States by the National Cooperative Soil Survey are made by field investigations, some are compiled from other sources. These kinds of soil maps are described in the following sections.

Generalized Soil Maps

Some users need soils information about areas larger than individual fields or tracts, as large as perhaps several square kilometers, but a detailed map tends to obscure the broad relationships. Generalized soil maps are made to reveal geographic relationships that cannot be seen readily on detailed maps. Most soil survey reports include a general soil map for the area. The scale of these maps depends on the intended uses.

Generalized soil maps are made by combining the delineations of existing soil survey maps to form broader map units. Scrutiny of a detailed map usually will find large areas in which a few soil series, commonly two or three, are consistently associated. A detailed map is generalized by enclosing those larger areas within which a few kinds of soil predominate in relatively consistent proportions and patterns. These larger areas are described in terms of the dominant soils. The map is interpreted to show the combined effects of the constituent soils of each map unit.

Some of the possible uses for generalized soil maps are for appraising the basic soil resources of whole counties, for assisting farm advisors in the geographic emphasis of their educational programs, and for guiding commercial interests. Increasingly, these maps are compiled for county and regional land-use planning. Other possible uses include predicting the general suitability of large areas of soils for residential, recreational, wildlife, and other nonfarm uses, as well as for agriculture. Suggesting alternative routes for roads and pipelines where the least problems with soils are expected is also a potential use. The information in generalized soil maps may be useful as one basis for zoning.

Soil maps that are already less detailed can be generalized further for purposes that require very broad perspective. For example, 4th-order soil surveys for individual counties at scales of less than 1:250,000 can be combined and generalized to provide maps of States or regions at a scale of 1:1,000,000 or smaller. Soil maps that show the soils of areas of a few square kilometers can be converted to maps having delineations of a few hundred square kilometers, or more. Areas defined as associations of soil series or their phases are combined in this process into larger areas that can be defined in terms of associations of taxa at higher categories. These broad soil associations can be divided into phases to specify ranges in physiography, soil texture, or other features if such distinctions are useful. Soil maps at such levels of abstraction are designed for very broad regional planning and other uses that focus on areas of hundreds of square kilometers.

Schematic Soil Maps

Schematic soil maps are also compiled, but they differ from generalized soil maps in being compiled from information other than pre-existing soil maps. Scale is commonly 1:1,000,000 or smaller, although useful maps are sometimes made at larger scales. Schematic soil maps are commonly made as a preliminary step to locate areas where further investigation is justified. For many areas, especially in undeveloped regions, a schematic soil map is useful in advance of an organized field survey. Some maps serve as the only source of soils information in areas where more intensive studies are not feasible.

Schematic soil maps are made by using many sources of information to predict the geographic distribution of different kinds of soil. First, all available data are assembled. Information about climate, vegetation, geology, landforms, and other factors related to soil are gathered and studied. Data obtained by remote sensing techniques, including aerial photography, may provide useful information. Any available information about the soil is used to the extent justified by its quality. Some soils information exists for most parts of the world, but in wild areas the information may be mainly notes by travelers and rough maps interpreted from aerial photographs without verification on the ground.

Schematic soil maps merge with 5th-order (exploratory) soil surveys without a sharp line of distinction.

A soil is the unique result of five interrelated factors: climate and living organisms, conditioned by relief (topography), acting on parent material for periods of time. If good geographic data about these factors are available, good soil maps can be compiled by experienced soil scientists who are familiar with the combinations of factors that produce the different kinds of soils. The amount of detail and verification by field investigation depends upon the purpose and intended use of the soil survey.

Footnotes   

1. Lava flows in very wet climates that support a nearly continuous plant cover, even though the amount of fine earth is small, are classified as soil and not as lava flows. Some soils of this kind have been in place for less than 100 years.
2. Methods and conventions for developing and displaying soils series interpretations will be described in chapter 6
3. "Delineations", "map units", "complex", "consociation", "association", "group", "similar soils", "dissimilar soils", "limiting dissimilar soils", and "inclusion" are explained in chapter 2. Soil survey legends, maps, and map scales are discussed in chapter 4. Chapter 5 explains information-recording procedures. The levels of soil classifications are explained in chapter 5 of Soil Taxonomy.

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