NSSH Part 627

Legend Development and Data Collection

627.00  Definition and Purpose

Soil survey legend development and documentation are those activities conducted in the field that organize, gather, describe, and delineate data needed to provide current and accurate soil maps and interpretations.

The purpose of soil survey legend and documentation procedures is to ensure the collection of meaningful and essential field data in the course of field activities. These data ensure that the objectives of the soil survey are met.

627.01  Policy and Responsibilities

The soil survey office (SSO) is responsible for legend development and field data collection. The SSO also initiates studies for soil performance data collection.

627.02  Field Studies for Legend Development

Field studies include:

  • Studying the survey area in detail especially in relation to other survey areas within the same major land resource area;
  • Delineating major landforms, climatic zones, vegetation, and lithology within the major land resource area and the survey area;
  • Identifying and studying the components within the major land resource area;
  • Test mapping; and
  • Developing a descriptive legend.

  1. Studying the Survey Area

    Soil survey field studies begin with study of the survey area and adjoining survey areas. Field studies follow the collection and review of available reference material. Visit survey areas in the same major land resource area as short reconnaissance trips. These trips assure an adequate understanding of the relationship between the survey being designed and those already completed and maintained. Join map units from adjacent soil surveys with the new survey.
  2. Identifying and Delineating Major Landform Units

    1. The SSO staff observes and delineates climatic zones, areas of contrasting vegetation patterns, unique landforms, such as a till plain, a terrace, a lake plain, a flood plain, or fan, and other broad ecological areas. The scientists record the delineations on a small-scale map, such as a county road map, a topographic map, or a photo index map.
    2. Next, identify the components of the broad ecological areas, such as the side slope, toe slope, and foot slope components of hills, aspect differences, areas of runoff and run on, and other subdivisions of broad ecological zones. Include current and historical land use. The specifications for map unit size detailed in the memorandum of understanding dictate if these components can be delineated. Identify, describe, and classify the kinds of soils that are associated with the components. Using multiple observations, identify a preliminary range in characteristics for all the identified components in the delineated areas. Soil patterns commonly coincide with broad ecological areas and individual soils correspond with individual ecological components.

      The objective of identifying and understanding the relationship between broad ecological areas and soils is to enable a soil scientist to predict the kind of soil before examining the soil profile. Expose sufficient soil profiles to ensure that the pattern is consistent. When an exposed soil profile is not what is expected, undertake additional study to understand the anomaly and variability. Further clarify the soil pattern and the relationship to ecological components. Prepare diagrams to illustrate the models.

  3. Test Mapping Sample Areas

    1. Design map units that represent sets of soil properties repeated on characteristic components. Map units must represent areas that can be delineated on maps and they must satisfy the objectives of the survey as detailed in the memorandum of understanding. Select sample areas that are representative of repeating patterns. Studying these sample areas in detail helps to determine the nature of the soil map unit components, their pattern of occurrence, and their size and shape. Outlining and evaluating combinations of soil characteristics create an understanding of their effect on soil behavior.

      Mapping sample areas helps to test the design of the map units and to develop the descriptive legend. This process begins in the preliminary stages of the survey and continues throughout the progressive survey. Check the following:
      • The predictive value of soil-ecological area features;
      • The properties of the soil on either side of natural boundaries to determine if they differ significantly;
      • The slope gradient and shape, vegetation, and position on the landform relative to surrounding soils to determine if they help predict the kind of soil;
      • The complexity of the soil pattern;
      • The composition of mappable delineations of map units;
      • The degree that concepts of map units furnish soil data required for soil interpretations; and
      • Other visual features, such as vegetation patterns, areas of rock, and photograph signature.

      Describe the map units that meet these tests. These map units in conjunction with the map units of joined surveys form the first draft of the descriptive legend.

    2. Information and data collected from farmers, planners, agronomists, sanitarians, engineers, foresters, range conservationists, soil consultants, environmental scientists, and others guide the development and separation of map units. However it is important for the map units to join the adjacent soil survey areas (refer to Part 609 of this handbook). Compromise is sometimes necessary to ensure that surveys join. An engineer assists the soil scientists to determine the interpretations for soils as a construction material, a foundation for a structure, or other engineering use. A range scientist, forester, or other discipline specialist studies the relationship among landform, soil, and vegetation with the soil scientists when rangeland or forestland areas are important. The various disciplines work as a team in data collection and documentation.
  4. Developing Provisional Soil Survey Map Units

    The soil survey regional office (SSRO) or appropriate lead agency reviews and approves the first draft of the descriptive legend during the initial field review. Any soil survey project member may propose provisional map units during the course of the survey. Describe and test the provisional map units to determine if there is justification and need for the unit in the legend. When the SSO staff is satisfied that the unit is needed, they request the SSRO or appropriate lead to tentatively approve the unit. The approving office adds the provisional map unit to the legend object in the National Soil Survey Information System (NASIS). This office also assures that the map unit description and information that justifies the map unit's addition to the legend is documented in the data mapunit object in NASIS. The SSO keeps a complete record on all provisional map units. They record the acres mapped, the exact locations where the units were mapped, results of field studies, results of testing, and records of soil behavior and interpretive data. The signature on the field review report and identification legend officially approves the change of the provisional map units to approved map units.
  5. Developing a Provisional General Soil Map

    1. Generally the Digital General Soil Map of the U.S. (formerly called STATSGO) map is the provisional general soil map. This general soil map serves as a guide for the soil scientists during all stages of the survey. It assists in the joining of surveys within MLRAs. The Digital General Soil Map of the U.S. serves as the final general soil map.
    2. Soil scientists refine the Digital General Soil Map of the U.S. as map unit concepts become clear and boundaries stabilize each year. States request a base map for each survey area from the National Geospatial Center of Excellence, at a scale of 1:250,000, to use in refining their general soil map. Topographic quadrangle sheets that were photographically reduced to a workable scale and joined provide contour information. Satellite imagery is also helpful. Sometimes the copy of the index map of the soil survey field sheets at the publication scale helps the refinement process. The SSO staff updates the general soil map each year to correspond with completed soil survey field sheets. By the end of the survey, the general soil map becomes final.

627.03  Map Units of Soil Surveys

  1. Definition

    A map unit is a collection of areas defined and named the same in terms of their soil components or miscellaneous areas or both. Each map unit differs in some respect from all others in a survey area and each map unit has a symbol that uniquely identifies the map unit on a soil map. Each individual area, point, or line so identified on the map is a delineation. The SSO staff specially designs map units to meet the needs of the major users in each major land resource area. Map units in adjoining survey areas are comparable especially within the same major land resource area.

    Use any category of soil taxonomy, miscellaneous areas, and accompanying terms to name map units. A map unit has specified kinds of soil or miscellaneous areas (map unit components), each with a designated range in proportionate extent. Map units include one or more kinds of soil or miscellaneous area. See Section 627.04 for more information on miscellaneous areas.
  2. Design of Map Units

    1. Design map units to meet the objectives of the soil survey as stated in the memorandum of understanding. Consider the following items in designing a map unit:
      • Kinds of map units;
      • Phase criteria used to identify map units;
      • Kind and intensity of field investigation and documentation;
      • Soil properties for which data are required;
      • Minimum size management unit relevant to the various uses; and
      • Characteristic signature in the landscape that can be recognized from aerial photography, topographic maps, or field observation.
    2. When map units consistently associate with landforms, landform segments, vegetation, slope gradient, slope aspect, geomorphic position, or other surface observable feature, the consistency of delineations improves. The correlation of map units with these surface features reduces the number of observations and samples needed to obtain a stated degree of confidence.
    3. The design of map units is flexible but should correspond to the other surveys within the MLRA. A map unit is defined by the important different kinds of soil and miscellaneous areas (components) and their proportionate extent within delineations of the map unit. Map units can have a single component or they can have many components. Chapter 2 of the Soil Survey Manual further discusses the design of map units.
    4. The components of a map unit are soils or miscellaneous areas. For naming map units the components are often grouped. The following groups of components can be helpful in describing and naming map units.
      • The named soils or miscellaneous areas that are dominant and co-dominant in extent;
      • Similar soils or miscellaneous areas that may be extensive but not as extensive as the named components; and
      • Dissimilar soils or miscellaneous areas that are minor in extent.
      Similar soil or miscellaneous area components are those that differ so little from the named components that their soil interpretations for most uses are very similar. The differences for management are small.

      Dissimilar soil or miscellaneous area components are those that differ enough from the named components to affect major interpretations. The differences for management are large.

      Soil components are minor in extent when they occupy a small percentage of the map unit. The percentage varies depending on how they effect the use and management of the map unit.

      Generally, dissimilar components are considered minor if they are less than 15 percent and limiting to management of the map unit. If they are not limiting to the management, they can occupy up to 25 percent of the map unit and still considered minor in extent. A single component that is dissimilar and limiting should not exceed 10 percent and remain as minor extent. Also, see Chapter 2 of the Soil Survey Manual.

      Components, whether major or minor, meet the following criteria:
      • Exist in most delineations;
      • Add to the understanding of the map unit;
      • Are contrasting to all other components in the map unit (do not list similar soils as separate components unless it helps in understanding the map unit); and
      • Allow for useful and significant soil data and interpretations to the users.
      Documented components that do not meet the above criteria are similar or nonrecurring or isolated features of the map unit. If appropriate, recognize nonrecurring, contrasting components with special or ad hoc features, or point or linear map unit delineations.
    5. The composition and purity of map units are important in the interpretation of soil maps. Most delineations of a map unit include dissimilar soils or miscellaneous areas of minor extent that are not identified in the map unit name but may be included in the database for the unit. Practical field mapping methods cannot delineate these components at the selected scale of mapping. But they may be associated with a specific landform segment different from that of the named components of the map unit. Some of these components could be delineated if smaller management units were needed.
    6. Incorporate soils that have properties similar to the named components (similar soils) with the named soils. Likewise, minor components that are contrasting with the named major components, but that are similar to one another, should be correlated to one minor soil component. By doing so, the number of components listed for any map unit is kept to a minimum.
    7. Attain a defined standard or level of confidence in the interpretative purity of map unit delineations by adjusting the kind and intensity of field investigations. If the objective of the survey requires delineation of areas of dissimilar soils as small as 2 acres in size, the soil scientist must carry out the field investigations in sufficient detail to identify accurately and consistently map 2-acre areas. Investigations that observe map unit boundaries directly and thoroughly provide greater control than those that observe map unit boundaries at moderately spaced intervals.
  3. Minimum Size Delineation

    The memorandum of understanding for the survey area states the minimum size map unit delineation. It represents the size of an area most users would agree is the smallest area that is managed for an intended land use. The memorandum of understanding also states the map scale. The scale must accommodate legible delineations of the smallest size map unit. A legible delineation is the smallest area on the map that reasonably accommodates a map unit symbol (about 1/2 cm square).
  4. Kinds of Map Units

    Soils differ in the size and shape of their areas, in their degree of contrast with adjacent soils, and in their geographic relationships due to soil formation or land use. Soil surveys use four kinds of map units to distinguish the different relationships: consociations, complexes, associations, and undifferentiated groups. Table 1 describes and compares these relationships.

    1. Consociations

      In a consociation, delineated areas use a single name from the dominant component in the map unit. Dissimilar components are minor in extent. The soil component in a consociation may be identified at any taxonomic level. Soil series is the lowest taxonomic level (category). A consociation map unit that is named for a miscellaneous area is dominantly that kind of area and any minor components present do not significantly affect the use of the map unit.

    2. Complexes and Associations

      Complexes and associations consist of two or more dissimilar components that occur in a regularly repeating pattern. The total amount of other dissimilar components is minor in extent. The following arbitrary rule determines whether “complex” or “association” is used in the name. The major components of a complex cannot be delineated separately at the scale of mapping. The major components of an association can be delineated separately at the scale of mapping. In either case, because the major components are sufficiently different in morphology or behavior, the map unit cannot be called a consociation. In each delineation of a complex or an association, each major component is normally present though their proportions may vary appreciably from one delineation to another.

    3. Undifferentiated Groups

      Undifferentiated groups consist of two or more components that are not consistently associated geographically and, therefore, do not always occur together in the same map delineation. These components are included in the same named map unit because their use and management are the same or very similar for common uses. Generally, they are grouped together because some common feature, such as steepness, stoniness, or flooding, determines their use and management. If two or more very steep soils that are geographically separated are so similar in their potentials for use and management that defining two or more additional map units would serve no useful purpose, they may be included in the same unit. Each delineation has at least one of the major components, and some may have all of them. The same principles regarding the proportion of minor components that apply to consociations also apply to undifferentiated groups.


    Table 1. Description of Kind of Map Unit

    Kind of map unit Number of major components in the map unit name Percentage of dissimilar components not included in the map unit name Other criteria
    Consociation One soil or misc. area (similar soils or similar misc. areas included with the percentage of the named component) 15% limiting,
    25% nonlimiting,
    <10% of any one, limiting, very contrasting component
    Complex Two or more soils or misc. areas (similar soils or similar misc. areas included with the percentage of the named components) 15% limiting,
    25% nonlimiting,
    <10% of any one, limiting, very contrasting component
    Cannot separately delineate the named soils or misc. area components on the map at the scale used
    Association Two or more soils or misc. areas (similar soils or similar misc. areas included with the percentage of the named components) 15% limiting,
    25% nonlimiting,
    <10% of any one, limiting, very contrasting component
    Can separately delineate the named soils or misc. area components on the map at the scale used
    Undifferentiated group Two or more soils or misc. areas (similar soils or similar misc. areas included with the percentage of the named components) 15% limiting,
    25% nonlimiting,
    <10% of any one, limiting, very contrasting component
    A limitation (e.g., slope or salinity) overrides the primary uses to such an extent that a separate map unit is not used for each component

627.04  Map Unit Components

Map unit components of soil survey consist of soils or miscellaneous areas. Components may be major components or minor in extent as previously defined in Section 627.03. Major components are typically used in the map unit name. Minor components are not typically used in the map unit name but, if contrasting to the named soils, are named and populated in the database. All map unit components recorded in NASIS are fully populated with data (see Part 617 of this handbook). Classify all soil components at the appropriate level of soil taxonomy. For soil components of minor extent that do not fit into or are not similar to an existing soil series, a new series may be established or a higher level of soil taxonomy may be used to name the soil component.

Soil components of minor extent do not need to have a typical pedon. They may be listed in the classification table in the correlation document.

The use of the series or higher level of soil taxonomy in the name does not imply that the component includes the full range of the taxonomic category. The range of characteristics of each soil component is separately determined and recorded for each specific map unit. For minor soils, the range will likely be based on limited observations and will need to include inferences from other similar soils nearby.

  1. Soil Series

    The soil series is the lowest categorical level of soil taxonomy. The most commonly used name for soil map unit components is the soil series name.
  2. Families

    The family is the categorical level immediately above the soil series. It is intended to group soils within a subgroup that have similar physical and chemical properties that affect their response to management. Designate the map unit component as a family in the Component Kind data element in the NASIS Component table. Family level components are named as follows:
    • Name the component for a soil series (if one exists) that represents the needed family. An example component name is “Jocity family”, for soils that classify in the family of fine-loamy, mixed, superactive, calcareous, mesic Typic Torrifluvents.
    • Use the polynomial spelling as given in Soil Taxonomy combining the subgroup name with the appropriate family class differentiae. An example is “Loamy-skeletal, mixed, superactive Vitrandic Argicryolls.”
  3. Taxonomic Categories Above the Family

    Soil components classified in taxonomic categories above the family level use the classification as a soil reference term with the following conditions:
    • Designate the map unit component as a taxon above family in the Component Kind data element in the NASIS Component table.
    • Use the proper spelling given in Soil Taxonomy for the names of components, if used as reference terms (e.g., Ustic Torriorthents).
    • A taxonomic name used as a reference term for a map unit component implies no specific range of properties beyond that which is represented in the map unit description and database.
    • • Use local phases, such as “Ustic Torriorthents, shallow”, as reference terms if needed.
  4. Taxadjuncts

    A taxadjunct is a soil (map unit component) that is correlated (named) as a recognized, existing soil series for the purpose of expediency. Taxadjuncts use a soil series name as a reference name but the soils have one or more differentiating characteristics that are outside the taxonomic class limits of the family or higher category for the named soil series. These properties in the aggregate, give responses to use and management similar to those of the named soil series.

    Use taxadjuncts in lieu of establishing a soil series that would be of limited use. Part 614 of this handbook provides information on soil series.

    To use a taxadjunct to assign a name to a map unit component, designate the map unit component as a taxadjunct in the Component Kind data element in NASIS. Populate the actual taxonomic classification of the taxadjunct in the Component table. The representative soil properties entered for the taxadjunct must support this classification. Component text notes may be used to explain why a component is correlated as a taxadjunct.

    In the final correlation memorandum, include a statement to identify that one or more map unit components using the series name is a taxadjunct (Exhibit 609-1).

    In the soil survey manuscript section titled “Classification of the soils”, place an asterisk in the classification table for each map unit component that is named as a taxadjunct to direct the reader to a statement explaining the taxadjunct. Include the actual classification of the taxadjunct in the classification table. List the official series classification for those components that are not taxadjuncts. Also in the manuscript, include a statement in the range in characteristics of the taxonomic unit description identifying the map units and components that are taxadjunct to the soil series and an explanation of their properties that cause them to be outside the classification of the named series.

    If a map unit component has properties that are slightly outside the official series range but is in the same family as the official series, it is not a taxadjunct. Take one of two alternative actions:

    1. Widen the official series range to include the properties of the component as correlated, or
    2. Place a statement in the final correlation memorandum to explain how the component differs from the official series and why the official series was not revised to include the aberrant property or properties.

  5. Miscellaneous Areas

    1. Definition

      Miscellaneous areas are map unit components that have little or no identifiable soil as defined in Soil Taxonomy or are bodies of soil that are heavily contaminated by substances such as oil, radioactive elements, or heavy metals.

    2. Application

      Use the names of miscellaneous areas as reference terms for map unit components as they are given in exhibit 627-1. Use no other names unless they are approved. The soil survey regional office (SSRO) requests additions to the list of miscellaneous areas in exhibit 627-1 or requests changes in the concepts of these areas. The National Soil Survey Center is responsible for approval.

    3. Correlation

      Design and delineate map units that contain miscellaneous areas the same as other soil map units. Less documentation is generally needed for map units having only miscellaneous areas as major components.

      The distinction between soils and miscellaneous areas is not always straightforward. Urban land and water are two miscellaneous areas that present correlation issues. In many instances, areas of urban land are underlain by recognizable soils. Similarly, some areas covered by water also support rooted subaquatic vegetation and meet the definition of soil (subaqueous soils). Judgment must be used to decide whether to recognize the soil or the miscellaneous area. In the case of urban land, the miscellaneous area is typically recognized when naming the map unit because it is the predominant determining factor for land use and management considerations. In the case of subaqueous soils, because the nature of the soils may be a critical consideration in the management of the resource, the map unit component chosen for correlation is a soil. In other instances where the management of the resource is not determined by an underlying subaqueous soil or where subaqueous soils do not occur (just non-vegetated sediment), the map unit component is correlated as the miscellaneous area water. The data needs of soil survey users are always a critical factor to consider when making basic correlation decisions about soils or miscellaneous areas.

      The concepts of some miscellaneous areas has changed with time. For example, rock outcrop is currently applied to areas of bedrock that possess a significant amount of geologic cementation to the point that exposures form distinctly angular surface profiles. When cementation is less, exposures of bedrock tend to form less angular but more sloping surface profiles due to geologic erosion processes acting upon softer rock. Such softer bedrock exposures are better correlated as badland to help eliminate confusion.

    4. Phases

      Miscellaneous areas may be phased in order to provide necessary interpretive information. Some common phase terms for miscellaneous areas include, but are not limited to, those presented in the following examples:
      • Beaches, cobbly;
      • Dumps, sanitary landfill;
      • Lava flows, pahoehoe;
      • Mined land, copper;
      • Pits, quarry;
      • Playas, occasionally ponded;
      • Rock outcrop, limestone;
      • Urban land, loamy till substratum; and
      • Water, saline.

      The component name entered in the component table of the NASIS database is just the term for the miscellaneous area (“Rock outcrop,” “Playas,” “Pits,” etc.). Terms for locally defined phases are entered separately in the column for the “Local Phase” data element.

    5. Data population

      The fact that miscellaneous areas, by definition, may not be soil does not preclude the population of key properties in the NASIS database. By populating data that can be documented and/or reliably estimated, interpretations can be generated. A suggested minimum data set that is tailored to the type of miscellaneous area includes:
      • Component table: component name, local phase, taxon kind, major component flag, slope gradient, T factor, WEI, WEG, hydric condition, hydric rating, drainage class, nonirrigated LCC, frost action, initial subsidence, hydrologic group, corrosion concrete, and corrosion steel.
      • Component child tables: geomorphic feature, hydric criterion, flooding (month, frequency, duration), ponding (frequency, duration, depth), parent material group, restrictions (kind, hardness, top and bottom depths, thickness), and surface fragments.
      • Horizon table: horizon designation, top and bottom depths, Rock >10, Rock 3-10, sieves (# 4, 10, 40, & 200), total sand, sand fractions (vcos, cos, ms, fs, & vfs), total silt, total clay, OM, Db (0.1 or 0.33 & oven dry), Ksat, AWC, water content (0.1 or 0.33, 15 bar, & satiated), LEP, LL, PI, AASHTO group index, EC, and pH H2O.
      • Horizon child tables: texture group, texture class or term used in lieu of texture, and texture modifier (required); horizon fragments, AASHTO, and Unified (optional).
    6. Map unit descriptions

      Describe miscellaneous areas in the map unit description in terms of characteristics of the local area. Follow the generalized definitions given in exhibit 627-1 but do not reproduce prewritten descriptions. The descriptions of miscellaneous areas include:
      • At least a rough composition of miscellaneous area (nonsoil) and soil components, where applicable;
      • Identification of minor soil components;
      • The geomorphology (landscape, landform, etc.);
      • The kinds of bedrock lithology;
      • The nature of recent sediment; and
      • Drainage and runoff characteristics, if appropriate.

      If a survey legend includes miscellaneous areas, measure the components, tabulate their acreages, and list their names in the interpretative tables for the survey publication. If the total acreage of map units composed mainly of miscellaneous areas is so small or of so little importance that they are not retained in the legend, combine these map units with adjoining map units in the correlation document. Populate the miscellaneous areas as minor components in the data mapunit or use special symbols on the map, as appropriate.

    7. Spot symbols

      Some miscellaneous areas are too small to be delineated as polygons on soil maps. Their presence can be shown with standard or ad hoc “spot” symbols, provided they are identified consistently. Standard landform and miscellaneous surface features or ad hoc features are special map symbols that locate miscellaneous areas when these areas are less than the minimum size for a map unit. See exhibit 627-5 for the list of these features which includes their names, symbols, digital labels, and descriptions. Their primary use is for orienting and locating features on the map to those on the ground. Point or linear map units can also be used for bodies of miscellaneous areas which are cartographically too small or narrow to delineate on soil maps with a traditional, closed polygon.

  6. Phasing Components

    Occasionally it is necessary to distinguish a map unit component when multiple components of the same taxonomic or miscellaneous area occur within the same map unit. Because soil properties and interpretations are shown by component, the phase helps to distinguish the correct component. Phases can be used at a local level to help identify soil components. Do not modify the map unit component name in the database. Use the local phase descriptor to separate components with the same name. Use a single term such as “saline” or “steep” or “sandy”. It is best not to use a property, such as surface texture, that is entered elsewhere.

627.05  Terms Used in Naming Map Units

Each map unit has a name that accurately and uniquely identifies the unit within the legend used. Consistent nomenclature provides understanding to the relationships and differences among map units. Conventions for naming map units provide consistency. The SSO staff names and defines map units according to the procedures in this handbook and the descriptions in the Soil Survey Manual.

The SSRO approves map unit names and descriptions progressively with the progress of the survey and in the final correlation memorandum. The state conservationist and the soil survey regional director sign the final correlation memorandum. These signatures certify that the soil survey is complete and accurate. Exhibit 609-1, item 19, provides more information.

  1. Naming Consociations

    1. The term for the reference component or kind of miscellaneous area appears first in the map unit name. Consociations use components at all levels of soil taxonomy and kinds of miscellaneous areas as reference names.
    2. List the surface texture or any term that designates the degree of decomposition of an organic surface layer after the reference name without a comma. Examples are Alpha loam and Beta muck.
    3. If a map unit also contains a surface texture modifier, insert the appropriate term between the name of the series and the texture class or term used in lieu of texture. Examples are Alpha gravelly loam, Beta woody peat, or Gamma very parachannery ashy sandy loam.
    4. Precede all other terms with a comma. Examples are Fluvents loamy, frequently flooded; Alpha loam, 3 to 8 percent slopes, eroded; and Beta silt loam, gravelly substratum, 3 to 8 percent slopes, eroded.
    5. Separate two or more terms, other than a surface texture modifier for fragments, by commas. An example is Alpha gravelly loam, 3 to 8 percent slopes, eroded.
    6. The last term in the name is the designation for erosion, deposition, flooding, rockiness, or classes of surface stones and boulders. Examples are Alpha loam, flooded and Beta gravelly loam, 0 to 3 percent slopes, stony.
    7. A designation for slope follows all other terms except those for erosion, deposition, flooding, rockiness, or classes of surface stones or boulders. An example is Alpha loam, gravelly substratum, 3 to 8 percent slopes, eroded.
    8. With the exception of the word “slopes” and the terms for some texture groups, the nouns used in map unit names are singular. Chapter 2 of the Soil Survey Manual provides more information about consociations. Examples of appropriate names for consociations are:
      • Beta silt loam, 0 to 7 percent slopes;
      • Rock outcrop; and
      • Alpha family, 0 to 10 percent slopes.
  2. Naming Complexes

    1. The reference names of the components form the first part of the name of a complex. Complexes use components at all levels of soil taxonomy and kinds of miscellaneous areas as reference names. Chapter 2 of the Soil Survey Manual gives a discussion of complexes. Two or three names that are joined by a hyphen usually form this first part. In some cases just one reference component is named in the first part, as in map units that are named for one taxon but have contrasting phase criteria. An example is Alpha complex, 0 to 3 percent slopes.
    2. If the surface textures of the components are different, the second part of the name is the word “complex,” as in Alpha-Beta complex, 0 to 3 percent slopes. If the surface textures of the named components are the same, the second part of the name can be either “complex” or the common surface texture, as in Alpha-Beta silt loams, 0 to 3 percent slopes.
    3. A third part may be necessary for uniquely naming other map units. Examples are Alpha-Beta complex, rarely flooded; Beta-Theta loams, 10 to 20 percent slopes; and Beta-Rock outcrop complex, 20 to 40 percent slopes.
    4. An example of a complex named using the short family name is Alpha-Beta families, complex, 10 to 20 percent slopes.
  3. Naming Associations

    1. The reference names of the components form the first part of the name of an association. Associations use components at all levels of soil taxonomy and kinds of miscellaneous areas as reference names. Chapter 2 of the Soil Survey Manual gives additional information on soil associations. Two or three names that are joined by hyphen form the first part. In some cases just one reference component is named in the first part, as in a map unit consisting of one soil that has contrasting surface texture. Examples of appropriate names are Alpha-Beta association and Alpha association, 0 to 15 percent slopes.
    2. The second part of the name is the word “association.” Examples of appropriate names are Beta association; Alpha-Beta-Theta association; and Alpha-Beta families, association.
    3. A third part may be necessary for separating other phases. Examples are Beta association, 10 to 30 percent slopes; and Beta-Theta association, stony.
  4. Naming Undifferentiated Groups

    1. The first part of the name of an undifferentiated group uses the reference name of the components. Undifferentiated groups use components at all levels of soil taxonomy and kinds of miscellaneous areas as reference names. Two names separated by “and” or three names separated by a comma and “and”, respectively, form the first part. Chapter 2 of the Soil Survey Manual gives additional information on undifferentiated groups.
    2. The second part of the name generally is the word “soils.” However, the following convention is optional. If the surface texture of the components is the same, the second part of the name is the common surface texture. Examples of appropriate names are the preferred Alpha and Beta soils and the optional Alpha and Beta silt loams, 0 to 10 percent slopes.
    3. A third part may be necessary for separating other phases. An example is Alpha, Beta, and Theta soils, moderately saline, 0 to 3 percent slopes.
  5. Naming Human-Altered and Human-Transported Soils

    The soils represented by this category include a great variety of culturally disturbed earthy materials. If these materials are capable of supporting plants, the components are identified as taxa of the lowest category that provides an appropriate name. For example, a large earthen dam might be large enough to be a complex map unit that does not use a named component of Dams. The components may instead be Arents for an earthen soil component and Rubble land for a riprapped miscellaneous area of the map unit. Name map units according to the conventions used for other categories of soils. If the earthy material does not qualify as soil, it receives an appropriate name for a miscellaneous area.
  6. Naming With Miscellaneous Areas

    Use normal conventions for naming map units when these map units contain components which are miscellaneous areas. Miscellaneous areas generally are capitalized in map units, but those consisting of two words have only the first word capitalized. Examples are Gullied land and Alpha-Badland complex, 15 to 45 percent slopes.
  7. Naming Areas Not Completed and Areas of Denied Access

    Areas not yet mapped or digitized are assigned a map unit named “No digital data available” and are labeled with the National mapunit symbol “NOTCOM”, through a linkage in the NASIS Legend Mapunit table. Areas of denied access are assigned a map unit named “Area not surveyed, access denied” as described in more detail in Section 608.03 of this handbook.
  8. Ecological Units

    An ecological unit is a mapped landscape unit used for ecosystem classification and mapping.

    1. The ecological map unit uses one or more ecological types as parts of the map unit name. An ecological type has a unique combination of potential natural community, soil, geology and geomorphology, climate, and differs from other ecological types in its ability to produce vegetation and respond to management. The soil component of the ecological type must be described and correlated using the standards and guidelines described elsewhere in this handbook.
    2. The ecological map unit name consists of the names of one or more ecological types as consociations, complexes, associations, or undifferentiated map units.
    3. Name ecological types using a minimum of two-part soils and plant community name. Use classes of soil taxonomy with or without accompanying terms to name the soil portion. Incorporate geologic, geomorphic, and/or landform names, either by phases of soils, or otherwise. Use the level of soil taxonomy (series, family, or higher category) which is needed to meet the objectives of the survey. Name the plant community portion according to potential natural community.

627.06  Phases Used to Name Soil Map Units

Two or more phase terms are commonly part of most soil map unit names. A phase term conveys important connotations, such as soil properties and surface attributes, about the map unit and distinguishes it from other map units. The classes (i.e., taxa) in any category of the taxonomic system, that are used in naming map unit components, may be subdivided to make a phase distinction. Examples are Fluvents, rarely flooded; Typic Medisaprists, clayey substratum; and Gamma fine sandy loam, saline, 0 to 1 percent slopes, occasionally flooded.

Phases are not a category of the classification system, nor are they an interpretive group. Chapter 2 of the Soil Survey Manual provides a discussion of phases. The kinds of phases most commonly used in naming map units are listed below.

  1. Surface Layer Texture Phases

    1. Texture phases of mineral surface layers help to name map units. The texture phase name is consistent with the surface texture listed in the data mapunit in the National Soil Information System. The surface texture for the map unit name corresponds to the surface texture of the representative map unit component for the dominant land use of the map unit. Use the basic texture class names, such as sand, clay, and silt loam. Make fine distinctions in the sand fraction for the basic texture classes of sand, loamy sand, and sandy loam if:
      • These distinctions are reasonably easy to recognize; and
      • These distinctions serve a useful purpose.
    2. Do not use general texture groups, such as coarse textured and medium textured, to name surface texture phases. Do not use surface texture phases if map units include components named for taxonomic categories above the soil series. Chapter 3 of the Soil Survey Manual provides the texture terms used in the names of phases.
    3. Use terms in lieu of texture for organic surface phases, such as muck, peat, and mucky peat, to name surface layers of organic soils. Examples are Alpha muck, Beta peat, and Gamma mucky peat. Chapter 3 of the Soil Survey Manual describes these terms.
    4. Chapter 2 of the Soil Survey Manual gives a detailed discussion of fragment phases of map units. Part 618 of this handbook provides more information on both artifacts and fragments in the soil.
      1. Modify the surface layer texture phase with a suitable texture modifier if rock fragments exceed critical values such as Alpha gravelly loam in the case of a horizon equaling or exceeding 15 percent by volume. Texture modifiers are available to reflect various soil properties of surface horizons such as rock fragments, pararock fragments, artifacts, fine-earth composition, carbon content, fiber content, and presence of limnic materials. See Part 618 of this handbook for more detailed information on the proper use of texture modifiers in surface horizons of mineral and organic soils.
      2. Use surface phases if stones, boulders, or smaller fragments constitute more than 0.01 percent of the soil surface and they are needed to separate map units or denote important information about the map unit. Do not confuse these phases with the use of fragments as texture modifiers. For example, Alpha loam, 10 to 20 percent slopes, bouldery, is a bouldery surface phase. Part 618 of this handbook provides more information on surface fragments.
      3. Use a rockiness phase, if desired, to name map units where rock outcrops make up 10 percent or less of the surface area. An example is Alpha very gravelly loam, 10 to 25 percent slopes, rocky. If rock outcrop makes up more than 10 percent of the surface area, name the map units as soil and rock outcrop. An example is Alpha-Rock outcrop complex, 0 to 25 percent slopes. Where rockiness phases are used, both “rocky” and “very rocky” phases can be named. Commonly units with less than 2 percent rock outcrop are named “rocky” and those with 2 to 10 percent are named “very rocky.”
  2. Slope Phases

    1. Soil map units that have simple slopes commonly have the slope gradient range in percent following their name. Map units that have complex slopes are sometimes named in a similar manner. Use slope gradient in percent to name consociations, complexes, and undifferentiated soil groups if soil series provide the reference name. Examples are Alpha silt loam, 4 to 8 percent slopes, cool; Alpha-Beta complex, 8 to 15 percent slopes; and Alpha, Beta, and Gamma soils, saline, 0 to 2 percent slopes.
    2. Use adjective slope terms for designating phases of map units that have complex slopes or that are named in reference to any taxonomic category above the soil series, in associations, and in some undifferentiated soil groups. Examples are Paleudalfs, steep; Alpha-Beta association, hilly; and Alpha and Beta soils, rolling.
    3. The slope phase designation follows the name of the reference taxon and other phase terms that are based on internal soil properties and is separated from them by a comma. Use the plural “slopes” if the gradient is specified in percent but omit the term if adjective names of slope classes are used.
  3. Eroded Phases

    1. Base eroded phases of a soil on significant differences in land use suitability, conservation needs, input requirements, or yields resulting from accelerated erosion. The potential for erosion is not a criterion for phases of eroded soil. Base phases of eroded soil on a comparison between the suitability for use and management needs of the eroded soil and those of the uneroded soil. Identify the phase of the eroded soil on the basis of the properties of the soil that remains. Describe an estimate of the amount of soil lost. Classes of erosion are in Chapter 3 of the Soil Survey Manual; and Chapter 2 gives guidelines for naming eroded soils. The classes given in Chapter 3 are useful, but make phase separations on the basis of relative differences in soil properties and the use and management of the soil as a result of erosion and not on the basis of class definitions.
    2. Identify erosion even if genetic soil horizons have been removed throughout most of the area and the soil is a different series than it was before erosion occurred. If the original soil taxon is no longer identifiable except in isolated spots, change the reference taxon. The soil properties that exist after erosion determine the characteristic of the taxon. Designate the unit as a phase of eroded soil of the taxon as currently classified, or designate it as a complex of eroded and uneroded taxa. Examples are Udorthents-Alpha complex, eroded and Alpha, eroded-Beta complex.
    3. In many map units of eroded soils, the surface layer has not been uniformly eroded from the site. Instead, the texture, color, and thickness of the surface layer vary over short distances. Use the dominant texture to name the map unit. Describe the variability of the surface layer in the map unit description. The term designating the eroded soil phase is the last term in the name of the map unit. An example is Alpha loam, 8 to 15 percent slopes, moderately eroded. Chapter 2 of the Soil Survey Manual describes the terms for map units eroded by water as slightly, moderately, and severely eroded and the term gullied. The phase terms for map units eroded by wind are eroded (blown) and severely eroded (severely blown).
  4. Depositional Phases

    In some places the soil material that was removed by wind or water deposits on other soils in amounts great enough to influence the management of the soil. If the recently deposited material is thick, consider the soil as a buried soil and do not use a depositional phase term. Refer to Soil Taxonomy for the definition of a buried soil. If the deposit is thinner than those limits and has not acquired the properties characteristic of the epipedon of the covered soil, name it as a depositional phase. Depositional phases are overblown, wind hummocky, and overwash. Place terms designating depositional phases last in map unit names. Examples are Alpha sandy loam, 2 to 8 percent slopes, overwash; and Beta loam, overblown. Chapter 2 of the Soil Survey Manual provides additional information about deposits on the surface.
  5. Depth Phases

    1. Measure depth phases from the surface of the soil down. Use depth phases to subdivide map units on the basis of depth to a component feature that is significant for purposes of the survey. A depth term, such as deep or shallow, refers to depth to bedrock unless another feature is specified. Chapter 3 of the Soil Survey Manual discusses root-restricting depth.
    2. Terms for depth phases identify the depth to a variety of features. The terms and their meanings are:
      • very shallow, less than 25 cm (< 10 inches);
      • shallow, 25 cm to less than 50 cm (10 to < 20 inches);
      • moderately deep, 50 to less than 100 cm (20 to < 40 inches);
      • deep, 100 to less than 150 cm (40 to < 60 inches); and
      • very deep, 150 cm or more (> 60 inches).
    3. Examples of phases for depth to a specified bedrock or strongly contrasting material are:
      • deep over basalt;
      • moderately deep over gravel;
      • moderately deep over sand;
      • shallow over clay; and
      • shallow over schist.
    4. Only specify the kind of rock in the name if it has some special value for interpretation.
    5. “Very shallow” soils are often included in “shallow.” Do not give a depth designation to the most extensive phase.
    6. Place the depth terms after surface soil texture in the map unit name and separate from them by a comma. Depth precedes any terms for slope, erosion, deposition, or surface phases of soils that have stones or boulders. An example is Alpha silt loam, shallow, 6 to 8 percent slopes, moderately eroded.
  6. Substratum Phases

    If material in the substratum contrasts sharply with that which is normal for the taxa, identify it by specifying it in the name. The identifying terms follow the name of the taxon and surface soil texture. It precedes any terms for slope, erosion, deposition, or surface phases of soils that have stones or boulders. An example is Alpha silt loam, gravelly substratum, 6 to 20 percent slopes, eroded. Chapter 2 of the Soil Survey Manual lists common substratum names.
  7. Soil Water Phases

    Soil water terms follow terms for surface soil texture and are separated from them by a comma. They precede any terms for slope, erosion, deposition, or surface phases of soils that have stones or boulders. Soil water phases include internal water terms such as “slightly wet”, “drained”, and “ponded.” Ponding is considered a soil water phase since ponded water commonly represents the level of the water table. Examples are Alpha silt loam, high water table; Beta silt loam, ponded, 0 to 1 percent slopes; and Gamma clay loam, somewhat poorly drained, 2 to 5 percent slopes, moderately eroded. Chapter 2 of the Soil Survey Manual gives additional information and examples of soil water phases.
  8. Salinity Phases

    Salinity phases distinguish the degrees of salinity that are important for soil use or management. In some instances, observed plant growth is evidence for salinity phases. Electrical conductivity values can be used as a guide. The general salinity phase term used is “saline.” See chapter 2 of the Soil Survey Manual for detailed information on specific salinity phases. The terms for salinity phases follow any terms for surface soil texture and are separated from them by a comma. They precede any terms for slope, erosion, deposition, soil water, or surface phases of soils that have stones or boulders. An example is Alpha silt loam, saline, 1 to 3 percent slopes, very stony. Chapter 3 of the Soil Survey Manual gives additional information on salinity and electrical conductivity.
  9. Sodicity Phases

    For some soils, recognizing a sodicity phase is useful. For example, a “sodic” phase designation added to a salinity phase designation may differentiate a sodic part of a normally saline soil. Use the term “sodic” as a phase designation without terms for degrees of sodicity. The term for a sodicity phase follows surface soil texture in map unit names. Separate the terms and are separated from them with a comma. It precedes any terms for slope, erosion, deposition, or surface phases of soils that have stones or boulders. An example is Alpha silt loam, strongly saline, sodic, 0 to 3 percent slopes. Chapter 3 of the Soil Survey Manual gives additional information on sodicity and sodium adsorption ratio (SAR).
  10. Physiographic Phases

    Landform or physiographic position can distinguish map units of a single taxon. Do not name the most common physiographic phase. Chapter 2 of the Soil Survey Manual gives additional information and examples of physiographic phases and Section 629.02 of this handbook contains a glossary of recommended terms that are used to designate physiographic phases. Do not use terms not present in Section 629.02 unless they are approved by the National Soil Survey Center. The terms for physiographic phases follow surface soil texture in map unit names. Separate the terms with a comma. They precede any terms for slope, erosion, deposition, or surface phases of soils that have stones and boulders. An example is Alpha gravelly loam, rock pediment, 0 to 8 percent slopes. State physiographic areas (e.g., Des Moines Lobe) may be useful phase terms within an MLRA to distinguish otherwise identically named map units. Names of MLRAs (e.g., Central Rolling Red Plains, Eastern Part) may be useful map unit phase terms within an initial survey area, when phasing on soil properties or other factors alone does adequately separate map unit names.
  11. Climatic Phases

    Use climatic phases to distinguish air and soil temperature, potential evaporation, wind exposure, soil moisture, and precipitation. Be sure the phases are identifiable and mappable and that the differences are significant for the purposes of the survey. These are useful for differentiating map units that differ only in crop yields or ecological sites and are preferred over using crop yields or plant interpretive groups to name phases. The appropriate term is connotative only in reference to the common atmospheric climate for the reference taxon. Describe it specifically for each map unit to which it applies. Give the appropriate climatic phase term after texture. An example is Alpha silt loam, 4 to 8 percent slopes, cool. Chapter 2 of the Soil Survey Manual gives additional information and examples of climatic phases.
  12. Other Phases

    If a taxon has too wide a range in properties for the interpretations needed or if some feature outside the soil itself is significant for management, then other phases terms are needed in a map unit name. Other phase terms commonly include only part of the range of features exhibited by a taxon, but phases can be based on attributes such as flooding, frost hazard, character of the soil surface, and differences in mapunit composition. Although there is a great variety of phase distinctions available, only identify those that are useful for the purposes of the survey, can be mapped consistently, and are needed to distinguish similarly named map units. Some examples of other phase terms are “burned,” “calcareous surface,” “[taxon name] minor component,” “hydric minor component,” “occasionally flooded,” and “1 to 2 meter water depth.” A burned phase, for example, might be used to name a map unit of organic soils that have lost enough of their organic material by fire to alter their potential use or their management requirements. This kind of phase term appears last in the map unit name. An example is Gamma fine sandy loam, saline, 0 to 1 percent slopes, occasionally flooded. Chapter 2 of the Soil Survey Manual gives additional information and examples of other phases.

627.07  Soil Performance Data Collection

  1. Planning

    Soil performance data collection begins by requesting assistance of discipline specialists, such as foresters, agronomists, range conservationists, engineers, soil consultants, environmental engineers, and wildlife biologists for planning and scheduling.
  2. Field Study

    Soil survey areas that have important riparian areas, rangeland, or forestland require field study by an interdisciplinary team. The team selects and studies sites on each important landform that has typical soils producing range plants or forestland plants. The soil scientists later study the same landforms in other land uses to determine if the soils are significantly different as a result of use. These studies may result in the development of new map units to meet user needs for soil interpretations and management decisions.
  3. Requirements

    Specific requirements to adequately document rangeland, forestry, agronomy, or other soil performance are in the various discipline manuals, such as the National Forestry Manual. The actual data collection responsibilities are to be addressed in the soil survey memorandum of understanding. Section 627.09 discusses ecological site and soil correlation.
  4. Crop Yields

    1. Crop yield data from research plots and field trials are valuable in estimating yields for individual soils. Classifying and describing the soil at the plot enables the transfer of information to other sites. Always record the management practices that were used. This information goes into a data file by soil map unit component.
    2. Crop yield data that are collected from farmers' fields are a good source of data. Data entirely from one soil map unit component are especially useful.
      1. Sequential testing refers to measuring crop yields on several kinds of soil within selected farm fields. It provides valuable data because the management and weather variables are essentially held constant within a given field. Thus the effect of soil on crop yield is easier to determine.
      2. Select fields for study to improve the understanding of soil performance on key soils. For example, to study the impacts of soil erosion, choose fields with eroded and uneroded soils of the same soil series. Obtain replications and narrow variables such as slope to a minimum.
      3. Select sites carefully within each field to represent the soils intended for study. Randomization to better understand soil variability is not one of the purposes of sequential studies. The area of the site selected to represent a given soil map unit component should be sufficiently large to assure that the yield test will be entirely on that soil component.
      4. At selected sites, obtain sufficient data on soil properties to complete the NRCS-SOI-1 form. In addition, consider laboratory analysis of samples to measure organic matter content, clay content, or other important properties.
      5. At the selected sites, carefully locate the boundaries or center point to enable visitations to the sites each year. Use geographic coordinates in distance from fixed points or a global positioning system. Collect yield tests over a period of several years. Multi-year data provides a better understanding of the probabilities of given yield levels. This helps in assessing the impact of erosion on yields in various weather conditions for various crops. Multi-year data also aids the evaluation of the impact of management practices on yields in crop seasons that are wetter, dryer, or shorter than normal, and for other purposes.
    3. Establish estimated yields for benchmark soils based on thorough review of yield data from all sources. Make such estimates for defined levels of management. Assembly and analyses of crop yield data for benchmark soils is an important state and major land resource area activity for NCSS agencies. Know the management practices and systems used for all yield data included in such analyses.
      1. Obtain enough yield data to evaluate various technologies in the productivity of given soils. For example, the differences in probable corn yields for no-till versus conventional tillage or for cropping systems with continuous corn, corn-soybeans, or corn following meadow in a rotation are very important. Soil scientists help assemble the needed data.
      2. Estimate yields for crops most commonly produced on the soil. Do not give yields for crops that are not grown. The needed data are lacking for such soils. After estimating yield for benchmark soils, develop them for other soils by comparing key soil properties such as available water capacity and slope. Use multiple judgments of informed soil scientists, agronomists, and conservationists. Use caution with schemes for calculating yields.
      3. Place yield estimates in the soil databases only after review by all states in which the map unit occurs. This is to assure that the scientists consider all yield data and all experience with a soil map unit component. Yield estimates in the soil database reflect the representative values of the soil properties that are the most important for productivity. Normally, the results are estimated yields that are applicable throughout a major land resource area. Where such applicability is not achieved, the correlation of the soil map unit component may be in error or the range in climate of the resource area may be too wide.
      4. Yields in the soil database are for a high level of management. This is a level obtained by leading farmers that produce the highest economic returns per acre. It includes the best varieties; balancing plant populations and added nutrients to the potential of the soil; control of erosion, weeds, insects, and diseases; maintenance of optimum soil tilth; adequate soil drainage; and timely operations.
    4. USDA agencies developed an interagency USDA Soil-Crop Yield Database. Entering data into this nationwide database greatly extends the value of the data.
      1. Use NRCS-SOI-1 data form and instructions for entering data into the database. Exhibit 627-2 and Exhibit 627-3 provide this information. Each state has a small supply of the form. The states reproduce this form as needed. NRCS supplies copies of the form to other agencies and instructions for its use.
      2. If the needed soil, management, and weather data are supplied, the following kinds of crop yield data are eligible for the database.
        • Yield measurement from commercial farm fields.
        • Yield measurements from field trials of special treatment practices (fertilizer trials, variety trials, and conservation tillage trials).
        • Yield measurements from small research plots at experiment stations or other research institutions.
      3. Submit completed NRCS-SOI-1 forms to the National Soil Survey Center. The center arranges data entry, storage, and access.
      4. Encourage those agencies which collect and use crop yield data to complete NRCS-SOI-1 forms. These agencies include the State Land Grant University, the Cooperative Extension Service, the Agricultural Research Service, the Farm Services Agency, the Economic Research Service, and NRCS.

627.08  Documentation

  1. Definition

    Soil survey documentation is scientific data from measurements and observations of basic soil properties and qualities and of spatial arrangements, that are collected in the field or remotely sensed using standardized procedures. This data is systematically recorded. Soil survey documentation is used to verify soil-landscape models, interpretations, and projections for use. The dominant type of documentation varies by soil order (Exhibit 627-8). The percentages of delineations that use any one type of documentation vary by the size and number of delineations of a map unit in a physiographic area. The information is presented as geographical descriptions of landscapes and boundaries, soil profiles, soil layers, chemical and physical properties, or temporal condition. It has spatial, temporal, physical, and chemical aspects. Documentation assures proper soil classification, uniform and consistent mapping, and supports inferences for application of the information to similar landscapes.

    Documentation is collected over time and permanently archived. The information is cumulative. It is organized by major land resource area. Documentation progressively refines and improves soil-landscape models.

    The SSO organizes and analyzes support data and adds it to the National Soil Information System. Field notes, including soil pedon descriptions, map unit descriptions, transects, laboratory data, and notes of an interpretive nature supplement soil maps. Soil maps and this descriptive information in the database become the primary records of a soil survey. Chapter 5 of the Soil Survey Manual gives helpful information about field notes and soil descriptions.

  2. Purpose of Documentation

    Documentation is collected for specific outcomes within each survey area. The main outcomes are:

    • To be able to develop science based soil-landscape models so we can delineate polygons of like soils;
    • To be able to build and store property data in a permanent database accessible to users;
    • To quantify soil spatial variability in order to make logical breaks in soil landscapes;
    • To better communicate with soil scientists and related professions (nomenclature, taxonomy, etc.);
    • To correlate ecological sites with soils;
    • To be able to classify and correlate soils consistently;
    • To be able to develop and test interpretations; and
    • To be able to test and report the reliability of soil survey information.
  3. Specifying Documentation

    The memorandum of understanding and the project plan specify the kind and amount of support data required. The requirements for documentation written into the memorandum are based on the evaluation of the deficiencies in the map units of the previous soil survey. Refer to Part 610 of this handbook for guidance on evaluations. For previously unmapped areas the requirements for documentation are based on the evaluation of the landscapes and map units of the surveys adjacent to the area. Generally map units that are not revised do not need further documentation other than that provided in the evaluation. Map units revised or redesigned need full documentation within the major land resource area.

    Because of the variable nature of parent material, landscape patterns, uniformity, land use, user needs, scale, access, and past documentation, flexibility is needed for requirements in the type and amount of field documentation for map units within each survey area. Agreements on documentation requirements that differ from standard field description standards should be spelled out in the memorandum of understanding for each survey area before field work starts. The soil survey regional office (SSRO) takes the lead, as part of quality assurance, in assuring these standards are reasonable and adequate for correlation and interpretation and are addressed in the memorandum of understanding. Reference Exhibit 606-1.
  4. Kinds Of Documentation

    1. Field notes are essential for the preparation of the descriptive legend and soil survey manuscript because:
      • Many of the facts obtained in the field cannot be recorded on the map or in standard soil descriptions;
      • The soil scientist cannot remember the details of all field observations, or the soil scientist may retire or transfer before completing the survey;
      • They help office staff to achieve consistent work among the project members;
      • They provide the data necessary for describing, classifying, and interpreting soils;
      • They provide data for long term records; and
      • They aid in developing and recording the map unit concept and criteria.
      • Soil scientists take field notes as they progressively map the soils. They:
      • Record them on location at the time of the observation;
      • Emphasize documenting the ordinary, the prevalent, and the commonplace;
      • If not a direct observation, clearly identify location, date, author, soil component, and source;
      • Use standard terminology and standard database programs;
      • Clearly separate observations from conclusions and speculations;
      • Summarize at regular intervals to determine the status of the documentation effort;
      • Add to the site observation table in NASIS; and
      • File in a logical manner, preferably by map unit component and map unit, for easy reference.
      Interpretive field notes are important in documenting soil behavior in the survey area. Interpretive notes result from direct observation or from information provided by resource specialists, farmers, extension personnel, agricultural teachers, fertilizer and farm equipment dealers, soil consultants, environmental scientists, county sanitarians, engineers, and other persons with experience or knowledge of soil relationships.
    2. Pedon descriptions are the primary records for soil identification, classification, and interpretation. Chapters 3 and 5 of the Soil Survey Manual provide helpful information, guidance, and standard terminology for describing soils. Typical pedons characterize each named component in a map unit. The SSO maintains a map that locates soil description sites, especially the typical pedons. Describe soils as they occur in order to represent each map unit component. All soil descriptions are to be taken in metric units of centimeters to avoid errors of conversion. One pedon description represents each component. It is permissible to use pedons from surveys sharing the data mapunit from within the same major land resource area and MLRA legend. Tentatively classify all pedons at the time when they are described. After sufficient descriptions have been taken, establish a central concept and range for a kind of soil. Consult the official soil series descriptions to determine proper series placement. If the soil differs significantly from all recognized soil series in the same taxonomic family, classify the soil in the lowest possible category of soil taxonomy.

      Pedons that have all soil characteristics representative of a given kind of soil often are difficult to locate or do not exist in an individual survey area. Soil scientists must objectively locate and describe pedons that are representative of the kind of soil in the area. Soil descriptions must be complete and legible. It is important to give the exact geographic location of pedons to allow for spatial analysis and revisitation of the sites.

    3. Map unit descriptions are based from the collection of field notes, transects, and soil descriptions provide the basic information needed to adequately describe map units. The notes and descriptions:
      • Characterize the soils within the map unit;
      • Determine the patterns of occurrence of different kinds of soils within the map unit, their proportionate extent, and their position on the landform; and
      • Determine the relationships of one map unit to another and the distinction between similar map units to support the descriptive legend.
    4. Images. Slides, black and white photos, color photos, and digital images taken during the soil survey illustrate and document field conditions for soil survey reports, information activities, and training sessions. Soil profiles, landscapes, vegetation patterns, typical landforms, rock exposure, and the results of management practices applied to particular soils are needed.
    5. Soil survey investigations may take the form of laboratory data obtained by collecting samples for chemical, physical, or engineering analysis. Other investigations may result in documentation of soil temperature, moisture, or other soil property or quality. Refer to Part 631 of the handbook for information on soil survey investigations.
  5. Field Description Standards

    The MLRA soil survey leader ensures the systematic collection of documentation by providing each staff member with a list of specific instructions about the kind of information needed for each map unit and soil map unit component.

    The memorandum of understanding for the survey area provides guidance for the type and amount of documentation. Documentation needs and standards may vary by map unit within the same survey area. Flexibility of guidance allows for sufficient data collection for each map, yet avoids the excess time and expense of redundant or superfluous data.

    1. Proposed series require descriptions of at least 5 pedons for new series with an extent of less than 2,000 acres. New series with an extent of over 20,000 acres require 10 complete pedon descriptions. The number and distribution of pedon descriptions must be adequate to classify, differentiate and develop a valid range of characteristics. Larger acreage units require more pedons descriptions to assure reasonable spatial representation across its extent.

      Laboratory data and field notes supplement these requirements. Section 614.06 of this handbook provides helpful information on proposing a soil series.

    2. Map unit soil components each have a unique description. This representative pedon description exhibits typical properties and horizonation of the map unit component as it exists within the major land resource area. Each major soil component named within a map unit of the major land resource area legend requires one pedon description from the map unit. Minor components that are not named in a map unit of the legend but that occur in the component list of the database need a minimum of one pedon description. Provisional map units are exempted. This documentation is adequate for map units where the extent of the map unit is up to 3,000 acres. Where the extent is over 3,000 acres, the amount of additional descriptions are agreed upon and recorded in the memorandum of understanding. Factors that need to be considered are uniformity of material, scale, land use, and access.

      To ensure that documentation is adequate for the correlation of soil component names to established soil series or higher taxonomic categories, at least three pedon descriptions are required for each taxon used in the legend. Descriptions gathered to typify the map unit component as mentioned above and descriptions within adjacent surveys within the major land resource area are included in this total.

    3. Map units require a minimum of 30 recorded points for each map unit to document the composition. The points need to be distributed throughout the full extent of the map unit to account for spatial variability. Depending upon the nature of the map unit, the points can come from a fixed interval transect, a line transect (points selected to represent line segments related to vegetation, hillslope position, photo tone, etc.) or other techniques to assure composition. This documentation is adequate where the extent of the map units are less than 2,000 acres. Where the extent is over 2,000 acres, add an additional 10 recorded points for each 4,000 acres. Sufficient documentation typically exists when the number of recorded points reach 60, given adequate spatial distribution. Due to unique situations and variability, the memorandum of understanding state specific requirements as needed based on uniformity of material, scale, land use, or access. Where applicable, the use of statistics can be helpful in determining the adequacy of recorded points.
    4. Exceptions to the minimum standards for documentation of map units and map unit components apply when adding small acreage map units along the boundary of an ongoing soil survey or modern published soil survey. Section 627.03 provides more details on map units of small extent. In these cases use the documentation from the joining soil survey area that has the larger acreage for correlation.

      The SSO regularly reviews and summarizes all documentation. Where applicable, a statistical analysis of data is done to objectively evaluate soil properties and map unit composition. The descriptive legend, manuscript, and database are updated periodically based on progressively gathered documentation. Documentation undergoes a quality assurance review at regular intervals by the SSRO. Determinations are made about the documentation in regard to:
      • Attaining the outcomes as stated above;
      • Meeting the Field Description Standards (or standards modified in the MOU); and
      • Identifying the need for additional documentation.
  6. Descriptive Legend

    A descriptive legend is required for all soil surveys and is unique for each progressive soil survey area. A single descriptive legend may serve two or more non-progressive soil survey areas. Prepare the first draft of the descriptive legend during the preliminary study of the soils. It is available for inspection at the initial field review. At a minimum update and review the legend during annual progress reviews. The descriptive legend has four parts:
    • The identification legend;
    • The feature and symbol legend;
    • The descriptions of map units, descriptions and classification of the soils; and
    • The general soil map and legend.

    Chapter 4 of the Soil Survey Manual also gives helpful information about the descriptive legend and survey area soil handbook.

    1. Identification legend. The identification legend consists of a list of map unit symbols and map unit names. Prepare the identification legend from map units and map unit components proposed and described. Only list those map units whose occurrence and justification were established during mapping. The SSO staff maintains records of all symbols and proposed changes to the identification legend. Field reviews record legend changes that are approved by the SSRO. The field review reports must account for all the map units and symbols used at any time during the survey. All field review reports include an updated identification legend. The National Soil Information System is the official depository of legends, correlation notes, and legend text. Chapter 4 of the Soil Survey Manual provides an example of an identification legend.

      The legend is sorted numerically or alphabetically by map unit symbol. Numerically sort and publish the legend, map units, and tables where map unit symbols (or labels) are numeric or alpha-numeric. Alphabetically sort and publish the legend, map units, and tables where map unit symbols (or labels) are alphabetical.
      1. Symbols. Map unit symbols are descriptive labels on soil maps. They are designed in a manner that avoids confusion with other symbols shown on soil maps representing specific features, such as those in the Feature and Symbol Legend for Soil Survey (Exhibit 627-5). Soil survey map unit symbols combine alpha, alpha-numeric, or numeric characters. Exhibit 627-4 gives several examples. Symbols should be as short as possible, but may contain up to six characters, including special characters like hyphens. Avoid the use of the lowercase letters “i”, “j”, “q”, and “l” because when handwritten these letters are easily confused with other letters or the number 1.
      2. Slope phases. Identification of a slope phase with a symbol is optional. However, a capital letter (A through G) commonly identifies a map unit slope phase. Examples are AoB for Alpha loam, 3 to 6 percent slopes, and 123B for Alpha sandy loam, 3 to 6 percent slopes. If two or more slope groups, such as, 3 and 6 percent and 6 to 9 percent, combine during correlation into a map unit, such as 3 to 9 percent slopes, only use one letter to identify slope. Use the symbol for the most restrictive slope from the named components if you combine slope groups. Consider using separate components, each with their own slope group, if these components would be dissimilar.
    2. Feature and Symbol Legend for Soil Survey.
      1. Each soil survey area requires a Feature and Symbol Legend for Soil Survey (NRCS-SOI-37A). See Exhibit 627-5. The legend identifies all approved map features that may be published in soil surveys including:
        • Area, line, and point soil features including soil boundary lines and soil symbols;
        • Ad hoc features and standard landform and miscellaneous surface features that are too small to be delineated as areas on soil map sheets at either 1:12,000 (<1.4 acres) or 1:24,000 (<5.7 acres) scale;
        • Cultural features, such as structures, political boundaries, road emblems, and airports; and
        • Hydrographic features, such as streams, springs, and wells.
        The descriptions of the standard landform and miscellaneous surface features are on the back of the form NRCS-SOI-37A. If the legend includes ad hoc features, write the description on the back of the NRCS-SOI-37A.
      2. Use standard landform and miscellaneous surface features or ad hoc features to show local areas of significantly contrasting soils or features too small to delineate at the publication scale. The need for these features depends on their significance to present or projected use of the soils and the soil map. These features are primarily for location purposes and only surface determined properties or responses define them. These features are not used to indicate soils or features that are identified in the name or description of the map unit delineated. Nor are these features used as identifying symbols in small delineations.
      3. Define ad hoc features on the 37A in the section entitled Descriptions for Ad Hoc Features. Define the specific kind and size of the area represented.
      4. All symbols must correspond exactly to those listed on form NRCS-SOI-37A.
      5. The SSO prepares the first draft of the feature and symbol legend before the initial field review of the survey area using the NRCS-SOI-37A. The review report includes the NRCS-SOI-37A. The back of the form includes the rules of application. All subsequent progress field reviews update and approve changes to this legend. Underline or otherwise highlight those features that are selected. Only compile those features that are highlighted.
    3. Descriptions and classification of the soils.
      1. Throughout the course of the survey, the SSO describes all map units and map unit components. The SSRO approves these units before they are added to the identification legend. The SSO makes minor revisions, such as adding minor components to map units, broadening the range for the taxonomic unit, or improving descriptions of the shape of delineations of the map unit.
      2. The SSRO approves major changes, such as the addition or deletion of a map unit or the change in concept of a taxonomic unit. The SSRO prescribes the manner for submitting proposals for additions or deletions, and the supporting information. Make approved changes in all copies of the descriptive legend, including those used by the SSO and the SSRO or lead agency. Keep a complete record of all major revisions, and record these revisions and the reasons for them in the report of the first field review that is made after the revisions are proposed. The National Soil Information System is the official depository of legends, correlation notes, and legend text.
      3. The SSRO or the appropriate supervisor of the lead agency arranges procedures with cooperating agencies to obtain their concurrence to revisions of the legend.
    4. General soil map and legend. The general soil map shows the geographic distribution of general soil areas within the survey area.
  7. Survey Area Soil Handbook

    1. Each soil survey area in which acres of field mapping are being reported includes a survey area soil handbook. The preparation of a survey area soil handbook starts at the beginning of the soil survey with the inclusion of the descriptive legend. The SSO prepares and keeps current a survey area soil handbook through the life of the survey. The SSO prepares an outline of the survey area soil handbook during the first year of the soil survey to meet the requirements of the survey area. The SSO similarly prepares a schedule that lists target dates for completion of all major parts of the survey area soil handbook. Exhibit 608-1 and Exhibit 608-2 of this handbook provide more information. The arrangement and format of material in the survey area soil handbook is similar to that in published soil surveys. In addition to the descriptive legend, the handbook includes the soil survey manuscript prewritten material, original material that is prepared by the SSO and guest authors, block diagrams, references, and pictures. The handbook is usually maintained in loose-leaf binders with dividers that separate major parts. Chapter 4 of the Soil Survey Manual and section 609.07 of this handbook provide additional information about the soil survey area soil handbook.
    2. The survey area soil handbook receives additions and revisions as the survey progresses to reflect the knowledge gained during fieldwork. Persons who need soil data before the survey is published often use this handbook. The handbook is available in the soil survey office and in the office of the district conservationist(s) for use and testing by other disciplines.
    3. At the time field activities conclude, the handbook encompasses the information needed to complete the manuscript for the survey area. The soil survey manuscript is essentially complete before the final field review.

627.09  Ecological Site and Soil Correlation Procedures

  1. Definition and Purpose

    Ecological site and soil correlation procedures are actions to consistently relate ecological sites and soil components. The soil is an integral part of the ecological site.

    Soil survey is often an ecosystem inventory. Ecosystem inventories include not only soil and vegetation but also include the associated topography, climate, water, animals, and other living organisms. Fire and air are sometimes included. These components are interrelated. Human actions and disturbance are considered. Any disturbance exerted on one component affects other components.

    Ecological site correlation relates ecosystem components within and between areas perceived as having the same historic climax plant community. Ecological site correlation procedures support consistent descriptions, documentation of the ecosystem components, and interpretations associated within the site.

    Correlation is a continuous process that is initiated at the beginning of any soil or vegetation survey and progresses through a final correlation (which may also include an interstate correlation).

    Soil-ecological site correlation normally takes place in conjunction with progressive soil correlation. However, ecological site correlation may also be necessary because of updates or revisions of ecological site descriptions.

    The National Range and Pasture Handbook (NRPH), Chapter 3, Section 1, and the National Forestry Manual (NFM), Section 537.30(j) define ecological site correlation procedures.
  2. Records of Site Descriptions

    The Ecological Site Information System (ESIS) – Ecological Site Description database is the official repository for all data associated with ecological site descriptions. The state office is responsible for entry and maintenance of site descriptions in this database.
  3. Updating Or Revising Site Descriptions

    Update site descriptions according to procedures established by NRCS in the NRPH and NFM.
  4. Juniper and Pinyon Communities

    For correlating sites involving juniper and pinyon communities to soils, refer to the guidelines in the USDA-NRCS publication “Inventorying, Classifying, and Correlating Juniper and Pinyon Communities to Soils in Western United States” published by the Grazing Land Technology Institute in September of 1997.
  5. Supporting Information

    1. Physiographic features. Include copies of field sheets and any support maps (geology, topographic, slope, etc.).
    2. Climatic features. Assemble data from nearest representative weather station(s), research or field study, soil moisture status, and soil temperature ranges.
    3. Soil features. List the range of soil properties typifying the known range of characteristics for the site. The National Soil Information System is the official source of soil properties. Standard soil property reports from this database can show the range of individual properties for the soils included in the site.
    4. Plant community. Complete sufficient supporting plant community data for each soil component listed in each site description. The ESIS – Ecological Site Inventory database can provide useful data in identifying plant communities. A plant association table (NRPH, Chapter 3, Section 1, 600.0302b and exhibits 3.1-1 and 3.1-2) or equivalent worksheet is helpful in identifying important plant community similarities and differences.
    5. Wildlife. Record historical accounts, special studies, and field observations.
    6. General. Gather field notes, photographs, and other general material.
    7. Exhibit 627-6 Ecological Site and Soil Correlation Checklist and Exhibit 627-7 Ecological Site Checklist help to document formal correlation activities.
  6. Interstate Correlation of Soils and Ecological Sites

    The following steps serve as a guideline for interstate correlation of soils and ecological sites. It is recommended to allow a minimum of six months to complete this process.

    1. Evaluate resource data and summaries for adequacy of use for site comparison. Include data on soils, vegetation, climate, landform, animals, and other living organisms.
    2. Exchange proposed and established site descriptions for the area.
    3. Jointly visit the sites.
    4. Document which sites can be correlated and those that cannot be correlated at this time.
    5. Make an initial grouping or separation of sites based on the criteria for comparison between sites (see Sections 627.09 (f) and (g) of the correlation guidelines).
    6. Submit a proposal to other states for correlating comparable sites and resolving the remaining issues.
    7. Coordinate with field staff to jointly select locations to be correlated. It is not necessary to visit every site if there are no disagreements.
    8. Provide all necessary documentation (see 627.09 (h) correlation guidelines), including soil pits at the review sites.

Exhibit 627-1—Miscellaneous Areas

Miscellaneous areas have essentially no soil or are bodies of soil that are heavily contaminated by toxic substances. They can result from active erosion and deposition, flooding and ponding, unfavorable edaphic conditions, or human activities. Some miscellaneous areas can be made productive, but only after major reclamation efforts. The paragraphs below discuss the 20 miscellaneous areas that are approved for use as component names. No other miscellaneous area names are used. See Section 627.04 (d) (2) for the process to revise the list of areas. Phase terms are not populated in the component name column of the database. Map unit names can consist of the concatenated miscellaneous area name and the local phase term (e.g., “Water, saline”). Local phase terms are developed as needed and have no finite limit or national approval process.

Badland is moderately steep to very steep barren land that is dissected by many intermittent drainage channels. Ordinarily, the areas are not stony. Badland is most common in semiarid and arid regions where streams and surface runoff have cut into soft bedrock such as shale. Local relief generally ranges from 10 to 200 meters in height. Potential runoff is very high and erosion is active.

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

Chutes are elongated areas on steep mountain slopes. The vegetation has been removed by avalanche or mass movement processes. Chutes consist of exposed bedrock, rock fragments, and large woody debris. Their slopes are parallel to the slope of the mountain and their lengths are at least ten times their widths.

Cinder land is composed of loose cinders and other scoriaceous tephra. The water-holding capacity of the tephra is very low and the trafficability is poor. Cinder land is commonly associated with cinder cone volcanoes, but not all cinder land occurs on the flanks of volcanic hills or mountains.

Dams are artificial structures, oriented across a watercourse or natural drainage area, for the purpose of impounding or diverting water.

Dumps are areas of smoothed or uneven accumulations or piles of waste rock and general refuse. Some dumps that are closely associated with pits are mapped as a complex map unit of dumps and pits.

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

Glaciers are large masses of ice that 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, they may be retreating, or they may be stagnant. Rocks and some earthy material may be on the surface of or imbedded within the ice. Permanent snowfields are associated with glaciers in some regions.

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 that indicate the kind of material remaining may be useful for some areas.

Lava flows are areas covered with barren lava. In most humid regions, the flows are of Holocene age, but in arid and very cold regions they may be older. Some flows have sharp, jagged surfaces, crevices, and angular blocks that are characteristic of slow-moving viscous lava. The Hawaiian term for a basaltic lava flow with these features is named “aa.” Other lava flows are relatively smooth and have a ropy, glazed surface due to hotter eruption temperatures, lower viscosity, and rapid flow rates. The Hawaiian term for this form of lava flow is “pahoehoe.” A little earthy material, ash, cinders, or accumulations of fresh organic material may be in a few fractures and sheltered pockets, but the flows are virtually devoid of soil. Lava flows have no vegetation other than lichens or other plant life growing in small pockets.

Mined land is areas which are significantly altered by mining activities. Soil material and rock has been moved into, out of, or within the areas designated. Because access to mined land may be limited by permissions or hazardous materials, identification of soil components can be difficult or impossible. Mined land may also have associated small excavations which could be correlated and delineated as pits if needed.

Oil-waste land consists of areas where liquid oily wastes, principally of salt water and oil, have accumulated. It includes slush pits and adjacent areas that are 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. Common kinds of pits are those that result from mining, gravel operations, and quarries. Pits are often closely associated with dumps.

Playas are barren flats in closed basins in arid regions. The largest playas occupy the dry beds of ancient, pluvial lakes. The sediments in playas are mainly fine-grained lacustrine deposits that accumulate from silt and clay particles settling in still water. Many playas are subject to removal of sediments by wind action and are a local source of fine particulate matter. Many playas are saline, sodic, or both and may have mineral crusts of soluble salts. Some nearly level playas are subject to intermittent ponding following periods of heavy precipitation and/or snowmelt. The water table may be near the surface at times, or it may remain at depth.

Riverwash is unstabilized sandy, silty, clayey, or gravelly sediment that is flooded, washed, and reworked frequently by rivers or streams that little or no vegetation can become established. The recent deposition of fresh alluvium precludes soil development.

Rock outcrop consists of exposures of barren bedrock, other than lava flows, chutes, and rock-lined pits. Some areas are large and are only broken by small areas of soil. Most rock outcrops are hard rock, but some are soft rock such as thin beds of weakly cemented shale interbedded with thick beds of strongly cemented sandstone.

Rubble land consists of areas of cobbles, flagstones, stones, and boulders in unstable deposits of sufficient thickness to significantly limit the establishment of vegetation. Rubble land is commonly at the base of mountains but in some areas consists of deposits of large rock fragments left on mountain slopes by glaciation or by periglacial processes.

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 and are often contaminated by metallic compounds.

Urban land is land covered by pavement, buildings, storage tanks, bridges. and other impervious, human-manufactured surfaces and structures. Pavement is a hard layered surface of concrete or asphalt that forms a walkway, road, street, highway lane, runway, parking lot, or similar paved area. Urban land can occur in urban areas such as large cities and industrial centers as well as in suburban neighborhoods and rural towns. If correlated properly, urban land consists of 100 percent manufactured surface. Older soil surveys correlating urban land with a less strict concept may consist of as little as 75 percent manufactured surface. Some modern soil surveys require identification of the materials below urban land. Urban land is an anthropogenic type of miscellaneous area which does not necessarily represent a permanent condition.

Water includes streams, lakes, ponds, and estuaries more than about 2.5 meters deep or less than 2.5 meters deep and lacks either distinguishable horizons or rooted vegetation in the bottom sediment. These areas are covered with water in most years, at least during the period that is warm enough for plants to grow. Many areas are covered throughout the year. Pits and playas that contain water most of the time are mapped as water.

Exhibit 627-2—Example of Form NRCS-SOI-1, Soil Crop Yield Data

Example of Form NRCS-SOI-1, Soil Crop Yield Data

High Resolution Image
(700 x 528, 22 KB, PNG format)

Exhibit 627-3—Instructions for Completing Form NRCS-SOI-1, Soil Crop Yield Data

  1. Line 1
    1. Sample number.
      1. State code. Use the two-character alphabetic Federal Information Processing Standards (FIPS) code, for example, VA.
      2. County code. Use the three-character numerical FIPS code.
      3. Site identification number within county. Set up a sequence of two-digit numbers for each field and another sequence of two-digit numbers for each site within the field. Keep a log of these numbers as a record for testing at the same sites in subsequent years.
    2. Kind of plot.
      Enter one of the following codes:
      1 = Yield measurements in commercial farm fields.
      2 = Yield measurements in field trails of special treatment practices (fertilizer field trials, variety trials, conservation tillage trials).
      3 = Yield measurements of small research plots at experiment stations (variety tests, fertilizer tests).
      4 = Yield estimates.

    3. Size of plot.
      Enter width x length in feet, for example, 4 x 10.9

    4. Location.
      Use a map such as a 7½° quad, aerial photograph or soil survey to record the location.
      1. X coordinate. Enter latitude north. Separate degrees, minutes, and seconds by a hyphen, for example, 25-05-03.
      2. Y coordinate. Enter longitude west, for example 108-25-49.
      3. Other location description, for example NE¼ sec. 12, T. 31 N., R. 11 W.
    5. Agency.
      Enter the abbreviation of the agency entering the data.

    6. Date.
      Enter the date the form is filled out, for example, 8/14/81.

  2. Line 2
    1. Soil symbol.
      Enter the soil symbol of the area at the sample site (if known).

    2. Soil name.
      Enter the name of the soil identified at the sample site or through reference to the soil survey, for example, NORFOLK FINE SANDY LOAM, 3-5 PERCENT SLOPE.

    3. Soil identified at site?
      Indicate whether soil is identified at the site by soil scientists. Enter Y for yes or N or no.

  3. Line 3

    2. USDA texture.
      Enter the codes for texture class and texture modifier of the surface layer, for example, GR-L for gravelly loam. Use only the approved codes shown in the National Soil Survey Handbook, Part 618, Subpart B, Section 618.94 Texture Class, Texture Modifier, and Terms Used in Lieu of Texture.

    3. Slope.
      Enter the percent slope gradient to the nearest whole number on slopes of 1 percent or more; enter to the nearest 0.1 percent for slopes less than 1 percent.

    4. Flooding.
      Enter the flooding frequency (see Part 618 of this handbook) that most nearly represents sample site. Use NONE, VERY RARE, RARE, OCCASIONAL, FREQUENT, or VERY FREQUENT.

    5. Other phase criteria.
      Enter phases used to name soil map unit components (see Section 627.06), other than surface texture, slope, or flooding, that are needed to select the correct capability and yield interpretations for the component, for example, SEVERELY ERODED.

  4. Line 4

    1. Erosion.
      Enter the code that most nearly represents the estimate of erosion:
      1 = Slight
      2 = Moderate
      3 = Severe

    2. Color of A horizon.
      Enter the color (Munsell notation) of the A horizon.

    3. Thickness of A horizon.
      Enter the thickness of the A horizon (inches).

    4. Organic matter.
      Enter an estimate or measurement of the percent of organic matter (organic carbon x 1.72) in the A horizon.

    5. pH.
      Enter the pH of the surface 4 inches at the time of harvest, for example, 6.7.

    6. Rooting depth (inches).
      Measure the depth to fragipan, bedrock, gravel, or other root-impeding layer. If greater than 60 inches, enter >60.

    7. Slope length.
      1. Through site (ft.). Enter the length of slope through the sample site, in feet. On terraced land, enter the distance between terraces. Slope length is the distance from the point of origin of overland flow to either (a) the point where the slope decreases to the extent that deposition begins or (b) the point where runoff enters an area of concentrated flow or channel.
      2. Above site (ft). Enter the length of slope from point or origin of overland flow to the sample point in feet.
    8. Slope.
      1. Kind.
        Enter the code that most nearly represents kind of slope at the sample site:
        1 = Summit
        2 = Shoulder
        3 = Back slope
        4 = Foot slope
      2. Shape.
        Enter the code that most nearly represent the slope shape:
        1 = Convex
        2 = Plane
        3 = Concave
        4 = Undulating
        5 = Complex

    9. Aspect.
      On slopes where aspect is important, enter one of the 8 points of the compass that the slope faces, for example, NE.

    10. K factor.
      Enter the soil erodibility (Kf) factor.

  5. Line 5

    1. Moisture reserve at planting time.
      Enter one of the following codes:
      1 = Above normal
      2 = Normal
      3 = Below normal

    2. Moisture reserve at beginning of spring growing season following fall planting (winter wheat and rye).
      Enter one of the following codes:
      1 = Above normal
      2 = Normal
      3 = Below normal

    3. Precipitation during the growing season.
      1. Qualitative. Enter the code that represents qualitative judgment:
        1 = Above normal
        2 = Normal
        3 = Below normal
      2. By month. If monthly records are available, enter to the nearest inch the precipitation for each month.
    4. Drought damage.
      Enter the code that represents the judgment of the amount of crop damage caused by drought:
      1 = None
      2 = Slight
      3 = Moderate
      4 = Severe

    5. Water damage.
      Enter the code that describes the amount of crop damage caused by excessive wetness:
      1 = None
      2 = Slight
      3 = Moderate
      4 = Severe

    6. R factor.
      Enter the R (rainfall) factor.

  6. Line 6

    1. Multiple-cropped.
      Is the site double or triple cropped? Enter Y for yes, or N for no.

    2. Current crop.
      Enter the crop name or code from the crop name and units of measure list in Exhibit 618-3.

    3. Cultivar (variety).
      Enter the name or identification of the crop variety.

    4. Previous crops.
      Enter the names or codes of the crops grown in first, second, and third previous crop seasons.

  7. Line 7

    1. Planting information.
      1. Date.
        Enter the date of planting (month/day/year) if known, for example 5/15/86.
      2. Timing.
        Enter the code that describes timeliness of planting:
        1 = Early
        2 = Normal
        3 = Late
      3. Crop yield.
        Enter the amount of harvested crop per acre, for example, 110. Use standard procedures for measuring yield.
      4. Unit of measure.
        Enter the unit of measure for the crop (see Part 618, Subpart B, section 618.82 of this handbook), for example, bu/acre.
      5. Residue yield (t/acre).
        Enter the air-dry tons per acre of crop residue (estimate if necessary).

  8. Line 8

    1. Commercial fertilizer.
      1. NPK
        Enter the pounds of elemental nitrogen, phosphorus, and potassium applied per acre.
      2. Other fertilizer materials (excluding lime).
        (A) Specify kind, for example, ZINC.
        (B) Enter the pounds per acre applied.

    2. Organic materials
      1. Enter tons of manure applied per acre.
      2. Enter the code representing the kind of manure:
        1 = Cattle
        2 = Poultry
        3 = Hog
        4 = Horse
        5 = Sludge (human)
        6 = Other

    3. Crop residues returned.
      Enter Y for yes, or N for no.

    4. Tillage.
      Enter the code that represents the kind of tillage practice at the sample site:
      1 = No till (slot tillage)
      2 = Strip till
      3 = Other conservation tillage
      4 = Nonconservation tillage (moldboard, disk plow, lister)

    5. Weed control.
      1. Were herbicides used for this crop?
        Enter Y for yes, or N for no.
      2. Enter the number of cultivations used primarily or partly for weed control.
      3. Enter the code that represents the extent of weed damage on this crop:
        0 = None
        1 = Slight
        2 = Moderate
        3 = Severe

    6. Insect and disease control.
      1. Were chemicals used to control insects or disease?
        Enter Y for yes, or N for no.
      2. If chemical control was used, enter the code that represents the kind of treatment:
        1 = Foliage
        2 = Seed
        3 = Soil
        4 = Two or more of the above treatments
      3. If foliage treatment, enter the number of chemical applications.
      4. Enter the code that represents the extent of insect or disease damage on this crop:
        0 = None
        1 = Slight
        2 = Moderate
        3 = Severe

  9. Line 9

    1. Other damage.
      Enter the code that represents the extent of damage from other causes such as hail, wind, lodging, and freezing:
      0 = None
      1 = Slight
      2 = Moderate
      3 = Severe

    2. Conservation practices, other than tillage and cropping sequence.
      Enter one of the following conservation practices codes. If more than one used, enter the code listed first:
      0 = None
      1 = Terraces
      2 = Stripcropping, contour
      3 = Stripcropping, field
      4 = Stripcropping, wind
      5 = Contour farming

    3. Irrigation.
      1. Was irrigation water applied to this crop?
        Enter Y for yes, or N for no.
      2. Type:
        1 = Furrow
        2 = Sprinkle
        3 = Drip
        4 = Flood
      3. Enter the code that represents the adequacy of the irrigation in meeting crop moisture requirements:
        1 = Good
        2 = Fair
        3 = Poor

    4. Drainage.
      1. Is this soil artificially drained?
        Enter Y for yes, or N for no.
      2. Enter the code that represents the damage to the crop caused by inadequate drainage system:
        0 = None
        1 = Slight
        2 = Moderate
        3 = Severe

    5. Factors.
      1. C factor. Enter the C factor (cover-management factor used in the Revised Universal Soil Loss Equation) applicable to the site.
      2. P factor. Enter the P factor (support practices factor used in the Revised Universal Soil Loss Equation) applicable to the site.
    6. Conservation Practice Codes.
      Enter __________applicable to the site.

    7. Recorder Name.
      The name of the individual recording the data.


Exhibit 627-4—Identification Legend of Map Unit Symbols and Names

Example of an alphabetic map unit legend for Alpha County, Any State:

Map Unit Symbol Map Unit Name
AaA Alpha silt loam, 0 to 3 percent slopes
AaB Alpha silty clay loam, 3 to 6 percent slopes
AAE Alpha association, moderately steep
AAG Alpha association, very steep
Ab Alpha-Beta complex
AbA Alpha, rarely flooded-Beta, occasionally flooded complex
ABG Alpha-Beta association, very steep
BTF Beta-Gamma association, steep
GE Gamma and Beta soils
ROF Rock outcrop
STC Sigma and Gamma soils, rolling
W Water
ZAB Zeta association, rolling

Example of an alpha-numeric map unit legend for Beta County, Any State:

Map Unit Symbol Map Unit Name
12A Alpha silt loam, 0 to 2 percent slopes
12B Alpha silt loam, 2 to 4 percent slopes
12B2 Alpha silt loam, 2 to 4 percent slopes, eroded
13 Beta silty clay loam
14 Beta silty clay loam, stony
17 Water, fresh
20 Water, saline
21 Gamma muck
23 Rock outcrop
27A Sigma sandy loam, 0 to 2 percent slopes
29A Sigma sandy loam, saline, 0 to 2 percent slopes
51D2 Zeta loamy sand, 8 to 15 percent slopes, eroded
52B Zeta fine sandy loam, 2 to 5 percent slopes
52C Zeta fine sandy loam, 5 to 8 percent slopes

Example of a numeric map unit legend for Gamma County, Any State:

Map Unit Symbol Map Unit Name
10 Alpha silt loam, 0 to 2 percent slopes
11 Alpha silt loam, 2 to 4 percent slopes
12 Alpha silt loam, 2 to 4 percent slopes, eroded
14 Zeta fine sandy loam, 2 to 5 percent slopes
15 Zeta fine sandy loam, 5 to 8 percent slopes
16 Zeta loamy fine sand, 8 to 15 percent slopes
17 Rock outcrop
20 Beta silty clay loam
21 Beta silty clay loam, stony
60 Sigma sandy loam, 0 to 2 percent slopes
62 Sigma sandy loam, saline, 0 to 2 percent slopes
99 Water
145 Gamma muck


Exhibit 627-5—Feature and Symbol Legend for Soil Survey, NRCS-SOI-37A

Exhibit 627-5 (front)

Feature and Symbol Legend for Soil Survey (front)

High Resolution Image (JPEG)
(3300 x 5100, 866 KB)

Exhibit 627-5 (back)

Feature and Symbol Legend for Soil Survey (back)

High Resolution Image (JPEG)
(3300 x 5100, 2130 KB)

Exhibit 627-6—Ecological Site and Soil Correlation Checklist

(Use to Supplement Soil Survey Quality Assurance Worksheet)

1. Name of area (including county, state and MLRA(s)) ______________________________________


2. Level of detail for vegetative data (indicate rangeland ecological site, forestland

ecological site, rangeland similarity index, or other special studies)

3. Has soil survey memo of understanding been reviewed in regard to vegetative

(rangeland, forestland, etc.) management needs? Yes _____, No _____.

4. Do soil survey project members and field office staff have copies of site

descriptions being used? Yes _____, No _____.

5. Is a site assigned to each soil component in the identification legend?

Yes _____, No _____.

6. Are all sections of the ecological site descriptions written? Yes _____, No _____.

7. Does documentation for each site support all soils correlated to the site?

Yes _____, No _____.

8. Field notes (how kept, by whom). _________________________________________________

9. Are soil-plant relationships adequately described and documented?

Yes _____, No _____.

10. Is the range of characteristics of the site description adequate? (Note kinds of


      a. Site Characteristics:

          1. Physiographic features

          2. Climatic features

          3. Influencing water features

          4. Representative soils features

      b. Plant Communities

          1. Description of the vegetation dynamics of the site

          2. State and transition model diagram

          3. Description of the common states that occur on the site and the transitions between the states. If needed, describe the plant communities and community pathways within the state.

          4. Plant community composition

          5. Ground cover and structure

          6. Annual production

          7. Growth curves

          8. Photos of each state or community

11. Are interpretations for the ecological site description adequate? (Note kinds of


Site Interpretations:

      1. Animal community

      2. Hydrology functions

      3. Recreation uses

      4. Wood products

      5. Other products

      6. Plant preferences by animal kind

      7. Other information

12. Is the supporting information for the site description adequate? (Note kinds of


      a. Supporting Information:

          1. Associate sites

          2. Similar sites

          3. Inventory data references

          4. State correlation

          5. Type Locality

          6. Relationships to other established classification systems

13. Is the supporting information for the site description adequate to separate this site

from other sites? Yes _____, No _____.

14. List of sites reviewed and status. (Indicate soils correlated to each site during

this review.)

15. Have sites been correlated with existing site descriptions? Yes _____, No _____.

16. Have sites been correlated to adjoining soil survey areas? Yes _____, No _____.

17. Have sites been named and numbered correctly? Yes _____, No _____.

18. Have appropriate Federal and State agencies reviewed or assisted in writing site

descriptions? Yes _____, No _____.

19. Have field office staff provided input or reviewed site descriptions?

Yes _____, No _____.

20. Deficiencies noted and recommended actions. (Be specific and provide dates for completion)

21. Scheduled dates for completion of the vegetation inventory are compatible with the

scheduled dates of the soil survey? Yes _____, No _____.

Date: _____________________________________

Signature: _____________________________________________


Exhibit 627-7—Ecological Site Checklist

1. Name of Area(s) ____________________________________________________________________

(County(s) State(s) MLRA(s))

2. Type of Survey(s) __________________________________________________________________

(Level of detail - soil and vegetation)

3. Participants ________________________________________________________________________




4. Site Content (Number reviewed _____________________________________________________)

a. Field sheets, maps, etc.

b. Range of characteristics for physiographic features:

c. Climatic features:

d. Water features:

e. Soil features and official soil series descriptions:

Range of soil properties for the site:

f. Vegetation data (417s, etc., and plant association tables)

g. Animal data:

h. General (field notes, photographs, etc.)

5. Sites with deficiencies:

6. Recommended actions:

7. Site description completed __________________________ (date)

Date: _____________________________________

Signature: __________________________________________


Exhibit 627-8—Matrix of Investigation Intensity of Soil Surveys and Documentation

The table below is a generalized matrix showing investigation intensity of soil survey (order) by the dominant type of documentation.

Within physiographic areas, percentages for the number of delineations can be assigned to the entries to specify required documentation. (i.e., 25% would indicate 25 of 100 delineations)

Key type of documentation to verify or identify map units in soil delineations
  Order 1 Order 2 Order 3 Order 4
Traversing Primary Primary Secondary Secondary
Observation ---------- Secondary Primary Secondary
Remotely sensed/ancillary data ---------- Secondary Primary Primary
Key type of documentation to determine composition of a map unit
Transecting ---------- Primary Primary Primary

Identification or verification of soil map units with a delineation is made by one of three methods. These methods provide documentation to the survey when the method is either recorded in the database or on the map as to type. These methods are:

  • Traversing - Describing the soil and conditions at stops selected to reference vegetation, position on the landform, photo tone, etc. This is an on-site identification of the soil and verification of the projected assignment of the map unit.
  • Observation - Visual notation of items as geologic features, vegetation, surface conditions, disturbed areas, etc without borings. This drive by or other sighted observation does not involve a soil examination, and instead relies on surface characteristics observed by the surveyor.
  • Remotely sensed/ancillary data - includes photo tone on aerial photographs, 3-D digital elevation models, topographic maps, geology maps, vegetative maps, etc.
  • Primary - the principal way polygons and properties are verified.
  • Secondary - additional methods in support of primary methods.
  • No entry - This category is generally not used in the specified order.
  • Transecting - Describing the soils and conditions at points (or continuously as with GPR) along a fixed length at regular intervals or by selecting points to represent measured line segments of various patterns. Transecting is used to identify the composition of a delineation and to design a map unit. A very small percentage of the total number of delineations of any one map unit actually have transects unless there are very few delineations of the map unit. As soil order increases the length and intervals of the transect would generally increase. A transect is different from grid or line mapping used for determining line placement.