MO6 General Guidelines for Selecting Type Pedons for NASIS Population Unique vs' Aggregated

1
MO6 General Guidelines for Selecting Type
Pedons for NASIS Population (Unique vs.
Aggregated)

• What are we talking about here?
• The Alpha series occurs in 3 different map units
  map units A, B, and C. For each map unit there
  exists at least one unique representative pedon
  description for Alpha.
• Do you use the unique pedon description for the
  map unit to populate the rv values for the
  component horizon information?
• OR
• Do you use one of the representative pedon
  descriptions from one of the map units and paste
  it into all the other Alpha components in the
  other map units? I.E. should the Alpha pedon
  from map unit A be copied and pasted in map units
  B and C?

2

• No policy can be written to cover every possible
  exception or scenario for determining whether to
  use a unique pedon or use the same pedon for all
  map units when populating NASIS.
• This MO6 guidance/document is only a guide and
  requires that sound professional judgment and
  reasoning be used by the soil scientist.

3

• NASIS interpretations are generated from the
  aggregated component data that resides in the
  data map unit table.
• The data is aggregated by component within that
  map unit. The data aggregation occurs within the
  map unit, not between map units.
• This ensures that the interpretations are correct
  for a component in a particular map unit.
• If we aggregate from multiple map units we risk
  degrading the integrity of our interpretations.

4

• The following is an excerpt from the National
  Soil Survey Handbook addressing unique pedons
  NSSH, part 627.08 (e) (2)
• Each map unit soil component has 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.
• NoteEven though MLRA legends are mentioned
  above, this policy also applies to non-MLRA
  legends.

5

• The MO6 policy is to use unique pedons when
  populating NASIS DMUs, except when it is
  appropriate to use the same pedon in multiple map
  units and DMUs.
• The question is, when is it appropriate and when
  is it not appropriate?

6

• The driving force behind this policy is to
  encourage the project staff to collect and
  analyze map unit and component data and make
  intelligent decisions about the data that has
  been collected.
• Automatically lumping all the aggregated data
  into one pedon to be used in every data map unit
  in NASIS must be avoided.
• This does not affect how we write taxonomic unit
  descriptions (TUD). Regardless of how many unique
  pedons are recognized, only one TUD is required.
  The pedon that best represents the taxon is used
  for the TUD profile, and the TUD ranges encompass
  all the unique map unit pedons and their data.

7

• The following are process steps for determining
  whether to use a unique pedon or use the same
  pedon for all map units
• For each map unit compile, analyze, and aggregate
  the data by component.
• Select a pedon that best represents the
  aggregated map unit component.
• Compare the representative pedons from each map
  unit.
• Do the pedons interpret differently, excluding
  differences for slope?
• If yes then use unique pedon for each map unit.
• If no go to b.
• Do the pedons interpret the same (excluding
  slope) but one pedon has a soil property or
  feature that is unique and consistent to one map
  unit but not to the other map unit?
• If yes then use unique pedon for each map unit.
• If no then use the same pedon for all map units.

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Example 1

• MU 1 - Alpha loam, 0 to 1 percent slopes
• MU 2 - Alpha loam, 1 to 3 percent slopes
• Analysis shows there to be no interpretive
  differences based on soil properties or features
  between the Alpha components in the two map
  units. The only interpretive differences are due
  to slope. Using the same pedon in both map units
  is appropriate.

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Example 2 (Beta Soil)

• MU 3 Beta-Delta complex, 5 to 15 percent slopes
• Representative Beta profile A- 0-2 inches,
  gravelly sandy loam
• Bt1- 2-5 inches, sandy loam
• Bt2- 5-25 inches, sandy clay loam
• R- 25 inches, UWB, sandstone
• MU 4 Kappa-Beta complex, 10 to 15 percent
  slopes
• Representative Beta profile A- 0-4 inches,
  gravelly sandy loam
• Bt1- 4-8 inches, sandy loam
• Bt2- 5-30 inches, sandy clay loam
• R- 30 inches, UWB, sandstone
• Analysis shows there to be no interpretive
  differences based on soil properties or features
  between the Beta components in the two map units.
  In addition there are no unique soil properties
  or features that occur in only one of the map
  units. Using the same pedon in both map units is
  appropriate.

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Example 3 (Delta Soil)

• MU 5 Beta-Delta loamy fine sands, 5 to 15
  percent slopes
• Representative Delta profile A- 0-5 inches,
  loamy fine sand
• Bt- 5-15 inches, gravelly sandy loam
• Btk- 15-60 inches, gravelly sandy
  clay loam
• MU 6 Delta sandy loam, 10 to15 percent slopes
• Representative Delta profile A- 0-3 inches,
  sandy loam
• Bt- 3-20 inches, gravelly sandy loam
• Btk- 20-60 inches, gravelly sandy clay loam
• Analysis shows there to be interpretive
  differences and properties for the surface
  horizons (Different textures, different K
  factors, different WEG, WEI) between the Delta
  components in the two map units. Using the same
  pedon in both map units is not appropriate here.
  Unique pedons for each map unit should be used.

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Example 4 (Omega Soil)

• MU 7 Gamma-Omega complex, 8 to 20 percent
  slopes
• Representative Omega profile A- 0-4 inches,
  loam
• BA- 4-10 inches, loam
• Bt1- 10-52 inches, clay loam
• Bt2- 52-60 inches, clay
• 2C- 60-80 inches, gravelly sandy loam
  
• MU 8 Omega-Epsilon complex, 2 to 8 percent
  slopes
• Representative Omega profile A- 0-3 inches,
  loam
• BA- 3-12 inches, loam
• Bt- 12-62 inches, clay loam
• 2C- 62-80 inches, gravelly sandy loam
• Analysis shows there to be no interpretation
  differences in the Omega soils. However, the
  Omega soils in mu 7 consistently have the heavy
  clay Bt just above the lithologic discontinuity.
  The Omega soils in mu 8 consistently do not have
  this heavy clay Bt. The AWHC and Ksat would be
  different for these Omega soils due to the
  presence or absence of the clay texture. Using
  the same pedon in both map units is not
  appropriate here. Unique pedons for each map
  unit should be used.