February 11, 2004

SUBJECT: SOI -- Interpretations - Minimum Data Set for Organic Horizons

TO: All State Conservationists File Code: 430-12-5

> All Regional Conservationists

All Center and Institute Directors

Pacific Basin and Caribbean Directors

> In response to State Soil Scientists\' request, the National Soil
> Survey Center (NSSC) is providing guidance regarding populating
> National Soil Information System (NASIS) data elements for O horizons.
> A draft list was circulated to states for comments in February 2003.
> The attached list was completed after receiving input from State Soil
> Scientists and MLRA Office Leaders and conferring with scientists
> developing the Wind Erosion Prediction System (WEPS) model. Effective
> today, the following list of data elements is the minimum data set for
> all O horizons, including Histosols, Folists, litter (duff) layers,
> etc.
>
> Presently data may not exist for several of the listed data elements.
> In the future, when sampling soils for characterization projects or
> reference samples, please sample associated O horizons and request
> appropriate laboratory data for items listed in the included table. As
> data is collected and populated, Soil Survey Interpretations staff at
> NSSC will begin to develop modified soil survey interpretations for
> use by those who wish to use them. For the near term, NSSC plans to
> have soil survey interpretations available for both scenarios - those
> with populated O horizon data and those without O horizon data
> populated. In the future, NSSC will eliminate the option to generate
> soil survey interpretations without O horizon data populated.
>
> If you have further questions, please contact Cathy Seybold at (402)
> 437-4132 or cathy.seybold@nssc.nrcs.usda.gov.

/S/

> MICHEAL L. GOLDEN
>
> Director, Soil Survey Division
>
> Attachment
>
> cc:
>
> Maurice Mausbach, Deputy Chief, Soil Survey and Resource Assessment,
> NRCS,\
> Washington, DC
>
> Robert J. Ahrens, Director, National Soil Survey Center, MS 32, NRCS,
> Lincoln, NE
>
> NCSS National-level Cooperators
>
> State Soil Scientists/MLRA Office Leaders

+-----------------------------------+-----------------------------------+
| **Horizon Level**                 |                                   |
+-----------------------------------+-----------------------------------+
| **Data Element**                  | **NASIS Data Field**              |
+-----------------------------------+-----------------------------------+
| **Horizon designation**           | horizon_designation               |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Horizon Depths**                | horizon_depth_top                 |
|                                   |                                   |
|                                   | horizon_depth_bottom              |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Rock fragments volumes (or wood | fragment_volume (1,rv,h)          |
| fragments)**                      |                                   |
|                                   | fragment_size (1,rv,h)            |
|                                   |                                   |
|                                   | fragment_kind                     |
|                                   |                                   |
|                                   | fragment_hardness (for any        |
|                                   | mineral material)                 |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **In-lieu of texture**            | terms_used_in_lieu_of_texture     |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Organic matter**                | organic_matter_percent (l,rv,h)   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Bulk Density**                  | bulk_density_one_third_bar        |
|                                   | (l,rv,h)                          |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Particle density**              | particle_density                  |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Ksat**                          | sat_hydraulic_conductivity        |
|                                   | (l,rv,h)                          |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Available water capacity        | available_water_capacity (l,rv,h) |
| (AWC)**                           |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **1/3 bar water**                 | water_one_third_bar (l,rv,h)      |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **15 bar water**                  | water_fifteen_bar (l,rv,h)        |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Calcium carbonate equivalent**  | calcium_carbonate_equivalent      |
|                                   | (l,rv,h)                          |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Gypsum**                        | gypsum (l,rv,h)                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Sodium Absorption Ratio** (SAR) | sodium_absorption_ratio (l,rv,h)  |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Electrical conductivity** (ec)  | electrical_conductivity (l,rv,h)  |
+-----------------------------------+-----------------------------------+
| **pH** - Populate the CaCl~2\ pH~ | pH\_.0lm_cac12 (l,rv,h)           |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **pH in water** - Populate if     | pH_1:1_water ((l,rv,h)            |
| available                         |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Cation Exchange Capacity**      | cation_exchange_capcty_NH4OacpH7  |
| (CEC-7) - populate if pH is  5.5 | (l,rv,h)                          |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Effective Cation Exchange       | effective_cation_exch_capacity    |
| Capacity** -(ECEC) Populate if pH | (l,rv,h)                          |
| is \<5.5                          |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+

+-----------------------------------+-----------------------------------+
| **Atterberg Limits (LL, PI)** -   | liquid_limit (l,rv,h)             |
| Populate only if the soils        |                                   |
| classify as organic OH or OL      | plasticity_index (l,rv,h)         |
| according to the UNIFIED          |                                   |
| classification. Do not populate   |                                   |
| for soils that classify as Pt.    |                                   |
| When organic soils are suspected, |                                   |
| a liquid limit test is performed  |                                   |
| on 2 samples of the soil. One     |                                   |
| liquid limit test is performed on |                                   |
| air-dried sample. The second test |                                   |
| is performed on oven-dried        |                                   |
| sample. If the ratio of the       |                                   |
| liquid limit performed on the     |                                   |
| oven-dried sample to the liquid   |                                   |
| limit value of the air-dried      |                                   |
| sample is less than 0.75, then    |                                   |
| the soil is an organic silt (OL)  |                                   |
| or an organic clay (OH). Populate |                                   |
| only the oven-dried Atterbergs.   |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **AASHTO and Unified** - If the   | unified_soil_classification       |
| AASHTO class A-8 and unified      |                                   |
| classes OH, OL, and Pt apply to   | AASHTO_group_classification       |
| the organic layer in question,    |                                   |
| then enter these classes.         |                                   |
| Otherwise, do not populate.       |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Particle Size Separates -**     | clay_total_separate (l,rv,h)      |
| Populate if the organic matter    |                                   |
| content is \< 35%. If the layer   | silt_total_separate (l,rv,h)      |
| contains andic soil materials,    |                                   |
| then populate if the organic      | sand_total_separate (l,rv,h)      |
| matter content is \< 50%. Also,   |                                   |
| populate the sand fractions       | very_coarse_sand_separate         |
| (total sand, vcos, cos, s, fs,    | (l,rv,h)                          |
| and vfs) for soil layers that     |                                   |
| have =\> 35% organic matter       | coarse_sand_separate (l,rv,h)     |
| (needed for wind erosion model).  |                                   |
|                                   | medium_sand_separate (l,rv,h)     |
|                                   |                                   |
|                                   | fine_sand_separate (l,rv,h)       |
|                                   |                                   |
|                                   | very_fine_sand_separate (l,rv,h)  |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Percent Passing Sieves** - If   | sieve_number_4 (l,rv,h)           |
| particle size separates are       |                                   |
| populated, then populate the      | sieve_number_10 (l,rv,h)          |
| sieves. Otherwise do not          |                                   |
| populate.                         | sieve_number_40 (l,rv,h)          |
|                                   |                                   |
|                                   | sieve_number_200 (l,rv,h)         |
|                                   |                                   |
|                                   | rock_frag_3_to_10_in (l,rv,h)     |
|                                   |                                   |
|                                   | rock_frag_greater_than_10_in      |
|                                   | (l,rv,h)                          |
+-----------------------------------+-----------------------------------+
| **K factor**                      | **DO NOT POPULATE**               |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Linear Extensibility            | **DO NOT POPULATE**               |
| Percent** - LEP                   |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| **Component Level**               |                                   |
+-----------------------------------+-----------------------------------+
| Identify and separate drained and | local_phase (to record drained &  |
| undrained map unit components -   | undrained)                        |
| Properties of organic horizons    |                                   |
| (AWC, bulk density, and exchange  |                                   |
| properties) in drained soils are  |                                   |
| significantly different than      |                                   |
| those in undrained soils.         |                                   |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| For organic soils and mineral     |                                   |
| soils with surface organic        |                                   |
| horizons - populate all standard  |                                   |
| component level data, including   |                                   |
| subsidence, dominant land cover,  |                                   |
| and soil water state.             |                                   |
+-----------------------------------+-----------------------------------+