NRCS Soils
Natural Resource Conservation Service (NRCS) is the federal agency responsible for mapping soils and designating prime soils and soils of significance.  It is good to keep in mind when looking at soil maps or thinking about soil distribution that soil types and classifications do not necessarily adhere to strict soil boundaries and adjoining soil types are layered into one another.  Every soil map unit includes some soils that belong to other taxonomic classes.  These other soils are called inclusions or included soils.  Therefore prime soils can include non-prime components and non-prime soils can include prime components. 

According to current NRCS soils scientists, updates to the official soil survey database are reviewed and entered annually.  This can include performing field verifications of soil map unit boundaries or re-evaluating criteria used to determine soil map unit designations.  The hardcopy Soil Survey of Whatcom County Area, Washington was published in 1992 and included a list of prime soils that Whatcom County Planning and Development Services has been using as the official prime soil list.  

The NRCS uses a program called NASIS (National Soil Information System) to manage and decipher soil database information.  This allows NRCS soil scientists to develop criteria for prime farmland classification that the NASIS program uses to enact farmland classifications across the full NRCS soil database, or Soil Survey Geographic Database (SSURGO).  

Whatcom County has updated its GIS soils data to reflect the most current NASIS farmland designation criteria.  This adjustment has included changing prime soil classification type for certain soils and has included the addition of several soils to the Prime and Other Important Farmlands list.  

Below is an updated list that demonstrates prime soil number and the type of prime soil it implies.  
Classification #
0 ~ Not prime farmland
1 ~ All areas prime farmland
2 ~ Prime if drained
3 ~ Prime if protected from flooding or not frequently flooded during the growing season
4 ~ Prime if irrigated
5 ~ Prime if drained and either protected from flooding or not frequently flooded during the growing season
6 ~ Prime if irrigated and drained
7 ~ Prime if irrigated and either protected from flooding or not frequently flooded during the growing season
8 ~ Prime if subsoiled, completely removing the root inhibiting soil layer
9 ~ Prime if irrigated and the product of I(soil erodibility) x C(climate factor) does not exceed 60
10 ~ Prime if irrigated and reclaimed of excess salts and sodium
30 ~ Farmland of Statewide Importance*
50 ~ Farmland of Local Importance**
70 ~ Farmland of Unique Importance***
taken from National Soil Survey Handbook Part 622
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