2010-09-22_REVISION - C1981008 (8)

Home Browse Search

Uedtod Stamm o parbse t of AOrtcnitun L�J NAa/ Rdrataow Candwvaftn SwON 102 Par Raw miAanww. CO 01401 p70,249434074NME dWWA* W4nMG— U@d 3) Similar soils are by definition two or more kinds of soils that can be separated using the tools ( taxonomy) of sod survey, that for an intensive purposes would have no significant impact of use and management for current or foreseeable future uses. If one examines the map unit 14, Bari fine sandy 10001,1 to 3 percent slopes from the San Miguel Soil Survey (see attached), it states "Bari and similar soils 85 percetit'. Now if you examine the two official soil series descriptions for Banc and Dorm — the soil described in the Intermountain report (see attached documents), these soils have m ea11y only one difference • One soil has a horizon that has evidence of trmlocated clay (Bt) in the form clay mlluviation and an increase in clay of at least 3 to 6 percent from the overlying horizons (Bart) compared to a soil (Darvey) that does not cAnibit this clay income. However, both of these soils have the same amount of clay for classification purposes (5a- loamy) and the same amount of calcium carbonate (calcic). In other words, these soils wmW be considered "similar sorts" for the purpose of agriculture (present use). Thane are no significant use or rmnaganaat differences for these two soils. Another thing to point out is the fact that there isn't any partiel"ize analyses data on any of the soil samples listed in the report from Intermountain. This would tend to indicate that texture was probably estimated in the field by the "ribbon method". From over 20 years experience as a soil scierntist hand texturing tens of thousands of samples, and comparing some of these clay estimates to oratory run samples, an experienced soil sciemrtist familiar area, lab with the can hope for at best with hand texturing, a clay estimate accuracy within 3 to 5 percent actual C14Y content about 85'/0 of the time. This accuracy is the margin of error between calling a horizon a Bt — arg&c and a Bw — cambic. And last, if Intermountain cow an order one soil survey as indicated, these two soils (Bart and Darvey) would, if distinguishable in the field, be separated for the intensity (order one) of the survey conducted. These two soils still (even separated) have no significant difference for agricultural purposes. The only reason that Darvey was not included in the Prime Farmland list for the San Miguel Soil Survey is that the Darvey soil was not identified and mapped within the survey arcs. If Darvey had bean identified and mapped under the saw slope, and not used for urban uses, it also would have bean x1entifiedi as Prime Fartnland (once again a similar soil to Barx). David A. Dearstyne . Sort Scientist-Project Leader USDA -MRCS M Eqw opporkml y P,oddrand Em~ Attachment 2.04.9 -6 -6