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Niwot Series,
<br />The Niwot series is made uo of deep, somewhat poorly drained
<br />soils that era shallow over Eravelly ssnd, These soils formed
<br />on low terraces and bottom lands in loamy alluvium super-
<br />imposed over ssnd and gravel. Slopes are 0 to 1 percent,
<br />Elevations are 4,900 to 5,500 feet, The native vepetstions
<br />is mainly bromegrass and water-tolerant grasses, Ann~isl
<br />precipitation is 12 to 18 inches, 'mean annual air tempera-
<br />ture is 48° to S2° ~'., and the frost-free season is al~out
<br />140 to 155 days ,
<br />In a representative profile the surface layer is dark arsc-
<br />ish-brown end grayish-brown clan loam and loam, about 14
<br />inches thick, that is :mottled in the lower Dart, The under-
<br />1?ing material that extends to a depth of 50 inches or more
<br />is Dale-brown gravelly ssnd that contains many mottle:i,
<br />In the surface layer, soil reaction is mildly alkalin<~, and
<br />below this, it is neutral,
<br />Niwot soils have mo~erate pemneabilit?, Available wst:er
<br />cspacitp for the profile is low to moderate. Roots ce~n
<br />penetrate to a depth of b0 inches or more, and the se~.sonal
<br />high water table is at a depth of between 6 and 18 inches,
<br />Most of this acreage is used for pasture, Some small areas
<br />are used for irrigated crops, and an increasing number of
<br />• areas are used for sand and gravel pits.
<br />Representative profile of Niwot al ay loam in an area cf
<br />Niwot soils that has slopes of 0 to 1 percent, located
<br />2,100 feet south and 100 feet west of the center of sec.
<br />10, T. 1 N., R. 6q W,;
<br />A11 - 0 to 6 inches, dark grayish-brown (10`!R 4/2)
<br />cls? loam, ver? dark brown (10~!R 2/z)
<br />when :Hoist; moderate, fine ¢ranular
<br />structure: soft, very friable: mildl^
<br />alkaline; clear, smooth bounder.,.
<br />A12 - 5 to 14 inches, gra;•ish-brown (10`rR 5/2)
<br />loam With common, medium, distinct, strorip-
<br />brown (7.SYR 5/b) mottles, very dark gra~•-
<br />ish brown (10YR 3/2) when moist; weak
<br />coarse, subangular blocky structure that
<br />parts to mo~erate, fine, granular; slight-
<br />ly hard, soft, ver? Friable: mildly
<br />alkaline; Rradual, wavy boundary,
<br />IIc - 14 to 60 inches, pale-brown (10`!R 6/3)
<br />gravelly sand with many, distinct
<br />large, stropsq-bro~+n (7.5YR $/b) mottles,
<br />brown (10XR 5/3) when tnoiat; single
<br />grain; loose dry or moist; neutral.
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