|
<br />The tezture~ranges from ~lbamy fine sand to fine
<br />sand throughout the profile. In places there are a
<br />few lime-coated pebbles on the surface. The soil
<br />:ommonly is leached of lime to a depth ranging from
<br />LS to 30 inches. The pH value ranges from 7.9 to
<br />3.4 in the A horizon and from 7.9 to 8.4 in the C
<br />iorizon. The alkali substratum phase has pH values
<br />.n the lower part of the C horizon ranging from 8.5
<br />:0 10.0.
<br />Space City loamy fine sand, 0 to 3 percent slopes
<br />SpB).--This sloping soil occupies areas along the
<br />~ase of Mount Blanca and a few isolated low ridges
<br />~n the valley floor. It has the profile described
<br />s representative for the Space City series. Sur-
<br />'ace runoff is very slow. The hazard of erosion is
<br />ery severe if the vegetative cover is removed.
<br />Included in mapping are small areas of Costilla
<br />oils.
<br />'[his soil is used mainly for range that is grazed
<br />y cattle, antelope, and deer. Some small areas on
<br />he valley floor are under irrigation and are used
<br />rr alfalfa, potatoes, and small grains. These
<br />teas generally are included in fields made up most-
<br />~ of other soils. Capability units IVe-1 (irri-
<br />ited) and VIIe-1 (nonirrigated); Sandy Bench range
<br />te.
<br />Space City loamy fine sand, alkali substratum, 0
<br />~ 3 percent slopes (SrB).--This soil occupies low
<br />dges on the valley floor, mainly in the northeast-
<br />n part of the survey area. A few small areas are
<br />~uthwest of the Rio Grande River. The soil has a
<br />ofile similar to the one described as representa-
<br />ve for the Space City series, except that it has a
<br />ep water table and is very strongly alkaline at a
<br />pth below 24 inches. Because the~soil is less
<br />kal ine above this depth, shallow-rooted plants
<br />n grow in it, and so can grasses that are not
<br />tali tolerant. Tn addition, however, the soil is
<br />ited to deep-rooted, alkali-tolerant plants, such
<br />greasewood and four-wing saltbush. Surface run-
<br />F is slow. The hazard of erosion is very severe
<br />the vegetative cover is removed.
<br />Included in mapping are a few small areas of
<br />•lett soils. Also included are small areas of
<br />:opaxi sand.
<br />This soil is used mainly for range. Indian rice-
<br />~ss, blue grama, sand dropseed, spike dropseed,
<br />~rt and tall rabhitb rush, four-wind saltbush, and
<br />~ greasewood make up the vegetative cover. A few
<br />11 areas are irrigated and are used for alfalfa.
<br />ability units IVe-1 (irrigated) and VIIe-4 (non-
<br />igeted); Valley Sand range site.
<br />Space City-Hooper complex, hilly (StE).--This
<br />Alex consists of Space City loamy fine sand, alka-
<br />substratum; Hooper loamy sand; and, in small
<br />ins, Hooper clay loam. These soils are in such
<br />ricate patterns that it is impractical to separate
<br />0 on the soil map.
<br />'he Space City soil occupies dune areas and makes
<br />t0 to 60 percent of the complex. The Hooper
<br />.s occur in low areas between the dunes and make
<br />
<br />up 40 to 60 percent of the complex. Surface runoff
<br />is very slow. The hazard of soil blowing is very
<br />severe if the vegetative cover is not maintained.
<br />The vegetation on the Space City soil consists
<br />of spiny mutely, blue grama, Indian ricegrass, spike
<br />dropseed, rabbitbrush, and some greasewood. The
<br />vegetation on Hooper loamy sand is saltgrass, alkali
<br />sacaton, and greasewood. Hooper clay loam supports
<br />only a few stunted greasewood plants. This complex
<br />is used as range for livestock and wildlife. Capa-
<br />bility unit VIIe-4 (nonirrigated); Space City soil
<br />is in Valley Sand range site; Hooper loamy sand is
<br />in Salt Flats range site; Hooper clay loam is not in
<br />a range site.
<br />Uracca Series
<br />The Uracca series consists of somewhat excessive-
<br />ly drained, moderately steep, very cobbly soils on
<br />alluvial fans at the foot of the Sangre de Cristo
<br />Range along the eastern edge of the San Luis Valley.
<br />These soils formed in alluvium, and there are many
<br />large cobblestones of acid igneous origin throughout
<br />the soil and covering a large part of the surface,
<br />Depth to cobblestones and gravel commonly is less
<br />than 2 feet.
<br />In a representative profile, the surface layer is
<br />very dark grayish-brown very cobbly loam. It is
<br />noncalcareous, moderately alkaline, and about 4
<br />inches thick, and approximately 60 percent cobble-
<br />stones. The subsoil is dark-brown or very dark
<br />grayish-brown very cobbly clay loam and very cobbly
<br />coarse sandy loam that is noncalcareous, moderately
<br />alkaline, and about 9 inches thick. It is 60 to 75
<br />percent cobblestones throughout. The substratum is
<br />dark-brown and dark grayish-brown very cobbly coarse
<br />loamy sand or very cobbly coarse sandy loam. It is
<br />noncalcareous in the upper part, is moderately cal-
<br />careous in the lower part, and is moderately alka-
<br />line. This layer is about 75 percent cobblestones,
<br />and the percentage of cobblestones increases with
<br />depth. Between depths of 23 and 60 inches are
<br />cobblestones, gravel, and some boulders.
<br />Uracca soils have moderate permeability in the
<br />subsoil and very rapid permeability in the substra-
<br />tum. They have very low available water holding
<br />capacity.
<br />The vegetation is pinyon pine, juniper, mountain
<br />mutely, blue grama, Arizona fescue, junegrass, mutton-
<br />grass, needle-and-thread, rabbitbrush, fringed sage,
<br />and mountain-mahogany. These soils are used as
<br />range for limited livestock grazing and for wildlife
<br />cover.
<br />Representative profile of Uracca very cobbly
<br />loam, 15 to 35 percent slopes, 0.1 mile west and
<br />0.15 mile north of the southeast corner of sec. 5,
<br />T. 29 S., R. 73 W.:
<br />Al--0 to 4 inches, grayish-brown (lOYR S/2) very
<br />cobbly loam, very dark grayish brown (lOYR 3/2)
<br />when moist; weak and moderate, medium, granu-
<br />lar structure; soft when dry, friable when
<br />moist; noncalcareous; pH 8.2; approximately 60
<br />percent cobblestones; clear, smooth boundary.
<br />33
<br />
|