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WELD COUNTY, COLORADO, SOUTHERN PART
<br />brief description of the soil profile. In each description,
<br />the .principal hazards and limitations .are indicated, and
<br />-the management concerns and practices needed are
<br />discussed.
<br />The map units on the detailed soil maps represent an
<br />area on the landscape made up mostly of the soil or soils
<br />for which the unit is named. Most of the delineations
<br />shown on the detailed soil map are phases of soil series.
<br />Soils that have a profile that is almost alike make up a
<br />aoi! series. Except for allowable differences in texture of
<br />'the surface layer or of the underlying substratum, all the
<br />soils of a series have major horizons that- aze similaz in
<br />'composition, thickness, and arrangement in the profile. A
<br />~R series commonly is named for a town or geographic
<br />',feature near the place where a soil of that series was
<br />fast observed and mapped. Olney and Nunn, for example,
<br />Rre names of two soil series.
<br />~<° $oiLs.of one series can differ in texture of the surface
<br />iJayer or in the underlying substratum and in slope, ero-
<br />'eion;•stoniness, salinity, wetness, or other characteristics
<br />that affect their use. On the basis of such differences, a
<br />•,go1 series is divided into phases. The name of a soil phase
<br />=epmmonly indicates a feature that affects use or manage-
<br />l[ICnt. For example, Olney fine sandy loam, 1 to 3 percent
<br />;®lopea, is one of several phases within the Olney series.
<br />Some map units aze made up of two or more dominant
<br />F~Clnde of soil. Such map units aze called soil"complexes and
<br />;;. ffferentiated groups.
<br />~'A soil complex consists of areas of two or more soils
<br />that are ao intricately mixed or so small in size that they
<br />Oanbot be shown separately on the soil map. Each area in-
<br />~Clttdea some of each of the two or more dominant soils,
<br />lad: the pattern and proportion aze somewhat similar in
<br />~sfl°areas. Midway-Shingle complex, 5 to 20 percent slopes,
<br />r~ aR example.
<br />At1 undifferentiated group is made up of two or more
<br />that could be mapped individually but are mapped as
<br />ONB~tmit because there is little value in separating them.
<br />,pattern and proportion of the soils are not uniform.
<br />:area shown on the map has at least one of the domi-
<br />~:
<br />~_(named) soils or may have all of them: Loup-Boel
<br />y sands, 0 to 3 percent slopes, is an undifferentiated
<br />in this survey area.
<br />ost map units include small, scattered areas of soils
<br />than those that appear in the name of the map unit.
<br />"af these soils have properties that differ substan-
<br />Ffirom those of the dominant soil or soils and thus
<br />gignifieantly affect use and management of the map
<br />xThese soils are described in the description of each
<br />;knit Some of the more unusual or strongly contrast-
<br />that aze included are identified by a special sym-
<br />the soil map.
<br />fi;-mapped areas include places-that babe little or no
<br />and support little or no vegetation. Such
<br />:are called miscella~zeous areas; they are delineated
<br />,,Haoii map and given descriptive names. Rock out-
<br />. ,an example. Some of these areas are too small to
<br />ted and are identified by a special symbol on
<br />feel........
<br />The acreage and proportionate extent of each map unit
<br />are given in table 4, and additionalinformation.on proper-
<br />ties, limitations, capabilities, and potentials for many soil
<br />uses is given for each kind of soil in other tables in this
<br />survey. (See "Summary of tables:') Many of the terms
<br />used in describing soils are defined in the Glossary.
<br />Soil descriptions
<br />71- tvan loam, 0 to 1 percent slopes. This is a deep,
<br />well drained soil on terraces at elevations of 4,500 to 4,900
<br />feet. It formed in old alluvium deposited by the major
<br />rivers. Included in mapping are small areas of soils that
<br />show evidence of poor drainage. Also included are small,
<br />long and narrow aeeas of sand and grave] deposits.
<br />Typically the surface layer of the Altvan soil is grayish
<br />brown loam about 10 inches thick. The subsoil is brown
<br />and light yellowish brown clay loam and sandy clay loam
<br />.about 15 inches thick The substratum is calcareous loamy
<br />sand about 6 inches thick-over gravelly sandy
<br />Permeability and available water capacity are
<br />moderate. The effective rooting depth is 20 to 40 inches.
<br />Surface runoff is slow, and the erosion hazazd is low.
<br />This soil is used almost entirely for irrigated crops. It
<br />is suited to all crops commonly grown in the area, includ-
<br />ing corn, sugaz beets, beans, alfalfa, small grain, potatoes,
<br />and onions. An example of a suitable cropping system is 3
<br />to 4 years of alfalfa followed by corn, corn- for silage,
<br />sugar beets, small grain, or beans. The high clay content
<br />and the rapidly permeable substratum slightly restrict
<br />some crops.
<br />All -methods of imgation are suitable, but .furrow ir-
<br />rigation is the most common (fig. 4). Proper~nigation
<br />water management is essential. Barnyard manure and
<br />commercial fertilizer aze needed for top yields.
<br />Windbreaks and environmental plantings of trees an
<br />shrubs commonly grown in the area are generaIIy we
<br />suited to this soil. Cultivation to control competin
<br />vegetation should . be continued for as manl. years- a
<br />possible following planting. Trees that are best suited and
<br />have good survival are Rocky Mountain juniper, eastern
<br />redeedar, ponderosa pine; Siberian elm, Russian-olive, and
<br />hackberry. The shrubs best suited are skunkbush sumac,
<br />lilac, Siberian peashrub, and American plum.
<br />This soil•can produce habitat elements that aze highly
<br />suitable for openland wildlife, including pheasant, cotton-
<br />tail, and mourning dove. Such crops as .wheat, corn, and
<br />alfalfa provide suitable habitat for openland wildlife,
<br />especially pheasant. Tree and shrub plantings and
<br />undisturbed nesting cover would enhance openland wil-
<br />dlife populations.
<br />This Altvan soil has fair to good potential fir urban
<br />and recreational development. The chief limiting soil fea-
<br />tures for urban development are the shrinl;-swell poten-
<br />tial of the subsoil as it wets and dries and the rapid
<br />permeability of the sand and gravel substratum. Septic
<br />tank absorption fields function properly, but in places the
<br />substratum does not coniain enough fines to properly
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