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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 />'iscussed.
<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 />soil 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 are. similar in.
<br />composition, thickness, and arrangement in the profile. A
<br />soil series commonly is named for a town or.geographic
<br />feature near -the place where a soil of that series was
<br />first observed and mapped. Olney and Nunn, for example,
<br />are names of two soil.series... .
<br />Soils of one series can differ.in texture of the surface
<br />layer or in the underlying. substratum and in slope, ero-
<br />sion, steniness, salinity, wetness, or other characteristics
<br />that. affect their use: On the' basis of such differences, a
<br />soil series is divided into phases.. The name of a soil phase
<br />commonly indicates a feature that affects use: or manage-
<br />ment. For example, Olney fine sandy loam, l.to 3 percent
<br />slopes, is one of several-phases within the Olney series.
<br />Some map units. aze made up of two or more dominant
<br />kinds of soil. Such map units are called soil complexes and
<br />undifferentiatedgroups. .
<br />6 soil complex consists of aeeas of two or more soils
<br />that are so intricately mixed or so small in size that they
<br />•annot be shown separately on the soil map. Each azea~in-
<br />iudes some of each of the two or more dominant soils,
<br />and the pattern and proportion are somewhat similaz in
<br />all areas: Midway-Shingle complex, 5-to 20 percent slopes,
<br />is an example.
<br />An .undifferentiated group is made up of .two or_ more
<br />soils that could. be mapped individually but are mapped as
<br />one unit because there is little value in separating them.
<br />The pattern and proportion of the soils are not uniform. I
<br />An area shown on the map has at least one of the domi-
<br />nant (named) soils or may have all of them. Loup-BoeI
<br />loamy sands, 0 to 3 percent slopes, is an undifferentiated
<br />group in this survey area.:
<br />Most map. units include small, scattered areas 'of soils
<br />other than those that appeaz in the name of the map unit.
<br />Some of these soils have properties that differ substan-
<br />tially from those of the dominant soil or soils .and thus
<br />could significantly affect use and management. of the map
<br />unit: These soils are described in the description of each
<br />map unit. Some of the more unusual or strongly eantrast-
<br />ing soils that aze included aze identified by;a special sym-
<br />bol.on the soil map. '
<br />Most mapped-areas include places that have little or na
<br />soil.material and support little or no vegetation. Such
<br />places are called miscellaneous areas; they are delineated
<br />on the sail map and given` descriptive names.. Rock out-
<br />crop is an example. Some of these areas are too small Eo
<br />tie delineated and are identified by a special symbol. on
<br />e soil -map.
<br />7.
<br />The acreage and proportionate extent of each map unit
<br />are given in ta61e 4, and additional information 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 />1-Altvan 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 areas of sand and gravel 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 Ever gravelly sand.
<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 craps commonly grown in the azea, inc7ud-
<br />ing corn, auger 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 eLiy content
<br />and the rapidly.. permeable substratum slightly .restrict
<br />some, crops.
<br />All 'methods of irrigation are suitable, but furrow ir-
<br />rigation is the most common (fig. 4). Proper imgation,
<br />water management is essential Barnyard manure and
<br />commercial fertilizer maze needed for top yields..
<br />Windbreaks and environmental plantings of trees and
<br />shrubs commonly grown in the azea are generally well
<br />suited to. this. soil. Cultivation to. control -competing
<br />vegetation should be continued for as many years as
<br />possible following pLinting. Trees that are best suited and
<br />have good survival are Rocky Mountain juniper, eastern
<br />redcedaz, ponderosa pine, Siberian elm, Russian-0live, and
<br />hackberry: The shrubs.. best suited are skunkbush sumac,
<br />lilac, Siberian peashrnb; 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 Wand
<br />undisturbed nesting cover would enhance openland wil-
<br />dlife populations.
<br />This Altvan soil. has fair to good potential. for urban
<br />and recreational development. The chief limiting soil fea-
<br />t~res for urban development aze the shrink-swell poten-
<br />tial bf 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 contain enough fines to properly
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