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18 Soil survey
<br />causes blue grama and buffalograss to form a dense
<br />sod. Continued overuse will result in the invasion of
<br />undesirable plants. Overgrazing increases runoff and
<br />water erosion. Mechanical practices such as pitting and
<br />contour furrowing help to decrease runoff.
<br />Badly deteriorated range can be improved or cropland
<br />converted to range by using a mixture selected from
<br />recommended varieties of western wheatgrass, little
<br />bluestem, sideoats grama, blue grama, and crested,
<br />pubescent, or intermediate wheatgrass. The seedbed
<br />should be firm and as free as possible of competition
<br />from perennial plants. The clean, firm stubble of
<br />sorghum or millet is suitable as a seedbed. For best
<br />results, seeding should take place early in spring.
<br />Wildlife habitat, especially for openland and rangeland
<br />wildlife, is an important secondary use for this soil.
<br />Habitat favorable for ring- necked pheasant, mourning
<br />dove, and many nongame species can be developed on
<br />cropland by establishing nesting and escape cover.
<br />Undisturbed nesting cover is vital for pheasants and
<br />should be developed, especially in areas of intensive
<br />agriculture. Rangeland wildlife, for example, the
<br />pronghorn antelope, can be encouraged by developing
<br />livestock watering facilities, by properly grazing livestock,
<br />and by range seeding, if needed. Openland wildlife can
<br />be encouraged by planting the trees and shrubs
<br />generally adapted for windbreak plantings.
<br />This soil generally is well suited to windbreaks and
<br />environmental plantings. Summer fallow a year before
<br />planting, supplemental water during planting and in the
<br />early stages of growth, and continued cultivation for
<br />weed control are needed to insure the establishment and
<br />survival of plantings. The trees that are best adapted
<br />and that have a good chance of survival are Rocky
<br />Mountain juniper, ponderosa pine, Siberian elm, Russian -
<br />olive, and hackberry; the shrubs are skunkbush sumac,
<br />lilac, Siberian peashrub, and American plum.
<br />This soil is well suited to use as sites for houses and
<br />as septic tank filter fields. However, because of the low
<br />bearing strength of this soil, foundation footings need to
<br />be sufficiently wide to provide a safety margin to support
<br />the weight of buildings.
<br />Capability subclass IVe, nonirrigated, and IIle, irrigated.
<br />11 —Colby silt loam, 6 to 15 percent slopes. This is
<br />a deep, well drained, rolling soil on low hills. It formed in
<br />calcareous loess. The areas of this soil are in the
<br />southeastern part of the county and are as much as
<br />1,200 acres in size.
<br />Included in mapping and making up about 10 percent
<br />of this map unit are Kuma silt loam and Keith silt loam
<br />and a dark - colored silty soil that is similar to this Colby
<br />soil and is at the base of slopes and in swales between
<br />hills.
<br />Typically, the surface layer is light brownish gray,
<br />calcareous silt loam about 8 inches thick. The underlying
<br />material, to a depth of 60 inches or more, is very pale
<br />brown, calcareous silt loam. In places, the surface layer
<br />/ ?.b
<br />is fine sandy loam. In some areas, the surface layer is
<br />darker than is typical.
<br />Permeability is moderate. The available water capacity
<br />is high. Surface runoff is medium. Water erosion is a
<br />severe hazard, and soil blowing is a moderate hazard.
<br />About 90 percent of the acreage of this map unit is
<br />rangeland, and about 10 percent is used for nonirrigated
<br />winter wheat. This soil is not suited to nonirrigated row
<br />crops because erosion accelerates if the soil is tilled.
<br />This soil is only marginally suited to irrigated crops
<br />because of the severe hazard of water erosion and the
<br />steepness of slopes. Erosion can be minimized by
<br />growing small grains, hay, or grasses at least half of the
<br />time, by leaving the crop residue on the soil, and by
<br />properly managing irrigation water.
<br />The potential native vegetation is dominantly
<br />needleandthread, sideoats grama, little bluestem,
<br />western wheatgrass, and blue grama. Continuous heavy
<br />grazing causes little bluestem, sideoats grama, and
<br />western wheatgrass to decrease in the plant community;
<br />blue grama and buffalograss will increase, forming a
<br />dense, low- producing sod. Grazing management can
<br />help to reduce runoff and improve the range condition.
<br />Mechanical practices are effective on the gentler slopes.
<br />Cropland can be converted to range or deteriorated
<br />range can be improved by seeding with a mixture
<br />selected from recommended varieties of western
<br />wheatgrass, sideoats grama, little bluestem, blue grama,
<br />and crested, pubescent, or intermediate wheatgrass. The
<br />seedbed should be firm and as free as possible of
<br />competition from perennial plants. The clean, firm
<br />stubble of sorghum or millet is suitable as a seedbed.
<br />Plant residue or stubble on the surface can help to
<br />reduce soil blowing and water erosion. For best results,
<br />seeding should take place early in spring.
<br />Wildlife habitat, especially for rangeland wildlife, is an
<br />important secondary use for this soil. Rangeland wildlife,
<br />for example, the pronghorn antelope, can be encouraged
<br />by developing livestock watering facilities, by properly
<br />grazing livestock, and by range seeding, where needed.
<br />This soil generally is suited to windbreaks and
<br />environmental plantings. Sites need to be carefully
<br />selected and special practices need to be used in
<br />planting. Site preparation includes construction of level
<br />terraces a year in advance in which to plant the trees.
<br />Weeds on the terraces need to be controlled before and
<br />after planting. The trees that are best adapted and that
<br />have a good chance of survival are Rocky Mountain
<br />juniper, ponderosa pine, Siberian elm, Russian - olive, and
<br />hackberry; the shrubs are skunkbush sumac, lilac,
<br />Siberian peashrub, and American plum.
<br />This soil is suited to use as homesites and septic tank
<br />filter fields. Special design is required in some areas
<br />because of the moderately steep slopes. Because of the
<br />low bearing strength of the soil, foundation footings for
<br />houses should be wide enough to provide a safety
<br />margin of support for the weight of the building.
<br />Capability subclass Vle, nonirrigated and irrigated.
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