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8 SOIL SURVEY filter the leachate. Sewage lagoons require sealing. Lawns, shrubs, and trees grow well Capability subclas Its ' ' 2-Altvan loam, 1 to 3 percent slopes. This is a dee , well drained soil on terraces at elevations of 4,500 to 4,900 feet. It formed in old alluvium deposited by the major rivers. Included in mapping are small azeas of soils that: show evidence of poor drainage. Also included are small, long and narrow areas of sa6d and gravel deposits. Typically the surface layer of this Altvan soil is grayish brown loam about 10 inches thick The subsoil is brown and light yellowish brown clay loam, and sandy clay loam about 14 inches thick. The substratum is calcareous loamy sand about 5 inches Lhiek over gravelly sand. Permeability and available water capacity aze moderate. The effective rooting depth is 20 to 40 inches. Surface runoff is medium, and the erosion hazard is low.. This soil is used almost entirely for irrigated crops. Tt is suited to all crops commonly grown in the azea, includ- ing corn, sugar beets, beans, alfalfa, small grain, potatoes, and onions. An example of a suitable cropping system is 3 to 4 years of alfalfa followed by corn, corn for silage, sugar beets, small grain, or beans. Land leveling, ditch lining, and installing pipelines may be needed- for proper water application: All methods of irrigation are suitable, but furrow ir- rigation is the most common. Barnyazd manure and eom- mercial fertilizer ai•e needed for top.yields. Windbreaks and environmental plantins of trees and shrubs commonly grown in the azea aze generally well suited to this soil. Cultivation to control competing vegetation should be continued for as many years as possible following planting. Trees that aze best suited and have good survival aze Rocky Mountain juniper, eastern redcedaz, ponderosa pine, Siberian elm, Russian-olive, and hackberry. The shrubs best suited are skunkbush sumac, lilac, Siberian peashrub, and American plum. This soil can produce habitat elements that are highly suitable for opexiland wildlife including pheasant,. cotton- tail, and mourning dove. Such crops as wheat, corn, and alfalfa provide suitable habitat for opexiland wildlife, especially pheasant. -~ Tree and shrub plantings and undisturbed nesting cover would enhance openland wil- dlife populations. ' This Altvan soil has fair to good potential for urban and recreational development. The chief limiting soil fea- tures for urban development are the shrink-swell poten- tial .of the subsoil as it wets and dries- and the rapid permeability of the sand and gravel substratum. Septic' tank absorption fields function properly, but in places the substratum does not contain enough fines to ,properly filter the leachate. Sewage lagoons require sealing. Lawns, shrubs, and trees grow well. Capability subclass IIe imgated. -~ 3-Aquo s an quen s, grave y su s ra um. Thxs nearly level map unit is on bottom lands and flood plains f all the major streams in the survey area. Aquolls, hick have a dazk colored surface layer, make up about 60 percent of the unit. Aquents, which have a lighter colored surface layer, make up about 35 percent. About 5 percent is Aquepts and Bankard sandy loam. These aze deep, poorly drained soils that formed in recent alluvium: No one pedon is typical. Commonly the soils have a mottled, mildly alkaline to moderately al- kaline loamy or clayey surface layer and -underlying material and are underlain by sand or sand and grave] within 48 inches. In places they have a gleyed layer in.the underlying material. Most of the acreage is subject to flooding. The water table is at or neaz the surface early in spring and recedes to as deep as 48 inches late in fall in some years. These soils are used for rangeland and wildlife habitat. Some small areas have been reclaimed by major drainage and leveling and aze used for irrigated crops. The potential native vegetation is dominated by alkali sacaton, switchgrass, and western wheatgrass. Saltgrass, sedge, rush, and alkali bluegrass aze also prominent. Potential production ranges from 3,000 pounds per acre in favorable years to 2,000 pounds in unfavorable years. As tinge condition deteriorates, .the switehgrass, alkali acaton, and- western wheatgrass decrease and saltgrass, sedge,and rush increase. Management of vegetation should be based on taking half and leaving half of the- total annual production. Seed- ing is difficult and costly because numerous tillage prac- tices aze required to eliminate the saltgrass sod. Switchgrass, western wheatgrass, alkali sacaton,. tall wheatgrass, and tall fescue aze suitable for seeding. They can be seeded. into a clean, firm seedbed. Seedbed preparation usually requires more than 1 year to eliminate the saltgrass sod. A grass drill should be used. Seeding early in spring has proven most successful Wetland wildlife, especially waterfowl, utilize this unit. The wetland planta provide nesting and protective cover, as well as some food. The nearby irrigated cropland, where wildlife obtain much of their food and fmd protec- tive cover, makes this unit valuable to both wetland and openland wildlife. Openland wildlife, especially pheasant, use this unit for cover and nesting. Deer fmd excellent cover in some areas. These valuable wildlife areas should be protected from fu•e and fenced to prevent encroachment and overuse by livestock They should not be drained. These soils have good potential as a source of sand and gravel. Capability subclass VIw; Salt Meadow ran a site. 4-Aquo s and Aquepts, flooded. This .nearly level map unit is in depressions'in smooth plains and along the bottoms of natural drainageways throughout the survey area. Aquolls, which have a dazk colored surface layer, make up about 55 percent of the unit. Aquepts, which have a lighter colored surface layer; make up about 25 percent. About 20 percent is soils that are well drained and soils that have sandstone or shale within 48 inches o_f the surface. - _