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Colby Sne sandy loam, 0 to 1 percent slopes (CfA).-
<br />1'his soil occurs mostly in irrigated areas on nearly level
<br />stream terraces. It has a weapcly stratified substratum in
<br />many places. In some places the substratum is below a
<br />dept of 30 inches and consists o[ sand.
<br />Water penetrates this soil moderately rapidlyy, and
<br />.surface drainsge is moderately slow. The water-holdin
<br />:specify is medium, and most of the water held in the soft
<br />.is available to plains. Natural fertility is moderate, but
<br />additions of phosphorus are generally needed in fields
<br />planted to alfalfa or sugar beets.
<br />A large part of this soil is under irrigation and is well
<br />suited to that use. The soil is easily worked and managed
<br />under imganon. Land leveling improves uniformity in
<br />Jthe spread of water. Barnyard manure and green-manure
<br />crops help in maintaining organic matter and fertility.
<br />Smap areas of this soil are dry farmed. In these areasi
<br />stubble-mulch tillage and stripcropping should be used so
<br />that moisture is conserved and wind erosion is controlled.
<br />Other areas are in native range grasses and are well suited
<br />to grazing. (Irrigated capability unit IIs-2; dryland
<br />capability unit lVe-3; Loamy Platns range silo)
<br />Hornman clay loam, sand substratum, 0 to 1 percent
<br />elopes (KnA).-This soil is on bottom lands or low ter-
<br />races that are nearer the channel of the Arkansas River
<br />than those occupied by other Kornman soils. Its subsoil
<br />is more stratified than that o[ the other Komman soils.
<br />Because this soil has a substratum of sand and gravel at a
<br />~ depth of 20 to 36 inches, internal drainage is more rapid
<br />than that of the less sandy Kornman soils, and conse-
<br />quently, the water-holding capacity is low.
<br />This soil is droughtyy and loses the water that penetrates
<br />deeply into its gravelly substratum; therefore tt needs to
<br />be u•ngated more frequently and more care[ul~y than soils
<br />that have a finer textured subsoil and substratum. Land
<br />leveling helps to spread the irrigation water uniformly.
<br />Barnyard manure and green-manure cro s help to main-
<br />rasa the content o[ organic matter and to improve filth.
<br />On this sus! timely tillage is important because rt prevents
<br />excessive cloddiness and compacting: (Irrigated capability
<br />~~ unit IVs-1) _ - - _ _ ..
<br />Las loam {0 to 1 percent slopes) (La).-This soil has e
<br />subsoil that is normally clay loam, though in some areas it
<br />is stratified loam. 'f'he soil is slightly to moderately
<br />salute. It is less saline in the places where drainage
<br />ditches have been established, and in chose places the
<br />water table is not so high.
<br />This soil takes in water at a medium rate, but pennea-
<br />bility of the subsoil is slow. The water-holding capacity ie
<br />high, and the water stored is readily available to plants,
<br />except in the snore saline areas. Tbis soil is essy to work
<br />and leas hi b natural fertility.
<br />This soil is used both for irrigated crops and for per-
<br />manent grass. IL is well suited to irngatton if tt is
<br />drained, leached of salts, and well managed. Yields of
<br />most craps grown on this soil are high. Sugar beets,
<br />sorghum, and truck crops are grown on a large acreage.
<br />7o cultivated areas a drainage system is generally used to
<br />lower the water table enough for plant growth, and this
<br />drainage system must be maintained. Land leceling helps
<br />to spread irrigation water uniformly. Barnyard manure
<br />,and green-manure crops help to maintain the content of
<br />organic matter and to improve soil filth. (Irrigated
<br />cappability unit IIw-2; dryland capabilbty unit 1'Iw-1;
<br />Salt'tfeadow range site)
<br />Lasloam,elaysubstratum to percent-slopes} (Lb).-
<br />This soil has s substratum of wet, mottled clay at a depth
<br />of 36 to 60 inches. Therefore, internal drainage is very
<br />slow. In some places the clay is underlain by sand.
<br />i Sorghum, sugar beets, and truck crops are grown on a
<br />~ large acreage and do well on this soil. This soil is also
<br />good for range, and it produces high yields of meadow
<br />~ grasses. It is difficult to drain; drainage must be estab-
<br />~ ~ished or maintained, however, to keep the water table
<br />lave enough [or the growth of crops. Careful managemeut
<br />of irrigatiou water is necessary to piecent ocerirri~ation.
<br />Land leceling helps to spread the water uniiponnly.
<br />Barnyard manure and green-manure crops help to main-
<br />tain the content of organic matter and to improve filth.
<br />(Irrigated capability unit IIIw-1; dryland capability
<br />unit~Iw-1; Salt Meadow range site)
<br />Las clay loam (0 to 1 percent slopes) (Lc).-This soil
<br />is silted end has a surface layer of heavy clap loam be-
<br />cause muddyy imgation water lies been used to irrigate
<br />the Selds. It is more difficult to work than the Las ]gams,
<br />and it takes in water at a slower rate.
<br />It it is managed well, this soil produces high yields of
<br />sorghum, sugar beets, alfalfa, and truck crops. In most
<br />irrigated areas, drainage ditches keen the water table low
<br />enough for the growth of crops. It u necessary to main-
<br />tain these drainage ditches. Land leceling helps to spread
<br />the irrigation venter uniformly. Alaintaining good filth is
<br />iimportant; timely tillage prevents excessive doddiness
<br />'end compacting. Barnyard manure and green-manure
<br />'crops help to maintain the content of organic matter end
<br />to improve soil filth. (Irrigated ca ability unit IIw-2•
<br />a~.i...,a ---_i.:r.......,:. vra._i. e..t.~t.re~.t.,a...,..,.o ~;fei
<br />Colby silt foam, 0 to I percent slopes (CmA).-This soil
<br />occurs on nearly level stream terraces m the irrigated part
<br />of the coun~ (fig. 9). The substratum commonly is
<br />wealtly strat ed loam and very fine sandy loam, and m
<br />some areas sand and gravel occur at s depth o[ 36 to 60
<br />inches. '
<br />This soil takes in water at a medium rate. The water
<br />holding capacity is hi h, and most o[ the water held in the
<br />soil is readily available to plants. Natural fertility is
<br />medium.
<br />This soil is used for irrigated [arming, d~yland farming,
<br />and grazing. It is welPsmted to imgated (arming and to
<br />all crops normally grown in the county. The soil is easy
<br />to work, but land leveling may be needed to spread water
<br />more uniformly. The response to fertilization and to
<br />imgation management is good. ___
<br />Drt--farmed areas are susceptible to wind erosion.
<br />Stubble-mulch tillage helps to maintain the conteut of
<br />organic matter, to conserve moisture, end to control
<br />erosion. Stripcropping helps to control wind erosion.
<br />This soil is e•ell suited to permanent grass. Areas i^
<br />native grasses should not be plowed and used for dry-
<br />[ermiug. (Irrigated capability unit I-1; dn-land caps-,
<br />bilit}' units I~'e-t in climatic zone C, ~'Ie-? in climatic
<br />zone D; Loamy Plains ren~e site)
<br />Gle a sad Havre sods, sand substrata, 0 to 1 percent
<br />slopes (GnA).-This mapping unit is 70 percent Glendive
<br />soil and 30 percent Havre soil. The Glendive soil is simi-
<br />lar to Glendive fine sandy loam, 0 to I percentslopes, and
<br />the Havre soil is similar to Havre loam, except that both
<br />of these soils overlie sand and gravel at a depth of 20 to 36
<br />inches. These soils occur only in areas that are irrigated
<br />from the canal system.
<br />Because these soils are moderately shallow to coarse-
<br />textured material, theyy have very rapid internal drainage
<br />and are droughty. 1'he water-holding capacity is low,
<br />but most o[ the water stored is teadil3• available to plants.
<br />Good management of water is needed in irrigated areas.
<br />Water is use~more efficiently if the irrigation runs are
<br />abort. Deep cuts should not be made when land leceling
<br />is done. In dry-farmed areas, stubble-mulcb tillage sad
<br />stripcropping are effective in conserving moisture and
<br />controlling erosion. (Irrig~~ed capability unit IlIs~l;
<br />dr}9and cepabilit)• units Ige-4 in c matic zone C, ~'Ie-4
<br />in climatic zone } ;Glendive soil is in Sand}.Bottom Lend
<br />rauge site, and_Ha~Te soil is in Loamy Plows range site)
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