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PROWERS COUNTY, COLORADO
<br />This soil is gravelly and has rough, broken relief that
<br />easily distinguishes it from other soils. Outcrops of
<br />limestone and sandstone are common. Except in small
<br />areas, the many small draws, gullies, and ravines that
<br />drain this soil occur close together in a dendritic pattern.
<br />These drainageways form a complex pattern on the slopes.
<br />Included in some areas mapped as this soil are smaller
<br />areas of Nihill, Potter, and Stoneham soils.
<br />This soil takes in water at a moderately rapid rate and
<br />has very rapid permeability in the subsoil. The water-
<br />holdin~ capacity is very low, but most of the water held in
<br />the. soil is readily available to plants. bight, frequent
<br />rains are therefore very beneficial to plants on this soil.
<br />Natural fertIlity is very low.
<br />If it is dry farmed, this soil is hard to work and to man-
<br />age. It is slightly susceptible to wind erosion and
<br />moderately susceptible to water erosion. Most drainage-
<br />ways are gullied, and some are severely guIlied. (Dryland
<br />capability unit VIIs-1; Gravel Breaks range site)
<br />Colby Series
<br />The Colby series consists of well-drained, moderately
<br />shallow to deep soils that developed in calcareous loamy
<br />and silty material. These soils occur throughout the
<br />cmutty.
<br />The surface layer is silt loam or fine sandy loam that
<br />is light brownish gray and soft when dry and brown and
<br />very friable when moist. It is about d ho 10 inches thick
<br />and has granular structure. Tho subsoil is silt loam
<br />that, in most places, extends to a depth of more than 5
<br />feet. The upper part of the subsoil is lighter colored
<br />than the surface layer, and the lower part is brown.
<br />These soils are calcareous throughout.
<br />The main variations in Colby soils are in the texture
<br />of the surface layer and in the depth to the contrasting
<br />substratum.
<br />Colby soils have a profile similar to that of the Wiley
<br />soils. They have weaker structure than the tiViley soils
<br />and a slightly coarser textured subsoil. They are slightly
<br />coarser textured than the Ulysses soils and have a lighter
<br />colored surface layer.
<br />The native vegetation in areas of silt loam is mostly
<br />blue grams and huffalograss, and in areas of fine sandy
<br />loam it is sand sage, little bhtestem, and sand dropseed.
<br />Common on the terraces are snakeweed and little rabbit-
<br />brush.
<br />/ Colby fine sandy loam, 0 to 1 percent slopes (CfA),-
<br />This soil occurs mostly in irrigated areas on nearly level
<br />etream terraces. It has a weakly stratified substratum in
<br />many places. 7n some places ttie substratum is below a
<br />depth of 30 inches and consists of sand.
<br />tiVater penetrates this soil moderately rapidly, and
<br />surface drainage is moderately slow. The water-holding
<br />capacity is medmm, and most of the water held iu the soil
<br />is awaflable to plants, 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 irrigation. Lturd leveling improves uniformity in
<br />the spread of water Barnyard manure and green-manure
<br />crops help in maintaining organic mat-ter and fertility.
<br />13
<br />Small areas of this soil are dry farmed. In these areas
<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 Its-2; dryland
<br />capability unit IVe-3; Loamy Plains range site)
<br />Colby fine sandy loam, 1 to 3 percent slopes (Cf6).-
<br />Most of this soIl has slopes of 1 to 2 percent, but in places
<br />the slope ranges a to 3 percent.
<br />Because this soil is more sloping than Colby fine sandy
<br />loam, 0 to 1 percent slopes, contour ditches and shorter
<br />irrigation runs are needed to obtain proper irrigation and to
<br />control erosion.-Fewer vegetable crops are grown on this
<br />soil than on Colby fine sandy loam, 0 to 1 percent slopes.
<br />Small areas of this soil are dry farmed. In these areas
<br />stubble-mulch tillage, contour farming, terracing, and
<br />stripcropping are needed to conserve moisture and to
<br />control erosion. Other small areas are in native range
<br />grasses and are well suited to grazing. (Irrigated capa-
<br />bility unit IIe-3; dryland capability trait IVe-3; Loamy
<br />Plains range site)
<br />Colby $ne sandy loam, 0 to 3 percent slopes (CfAB),-
<br />This soil occurs mostly on uplands south of the sandhills,
<br />where the soils are deeper and more uniform in texture
<br />than those on stream terraces.
<br />This so$ is used mostly for dryland farming and for
<br />native range gt•asses, Sorghum is best suited to dry-
<br />farmed areas, though wheat can be grown if crop residue is
<br />kept on the surface to control soil blowing, Stubble-
<br />mulch tillage, contour farming, terracing, and strip-
<br />cropping help to conserve moisture and to control erosion.
<br />Barnyard manure and green-manure crops in irrigated
<br />areas help to maintain the supply of organic matter. In
<br />irrigated areas land leveling may be needed to spread
<br />irrigation water more uniformly. (Irrigated capability
<br />unit IIe-3; dryland capability unit IVe-3; Loamy Plains
<br />range site)
<br />Colby fine sandy loam, 3 to 5 percent slopes (CfC).-
<br />This soil occurs on uplands south of the sandhills. It is
<br />deep and has a substratum of uniform texture.
<br />This soil is used both For range and dryland cultivation.
<br />It is well suited as range but is highly susceptible to erosion
<br />in dry-farmed areas. Stubble-mulch tillage, contour
<br />farming, and contour stripcropping help to conserve
<br />moisture and to control water and wind erosion. 'Terrac-
<br />ing helps to conserve moisture and to control water ero-
<br />sion. Emergency tilla;e is ofte¢ needed. (Dryland
<br />capability traits IVe-6 m climatic zone C, VIe-2 in cli-
<br />matic zone D; Loamy Plains range site)
<br />Colby silt loam, 0 [0 1 percent slopes (CmA).-This soil
<br />occurs on nearly level stream terraces in the irrigated part
<br />of the county (fig. 9). 'The substratum commatly is
<br />weakly stratified loam and very fine sandy loam, and in
<br />some areas sand and gravel occur at a depth of 36 to 60
<br />inches.
<br />This soil takes in water at a medium rate. The watet•-
<br />holding capacity is high, and most of the water held in the•.
<br />soil ie readily available to plants. Natural fertility is
<br />medium.
<br />This soil is used for irrigated farming, dryland farming,
<br />and grazing. IL is well suited to irrigated farming and to
<br />all crops normally grown in the county. The soil rs easy
<br />to work, but l:md leveling may be needed to spread water
<br />more uniformly. The response to fertilization and to
<br />irrigation management is good.
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