SOIL

Soil moisture regime of Tatanka Wakpala: Typic Ustic
Ustic moisture regime.—The ustic (L. ustus, burnt; implying dryness) moisture regime is intermediate between the aridic regime and the udic regime. Its concept is one of moisture that is limited but is present at a time when conditions are suitable for plant growth. The concept of the ustic moisture regime is not applied to soils that have permafrost or a cryic soil temperature regime.
LINK TO SOIL MOISTURE REGIME MAP
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Soil temperature regime of Tatanka Wakpala: Mesic
Mesic indicates a mesic temperature regime, that is, the mean annual soil temperature is between 8 and 15 degrees C (47 and 59 degrees F) and the soil temperature fluctuates more than 8 degrees C between summer and winter. In other words, the soils are somewhere in the midlatitudes, summer is warm or hot, and winter is cool or cold.
LINK TO SOIL TEMPERATURE REGIME MAP
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Dominant Soil Orders
Tatanka Wakpala: Entisols & Vertisols…perhaps Mollisols
LINK TO DOMINANT SOIL ORDERS MAP

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DOMINANT SOIL DESCRIPTIONS

ENTISOLS
“The central concept of Entisols is that of soils that have little or no evidence of the development of pedogenic horizons. Most Entisols have no diagnostic horizons other than an ochric epipedon. Very few have an anthropic epipedon. A few that have a sandy or sandy-skeletal particle-size class have a horizon that would be a cambic horizon were it not for the particle-size class exclusion. Very few Entisols have an albic horizon. In coastal marshes some Entisols that have sulfidic materials within 50 cm of the mineral soil surface have a histic epipedon.

On many landscapes the soil material is not in place long enough for pedogenic processes to form distinctive horizons. Some of these soils are on steep, actively eroding slopes, and others are on flood plains or glacial outwash plains that receive new deposits of alluvium at frequent intervals. Some Entisols are old enough to have formed diagnostic horizons, but they consist mostly of quartz or other minerals that are resistant tothe weathering needed to form diagnostic horizons. Buried diagnostic horizons are permitted in Entisols if they meet the requirements for buried soil defined in chapter 1 (SEE LINK BELOW).

Entisols may have any mineral parent material, vegetation, age, or moisture regime and any temperature regime, but they do not have permafrost. The only features common to all soils of the order are the virtual absence of diagnostic horizons and the mineral nature of the soils.

VERTISOLS
The central concept of Vertisols is that of clayey soils that have deep, wide cracks for some time during the year and have slickensides within 100 cm of the mineral soil surface. They shrink when dry and swell when moistened. Vertisols make up a relatively homogeneous order because of the amounts and kinds of clay common to them; however, their microvariability within a pedon is great. Before the advent of modern classification systems, these soils were already well known for their characteristic color, the cracks they produce during the dry season, and the difficulty of their engineering properties.

In many countries where Vertisols are extensive, they are known by local names, such as cracking clays (Australia), Adobe (Philippines), Shachiang (China), Black Cotton soils (India), Smolnitza (Bulgaria, Rumania), Tirs (Morocco), Makande (Malawi), Vleigrond (South Africa), and Sonsosuite (Nicaragua). In addition, numerous coined terms have been used to identify the soils. Examples are Margalite soils (Indonesia), Densinegra soils (Angola), and Grumusols (United States).

These soils generally are sticky in the wet season and hard in the dry season, so they require special cultivation practices regardless of whether modern equipment or traditional implements, such as a hoe or bullock-drawn plow, are used. Because their unique properties restrict engineering uses, the soils are well known among engineers. The movement of these soils can tilt trees; throw fenceposts, telephone poles, and power poles out of line; and break pipelines, highway pavements, and the masonry foundations of buildings.

MOLLISOLS
Mollisols commonly are the very dark colored, base-rich, mineral soils of the steppes. Nearly all of these soils have a mollic epipedon. Many also have an argillic, natric, or calcic horizon. A few have an albic horizon. Some also have a duripan or a petrocalcic horizon.

Mollisols are extensive in subhumid to semiarid areas on the plains of North America, Europe, Asia, and South America. They lie generally between the Aridisols of arid climates and the Spodosols or Alfisols of humid climates. They are most extensive at mid latitudes, but they also occur at high latitudes and high altitudes and in tropical regions.

Many of these soils developed under grass at some time, although many apparently were forested at an earlier time. Some of the soils that are in the mountains or that were derived from highly calcareous parent material apparently formed under forest vegetation. Mollisols may have any of the defined temperature regimes but do not have permafrost. Soils with mollic epipedons and permafrost are Gelisols. Mollisols can have any moisture regime, but enough available moisture to support perennial grasses seems to be essential.

Most Mollisols at high latitudes formed in late-Pleistocene or Holocene deposits. Beyond the limits of glaciation, Mollisols may be in areas of older deposits or on older surfaces dating back perhaps to the mid Pleistocene or earlier, and these commonly have an argillic horizon with a reddish hue.

In frigid or warmer areas where slopes are not too steep, Mollisols are used mainly for small grain in the drier regions and maize (corn) or soybeans in the warmer, humid regions. ”
LINK TO USDA SOIL TAXONOMY

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Ground-Penetrating Radar (GPR) Soil Suitability
LINK TO GPR SUITABILITY MAP
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DEWEY COUNTY SOIL SURVEY

(snippets below)
The soil located in the area of Tatanka Wakpala is likely either opal-sansarc-promise, or sansarc-opal.

Soil association in Dewey County, SD

Soil associations in Dewey County, SD

Well-Drained Soils Formed in Material Weathered From Clay Shale; on Uplands
This group consists of shallow to deep clayey soils on uplands. These soils are mostly gently sloping to moderately steep, but are nearly level on isolated flats and are steep or very steep near Lake Oahe. Many draws and deeply entrenched drainageways dissect the landscape. About 1 percent of the acreage is cultivated. The rest is in native grass and is used for range.

7. Opal-Sansarc-Promise association

Shallow to deep, well-drained, nearly level to moderately steep clayey soils
This association is a shale plain on uplands. It is mostly gently sloping, but is steeper on the sides of some ridges and on the sides of entrenched drainage-ways. Slopes are long and smooth.

This association makes up about 24 percent of the land area in the county. It is about 40 percent Opal soils, 20 percent Sansarc soils, 15 percent Promise soils, and 25 percent minor soils.

The mostly gently sloping to strongly sloping Opal soils are moderately deep over shale. They have a surface layer and subsoil of grayish-brown clay. The underlying material is light yellowish-brown clay and pale-olive shaly clay. Light olive-gray and very dark gray shale is at a depth of 33 inches.

The sloping to moderately steep Sansarc soils are shallow over shale. Slopes generally are short and convex. Sansarc soils have a thin surface layer of grayish-brown clay and underlying material of light brownish-gray clay and shaly clay. Light brownish-gray shale is at a depth of 17 inches.

The deep Promise soils are nearly level to gently sloping. Slopes are long and smooth. The surface layer is dark grayish-brown clay and the subsoil is dark grayish-brown and grayish-brown clay. The underlying material is light brownish-gray silty clay.

Minor soils in this association are Agar and Reliance soils on smooth tableland near Lake Oahe, Chantier and Swanboy soils on fans, Dupree soils intermingled with Opal and Sansarc soils, and Hurley soils and Slickspots in drainage sage and on upland flats.

These soils are difficult to work and are very slowly or slowly permeable. Available Water Capacity ranged from very low to moderate. Runoff is medium on much of the association, but is rapid on the steep soils. Controlling erosion and soil blowing and conserving moisture are the main concerns in management.

Many areas are in native grass and are used for range. Most of the farming is on Agar, Promise, and Reliance soils. Some areas of the Opal soils are cropped. Wheat, oats, and alfalfa are the main crops. Some corn is grown. Livestock ranching and wheat farming are the main enterprises.

8. Sansarc-Opal association

Shallow and moderately deep, well-drained, gently sloping to steep clayey soils
This associations is a dissected shale plain adjacent to the larger streams in the county. It it dominantly strongly sloping to moderately steep. Slopes in much of the association are short and convex. The less sloping parts are the sides of the drainage divides, and the steepers parts are the sides of entrenched drainage-ways. Many small draws flow into the entrenched drainageways (fig. 6). In some areas the draws and drainageways are gullied.

This association makes up about 36 percent of the land area in the county. It is about 30 percent Sansarc soils, 28 percent Opal soils, and 42 percent minor soils.

The shallow Sansarc soils are mostly moderately steep and have short, convex slopes. They have a thin surface layer of grayish-brown clay and underlying mater of light brownish-gray clay and shaly clay. Light brownish-gray shale is at a depth of 17 inches.

The moderately deep Opal soils are gently sloping to moderately steep. They have a surface layer and subsoil of grayish-brown clay. The underlying material is light yellowish-brown clay and pale-olive shaly clay underlain by shale at a depth of 33 inches.

Minor soils in this association are Agar, Canning, and Reliance soils on isolated high terraces near Lake Oahe, Chantier and Swanboy soils on fans below steeper soils, Hurley soils and Slickspts in shallow drainage sags, and Promise soils on nearly level drainage divides and also near Swanboy soils on low terraces and fans along the larger drainage-ways. Also in this association are small areas of Shale land on the sides and around the heads of some drainage-ways.

The dominant Sansarc and Opal soils are slowly or very slowly permeable and have very low or low available water capacity. Runoff is rapid over much of the area. The Sansarc soil is not suitable for cultivation, and most of the Opal soil in this association is too steep for cultivation.

Most of this association is in native grass and is used for range. Small areas of the Opal soil and some minor soils are used for small grain and alfalfa. The small areas of the Canning soil are a potential source of limited amounts of sand and gravel. Livestock ranching in the main enterprise in this association.” (pages 7-9 of Soil Survey Dewey County, South Dakota)

Patter of soils in Sansarc-Opal association

Pattern of soils in Sansarc-Opal association

An area of Sansarc-Opal soils.

An area of Sansarc-Opal soils.

Opal Series (mesic, Mollisols)

The Opal series consists of moderately deep, well-drained, nearly level to moderately steep clayey soils on uplands. These soils formed in material weathered from the underlying shale. The native vegetation is mainly mid and short grasses.

In a representative profile the surface layer is grayish-brown clay about 5 inches thick. The subsoil, about 15 inches thick, is grayish-brown clay. It is extremely hard when dry, extremely firm when moist, and very sticky and plastic when wet. The lower part is calcareous and has spots and streaks of lime that extend into the underlying material. The underlying material to a depth of 33 inches is light yellowish-brown clay and pale-olive shaly clay. Below this is light olive-gray and very dark gray shale.

Opal soils are medium in fertility and are moderate in content of organic matter. Runoff is medium or rapid, and permeability is very slow. Available water capacity is low or very low.

Most areas are in native grass and are used for range. Some areas are cultivated.

Promise Series (mesic, Mollisols)

The Promise series consists of deep, well-drained, nearly level to gently sloping clayey soils on uplands and terraces. These soils formed in material weathered in place from clay shale or washed in from adjacent soils. The native vegetation is mainly mid and short grasses.

In a representative profile the surface layer is dark grayish-brown clay about 4 inches thick. The subsoil, about 27 inches thick, is clay that is dark grayish brown in the upper part and grayish brown in the lower part. The upper part is extremely hard when dry, extremely firm when moist, and very sticky and plastic when wet. The lower part is calcareous. The underlying material is light brownish-gray, calcareous silty clay.

Promise soils are medium in fertility and moderate in content of organic matter. Runoff is slow or medium, and permeability is slow or very slow. Available water capacity is low or moderate.

Many areas are in native grass and are used for range. Other areas are cultivated.

Sansarc Series (clayey, mesic, Entisols)

The Sansarc series consists of shallow, well drained, sloping to very steep, calcareous clayey soils on uplands. These soils formed in material weathered from the underlying shale. The native vegetation is mid and short grasses.

In a representative profile the surface layer is grayish-brown clay about 4 inches thick. The underlying material to a depth about 17 inches is light brownish-gray, calcareous clay and shaly clay. It is hard when dry and friable when moist. Below this is light brownish-gray bedded shale.

Sansarc soils are low in fertility and are moderately low in content of organic matter. Runoff is medium to very rapid, and permeability is slow. Available water capacity is very low.

Almost all areas are in native grass and are used for range.

GUMBO ‘SOIL’ AT TATANKA WAKPALA
Sticky when wet. This ‘soil’ in the garden is about the best on-site. The rest has much more clay content.

Use and Management of the Soils

The soils of Dewey County are used extensively for range and also crops, tame pasture, windbreaks, and wildlife. This section suggests how the soils can be managed for these purposes. It also contains a section on engineering (see charts below), which has information of value to engineers, planning commissions, and others.

Range

Except for stingers of trees along streams and some of the drainageways, the native vegetation of Dewey County was grass. As the county was settled, some of the grassland was broken and farmed. Most areas selected for cultivation were gently sloping soils. Many areas in native grass are soils that are not suitable for cultivation because they are shallow and steep or have a restrictive claypan subsoil.

About 88 percent of the land area is in native grass and is used for range. This acreage is dominantly in the Opal-Sansarc-Promise, Sansarc-Dupree, Sansarc-Opal, and Wayden-Cabba associations.

If well managed, most of the range supports a good stand of grass. A considerable acreage is heavily grazed, which results in less than maximum returns.

Windbreaks

About 2,000 acres of Dewey County is native woodland and brush. Most of the native trees and shrubs are on bottom land, in natural draws, and on steep, north-facing slopes.

The principal species of native trees and shrubs are American elm, boxelder, buffaloberry, bur oak, chokecherry, eastern redcedar, gooseberry, green ash, hawthorne, juneberry, plains cottonwood, poison ivy, skunkbrush, snowberry, Virginia creeper, wild grape, wild plum, wild rose, and willow. Eastern redcedar is mainly in small patches in the breaks bordering the Moreau River.

The native woodland and brush in the county are of value mainly for livestock shelter, wildlife habitat, recreation, esthetics, erosion control, and watershed protection.

Windbreaks have been planted in the county since the time of settlement. Most plantings were for the protection of farmsteads and feedlots. In recent years a few field windbreaks have been established. Additional windbreaks of all kinds are still needed. Supplementary plantings would make many of the existing windbreaks for effective.

Windbreaks return many economic and environmental benefits to the landowner. They prevent snow from accumulating on the farmstead; they protect the home and livestock from wintery winds, thereby reducing fuel and feed costs; and they protect field crops, gardens, and orchards from damaging winds. Windbreaks also reduce evaporation of moisture, provide favorable habitat for birds and other wildlife, help control soil blowing, and enhance the beauty of a rural home and its surroundings.

RESOURCE FOR WINDBREAKS ON GREAT PLAINS

Wildlife

The level of wildlife production depends on essential habitat containing both food and cover. The kind and adequacy of habitat plantings, introduced and native, is closely associated with suitability of the soil.

Suitability of the major soils in the 10 associations in Dewey County for producing habitat appropriate for four particular kinds of wildlife is given in table 4 (see below). The kinds of wildlife in the county are describe in the following paragraphs.

Farmland wildlife frequents cropped areas, pastures, meadows, and planted woodland. Farmland wildlife also frequents other areas, such as natural woodland and heavily vegetated marshes, but it is most closely associated with cultivated areas. Examples of farm wildlife are pheasant, gray partridge, bobwhite, mourning dove, cottentail, jackrabbit, fox, raccoon, and white-tailed deer.

Woodland wildlife inhabits naturally wooded areas, bordered by and frequently a part of farms, range, and pasture. Suitability ratings in table 4 are for natural woodland. Planted woodland is not considered. Examples of woodland wildlife are mule deer, white-tailed deer, cottontail, tree squirrels, raccoon, coyote, turkey, ruffed grouse, thrushes, vireos, and scarlet tanager.

Wetland wildlife requires natural wetland or improved natural wetland for all or part of their breeding habitat. Ducks, herons, shorebirds, coot, redwinged blackbird, mink, muskrat, and beaver are examples.

Rangeland wildlife occurs on extensive areas of range that in many places includes wooded draws, wooded alluvial land, farm areas, and some planted woodland. Mule deer, whitetailed deer, antelope, jack-rabbit, coyote, sharptailed grouse, sage grouse, prairie chicken, magpie, horned lark, lark bunting, and mourning dove are examples of rangeland wildlife.

Table 4. -Wildlife habitat, by soil associations

Table 4. -Wildlife habitat, by soil associations

The ratings in table 4 are described as follows:
_GOOD: The habitat can be easily established, constructed, improved, or maintained. Few or no soil limitations occur in habitat management, and satisfactory results are generally assured.
_FAIR: The habitat usually can be established, constructed, improved, or maintained, but there are moderate soil limitations that affect habitat construction or management. A moderate intensity of management and fairly frequent attention may be required if results are satisfactory.
_POOR: The habitat can frequently be established, constructed, improved, or maintained on these soils, but there are rather severe soil limitations. Establishment, construction, or management of habitat can be difficulty, expensive, or require intensive effort. Results are questionable.
_VERY POOR: Naturally occurring habitat can sometimes be maintained under specific management, but establishing, constructing, or improving habitat is generally not possible or feasible.

Engineering

This section is useful to those who need information about soils used as structural material or as foundation upon with structure are built. Among those who can benefit from this section are planning commissioners, town and city managers, sanitarians, land developers*, engineers*, contractors, and farmers* and ranchers.

Among the properties important in engineering are permeability, shear strength, compaction characteristics, soil drainage, shrink-swell potential, grain size, plasticity, and soil reaction. Also important are depth to water table, depth to bedrock, and soil slope. These properties, in various degrees and combinations, affect construction and maintenance of roads, airports, pipelines, foundations for small buildings*, irrigation systems*, ponds and small dams*, and systems for disposal of sewage and refuse*.

*Asterisk represents particular interest to Tatanka Wakpala

Table 5. -Estimated physical and chemical properties

Table 5. -Estimated physical and chemical properties

Table 6. -Engineering interpretations

Table 6. -Engineering interpretations

Estimated properties significant in engineering (Table 5 explanation)
Estimates of physical and chemical soil properties significant in engineering are shown in table 5. Evaluations are made for the representative profile of each soil series, by layers sufficiently different to have significance in soil engineering. The estimates are based on field observations made in the course of mapping, and on experience with the same kinds of soil in other counties. Following are explanations of some of the columns in table 5.

Depth to bedrock is the distance from the surface of the soil to the upper surface of the rock layer. Depth to seasonal water table is distance from the surface downward to the highest level reach by ground water in most years.

The dominant soil texture is expressed in standard terms used by the United States Department of Agriculture. These terms are based on the percentages of sand, silt, and clay in soil material that is less than 2 millimeters in diameter. “Loam” for example, is soil material that is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand. If the soil contains gravel or other particles coarser than sand, an appropriate modifier is added, as for example, “gravelly loamy sand”.
USDA SOIL TEXTURAL CLASSIFICATION GUIDE (from CSU)

Liquid limit and plasticity index pertain to the effect of water on the strength and consistence of soil material. As the moisture content of a clayey soil is increased from a dry state, the material changes from a plastic to a liquid state. The plastic limit is the moisture content at which the soil material changes from the semisolid to the plastic state, and the liquid limit from the plastic to the liquid state. The plasticity index is the numerical difference between the liquid limit and the plastic limit. It is the range of moisture content within which a soil material is plastic. Liquid limit and plasticity index in table 5 are estimates (more detailed tables in PDF).

Permeability is the quality that enables a soil to transmit water or air. It is estimated on the basis of soil characteristics observed, particularly structure and texture. The estimates do not take into account lateral seepage or transient soil features, such as plowpans and surface crusts.

Available water capacity is the capacity of a soil to hold water for use by most plants. It is commonly defined as the difference between the amount of water in the soil at field capacity and the amount at the wilting point of most crops.

Reaction is the degree of acidity or alkalinity of a soil, expressed in pH values. A soil that tests to pH 7.0 is precisely neutral in reaction because it is neither acid not alkaline. An acid, or “sour”, soil is one that gives an acid reaction; an alkaline soil is one that is alkaline in reaction. In words, the degrees of acidity of alkalinity are expressed thus:
pH levels

Salinity refers to the amount of soluble salts in the soil. It is expressed as the electrical conductivity of the saturated soil extract in millimhos per centimeter at 25 degrees C. Salinity affects suitability of a soil for crop production, its stability when used as construction material, and its corrosivity to metals and concrete. The salinity rating and the corresponding salinity in millimhos per centimeter are as follows:

    Salinity rating / salinity in millimhos per centimeter
    None………………….Less than 2.0
    Low…………………..2.0 to 4.0
    Moderate………………4.0 to 8.0
    High………………….8.0 to 16.0
    Very high……………..More than 16.0

Shrink-swell potential is an indication of the volume change in the soil material to be expected with changes in moisture content. Shrinking and swelling of soils cause much damage to building foundations, roads, and other structures. A high shrink-swell potential indicates a hazard to the maintenance of structures constructed in, on, or with such material.

As used in table 5, risk of corrosion pertains to potential soil-induced chemical action that dissolves or weakens uncoated steel or concrete. Rate of corrosion of uncoated steel is related to soil properties, such as drainage, total acidity, texture, and electrical conductivity of the soil material. Risk of corrosion for concrete is influenced mainly by the content of sodium or magnesium sulfate but also by soil texture and acidity. Corrosion is more likely to damage installations of uncoated steel that intersect soil boundaries or soil horizons than installations entirely in one kind of soil or in one soil horizon. A corrosivity rating of low means that the probability of self-induced corrosion damage is low; high means that there is a high probability of damage so that protective measures for steel and more resistant concrete need to be used in avoiding or minimizing damage.

Engineering interpretations (Table 6 explanation)
Those below with an asterisk* may be of particular interest to Tatanka Wakpala
Interpretations in table 6 are based on the engineering properties of soils shown in table 5, on test data (see PDF), and on the experience of engineers and soil scientists with the soils of Dewey County. In table 6, ratings summarize the limitation of suitability of the soils for all listed purposes other than drainage of cropland and pasture, irrigation, pond reservoirs, embankments, and terraces and diversions. For these uses, table 6 lists the soil features not to be overlooked in planning, installation, and maintenance.

Soil limitations are indicated by the ratings slight, moderate, and severe. Slight means that soil properties are favorable for the rated use. Moderate means that some soil properties are unfavorable but can be overcome by special planning or design. Severe means that soil properties are so unfavorable and so difficult to correct or overcome that major soil reclamation and special designs are required.

Septic tank absorption fields* are affected by the kind of soil material within a depth of 18 inches to 6 feet.. Permeability, depth to water table, depth to bedrock, and susceptibility to flooding are soil properties that affect the absorption of effluent. Soil slope affects difficulty layout and construction and also increases the risk of soil erosion, lateral seepage, and downslope flow of effluent.

Sewage lagoons are affected by such soil properties as permeability, soil slope, depth to water table, depth to bedrock, and susceptibility to flooding.

Shallow excavations*, less than 6 feet deep, refer to those made for basements, graves, open ditches, pipelines, sewer lines, and underground cables. The ratings are affected by depth to water table, depth to bedrock, soil slope, soil texture, and susceptibility to flooding.

Dwellings with basements given ratings are affected by properties that relate to ability of the soil to support load and resist settlement under load and to ease of excavation. The soil properties rated are shrink-swell potential, potential frost action, soil slope, depth to bedrock, and wetness resulting from a water table or from flooding.

Sanitary landfill* is a method for disposing of solid wastes on or in the soil by spread the waste in thin layers, compacting it to the smallest volume, and covering it with soil in a manner that provides maximum protection of the environment. The best soils are deep, well-drained soils that are moderately slowly permeable, or moderately permeable, can withstand heavy traffic, and are easy to excavate.

Local roads and streets have an all-weather surface that is expected to carry automobile traffic all year, but no fast-moving heavy trucks. Ratings are based on soil drainage, soil slope, the AASHO and Unified classifications of soil material, shrink-swell potential, susceptibility to frost action, and depth to bedrock.

Road fill is soil material used in embankments for roads. The suitability ratings reflect the ease of excavating the material at borrow areas and the predicted performance of soil after it has been placed in an embankment that has been properly compacted and provided adequate drainage.

Ratings for sand and gravel are based on the probability that a soil is a source of sand and gravel. These areas are identified on the soil map (see PDF for more details)

Topsoil* is soil material to be used in topdressing an area where vegetation is to be established and maintained. Suitability of a soil as a source of topsoil is affected by soil texture, slope, thickness of the material, coarse fragments, and the presence or absence of soluble salts or other toxic substances that affect fertility.

Pond reservoir areas are affected by soil features that influence seepage and storage potential. Those considered are permeability, depth to bedrock or other unfavorable material affecting seepage, depth to water table, and soil slope.

Embankments, dikes, and levees* require soil material that is resistant to seepage and piping and is of favorable stability, shrink-swell potential, shear strength, and compactibility.

Drainage for crops and pasture is affected by soil properties that affect the installation and performance of surface and subsurface drainage systems. These are soil permeability, depth to water table, stability in ditchbanks, flooding, and availability of outlets.

Irrigation* is influenced by water intake rate, permeability, available water capacity, depth of rooting zone, salinity, soil slope, depth to water table, susceptibility to flooding, and the hazard of erosion and soil blowing.

Terraces and diversions* are affected by features affecting their stability or hindering layout and construction. Other hazards are sedimentation in channels and the difficulty of establishing and improving a plant cover. Features that affect the suitability of a soil are the uniformity and steepness of soil slope, permeability, depth to bedrock or other unfavorable material, and susceptibility to erosion and soil blowing.

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