Soils in South Dakota may be thick or thin, stony or not stony, saline
or non-saline , sandy, clayey , or of medium texture,
sloping, flat, or in basins , and may occur where climates are moist or dry and warm or cool. The unique combinations of
soil forming factors in South Dakota give rise to more than 550 different soils. These soils have characteristics that influence
their suitability for various uses. It is important to understand how soils form and develop, because many of the
characteristics that are critical for land use decisions are determined by soil formation. When a state depends heavily upon
agriculture, soil management becomes especially important.
South Dakota is an agricultural state with an area of 77,047 square
miles and a population density of 9 persons per square
mile. In 1996, cash receipts, excluding government payments, from farming and ranching totaled more than $3.7 billion, with
50% from livestock and livestock product sales and 50% directly from crop sales (S.D. Ag. Stat. Serv., 1997).
|In 1996, South Dakota ranked nationally in agricultural
production as follows: 1st in oats and all hay; 2nd in rye, flaxseed,
alfalfa hay, and sunflowers; 4th in hard red spring wheat; 5th in all wheat and durum wheat; 6th in corn; 7th in all other hay;
9th in soybeans; 10th in grain sorghum; 11th in barley; 17th in potatoes; and 21st in cash receipts from crops. These crops
and their products, along with forage, range, and pasture grown in the state, provide feed for large numbers of livestock. In
1996, South Dakota ranked nationally 3rd in honey and lamb crops; 5th in beef cows that calve and all sheep and lambs; 8th
in all cattle and calves; 9th in red meat production; 11th in all pigs and hogs; 26th in milk production; and 17th in cash
receipts from livestock (S.D. Ag. Stat. Serv., 1997). This production is possible because South Dakota has large areas of productive soils.
What Are The Major Soil Regions of South Dakota?
Except for the forested Black Hills and scattered areas of trees in
flood plain s and along streams, South Dakota was a vast
sea of grass for thousands of years before its soils were cultivated. This grassland environment and its associated climate
are the two factors that have most influenced the development of the state's soils.
Climate and vegetation have interacted in South Dakota to produce seven
major soil regions (Figure 1). These regions are
named: Cool Moist Forest; Cool, Very Dry Plain; Warm, Very Dry Plain; Cool Dry Plain; Warm Dry Plain; Cool
Moist Prairie; and Warm Moist Prairie.
The Cool Moist Forest Region in the Black Hills is unique in South Dakota
because the soils have developed under forested
conditions in a cool, humid to subhumid climate. In the other regions, soils have developed under grass vegetation in
climates ranging from moist subhumid to semiarid. In Figure 1, arrows indicate the general kind of soil profile that has
developed on well-drained lands in each region.
In South Dakota, the lines of equal temperature and the lines of equal
precipitation cross roughly at right angles (except for
Black Hills). Relatively speaking, this makes the southeast warm and moist, the northeast cool and moist, the southwest
warm and very dry, and the northwest cool and very dry.
How Do Soils Differ?
Amount of Aeration: Aeration is the exchange of air in the soil with
air from the atmosphere. Well-drained (aerated) soils
contain air that is similar in composition to that in the atmosphere. Air in poorly-drained soils that have poor aeration tends
to have high levels of carbon dioxide and low levels of oxygen.
Amount of Organic Matter and Nitrogen: Native grassland vegetation,
which was greatly influenced by climate, has
determined the amounts of organic matter in the soils. In general, the more humid eastern portion of the state supported tall
grasses that left large amounts of organic matter in the soils. Moving westward, the grass type changed to mid- and finally to
short grasses in response to the drier climate. This change in vegetation is reflected in the lower amounts of organic matter in
the soils developed under drier climates.
Temperature has also played a part in determining the organic matter
content of the soils. In the cooler northern part of the
state, more soil organic matter and total organic nitrogen are present than in the southern part under comparable
precipitation. This difference is due to slower rates of decay under cooler temperatures.
Organic matter and total organic nitrogen content of most cultivated
soils in the state today are substantially lower than when
the original prairie sod was broken. These losses are generally about one-third of the original total throughout the state.
Therefore, present contents of organic matter and total organic nitrogen in cultivated soils reflect the original amounts, but
are one-third less.
Depth of Carbonate Leaching: One way in which the climate is reflected
in the soils is in the depth of carbonate (lime)
leaching . Figure 1 shows that the depth of leaching is greater in the humid east than in the drier west and greater in the
warmer south than in the cooler north.
Productivity: Not all soils are equally well-suited for plant growth.
A soil's ability to sustain plants is referred to as its
productivity level. A productive soil is one with chemical, physical, and biological characteristics favorable for the
sustainable and economic production of crops suitable for the climate.
Nitrogen Release: Research in South Dakota has shown that nitrogen release
to plants is more a function of temperature
than of precipitation. Thus the southern and western soils release nitrogen faster than the northern and eastern soils. In
southeastern South Dakota, slightly over 2% of the total organic nitrogen usually is released annually to plants. In
northeastern South Dakota, slightly less than 2% of the total organic nitrogen of the soils is released annually.
Permeability: Soils differ in their ability to transmit fluids. Soil
permeability is measured by the number of inches per hour
that water moves downward through a saturated sample of soil. Factors such as texture, structure, and amount of organic
matter influence a soil's permeability . In sandy soils, for example, water flows quickly, while some clayey soils barely let
pH Level: The pH scale is a numerical measure of acidity or alkalinity
ranging from 0 (very acid) to 14 (very alkaline). A
soil that tests at a pH of 7 is considered neutral while one at pH 4.5 or lower would be very strongly acid. Soils with a pH
of 9.1 or higher are very strongly alkaline.
Salinity: Soils differ in the amounts of soluble salts they contain.
If a soil is so high in these salts that plant growth in the soil
is impaired, the soil is referred to as saline. A saline soil has high electrical conductivity. A saline soil does not contain
excess amounts of exchangeable sodium.
Sodium Content : Some salt-affected soils have levels of sodium that
are so high that the soil's physical and chemical
properties are changed and the soil's ability to support plant growth is adversely affected. Such soils are called sodic .
Soil Colors : Soil color correlates well with total amounts of organic
matter and organic nitrogen present. Differences are
apparent in the surface soil color in the various areas of the state. It is possible to determine soil colors scientifically by
comparing them with specially prepared color charts.
The darkest soils are found in northeastern South Dakota, where the
climate is cool and moist. These soils have the highest
organic matter and total organic nitrogen supplies in the state. The soils of southwestern South Dakota have the lightest
color, are browner, and have the least organic matter and total organic nitrogen. The climate there is warm and very dry.
Soil Texture and Particle Size : Soils also differ in their texture,
which is the result of the relative amounts of sand, silt ,
and clay they contain. Clay soils have very fine particles, can have a powdery texture when dry, and be very sticky or
slippery when wet. Silty soils feel smooth and silky, like wet talcum powder or flour. Sandy soils have larger, granular
particles, are gritty in texture, and are not slippery when wet. Loam has a medium texture, the highest plant-available water
holding capacity, and is usually quite productive. It is about equally influenced by sand, silt and clay , and also contains a
good amount of organic matter.
Soil Layers: Anyone who has looked closely at a recently dug hole or
at a roadside cut has noticed that soils contain layers
that differ in their appearance. These layers, or horizons, occur in a vertical sequence through the soil. The type and depth of
these horizons create the soil profile. In most soil profiles, the horizons are separated by transitional zones, although some
of the profiles have sharply defined boundaries between horizons .
Soils vary in the types and number of horizons present. Very young soils
may have only one or two soil horizons . These
young soils often have distinct layers in their profile due to deposition or geologic events that are not the result of soil
formation. As soils develop, the horizons become more easily identified until soils become so old that horizons begin to
fade. The soils in South Dakota are relatively young, and thus, horizon development is minimal to moderate.
A= Annual Temperature; B = Annual Precipitation; C = Native Vegetation
What Factors Affect Soil Formation?
The kind of soil that develops in any area is the result of the interaction
of the five soil forming factors: climate; plants and
soil organisms in the area; parent material; topography , and time .
Climate controls the distribution of plants. Together, climate, plants
and soil organisms are called the "active factors" of soil
formation. This is because on gently undulating topography, within a certain climatic and vegetative zone, a typical soil will
develop, unless parent material differences are very great. Thus, the tall and mid-grass prairie soils have developed across
a variety of parent materials . Parent material exerts its influence on soils principally by determining soil texture and
mineral composition. Topography determines what drainage a soil will have. Steep slopes have excessively drained, thin
soils; flat or depressed topographic areas usually have poorly drained, thick soils. The factor of time can be illustrated by
comparing a soil on a flood plain that receives annual deposits of alluvium with a soil on a stable upland ridge. The flood
plain soil is without developed horizons , although it may have layers of contrasting alluvium, while the soil on the stable
upland ridge usually has a well-developed soil profile .
Climate: South Dakota, because of its inland position, has a continental
climate with extremes of summer heat, winter cold,
and rapid fluctuations of temperature. Temperatures during the winter months often drop to -20 F (-29 C) or lower, while in
the summer readings of 100 F (38 C) or more are common in the state. The average annual temperature is 46 F (8 C) and
ranges from 48 F (9 C) in the south to less than 44 F (7 C) in the north.
Annual precipitation ranges from 25 inches (64 cm) in the southeast
to less than 14 inches (36 cm) in the northwest. Most
precipitation occurs in spring and early summer. Seasonal snowfall averages about 30 to 50 inches (76-127 cm) in the lower
elevations of the state to over 100 inches (255 cm) in the Black Hills.
The average depth of frost penetration ranges from 25 inches (64 cm)
in southwestern South Dakota to 50 inches (127 cm) in
the northeast. Depth of frost depends on the amount of residue cover, soil moisture content, and the amount and timing of
snowfalls in relation to temperature extremes. For the area excluding the Black Hills, the average last spring frost ranges
from May 5 in the southeast to May 20 in the northwest. Average first fall frosts range from September 15 in the northwest to
October 5 in the southeast. Average length of time without killing frost varies from 120 days along the northern part of the
state to 160 days in the southeast. The Black Hills area generally has shorter growing seasons than the rest of the state, with
average of frost-free days ranging from 110 to 130 days.
During cold seasons winds are from the northwest, while during warm
seasons they are from the southeast. Annual average
surface wind velocity for the state is 10 to 12 miles (16-19 km) per hour.
Native Vegetation: Except for the Black Hills, which were timbered,
and the river valleys where trees grew, the native
vegetation of South Dakota was originally grassland. Starting with the eastern border of the state and extending to the eastern
edge of the James River Valley, the principal vegetative was tall grass. Big bluestem, sand dropseed, and switchgrass were
present along with forbs . Moving westward across the James River Valley, the tall grasses gradually become less common,
being found only on sandy soils and on cool northern exposures. The medium and short grasses assumed dominance.
Important species of the midland area were needleandthread, green needlegrass, western wheatgrass, slender wheatgrass,
blue grama, prairie junegrass, and buffalo grass. In western South Dakota, shorter grasses dominated because of decreased
rainfall. Important shortgrass species were blue grama, western wheatgrass, needleandthread, prairie junegrass, and little
bluestem. Variations in plant associations occurred west of the Missouri River as a result of differences in soil texture. For
example, on the Pierre Plain, an area of clayey soils, the principal grasses were western wheatgrass, blue grama grass, and
buffalograss. In the Sand Hills of southwestern South Dakota, little bluestem, prairie sandreed, and needleandthread were
Parent material : South Dakota soils have developed from a wide variety
of materials (see Figure 2). They include ancient
crystalline and metamorphic rocks in the Black Hills, sedimentary rocks including shale , sandstone , and limestone in
western South Dakota, and glacial materials of several ages in the east. Additional parent materials include loess ,
alluvium , and colluvial materials formed from upland deposits.
Crystalline rocks, in the central core of the Black Hills, were formed
by cooling of molten magma deep beneath the earth's
crust. Over time, these rocks have been thrust upward and exposed by erosion . Granite is the dominant crystalline rock type
and the resulting soils tend to be gravelly with loamy to sandy surface textures. Mocmont is a soil series developed from
weathered granite. Along the edges of the crystalline rocks, metamorphic rocks are found, the most common types being
schists and slate. The resulting soils tend to be loamy with a rock fragment content of at least 15% in surface horizons . The
rock content increases as soil depth increases until bedrock is reached at 40 to 60 inches (102-152 cm). Buska, Pactola, and
Virkula are soil series developed from weathered metamorphic rocks.
Sedimentary rocks were formed by consolidation of loose sediments or
by precipitation of carbonates from solution. Much
of this took place on the floors of ancient seas. The sands formed sandstone , the silts and clays formed siltstone and shale ,
and the basic carbonates formed limestone. Few of these rocks in South Dakota are pure--instead they are calcareous
sandstone s, sand y limestones , and so on. The principal sedimentary rock parent materials include: (1) Pierre shale of
the central part of the west river area; (2) Upper Cretaceous sandstone s and sandy shales of northwestern South Dakota;
and (3) Tertiary sandstone s and siltstone s in the southwest.
The Pierre shale area is sometimes called the "gumbo region" because
of the plastic clay that weathers and forms from the
shale . Layers of the Pierre shale are soft and easily eroded. They generally are not butte -formers, rather they weather into
soft rounded hills and ridges. Kyle, Lismas, Pierre, Sansarc, and Samsil are soil series developed from Pierre shale . Some
sedimentary beds in the Pierre shale area (the Pierre, Niobrara, and Morrison formations) occasionally have high amounts
of selenium, a chemical element of the sulfur group. These geologic formations are not uniform in their selenium content.
High selenium levels in plants grown on these soils may cause harmful effects to livestock and humans.
Upper Cretaceous sandstone s and sandy shales of northwestern South
Dakota give rise to many soil textures. The
sandstone s weather to form sandy soils and the shales, which primarily contain mixtures clay and silts (plus small amounts
of sand), are parent materials for sandy loams , loams , clay loams , silty clay loams , silty clays , and clays . The dominant
textures are sandy loams and loams . Morton, Ralph, and Vebar are soil types in this area. There are significant areas of
sodium-affected soils in this region. The Bullock, Daglum, Gerdrum, Hisle, Parchin, and Rhoades series are soils with a
severe sodium problem.
Tertiary sandstone s and siltstone s of southwestern and south-central
South Dakota form sandy and silty soils. The sandy
materials (Valentine and Anselmo soil series ) on the south are an extension of the Nebraska Sand Hills. Going north the
materials progressively have higher silt content (Keith, Canyon, and Rosebud soil series ) and clay content (Pierre and
Samsil soil series ). Some of the strata in this area, and also some of those of the Upper Cretaceous area in northwestern
South Dakota, form benches, plateaus, and buttes , because they are more resistant to erosion than associated materials.
Pleistocene -age glaciers entered South Dakota from the northeast or
north, and flowed south and west, the western margin
of glaciation being the Missouri River. As the ice moved over the land, it filled valleys, planed off hills, cut new valleys,
piled up ridges, and otherwise changed the topography. The character of the rocks of the pre-glacial surface helped
determined the composition of the glacial deposits formed from them. This is because most glacial deposits consist of
altered rocks of local origin. Glacial deposits primarily cover the state east of the Missouri River. They are divided into
four groups: till , outwash , glacial lake deposits, and ice contact stratified drift.
Till , which is the most abundant, is a mixture of all sized particles,
boulders to clay . It is thought to have been deposited
from under part of the flowing ice. Barnes, Clarno, Ethan, Forman, Houdek, and Poinsett are soil series developed from till .
Houdek is the state soil for South Dakota.
Outwash, mostly gravel and sand, was deposited by glacial melt water
as it flowed away from the ice. Ordinarily the
outwash material is covered by alluvium, as is the case in Delmont, Enet, and Fordville soils; or loess , as is the case of
Brandt and Estelline soils.
Glacial lake deposits, called lacustrine materials, consist of parallel-bedded
silt and clay with a small amount of sand
sometimes mixed in. They formed in depressions temporarily blocked by glaciers and filled with water. The Aberdeen,
Beotia, Harmony, and Sinai, are soil series developed in these deposits.
Ice contact stratified drift accumulated on or against melting glacier
ice. It occurs as knobs or small hills, usually in rough
terrain. The Sioux series is an example.
Loess is a non-glacial deposit of wind blown particles of silt size.
The loess in South Dakota came from mixing of silt from
non-glacial deposits to the west with silt blown out from glacial outwash . Loess deposits are found throughout the state and
range from thin layers of less than 12 inches (30 cm) to deposits 30 feet (9 m) or more in thickness. Colby, Keith, Moody,
Nora, and Trent are soil series developed in these deposits. Strictly speaking, loess refers to particles of silt size. Sandy and
silty clay materials, also carried and deposited by the wind are called eolian sand and eolian clay . They also are important
South Dakota soil parent materials . Distribution of these wind-deposited sediments is shown in Figure 2.
Alluvial soils form when gravel, sand, silt , and/or clay, settle out
of flowing water. These materials are almost always
mixed. Generally, the alluvium of west river is clayey in texture, while that in the east is mostly loamy . Bon, Clamo,
Glenberg, Haverson, Havre, LaDelle, Lamo, Lamoure, Lohmiller, Ludden, and Swanboy are soil series developed from
Local alluvium is a water-laid deposit along upland depressions. It
is usually sorted and is finer textured than surrounding
soils. The texture however, can vary from sand to clay . Arnegard, Bonilla, Brookings, Hoven, Kolls, Onita, Parnell,
Parshall, Shambo, Tonka, Trent, and Worthing are soil series developed in local alluvium .
Colluvium is a deposit of rock fragments and unconsolidated earth materials
accumulated at the base of slopes as a result of
gravity and runoff. It is usually unsorted because gravity can move all sizes. The soils can have textures ranging from sands
to extremely bouldery clay . Arvada, Davis, Hilger, Rockoa, Sawdust, Slimbutte, and Vanocker are soil series developed in
How Do Soils Form?
Soils develop gradually through a series of changes, beginning with
the accumulation of parent material, such as rock,
glacial till , loess , or alluvium. Weathering processes release simple compounds that serve as food for bacteria, fungi, and
other soil organisms. These simple forms of life live and die by the billions. Their bodies decay in the parent materials and
thus organic matter (humus) begins accumulating. Gradually the developing soil is able to support higher forms of plant and
animal life. The present level of humus in our soils is due principally to the activity of higher forms of plant life. As plants
grow, upper layers of the loose parent material at the surface accumulate humus, pH is reduced, and leaching takes place.
These changes form distinctive soil layers called horizons.
The amount of horizon development that occurs in a soil is determined
by the soil forming factors of time, parent material ,
topography, climate and organisms (Malo, 1996). Climate and organisms (particularly vegetation) cause regional soil
differences, as between eastern and western South Dakota. Topography, parent material , and age (time soil has been
developing) cause local or county differences in soils.
From Westin and Malo, 1978.
There are four types of processes involved in horizon development. Additions
to the soil come from precipitation, organic
matter, and solar energy. Losses are processes that often are destructive, such as erosion , leaching of nutrients, night
radiation of energy, nitrogen losses by microbial activity, and water loss through plant transpiration . Movement of
materials within the soil occur through nutrient cycling by plants and soil mixing by organisms. Lastly, new compounds are
formed within soil from weathered rocks and minerals.
What Soil Horizons Are Found In South Dakota?
Soil horizons , which can be seen on the walls of a fresh road cut,
consist of a succession of layers in vertical section down
through the soil. Horizons in soils are identified by standard symbols (i.e. A, B, k, w, t, and many others). Each symbol
shows how the material has been altered, when compared to the original parent material . There are three types of symbols
used to name soil horizons ; capital letters, lower case letters, and Arabic numbers. The capital letters are used to describe
major layers. Most major soil horizons have only one capital letter (i.e. A, B, C, E, O, and R), but some require two (i.e.
AB, EB, AC, BC, E/B, and others) if the layer is mixed or composed of two major horizons, or is a transitional layer.
An O horizon is a layer dominated by organic materials (i.e. leaves,
needles, twigs, moss, and other un-decomposed or
partially decomposed plant litter). O horizons are common in forest-derived and saturated wetland soils. Sometimes O
horizons are called the "topsoil or surface soil" and in some profiles O horizons may be found buried under other major
layers. Organic matter content in O horizons commonly exceeds 35%.
An A horizon is a mineral layer that is high in humus (1-10%), or shows
the influence of cultivation, grazing, or similar
agricultural disturbance. Most of the soils in South Dakota have an A horizon that was formed by humus accumulating in the
surface soil materials. Usually, the A horizon is called "topsoil ." A horizons are usually found at the soil surface, but can
be found below an O horizon .
A B horizon is a mineral layer that forms beneath an A, E, or O horizon
. In South Dakota, the B horizon has one or more of
the following: 1) accumulation of clay , humus, carbonates, sodium, gypsum, iron/aluminum oxides, other salts; 2) removal
of carbonates; 3) formation of soil structure ; or 4) color change. All B horizons represent changes in the parent material
as a result of soil formation. B horizons are sometimes referred to as the "subsoil ."
A C horizon is usually found beneath O, A, B, or E horizons . C horizons
are soil layers that are little changed. If the parent
material is just forming (i.e. volcanic area, sand dunes ), there maybe a C horizon at the soil surface. Occasionally, the C
horizon can have accumulations of various types of salt. Some C horizons are composed of soft bedrock , such as shale ,
siltstone , weathered sandstone . The C horizon is often called "parent material."
The E horizon represents a layer where there has been significant loss
of clay , humus, and iron/aluminum oxides, resulting
in a layer that is lighter in color and coarser textured than the layers above or below. E horizons occur above B horizons
and are found at or near the soil surface. They may or may not be beneath O or A horizons . E horizons are most commonly
found in forest-derived, sodium-affected, or depression soils.
The R horizon is hard bedrock . It is harder than a spade. Examples
of hard bedrock in South Dakota include granite,
limestone , and sandstone. This horizon does not exhibit evidence of soil formation or weathering.
Lower case letters are used as suffixes to the major horizons . These
letters further define the properties of the layer. The
most common subhorizons used in South Dakota are: b (buried genetic horizon ); g (gleyed colors, saturated soils); k (lime
or carbonate accumulation - both calcium and magnesium ); n (sodium affected); p (cultivated or pastured); r
(soft/weathered bedrock ); ss (high clay content soils that significantly shrink and swell); t (clay accumulation); w
(development of only color and structure ); y (gypsum accumulation); and z (other salt accumulation).
If a layer needs to be subdivided, then suffix Arabic numbers are used
(i.e. Ap1, Ap2; Bt1, Bt2, Bt3; C1, C2). Arabic
numbers are used only when the capital and lower case letters are the same.
The principal horizons names used in South Dakota for prairie soils
are: Ap(if cultivated) or A, AB, Bt or Bw, Bk, and C.
The principal horizons for forested soils are: O, A, E, Bt, C or R. Sodium affected soils usually have A or Ap (if
cultivated), E, Btn, Bkyz, and C horizons present. Depressional soils have A1, A2, E, Bt1, Bt2, and C horizons present.
Many of the young erosional, dunes, or flood plain soils have A, AC, C1, and C2 horizons . Usually, all the horizons and the
upper part of the parent material occur with a depth of five feet (1.5 m).
All of the horizons and subhorizons listed above do not occur in every
soil. Many soils may have horizons other than those
discussed. Consult the Soil Survey Manual for a more complete discussion on soil horizons (Soil Survey Division Staff,
Protecting the quality of our soils is critical to the welfare of our
people and our economy. There are four major concerns in
soil conservation: loss of moisture; loss of organic matter and nitrogen; loss of mineral nutrients; and loss of topsoil through
Moisture loss occurs through evaporation, transpiration ,, leaching,
and runoff. Evaporation and runoff are particularly
serious when water does not quickly soak into the soil. Soil texture and structure determine how quickly water will be
absorbed. Sandy soils will take up water much more quickly than will clays . These finer textured soils tend to cause
puddling when rain drops splash on the bare soil if soil structure is poor and organic matter levels are low.
One way to increase water uptake and storage by soils is to increase
the amount of organic matter in the soil. Organic matter
acts like a sponge, thus reducing the puddling problem. Other solutions include leaving stubble in the fields, mulching, and
increasing the surface roughness.
Moisture loss through weed transpiration can be significant. One crop
of foxtail grass will remove about 2 acre-inches of
moisture from soil. Weed reduction can be accomplished through planting weed-free seeds, applying herbicides, and using
tillage and crop rotations.
Organic matter and nitrogen loss from soils can seriously reduce crop
yields and make soils more susceptible to erosion .
South Dakota soils have lost about one-third of their organic matter and organic nitrogen as a result of years of cropping.
Some farmers and ranchers leave fields fallow for a season to renew the soil's productivity. Nitrogen can be returned to the
soil through application of natural waste products, commercial organic and inorganic fertilizers, or through the planting of
nitrogen-fixing plants, such as alfalfa or clover. Alfalfa and other legumes have nodules on their roots that contain bacteria
that can transform atmospheric nitrogen to a form usable by legume plants. Building up the organic matter content in the soil
is difficult with conventional tillage.
Mineral nutrient losses due to erosion varies from one nutrient to another.
Nutrients such as potassium, calcium, and
magnesium are usually present in adequate amounts in South Dakota soils. Phosphorus content, however, is low in most soils
of the state, and is highest in topsoil, which is lost in erosion. Generally, in soils with high calcium content, phosphorus
availability is low because it combines with the calcium to form an insoluble substance. Phosphorus can be returned to the
soil by adding waste products and commercial fertilizers.
Soil loss from erosion can be caused by the action of wind and/or water.
Soil texture, soil structure, slope of the land, and
the amount of plant cover affect the amount of soil erosion that can occur.
Wind erosion is caused by a problem called "saltation." Erosion is most
prevalent in soils with sand-sized grains. These
sand-sized grains are blown several feet into the air by the wind and then are driven at high speeds into the ground. The
impact sprays more soil, often very fine particles, into the air. These fine soil particles are carried away by the wind. Soil
blowing can be reduced through conservation tillage that keeps a growing crop or crop residues on the land throughout the
year. No-till is a conservation tillage strategy in which the soil is disturbed only in the immediate area of the planted seed
row. If soil blowing begins when the land is bare, it can be reduced by roughing up the soil surface or by tilling ridges
perpendicular to the direction of the wind.
One way to reduce wind erosion of soil is to plant shelterbelts. These
plantings of trees and shrubs to break up large, open
tracts of land were first undertaken in the 1930's, in response to the severe drought and soil blowing problems at that time.
Shelterbelts also provide valuable wildlife habitat where animals can be sheltered from predators and the harsh climate.
Modern shelterbelts are narrower than those planted in the 1930's. The Natural Resources Conservation Service (NRCS -
formerly the Soil Conservation Service), the Cooperative Extension Services (CES), and the Agricultural Experiment
Station at SDSU will advise land owners on the size and species composition of effective shelterbelts. Maintenance of
established shelterbelts is an important task for continued protection of the state's soils.
Water erosion from runoff can be reduced through residue management,
terracing , contour farming and contour strip
cropping , all of which lessen the impact of land slope. The key step in water erosion control is stopping the raindrop from
directly striking the soil surface. Water erosion on sloping lands is a serious problem in eastern South Dakota. Crop rotation
with legumes will increase the organic matter in the soil, and make it less prone to erosion.
The NRCS (federal agency) and the CES (county agency), and the Agricultural
Experiment Station at SDSU (state agency)
work with South Dakotans to implement good soil conservation measures appropriate to the soil type at each location.
Addresses and phone numbers for these offices in South Dakota are included in the government pages of your phone book.
Flint, R.F. 1955. Pleistocene Geology of Eastern South Dakota. Geological
Survey Professional Paper 262. U.S. Dept.
Interior. Washington, D.C.
Kaul, R.B. 1986. Physical and Floristic Characteristics of the Great Plains. In Flora of the Great Plains. T.M. Barkley ed.
University of Kansas Press. Lawrence, KS. p. 7-14.
Kubota, J. and W.H. Allaway. 1972. Geographic Distribution of Trace Element Problems. In Micronutrients in Agriculture.
J.J. Mortvedt, P.M. Giordano, and W.L. Lindsay ed. Soil Science Society of America, Inc. Madison, WI. p. 525-554.
Malo, D.D. 1993. South Dakota Geological Highway Map. Plant Science Department. South Dakota Agricultural Experiment
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Douglas Malo, Distinguished Professor, Plant Science Dept., SDSU, Brookings, SD 57007 1997.
Elmer Ward, District Conservationist, Natural Resource Conservation Service, Huron, SD.
Publication of the Soils of South Dakota fact sheet was funded
by the Northern State University CUEST Center for
Environmental Education, Aberdeen, SD.