Soil is Iowa’s greatest natural resource. However, there are many diff erent soils in Iowa, 

each possessing a unique set of properties.

The enclosed map does not attempt to show all of the soils in Iowa. Rather it shows the 

geographic areas where major soil groups occur. These soil groups are called soil associations, and the map is called a soil association map. A soil association is a group of soils that 

are closely associated geographically and occur in a characteristic pattern. More information about soil associations is available on the Iowa NRCS web site at 

www.ia.nrcs.usda.gov/soils.html. More detailed information about soils is available online 

through the U.S. Web Soil Survey at http://websoilsurvey.nrcs.usda.gov/app/. 

This brochure is a cooperative eff ort between the Iowa Department of Agriculture and 

Land Stewardship, Iowa Department of Transportation, United States Department of 

Agriculture’s Natural Resources Conservation Service and Iowa State University Extension.

Loess over glacial till – low rainfall

Moody - Trent Soils

These soils formed in a mantle of loess and occur in the far northwest corner of 

the state. This area is considered the driest part of Iowa. Moisture is limited, but is usually 

present when conditions are suitable for plant growth. The landscape consists of gently 

undulating to steep soils with long smooth slopes and well defi ned drainage ways. The 

hills have broad undulating to rolling ridgetops and hilly to steep valley sides. The valleys 

generally are narrow, but the major rivers and other large tributaries have broad fl ood 

plains and terraces. 

Nearly all of this area is farmed. Corn and soybeans are the major crops. Feed grains and 

hay crops are also widely grown. Native vegetation was mixed tall and short grass prairie 

Fun Fact: This area receives the least precipitation at an average of 26 inches. The 

overall State precipitation average is 34 inches.

Northwest Iowa Loess

Galva – Primghar Soils

Most of the soils of this region formed in loess. Most slopes are nearly level and 

gently sloping but some slopes bordering major stream valleys are steep. A few large rivers have nearly level and broad valley fl oors and stream terraces. 

Nearly all of this region is cultivated. Corn and soybeans are the principal crops. Native 

vegetation varied between tallgrass prairie vegetation on moist soils to short grass vegetation on slopes and uplands. Timber made up less than 1 percent of the area.

Fun Fact: Prehistoric fossils found in this area include crocodiles, large turtles, and 

sharks.

Tazewell Glacial Till

Everly - Wilmonton – Letri Soils

This area has soils formed in a thin mantle of loess or erosional sediments and 

the underlying Tazewell glacial till. The landscape consists of broad, plane and convex 

ridges, long, convex side slopes, and concave drainageways. Slopes are nearly level to 

moderately sloping.

Nearly all of this region is cultivated. Corn and soybeans are the principal crops. Native 

vegetation is mixed tall and short grass prairie.

Fun Fact: Unique wetlands called ‘fens’ are common in this region. Fens typically are 

formed on sidehills from groundwater discharge. Fens in Iowa contain about 200 different plant species, of which 20 are rare and endangered.

Loamy Wisconsin Glacial Till

Clarion – Nicollet – Webster Soils

This area is commonly referred to as the “Des Moines Lobe” of the Wisconsin-age 

ice sheet that covered the north central United States about 12,000 years ago. Most of this 

area is a nearly level to gently rolling till plain. The city of Des Moines was built on the high 

moraine at the farthest south extent of this lobe. Natural lakes dot this region and numerous bogs, swales and circular depressions indicate sites of previously ponded water. Much 

of the area is tile drained. End moraines have a banded pattern across this area and are 

typically described as knob and kettle topography. These soils formed in loamy glacial till, 

glacial outwash, and/or local alluvium.

Nearly all this area is cropland. Corn and soybeans are the major crops. Some cropland is 

used for hay. Native vegetation was mixed tall and short grass prairie.

Fun Fact: As the glacial ice stagnated, long ridges called moraines were formed. The 

Iowa State Capital sits atop the far Southern end of the Wisconsin glacial advance.

Clayey Lake Deposits

Marna – Kossuth – Bode Soils

These soils formed in silty and clayey glacial lacustrine sediments overlying 

calcareous loamy glacial till within the Loamy Wisconsin Till area. They contain more clay 

and less sand than the typical soils of the Des Moines Lobe. In contrast to the Wisconsin till 

plain, this area’s relief is low. Knobs of well drained soils are less common and less distinct, 

and depressions are few, shallow, and indistinct. 

Nearly all this area is cropland. Corn and soybeans are the major crops. Native vegetation is 

tall grass prairie.

Fun Fact: Nearly all of Iowa’s naturally formed lakes are found in the north central 

part of the State.

Iowan Erosion Surface

Kenyon – Clyde – Floyd Soils

This land surface is level to gently rolling with long slopes, low relief and open 

views. The soils in this area formed in a mantle of silty or loamy sediments and the underlying glacial till. Recent alluvium consisting of clay, silt, sand, and gravel fi ll the major river 

valleys. Drainage is well established, though stream gradients are often low and a few 

areas of poor drainage or bog conditions occur. A typical feature of this area is scattered 

large boulders partially buried or lying on the surface. These erratics, composed of rock 

types not found in the area are clearly of glacial origin. A few scattered pahas occur in the 

southern part of this area. They typically are elongated and are oriented in a distinct northwest-southeast direction.

Nearly all of this area is farmed. Corn and soybeans are the major crops. A small portion is 

wooded, mainly on wet bottom land and on steep slopes bordering stream valleys. Many 

of the wet soils require artifi cial drainage for timely fi eld operations and good crop growth. 

Native vegetation is mixed tall and short grass prairie. 

Fun Fact: Fossils found in this area show that tundra conditions were well established 

in Iowa 17,000 years ago.

Shallow To Bedrock

Rockton Soils

This region is located in the northeastern portion of the state. It consists of 

nearly level to very steep soils underlain by limestone and shale. Limestone is found at 

a depth of 20 to 40 inches and occur on sides slopes and crests of upland ridges and on 

stream terraces.

Row crops typically are grown on the nearly level to gently sloping uplands and on the 

greater part of the stream terraces. The moderately sloping to very steep areas generally 

are in pasture or woodland. 

Fun Fact: Dairies are common in northeast Iowa. Iowa ranks 12th in the nation in annual milk production.

Loess with Bedrock Outcrops

Downs – Fayette – Nordness Soils

This region is commonly incorrectly referred to as the “Driftless Area” because it 

suggests that this area was never glaciated. However, soil scientists and geologists have 

documented evidence of glacial deposits scattered throughout the area. Scenic landscapes with deep valleys, abundant rock outcrops, high bluff s, caves, crevices, sinkholes 

and an angular stepped skyline occur in this area. Along many of the steepest slopes, bare 

limestone forms rock outcrops. Often valleys take abrupt, sharp-angled turns indicating 

the local drainage network is controlled by joint patterns in the underlying bedrock.

Nearly all this area is in farms, but only about one-half is cropland. Feed grains and forage 

for dairy cattle and other livestock are principal crops. Native vegetation of the upland 

soils is hardwood forest.

Fun Fact: The types of bedrock found in this region have resulted in the formation of 

many sinkholes, springs, and caves.

Shallow Loess over Glacial Till

Dinsdale – Klinger Soils

The characteristic landscape of this region is wide, gently sloping, convex 

ridgetops and moderately sloping side slopes. The upland soils in this region formed in a 

thin mantle of loess and the underlying glacial till. 

Nearly all of this area is in cropland. Corn and soybeans are the major crops. Many of the 

wet soils require artifi cial drainage for timely fi eld operations and good crop growth. Native vegetation is mixed tall and short grass prairie.

Fun Fact: More than 2 billion bushels of corn are produced annually on rich Iowa soils, 

such as those found in this region.

Loess Ridges and Sideslopes

Tama – Muscatine - Downs Soils

This region consists of nearly level to steep soils that formed in loess. The side 

slopes typically have many drainageways.

Tama and Muscatine soils formed under tall prairie grasses, and Downs soils, which typically are located on steeper slopes along the major river systems, formed under a mix 

of deciduous trees and tall grass prairie. Nearly all of this region is cultivated. Corn and 

soybeans are the principal crops. Some of the steeper areas are used for hay and pasture 

or remain in timber.

Fun Fact: The Muscatine Soil is rated as the top crop-producing soil in Iowa.

Loess with exposures of Glacial Till

Marshall – Shelby Soils

This region is characterized by broad, rounded ridgetops and gently sloping to 

strongly sloping side slopes with wide river valleys. Most of the soils on the ridgetops and 

upper portions of the slopes in this region formed in deep loess. On the steeper portions 

of the slopes, glacial till commonly is exposed. Nearly all of this region is cultivated. Corn 

and soybeans are the principal crops. Some of the steeper areas are used for hay and pasture. Native vegetation is mixed tall and short grass prairie.

Fun Fact: The native prairie vegetation resulted in soils with topsoil as thick as 20 

inches.

Very Deep Loess

Monona – Ida – Napier Soils

This region has nearly level to moderately sloping ridgetops and moderately 

sloping to steep side slopes. It is dissected by numerous drainageways in which gullies are 

common. 

Monona and Ida soils formed in deep loess. Monona soils typically occur on the broader 

ridges and long smooth side slopes. Ida soils typically occur on narrow ridgetops and the 

steepest portion of the hill slope. Napier soils formed in local alluvium and occur in most of 

the narrow drainageways and on footslopes. Nearly all of this region is cultivated. Corn and 

soybeans are the principal crops. Some of the steeper areas are used for hay and pasture. 

Native vegetation is mixed tall and short grass prairie.

Fun Fact: Man-made terraces cross the landscape in this region to protect these soils 

from gully erosion.

Missouri River Bluff s

Ida – Hamburg Soils

This region consists of a narrow band of soils that formed in thick loess under 

prairie grasses in the bluff s area east of the Missouri River fl oodplain. It is characterized by 

narrow, rounded ridgetops; long, steep to very steep side slopes; and very deep, raw gullies.

These steep and very steep soils formed in deep loess. The Hamburg soils typically occur 

closest to the fl oodplain and are characterized by the ‘catsteps’ formed by small earth slips 

on the very steep slopes. Napier soils formed in local alluvium and occur in most of the 

narrow drainageways and on footslopes.

Some ridgetops and side slopes and small areas along drainageways are cultivated and 

used for row crops and pasture. Most of the steeper areas are in permanent pasture or 

timber.

Fun Fact: Landscapes similar to the loess bluff s only exist in the corresponding latitudes of China along the Yellow River. 

Missouri River Alluvium

Albaton – Luton – Onawa Soils

This region of the Missouri River fl oodplain is characterized as a nearly level, 

broad, valley fl oor. Although once a braided river system with numerous islands and 

channels, the main channel of the Missouri River was narrowed to about half of its original width, and most of the islands eliminated. The river carries large loads of sediment. 

Tributary streams also carry large loads of sediment because of the erosive nature of the 

adjacent loess mantled hills.

The soils in this area formed from alluvium deposited by the Missouri River and its tributaries, and from soil washed from the adjacent loess covered hills. 

Nearly all of this region is dominated by agriculture. Corn and soybeans are the principal 

crops. A few old oxbow river channels still remain as wildlife habitat and recreational areas.

Fun Fact: The Lewis and Clark Exploration traveled this region noting the appearance 

of deer, bear and elk for 37 days in 1804.

Loess Ridges/Glacial Till – SW Iowa

Sharpsburg – Shelby – Adair Soils

Slopes in this region are mostly rolling to hilly but some broad ridge tops are 

nearly level to undulating. The slopes bordering major stream valleys are steep. A few large 

rivers have nearly level and broad valley fl oors.

Deep loess soils, such as Sharpsburg, make up a good share of the upland hillslopes. 

Where slopes are steeper and sharper, glacial tills soils such as Shelby and Adair are more 

prominent.

Historically, this area was dominated by prairie with the remainder of its landscape covered by forest, savannas, or shrub lands. Today, this region is dominated by agriculture, 

with only about 5 percent of land covered by native vegetation.

Fun Fact: Thin layers of volcanic ash originating from now extinct volcanoes in Yellowstone can be found here sandwiched between layers of glacial till.

Loess, Shale, and Glacial Till

Pershing – Gosport – Gara Soils

This region consists of gently sloping to strongly sloping soils that formed in 

loess and strongly sloping to steep soils that formed in shale and glacial till. Pershing, 

Gosport, and Gara are the major soil in this region. These soils are gently sloping and moderately sloping. They formed in loess under mixed prairie grasses and trees. Gosport soils 

formed in residuum from shale under forest vegetation and occupy the steepest parts of 

the slopes. Gara soils are on strongly sloping to steep convex side slopes. They formed in 

glacial till under mixed prairie grasses and trees.

The steeper areas of this region are used mostly for hay, pasture, and woodland. The gently 

sloping soils are used for row crops. 

Fun Fact: Fossils dating back 300 million years from extinct marine animals identifi ed 

as ‘conodonts’ are common in the shales of this region . 

Loess Ridges/Glacial Till – SE Iowa

Otley – Ladoga Soils

This region consists of soils developed in loess on broad, convex ridgetops and 

upper side slopes. Soils developed in glacial till soils dominate the steeper side slopes. The 

side slopes are dissected with many drainage ways and small streams. A few large rivers 

have nearly level and broad valley fl oors.

Otley and Ladoga formed in loess and contain 35 to 42 percent clay in the subsoil. Gara 

soils formed in glacial till and contain 30 to 35 percent clay in the subsoil. Native vegetation of Otley soil is tall grass prairie. Ladoga and Gara soils developed under mixed prairie 

grasses and deciduous forest.

Most of this region in farmed, with about 70 percent in cropland. Common crops are corn 

and soybeans, with some hay. Swine and cattle operations are common. 

Fun Fact: European settlement occurred in this region as early as the 1830s along the 

region’s many rivers, which provided a source of fresh water.

Eolian Sand

Sparta – Chelsea – Dickinson Soils

This region consists of well-drained and excessively-drained soils that formed 

from windblown sandy and loamy parent material. These soils occur on high stream 

benches and upland side slopes, mainly along the bluff s and breaks of the major rivers.

Most of the soils in this area are droughty and are susceptible to wind and water erosion. 

Flatter areas are used for cultivated crops but the steeper slopes are used for pasture, 

woodland, and wildlife habitat.

Fun Fact: As glaciers melted, strong winds blew the exposed soil and formed sand 

sheets, dunes, and stringers in Iowa.

Loess –Timbered

Fayette Soils

This region consists of soils on broad to narrow, convex ridgetops, and long 

convex side slopes. Many of these areas occur on the steeper slopes near major streams. 

The side slopes are dissected by numerous waterways. The landscape is undulating to very 

steep. The dominant soil of this area, Fayette, formed in loess under native forest conditions.

Most of the less sloping areas of this region are farmed but some of the steepest areas 

remain in timber or are used for pasture.

Fun Fact: The native forest conditions result in an abundance of Morel mushrooms in 

the Spring.

Alluvium

Colo – Chequest – Titus Soils

Alluvial soils occur on fl oodplains along rivers and streams throughout Iowa. In 

the southeastern portion of the state, the poorly drained Colo, Chequest, and Titus soils 

make up a large portion of fl oodplain soils. Most of these soils are artifi cially drained and in 

cropland, but some oxbow wetlands remain. Corn and soybeans are the major crops.

Fun Fact: The lowest elevation in Iowa at 480 feet above sea level occurs where the 

Des Moines River joins the Mississippi.

Loess Ridges/Glacial Till Sideslopes

Grundy – Haig – Arispe – Gara Soils

This region consists of soils developed in loess on broad, convex ridgetops and 

side slopes and glacial till on strongly sloping to steep side slopes. Grundy, Haig, and 

Arispe are the major soils on slopes of less than 9 percent. These soils typically contain 42 

to 48 percent clay in the subsoil. Many of the side slopes that are steeper than 9 percent 

developed in glacial till. Gara is the major soils on these positions. 

Nearly all of this area is farmed. Corn and soybeans are the major crops. Native vegetation 

of Grundy, Haig, and Arispe is tall grass prairie. Gara soils formed under a mix of prairie 

grasses and deciduous trees.

Fun Fact: Natural geologic erosion in this region has left the oldest landscape surfaces 

at the highest elevations, while younger surfaces are cut into lower landscape positions.

Loess Ridges/Clay Paleosol

Seymour – Edina - Clarinda Soils

This region consists of nearly level to moderately sloping soils formed in loess on 

wide upland divides and upper side slopes, and moderately sloping to steep soils formed 

in glacial till or a paleosol formed in glacial till on side slopes. Seymour, Edina, and Clarinda 

formed under prairie grasses and are the major soils. Seymour and Edina formed in loess 

and Clarinda soils formed in a paleosol formed in glacial till. These soils typically contain 

more than 45 percent clay in the subsoil. Gara soils formed in glacial till under mixed prairie grasses and trees, and typically occur on the steepest slopes. 

The majority of the nearly level to moderately sloping soils are farmed. Corn and soybeans 

are the major crops. Many of the steeper slopes are in pasture.

Fun Fact: This was one of the main coal mining regions in Iowa during the fi rst third of 

the 20th century.

Iowa Soil Associations

1

2

3

4

5

6

7

9

10

11

12

13

14

15

17

18

19

20

21

22

Detailed information about individual soil series can be found at: 

http://ortho.ftw.nrcs.usda.gov/cgi-bin/osd/osdname.cgi

8 16
21

4

22

15

2 6

8

12

10

11

9

5

14

1

17

19

7 3

16

20

13

18

9

Linn

Sac

Lee

Ida

Tama

Sioux

Polk

Clay

Iowa

Lyon

Kossuth

Cass

Jasper

Story

Page

Adair

Clayton

Fayette

Benton

Clinton

Cedar

Butler

Dallas

Jones

Mills

Plymouth

Davis

Floyd

Scott

Wright

Boone

Webster

Taylor

Monona

Shelby

Hardin

Woodbury

Carroll

Marion

OBrien

Harrison

Warren

Guthrie

Greene

Wayne

Crawford

Jackson

Keokuk

Henry

Union Lucas

Franklin

Johnson

Decatur

Calhoun

Dubuque

Pottawattamie

Grundy

Marshall

Clarke

Worth

Madison

Hancock

Mahaska

Hamilton

Allamakee

Palo Alto

Delaware

Louisa

Fremont

Howard

Adams

Cherokee

Mitchell

Bremer

Ringgold

Winneshiek Emmet

Monroe

Buchanan

Wapello

Poweshiek

Black Hawk

Osceola

Pocahontas Buena Vista

Audubon

Washington

Van Buren

Chickasaw

Jefferson

Cerro Gordo

Appanoose

Humboldt

Muscatine

Dickinson

Des Moines

Winnebago

Montgomery

Des Moines Adel

Logan

Onawa Boone

Osage

Harlan

Newton

Nevada Toledo

Vinton

Eldora

Algona Garner

Sibley

Waukon

Cresco

Bedford Corydon

Red Oak

Corning

Creston

Ottumwa

Wapello

Audubon

Marengo

Denison Carroll

Clinton

Anamosa

Le Mars

Dubuque

Waverly

Allison

Spencer

Decorah

Clarinda

Glenwood

Chariton

Atlantic

Sac City

Waterloo

Mount Ayr Keosauqua

Fairfield

Knoxville Oskaloosa Indianola

Muscatine

Montezuma

Davenport

Iowa City

Jefferson

Ida Grove

Maquoketa

Northwood

Burlington

Greenfield

Washington

Sioux City Fort Dodge

Storm Lake

Manchester

Emmetsburg

West Union

Mason City

Centerville

Dakota City

Orange City

Forest City

Rock Rapids

Estherville Spirit Lake

Fort Madison

Marshalltown

Cedar Rapids

Webster City

Grundy Center

Mount Pleasant

Council Bluffs

Leon

Albia

Sidney

Tipton

Osceola

Clarion Hampton

Elkader

Cherokee

Primghar

Winterset

Sigourney

Bloomfield

Pocahontas

New Hampton

Independence

Charles City

Rockwell City

Guthrie Center

80

680

35

380

280 235

29

52

169

20

151

30

18

75

34

61

65

59

71

69

218

63

275

67

61

63

71

52

52

75

69

63

59

69

169

65

59

151

218

71

65

69

136

64

3

31

62

76

140

130

13

4 39

12

10

141

15

148

93

281

149

2

183

21

38

57

5

14

210

92

175

48

16

1

17

25

78

7

188

56

22

330

346

212

187 150

83

26

191

70

27

37

146

117

96

316

415

28

196

51

173

143

110

8

137

9

370

81

38

7

175

16

10

202

21

14

141

2

13

17

141

12

4

149

150

4

21

175

28

7

175

25

15

10

78

80

80

35

35

9

218

218

86

71

9

18

76

18

9

9

52

61

52

136

1

148 6

34

169

69

14

5

65

151

60

20

20

30

2 63

5

18

63

85

61

34

34

1

141

144

44

169 65

3

44

30

29

29

163

34

92

92

218

92

Illinois

Missouri

Minnesota

Nebraska

Wisconsin

South Dakota

Iowa Soil Regions

Legend

Soil Regions

1 Loess over glacial till - low rainfall

2 Northwest Iowa Loess

3 Tazewell Glacial Till

4 Loamy Wisconsin Glacial Till

5 Clayey Lake Deposits

6 Iowan Erosion Surface

7 Shallow to Bedrock

8 Loess with Bedrock Outcrops

9 Shallow Loess over Glacial Till

10 Loess Ridges and Sideslopes

11 Loess with exposures of Glacial Till

12 Very Deep Loess

13 Missouri River Bluffs

14 Missouri River Alluvium

15 Loess Ridges/Glacial Till - SW Iowa

16 Loess, Shale, and Glacial Till

17 Loess Ridges/Glacial Till - SE Iowa

18 Eolian Sand

19 Loess - Timbered

20 Alluvium

21 Loess Ridges/Glacial Till Sideslopes

22 Loess Ridges/Clay Paleosol

23 Water

0 12.5 25 50 75

Miles

ith: W tion a ooper In C

ial er t or ma m f er al t a gener lluvium– lluvial/A A

, , sand el var , including g eams y str ed b deposit

es of tur tions and mix ia ar , and all v y silt, and cla

. these

t calcium cien taining suffi on soil c eous– ar alc C

ed t ea e visibly when tr esc v er o eff e t t bona car

. ic acid ochlor dr y ed h old dilut with c

ommon es c tur ea -like f case the stair eps– tst aC

a. w n Io er est ills of w oess H on hillslopes of the L

ed in ial deposit er t soil ma olluvium– olluvial/C C

, soil y vit ar tion of g y the ac ootslope positions b f

ash. , or local w eep cr

ed and non- t onsolida ally unc gener Glacial till–

y a glacier tly b ec ed dir ial deposit er t ed ma tifi a str

, er t a y melt w ing b k or ew t r without subsequen

, ones , st el var , g , silt, sand y onsisting of cla and c

tion. opor y pr mingled in an er t and boulders in

ting an undula –y aph opogr ettle t Knob and k

ed assemblage of der landscape in which a disor

- er t idges of glacial till is in , or r , mounds nolls k

. essions egular depr r spersed with ir

ed in ial deposit er t ma ts– acustrine sedimen L

er t a eding w ec y r er exposed b t er and la t a lake w

. els lev

y ed b ed and deposit t anspor ial tr er t ma oess– L

ed -siz ely silt t edomina onsisting of pr wind and c

. ticles par

aphi- r opog , or other t idge , r a mound – aine Mor

tion of glacial till depos- cumula t ac cally distinc

. e tion of glacial ic t ac ec y the dir ily b imar ed pr it

om ed fr t ien ypically or t hills t ominen pr aha– P

o be in the end t t t o southeast, tha est t wth nor

, and e fac osion Sur an Er w t of the Io n par souther

ge deposits of loess on them. e lar v ypically ha t

ing the med dur or as f t w a soil tha aleosol– P

ed v eser ied and pr as bur ic past and w geolog

ied soil his bur T tion. ta t sedimen en ec e r y mor b

y e b fac n sur eexposed on the moder en r t is of

osion. t er subsequen

th- ea tly w ed and par t onsolida unc Residuum–

- et y disin ed b t cumula ials ac er t al ma ed miner er

. e ock in plac ed r t onsolida tion of c ar g

ing a der e bor fac eplike sur a st –e ac err eam t tr S

mer position or ts the f esen epr t r oor tha alley fl v

oodplain. of a fl

e of the anc liest adv the ear ell glacial till– we az T

onsid- a; c w iod in Io tion per t glacia en ec most r

o 40 ely 26 thousand t t xima o o be appr ed t er

t. esen e pr or ears bef thousand y

.r ey lo p me and r de vi or py tunit A is an equal oppor USD

HIGHWAY GUIDE

IOWA SOIL ASSOCIATIONS

OF

Glossary of Terms