Content adapted from Indiana University Purdue University Indianapolis and Indiana State University, partners in the Natural Heritage of Indiana Project.
Indiana possesses a wide range of soils: several hundred types fall into gray-brown podsolics, prairie soils, planosols, wisenbodens, and alluvial soils.To understand Indiana soils and all their complexity, it is a good idea to be familiar with soil science. Then, you can go straight to the soil survey reports themselves.
Basics of soil science
Official Indiana soil surveys
The official soil surveys for Indiana can be found on the US Department of Agriculture Natural Resources Conservation Service's site.
The Soil Regions of Indiana
Content reproduced with permission from Indiana University Press. The following essay was published in The Natural Heritage of Indiana, copyright 1997, Indiana University Press.
THE SOIL REGIONS OF INDIANA
The simple story of the soils of Indiana is largely one of glacial action. Thousands of years ago great ice sheets hundreds of feet thick spread over most of the state, scraping down hills, filling valleys, and grinding the rocks to gravel and flour.
-T. M. Bushnell, The Story of Indiana Soils (1944)
(Regions 1 and 4). In Soil Regions 1 and 4, sandy material was deposited by water, and some of this material was subsequently moved by wind and piled into dunes. At the southern tip of Lake Michigan, sand was deposited on the beach and then blown into high dunes. This area is part of the Calumet Lacustrine Plain physiographic region (see block diagram). Soils formed on these dunes (eg, Oakville) are relatively young and have weakly developed horizons. Black oak and white oak were the dominant pre-settlement trees on these soils, whereas such mesic species as sugar maple and American beech occupied the coves among the dunes. The soils in the low-lying sandy lake plains (e.g, Maumee) have dark surface horizons and B horizons that are gray because of their wet and reduced condition.
South of Lake Michigan in the Kankakee Outwash and Lacustrine Plain, sandy materials were deposited when the ancestral Kankakee River meandered over the sandy lake plain. The wind piled some of this material into dunes that are smaller and have stronger soil development than in those along Lake Michigan. In many soils the subsoil has thin bands, called lamellae, that are finer in texture than the surrounding material.
The low-lying Maumee and Morocco soils of Region 1 have been farmed for many years, while the soils on the dunes were left in forest. More recently, the trees were bulldozed from some of the dunes and the soils were irrigated and planted to crops. These soils are very poorly suited to crop production, however, because they are highly wind-erodible and their water holding capacity is very low. The low-lying sandy soils, which are saturated with water in the subsoil several months of the year, have been drained to lower the water table and permit crop production.
Soil Region 4 occurs in north-central and southwestern Indiana.
In this region, sandy outwash materials were deposited on outwash plains or terraces; the wind then moved some of the sandy material into dunes. In contrast to those of Region 1, almost all soils of Region 4 lack wetness features. The soils on dunes also have a higher available water-holding capacity and better nutrient-holding ability than those in Region 1, and can be used effectively for crop production. Many of these soils along the lower Wabash and White River valleys are used for growing cantaloupes, watermelons, and tomatoes. Other soils of the region are used for more conventional farm crops such as corn, wheat, and soybeans.
Soils on water-deposited materials.
(Regions 2 and 3) These soils formed in glacial outwash, lacustrine (lake) deposits, and alluvium in various parts of the state. Soils formed in outwash deposits occur on two landscape units, outwash plains and terraces. Outwash plains are generally on upland positions, while a terrace is enclosed in a river valley Typically, coarse material settled out of the outwash streams before finer material, hence these soils formed in loamy material over sandy and gravelly material (e.g., in the Fox, Oclzley; and Wea soils).
The soils are mainly on broad, flat areas with some swells. At some depth below the outwash, in many places there is a less permeable layer that holds up the water. If that layer is near the surface, the soils are more poorly drained, and if it is deeper, the soils are better drained, ever on nearly level slopes. The Fox and Ockley soils formed under forest vegetation, mainly American beech, sugar maple, and white oak, and Wea formed under prairie.
Most of the soils that formed in outwash are used for crop production Where the water table is close to the surface, crop yields are consistently high, and these soils ran k among the most productive in the state. Where the water table is deep, crop yields can be severely reduced in a dry year, and many of these soils are irrigated Soils on outwash deposits that have a coarse-textured surface horizon are subject to wind erosion and should be covered at all times.
In contrast to outwash that was deposited from moving water, finer-textured sediments were deposited as lacustrine deposits from meltwater streams that had become ponded in lakes or in slackwater terraces some distance from the major stream. The resulting landscape units are lake plains. These soils range in texture from loamy to clayey and frequently have wetness features. Soils on swells (e.g., Nappanee) have light-colored surface horizons, while surfaces of those in swales (Hoytville) are dark-colored Beech, maple, white oak, and hickory were the dominant species on these soils.
Most of these soils have been drained by tile lines and are highly productive for row crops. Some of them are difficult to drain, however, because they are so high in clay or because they lie so low in the local landscape that it is difficult to find an outlet for the underground drainage lines. Such soils are considered to be wetlands.
The major floodplains form part of Soil Region 3, but smaller floodplains occur along numerous small streams throughout the state. As a result of differences in texture, carbonate content, pH, organic matter content, stoniness, and other properties, there are many different kinds of soils on floodplains.
Soils formed in thick loess.
(Region 5). In Soil Region 5 along the Lower Wabash and White rivers in the Wabash Lowland, loess is thick enough that the entire soil formed in it. Most of these soils are hilly, but some are on broad flats. In many other parts of the state, loess, is the parent material of the upper parts of many soil profiles.
Loess is an ideal soil parent material. It is loose, and most soil horizons formed in it have a relatively large percentage of pore space, permitting water to move through these pores readily and roots to penetrate with few restrictions. The silt particles of loess hold much water after a rainy period, and plants can absorb most of it, so these soils have a high available water-holding capacity Silt-size particles, however, are most subject to water erosion. Sand grains, in contrast, are heavy enough that they are not easily moved by water flowing over the soil, and clay particles attach to each other and to organic matter to form aggregates that also are not readily transported.
Alford soils formed where loess is more than about 7 feet thick, whereas soils with fragipans (eg., Hosmer) formed in loess of intermediate thickness (4 to 7 feet). Fragipal1s are dense, brittle subsoil horizons that restrict water movement and root penetration. They commonly are 20 to 30 inches thick and begin at depths from 20 La 50 inches. They consist of large prisms surrounded by lightcolored, silty zones that form a polygonal pattern when viewed in a horizontal section. Fragipans tend to be deeper in more poorly drained soils.
Originally these soils were forested, primarily black and white oak and American beech, but most of the deep loess soils, especially the flatter ones, are now farmed. Some of the sloping soils are used for fruit trees such as apples and peaches, and some are in pasture. It is important to keep these soils covered at all times to reduce erosion. This can be done by using crop rotations that include perennial crops, leaving crop residue on the soil, and growing winter cover crops.
Soils formed in Wisconsinan glacial till.
(Regions 6, 7, 8, and 9).
A round 21,000 years ago, the Wisconsinan glacier advanced to the southern limit of Soil Region 9. It ground up and mixed most of the material over which it moved, so most soils previously formed were destroyed. The glacier left a nearly level to undulating surface, called a ground moraine or till plain, in the areas where it kept moving, and an undulating to hilly surface, called an end moraine, where it stood still for a time near its outer margin. The large, nearly level glacial surface in central and northern Indiana is called the Tipton Till Plain.
Immediately after the glacier retreated, loess was deposited over these surfaces. On the till plains, loess filled in the low places in the landscape and thus tended to level out the surface, creating a loess surface that is smoother than the surface of the till below it.
In the forested part of the state, the soils in the concave swales (e.g., Brookston) are dark-colored and those on the convex swells (e.g., Crosby) are light-colored. Organic matter from tree leaves and understory vegetation was incorporated into the soil of the swales and preserved by the low-oxygen, wet conditions, thereby forming dark-colored humus.
On the swells, however, the water table was lower and the organic matter in the soil was not so well preserved, resulting in soils much lighter in color. This gives soils on the till plains a distinctive "salt and-pepper" appearance, especially visible from the air during the spring planting period, when many have been tilled. In some areas, better-drained soils have been eroded, exposing the reddish-brown subsoil, thereby adding another color to the pattern.
The Miami, Crosby, and Brookston soils make up a soil catena, a sequence of soils that are similar in all environmental factors of soil formation except topography, and thus natural soil drainage. In the reddish-brown areas are eroded well-drained Miami soils, the light gray areas are somewhat poorly drained Crosby soils, and the dark areas are poorly drained Brookston soils. Beech, sugar maple, white oak, and red oak were common on all these soils; hickory, ash, and elm were more common on the wetter soils. In the formerly prairie area of a large part of west-central Indiana, all of the soils are darker than their forest counterparts, with fewer color contrasts.
Within the Wisconsinan till area, the soils differ mainly by the texture of the glacial till, the depth of loess over the till, and the depth to wetness features, which are related to topography Much of the glacial till in these soil regions is dense and very slowly permeable to downward-moving water. Thus, the soils on the till plain are wet much of the year and need to be artificially drained to be used for crop production. Underground drains empty into ditches, which in turn flow into natural streams, thereby lowering the water table to accommodate spring planting.
The soils on the till plains of these regions are nearly all used for farming, largely for growing corn, soybeans, and wheat. These soils are the most productive in the state, or for that matter in the world. They have high natural fertility because the soils are relatively young, and many of the plant nutrients released from the rocks ground up by the glacier have not been leached from the soil as they have in some older soils. In most of the area, loess covers the till to different depths. Loess-derived soil horizons have a high water-holding capacity, and most of this water is available for use by plants.
Soils on the moraines are more hilly than those on the till plains, but in some moraines, especially those in Soil Region 7, the topography is barely distinguishable from that in the till plains. On the sloping soils, erosion by water is the most serious problem.
Soils on Illinoian glacial till.
(Region 10) Soil Region 10 has been called the Illinoian Till Plain, but recent investigations suggest that its glacial drift may have been deposited earlier than Illinoian time. This plain consists of broad, very flat surfaces cut by sharp ravines. Soils were formed on this glacial drift during the warmer interglacial time (Sangamon), and many of them were later eroded. This erosion surface was subsequently covered by about 40 to 100 inches of loess during Wisconsinan time.
The present soils on the loess-covered till plains have very lightcolored surface horizons because they are very low in organic matter. Soil wetness features are near the surface in the Clermont (Cobbsfork) soils on the till plain interior. They become progressively deeper in the Avonburg soils at the edge of the till plain, and in the Cincinnati soils on the shoulder of the till plain bevel. Fragipans are present in these three soils, but they are lacking in Grayford soils on the steeper backslopes. Beech and white oak were the predominant species on all the soils. In addition, the wetter soils supported more tuliptree and sweet gum, and the better-drained soils, Avonburg, Cincinnati, and Grayford, had more sugar maple.
The soils on the broad flats of this till plain are used mainly for row-crop agriculture, but poor physical conditions and compaction by farm machinery are special problems. For best crop yields, these soils should be drained with an underground drainage system, but in many areas it is difficult to find an outlet for the water.
Soils formed in clastic bedrock.
(Regions 11 and 13). The glaciers did not override the bedrock highs of south-central Indiana, so in this region the rugged topography was not ground down and smoothed as it was in the northern part of the state. Soil Region 11 is on clastic rocks such as sandstone, siltstone, and shale. It includes the Norman Upland (east part of the region) and the Crawford Upland (west part).
Water does not penetrate these rocks readily, so it runs off and carves an open drainage system in which the streams form a dendritic pattern. These regions have narrow ridgetops and steep side slopes. Most soils on less than 12 percent slopes have fragipans, illustrated by the Johnsburg soil on summits and the Zanesville soils on shoulders. On the backslopes, Wellston soils are on the moderate slopes, and the shallow Berks soils are on the steeper slopes.
White oak, other oak species, and hickory were the common species at the time of settlement. Now, oak and hickory predominate on the south- and west-facing slopes, but beech and maple are more abundant on the north- and east-facing slopes, which receive less direct solar radiation.
Soils on more gentle slopes are used mostly for pasture, but some are in forest and some are cultivated. Where sloping land is farmed, water erosion is a serious problem. Farmers are advised to keep the soil covered all the time, by growing winter cover crops to protect it when row crops are not in place, and by leaving all the crop residue on the surface instead of plowing it down. Around 50 to 60 years ago, many of the steep slopes were farmed and were severely eroded. Some of these areas are now healing under forest or permanent pasture vegetation.
The topography in Soil Region 13 is similar to that in Region 11, but the rocks are mainly shale with interbedded limestone strata. Where shale is dominant, the soils resemble those in Soil Region 1l. Where limestone strata are thicker, however, the soils tend to be better drained and resemble those in Soil Region 12.
Soils over limestone
(Region 12). This region has a drainage pattern much different from that in Regions 11 and 13. Here percolating water penetrates the limestone and dissolves it to form an underground drainage network. Much of the surface drainage is into the bedrock through closed depressions called sinkholes. Most sinkholes drain out the bottom, but some hold water. There are very few surface streams, and they flow only during intense rains. This kind of drainage results in a topography dotted with sinkholes called a karst plain. Bedford soils, with more than 30 inches of loess on the karst plain, have fragipans, but they are lacking in the Crider soils of steeper slopes where the loess is thinner. Caneyville soils are shallow to limestone rock.
In general the slopes in Region 12 are moderately sloping, so much of the limestone region is used for pasture and crops. Like those in Regions 11 and 13, the soils are very erodible, so slopes should be kept under cover at all times. Most of the more steeply sloping soils are in forest.
USE OF OUR SOIL RESOURCES
History celebrates the battlefields whereon we meet our death, but scorns to speak of the plowed fields whereby we thrive.
-j. Henri Fabre, French naturalist
How we use our soil resources affects all people, not just those who currently own or manage the land: If we use them properly, they will last forever. If we misuse them, however, we can also ruin them forever. We can misuse our soil resources by removing land from the natural system or the crop production system, thus decreasing the quantity of soil available for growing plants, and by mistreating the soil and-decreasing its quality. We must be concerned about how much natural or productive land we turn over to our descendants and how good the soil is. The quantity of soil available for growing plants is determined mainly by our decisions about land use. The main processes that decrease the quality of soil in Indiana are soil erosion, soil compaction, and chemical contamination.
We abuse our land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect. ... That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics.
-Aida Leopold, A Sand County Almanac (1949)
In Indiana, recent development has encroached onto farmland at urban perimeters and along roads and highways. Once land is used for a highway, shopping mall, factory, or home site, it will never again be returned to natural vegetation or used to grow crops. Thus, we are continually losing farmland and natural areas.
Also, it is much more difficult and expensive to supply public services, such as utilities, fire and police protection, and transportation, in sprawling developments than in areas with higher population density People in countries that have fewer land resources relative to their population (in Europe, for example) have learned that more compact development is necessary if the living environment is to be maintained. Hoosiers should also be more concerned about urban sprawl and related land-use changes.
For example, we could make better use of land already within a city instead of converting surrounding farmland to urban uses. Our ancestors settled and created towns on the good soils; when we convert farmland to other uses, we are losing some of our most productive farmland. We must consider how to preserve these soil resources, as an increasing population will require more food, recreation, and open space. Each of the soil landscapes described in this chapter has characteristics which make it better suited to some uses than others. These characteristics should be used in directing our decisions and planning for our future environment. Indiana does not have a state land-use plan, so it is important that we support local planning efforts.
The soil is the basis for a $4 billion industry in Indiana. However, despite nearly a half-century of efforts to combat erosion, more than 100 million tons of soil are eroded each year through the action of wind and water. That is enough to make a mound two feet wide and one foot high stretching from Indianapolis through the Mississippi Delta, and well into the Gulf of Mexico.
-Governor's Soil Resource Study Commission (1984)
Every year some soil forms from the geologic material below it. This amount of soil loss can be tolerated without reducing the thickness of the soil.
Soil formation, however, is measured in terms of thousands of years, so the amount of soil loss that can be tolerated in anyone year is negligible. Except on very flat land, soils exposed to rain and wind with no cover on them will erode.
Falling raindrops strike the soil with much force, detaching soil particles in the process. Erosion continues as rainfall accumulates on the surface and then runs off the soil, carrying with it these detached soil particles. Accompanying the removal of the soil itself are losses of fertilizers, agricultural chemicals, and native soil fertility which enter the state's waters causing turbidity, pollution, and premature eutrophication of streams, ponds, lakes, and reservoirs.
Soil cover, in the form of living plants or dead crop residue, greatly retards erosion. First, this cover breaks the impact of raindrops on the soil surface. Plant roots anchor the soil mass and create pores in the soil for water to enter, reducing the amount of runoff. Plant residue also forms small dams on the soil surface that slow down the runoff.
Thus, farmers should keep practically all soils under cover all the time. This can be done by keeping the land in forest, pasture, or forage crops (hay), using crop rotations that include forage crops, and keeping the soil at least partially covered when growing row crops. In Indiana, most farmland is used to grow row crops such as corn and soybeans that traditionally have been grown in cleanly tilled fields. Soil erosion can be controlled in these fields by using conservation tillage techniques which leave the soil surface covered at planting time. The practice of planting a new crop into a soil that still has all the residue on it from the previous crop is called "no-till." In cornfields, the required 30 percent cover necessary to control erosion can be accomplished by leaving the residue from the previous crop on the soil, and not plowing it down. Soybeans, however, produce less residue than corn, and it decays quickly, so former soybean fields might require the planting of a winter cover crop in early fall
An Indian watched as a pioneer settler was breaking prairie sod with a moldboard plow pulled by a yoke of oxen, then came to the scene of the plowing and stated in broken English, "Land wrong side up." The farmer, not comprehending, went back to turning the soil
-Paraphrased from Ernest Swift, in Conservation News (mid-1960s)
Wind also erodes soil, as can be seen by the dirty snow that sometimes falls and accumulates in Indiana. Soil cover also greatly reduces wind erosion. Another practice that reduces it is to break up the length of a field that is exposed to the wind with strips of green crops, fencerows, or windbreaks in the form of rows of trees and shrubs.
To make specific recommendations for managing soils, we need to know how various soil properties affect erosion. For example, the main factors that determine the ·amount of water erosion are the intensity of rainfall, the erodibility of the soil material, and the length and steepness of the slope. These factors are balanced by the practices the farmer uses, e.g., the amount of soil cover, tilling on the contour, etc. All these factors are represented in models that soil conservationists use to help the farmer select management practices that will reduce soil losses by wind and water erosion to tolerable levels.
Farmers and others can get technical help through the U.S. Natural Resources Conservation Service, the Indiana Department of Natural Resources, and the Purdue Cooperative Extension Service. Together they sponsor the "T by 2,000" program, which strives to control erosion within tolerable levels (T) by the year 2000.
Plant roots need nutrients, water, and air to grow.
Roots, water, and air all move through soil voids, spaces, or pores. If the soil has sufficient pore space, roots have room to grow, and water and air can move to the growing roots. If the soil is compacted by plowing or by heavy equipment being driven over it when it is wet, water and air cannot move readily through it. This is a special problem in Indiana because the soils are wet and most subject to compaction in the spring, when farmers do much of their field work.
Soil compaction is minimized by reducing the amount of traffic by tractors, plows, and other equipment through the field. The no-tlll method, used to combat soil erosion, also helps to reduce compaction because it reduces the traffic through the fields. Waiting to get on a moist field until it dries out also helps.
Use of chemicals.
Modern farming methods include the use of chemical fertilizers to supply essential nutrients, herbicides to kill weeds, insecticides to control insect infestations, and fungicides to control diseases When used properly, most of these chemicals do not damage the soils or the environment. Improper use, however, causes problems. For example, groundwater or surface waters can be contaminated by nitrate-nitrogen if nitrogen fertilizer rates are too high Recommended nitrogen fertilizer application rates now matcb the amount of nitrogen known to be removed by the crop to be grown, so nitrate does not accumulate in the soil.
Reduced tillage greatly reduces the risks of soil erosion and compaction. The practice requires that weeds be controlled with chemicals instead of by cultivation, however. Many herbicides specifically kill a few kinds of weeds, so farmers can use small amounts of these chemicals only on the parts of the field where these weeds are a problem. Similarly, disease and insect problems can be controlled by smaller applications of specific chemicals.
Through integrated pest management (IPM), trained technicians scout a field, identify specific problems related to plant nutrition, soil compaction, weeds, insects, and diseases, and recommend the management practice or chemical application that should be used on certain areas of the field. Farmers who once tended to use large applications of chemicals to make sure that a problem was solved are now using these IPM techniques, which greatly reduce the amount of chemicals applied.
Application rates of many chemicals depend on soil properties, so farmers must have detailed knowledge about the kinds of soils in their fields. New techniques are being developed to farm by specific kinds of soils instead of by fields. This is accomplished by two different approaches. In one, a map of soil conditions is stored on a computer in the truck making the application, and the computer changes the application rate of fertilizer or pesticide as the truck moves through the field. In the other, an instrument mounted on the applicator truck senses a soil property, such as organic matter content, and a computer adjusts the application rate according to that property.
We have known for a long time that many kinds of small animals live in the soil, but they were mainly considered to be a curiosity. Farming practice emphasized chemical and physical processes. Now we have more appreciation for the biological processes.
An abundant and healthily functioning population of soil microbes is essential to many soil processes and soil-plant interactions. Nitrogen fixation, nutrient cycling, organic matter decomposition, and nutrient and water uptake all require suitable numbers of the appropriate bacteria, algae, protozoa, invertebrate animals, and mycorrhizal fungi. Many plant species simply cannot survive if their specific mycorrhizal symbiont is not present in the soil to sheath their roots, thereby facilitating nutrient and water absorption.
Earthworms are also receiving much attention, especially the large nightcrawlers. Their deep burrows allow water to percolate through the soil rather than running off the surface. Also, they mix the soil to considerable depth. In some soils, the subsoil contains more nutrients, such as calcium and potassium, than the surface horizon, and worms (ants also) can bring these nutrients to the zone where plant roots are most abundant.
Previously it was thought that compacted soil layers could be broken up by plowing them. Now it is known that breaking up one compacted zone often causes compaction in another zone, usually lower in the soil where it is more difficult to treat. We have learned that often the most effective way to counteract compaction is to grow deep-rooted plants and encourage earthworms. We are also noticing that when the same crop is grown year after year, its yield is reduced, probably because the soil biological community is becoming less diverse. Finally, researchers are· studying biological control of pests.
Preservation of wetlands.
In recent years, the public has become much better informed about the importance of wetlands in replenishing groundwater supplies, hosting wildlife, and controlling floods. Consequently, the u.s. Congress has passed legislation that requires that certain wetlands be left in their natural state, or if a wetland is removed from its natural state, it must be replaced by equal land area that is converted to wetland.
Wetlands are defined according to soil, plant, and hydrologic criteria. Soils are an essential part of this determination because the morphology of a soil integrates the effects of soil wetness throughout the life o£ the soil-thousands of years. Climate varies considerably, so the length of time a soil is saturated and the depth of saturation vary greatly from one year to the next, but soil morphological properties are relatively constant. This makes soil a reliable indicator of wet conditions.
Responsibility for the soil resource.
People are becoming more aware of the importance of using our soil resources, and other resources, in an ecologically sound manner. To accomplish this requires a better understanding of our soils and continued research in soil science and management. II also requires delicate adjustments to balance ecological concerns with the economic realities, because many of the ecologically sound practices are not cost-effective in the short term, and many of the seemingly economically sound practices are destructive in the long run.
Because the entire public will benefit from ecologically sound management techniques, their costs must be partially borne by the public rather than the landowner. This issue of how we use our soils is too important to be left in the hands of only scientists and agriculturists. Everyone's descendants depend on soil resources, so everyone should be concerned about them.
We can take no comfort at all in the fact that the problem [of exploitation of soil and water resources] is universal. Absurdly, nations fight wars over every inch of their political boundaries while mindlessly sacrificing whole regions to environmental degradation. Their patriots salute the flag and take up arms to defend the country against external enemies, while neglecting its environment and ignoring the real attacks being waged from within on the land they purport to love. Thousands of years are required for a soil to form in place, yet this amazingly intricate work of nature can be destroyed by man, with remarkable dispatch, in Just a few decades. We must understand that, on the time-scale of human life, the soil is a non-renewable resource. So is a mature forest, a river, or an aquifer They belong not only to those who are the titled owners at this moment, but to future generations as well. In an even more profound sense, both soil and water belong to the biosphere, to the order of nature, and-as one species among many, as one generation among many yet to come-we have no right to destroy them.
-Daniel Hillel, Out of the Earth (1991)