Hole, Francis Doan, 1913-2002 / Soils of Wisconsin
Chapter 1 introduction, pp. 3-8
THE SOILS OF WISCONSIN The soils of Wisconsin constitute a layer as much as 4 or 5 feet thick that has a dry weight of nearly 300 billion tons and covers about 35 million acres. We are not used to thinking of our soil resource in terms of tonnages as we think of gravel deposits and ores. The fact is that soil is a prime organo- mineral resource of importance to the stability of buildings and highways, the economy of our cities, the productivity of our farms and forests, the quality of our nutrition, and the vitality of wildlife and wilderness areas. Eroded soil materials in the nearly one million acres of Wisconsin now under lakes and streams influence water quality by yielding or by adsorbing pollutants. The soils of this state have been the subject of ex- tensive soil investigation for nearly a century, during which time a vast amount of information on specific areas and soils has been reported. Three colored wall maps of the soils of the state have been published (in 1882, 1927, and 1968). Our pres- ent knowledge of the soils of Wisconsin, of which this report is a summary, is a basis for sound land management and for future research in pedology and soil-water conservation. Areal analysis of the soil map (Plate 1) indicates that Wis- consin subsoil materials are deep (more than 2 feet thick over consolidated bedrock in 95% of the state). A third of the soil area is derived from glacial outwash sand and gravel, a third from glacial till loams, a tenth from deposits in ancient glacial lakes, and a tenth from bedrock-derived residuum. Wetland soils (both organic and inorganic) are shown on the map to cover nearly 10% of the state, but bodies too small to show probably more than equal that. About 40% of the land is cov- ered with a foot or more of weathered bess, from which some of the most productive soils have formed. Wisconsin is crossed by a southeast-trending climatic and ecological tension zone that separates cool-summer forest soils on the northeast from warm- summer prairie and prairie-forest transition soils on the south- west. Forest soils have formed on two thirds of the area, and prairie- and savanna-influenced soils have developed on the remaining third. Clayey soils cover about 10% of the state; silty soils, about 40%; loams and sandy loams, 25%; sands, 20%; and peats and mucks, about 5%. The state has nine major soil regions, with interspersed wet- lands constituting a tenth unit. (A) The southwestern region is a two-story landscape with productive ridge and valley soils separated by wooded steep shallow soils and rockland. The great variety of soils and topography contributes to a scenic landscape, but demands careful land and water management to handle problems of erosion and waste disposal. (B) The southeastern upland has an intricate soil pattern of wetlands and plains, hills, drumlins, and ridges, including the promi- nent Kettle Moraine. The contribution of dolomitic limestone to subsurface materials is associated with a high level of native subsoil fertility. (C) Soils of the central sandy uplands and plains inherit their coarse texture from Cambrian sandstone and deposits of sandy outwash from the melting of glaciers thousands of years ago. Buried silts and clays of ancient lake beds, rocky sandstone crags of scattered mounds and mesas, and intermixtures of dry and wet soils are features of the land- scape of the central sandy region. (D) Soils of the western sand- CHAPTER 1 Introduction stone uplands, valley slopes, and plains include shallow silt loams and deep sandy loams, some steep stony land, and im- perfectly drained fiats. (E) Northern and eastern sandy and loamy reddish drift uplands and plains have a mixture of sands, reddish silts, and clays, interlayered in some areas. (F) The northern silty uplands and plains are characterized by shal- low to moderately deep silty soils over compact acid loamy and sandy glacial drift. Soil drainage is a problem in many places. (G) The vast northern loamy uplands and plains consist of acid stony and somewhat sandy soils on glacial moraines, drumlins, eskers, and outwash flats. (H) The northern sandy uplands and plains include sands of extensive pine and oak barrens on pitted glacial drift and nearly level outwash plains. (I) Soils of the northern and eastern clayey and loamy reddish drift up- lands and plains have high clay content and plant nutrient levels. Management problems on these soils include tillage, drainage, and disposal of liquid wastes. (J) Stream bottoms and wetlands of the state are occupied by mineral soils and peats and mucks with high water tables. Naturally well-drained allu- vial soils are not extensive. DEFINITION OF SOIL Soil is considered here as a natural unit in a pedological (soil science) or ecological sense, rather than in an engineering sense. It is geologic material altered by plants and animals and climate. Soil is a body of mineral and organic matter occurring naturally on the land surface of the earth, interrupted by bodies of 'not-soil,' which include rock outcrops, lakes, and streams. The soil envelope of the earth, sometimes called the pedo- sphere, lies at the interface between the biosphere and the litho- sphere. It is a blend of the biologic and geologic materials. The pedosphere may bethought of as a mosaic, made up of specific soil bodies. In plowed fields, dark bodies of soil commonly show up distinctly in a setting of higher lying, light-colored soil bodies. Thus, examples of the basic unit of soil classification, the soil body, may be easily seen in the landscape when the fields are newly plowed. Soil bodies in Wisconsin range from 1 to 7 feet deep, and are commonly 4 feet thick. The lower sur- face of a soil body is marked by the limit of leaching of nat- urally occurring lime (carbonates) in many soils and by the lower limit of common rooting of native perennial plants in all soils. Loose material below this level is not considered soil in the pedological sense, as indeed loose material on the moon is not. Because soil bodies are hundreds or thousands of feet across,
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