Introductory Soils Lab 3A. Soil Survey Maps and Reports NRES 201 Page 1 of 6 LABORATORY 3A A: USE OF SOIL SURVEY MAPS AND REPORTS Soils are distributed in sufficiently uniform patterns and exist as sufficiently recognizable entities to allow mapping and compilation of these maps along with the properties and suggested uses of the soils into reports. Soil surveys are made cooperatively by federal and state governments. The USDA Natural Resource Conservation Service, or NRCS, (formerly the Soil Conservation Service) is the federal agency which has the primary responsibility for soil survey activities. In some surveys, the Forest Service, Bureau of Indian Affairs, Bureau of Reclamation, or Bureau of Land Management may cooperate. Land grant universities and colleges (usually state experiment stations) bear the primary responsibilities in representing the States. Other State agencies such as the Department of Natural Resources or Conservation, and county or city governments may also cooperate. This joint effort is called the National Cooperative Soil Survey. The Standard Soil Survey is the major type of survey now being produced. The Standard Soil Survey is usually made on a county basis with the counties sharing in the cost of the survey. Less detailed surveys include reconnaissance and soil conservation surveys. The surveys of soil resources are designed to meet the particular needs of each geographical area. Humid region farmers have different needs than arid region farmers and ranchers that depend on irrigation. Engineers, Foresters, and Conservationists all need different information about soils in a region. The Soil Survey is designed to provide a variety of information about the soils so that all potential uses of the soil can be explored with a high degree of rigor. The Soil Survey is often used to provide equitable tax assessment based on potential soil productivity. 3A.1 RECTANGULAR SURVEY This system describes the location of a parcel of land relative to the intersection of an east-west base line with a north-south principal meridian. There are 34 surveyed principal meridians in the U.S. Lines parallel to the base line are surveyed every six miles north and south of the base line. The six mile wide strips of land are called townships and are assigned a number and direction to identify their distance from the base line (i.e., T 21 N is the township 21 strips north of the base line). Lines parallel to the principal meridian are surveyed every six miles east and west of the principal meridian. These six mile strips of land are called ranges and are also assigned numbers to identify their location relative to the principal meridian (i.e., R6W is the range 6 strips west of the principal meridian). A diagram showing the concept of townships and ranges is Figure 1. Figure 2 shows the base lines and principal meridians used in Illinois.Introductory Soils Lab 3A. Soil Survey Maps and Reports NRES 201 Page 2 of 6Introductory Soils Lab 3A. Soil Survey Maps and Reports NRES 201 Page 3 of 6 The intersection of the township strips with the range strips forms squares, six miles on each side (36 square miles). These 36 square mile areas of land are called congressional townships. Townships are further divided into l mile square areas of land called sections. Each township contains 36 sections which are numbered starting in the northeast corner. Each section (640 acres) can be further divided into smaller units. Figure 3 illustrates the numbering system used for sections and how the sections are subdivided into smaller units. Theoretically, a township is a square tract of land with sides of six miles each, and containing 36 sections of land. In actuality the rectangular survey system imposes a rectangular system on a curved surface. This results in a need to correct for the convergence of the north-south lines in order to keep the east-west parallel. On the average, sections are about 50 feet shorter on the north edge than on the south edge so that every 24 miles (4 townships) a correction line is established parallel to the base line and the sections are again one mile on a side. The deviations from the square that result from the earth's curvature are compensated for in a systematic manner. Sections 1 through 6 on the north side and sections 6, 7, 18, 19, 30 and 31 on the west side may be smaller or larger than 640 acres as required. All other sections are exactly 640 acres whenever possible.Introductory Soils Lab 3A. Soil Survey Maps and Reports NRES 201 Page 4 of 6 3A.2 USE OF SOIL SURVEY REPORTS Print Soil Surveys Soil Survey reports are divided into two sections; the first section contains, descriptive material about the county, profile descriptions, soil classifications, tables giving information about engineering uses, soil productivity, wildlife and forest plantings and other uses of individual soils. The section contains detailed soils maps for the county. The maps are drawn on aerial photographs and contain a great deal of detail. Soil mapping units shown on soil maps include the series, slope, erosion class, and other special features. In Illinois, the soil series are numbered uniformly throughout the state, thus 171 is Catlin wherever it appears in any Illinois soil survey. An example of a soil mapping unit: 171B2 = Catlin Silt Loam, 2-5% slope, moderately eroded. Web Soil Survey Much of the soil survey of the country is now on the web: http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx Through Web Soil Survey you can delineate areas of interest and produce soil maps with a table of soil map unit (SMU) coverage. This is a quick (usually, depending on your bandwidth) way to select a place for which you want soils information and easily get the extent of the SMUs. Laboratory Procedure Answer the following questions using the Web Soil Survey and the Peoria County Soil Survey report. The answers are due at the end of the laboratory period. If a different soil survey report is used, the instructor will hand out a modified set of questions that are specific for that county.Introductory Soils Lab 3A. Soil Survey Maps and Reports NRES 201 Page 5 of 6 Lab 3A Assignment Name ___________________________________ Date