- - AGRICULTURE CORE CURRICULUM - - (CLF7000) Advanced Core Cluster: PLANT AND SOIL SCIENCE (CLF7400) Unit Title: SOILS ____________________________________________________________________________ (CLF7411) Topic: SOIL CLASSIFICATION Time Taught in Year(s) SYSTEMS AND SOIL SYSTEMS 2 hours 3 and 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome #: (G-19) - Define classification and list two types of soil classification systems. (G-20) - Learn types of information found within a soil survey and how to use a soil survey. Special Materials and Equipment: Local soil survey maps. References: Donahue, Roy L. SOILS. (1983). pages 508 to 560. Brady, Nyle C. THE NATURE AND PROPERTIES OF SOILS. Pages 429 to 473. Buol, S.W. McCracken, R.J and Hole, F.D. SOIL GENESIS AND CLASSIFICATION. Evaluation: Quiz by instructor TOPIC PRESENTATION: SOIL CLASSIFICATION SYSTEMS A. Many systems have been developed to relate individual soil mapping units to specific usage. 1. The latest U.S. soil classification (soil taxonomy) system is the U.S. Comprehensive Soil Class System. a. It is used in many countries, but is only one of many systems found worldwide. b. In this system all soils are fitted into 11 orders and 47 suborders. 2. Another system used to rate soils was developed by the Soil Conservation Service and is called U.S.D.A. (United States Department of Agriculture) Land Use Capability Classification System. 3. We will study and compare some of the specific details of these two systems. B. The U.S. Comprehensive Soil Class Systems was officially adopted by the U.S. in 1965. 1. Since this system has worldwide application many countries have adopted it in preference to other systems. 2. This system is based on the properties of soils as they are found today. 3. The main criteria used is to place soils into groups by the characteristics of soil properties 4. It focuses on the soil rather than related sciences such as climatology and geology. 5. There are six categories of classification in this system: a. Order d. Subgroup b. Suborder e. Family c. Great Group f. Series 6. Order is the broadest category, series, the most specific category. 7. The six categories were inspired by the six categories in the worldwide system of plant and animal taxonomy. 8. A brief description of the six soil categories follows. a. Order - All soils fit into one of eleven orders. This category is based mainly on soil forming processes. The names of orders are always capitalized. b. Suborders - Suborders within a soil order are separated largely on the basis of soil properties and horizons that result from different soil moisture and soil temperature conditions. Today over 50 suborders are recognized in the United States. Suborders are distinctive to each other and are not interchangeable to other orders. c. Great Group - These are subdivisions of suborders. There are over 200 great groups recognized in the United States. They are established mainly on the basis of differentiating soil horizons and soil features. d. Subgroup - These are divisions of the great groups. About 1000 subgroups are found in the United States. e. Family - Soil families are separated within a subgroup of the basis of soil properties important to the growth of plants or behavior of soils when used for engineering purposes. About 4500 families are found in the United States. Differences in texture, temperature, mineral composition, and soil depth are the basis for differentiation. f. Series - Its differentiation is based primarily on the kind and arrangement of horizons. About 13,000 are recognized in the United States. C. The U.S.D.A. Land Use Capability Classification System includes eight land capability classes. 1. These classes are numbered from I to VIII. 2. Soils having the greatest capabilities for response to management and the least limitations in the ways they can be used are in Class I. 3. Those with the least capabilities and the most limitations are in class VIII. 4. Classes I to IV can be used for cultivation. 5. Classes V through VIII cannot be cultivated in their present state under normal management. 6. Following is a brief description of the characteristics and use of soils in each class. a. Class I - These soils can be used continuously for intense crop production with minimum attention other than good farming practices. The soils are deep, well drained, and the land is nearly level. b. Class II - These soils have more limitations than Class I for intense crop production, such as moderately steep slopes (2-5 percent). They require some conservation practices. c. Class III - Soils in this class have severe limitations and require more special conservation practices than class II to keep them continuously productive. They have shallow soils and steep slopes of about 6 to 10 percent or shallow water tables. d. Class IV - These soils have severe limitations and need a greater intensity of conservation practices for cultivated crops than class III soils. Most of the time these soils should be in "permanent" crops such as pastures. e. Class V - These soils are not likely to erode but have other limitations such as boulders or wetness, which are impractical to correct and so cannot be cultivated. They should be used for pasture, range, woodland, or wildlife habitat. f. Class VI - These soils are suitable for the same uses as Class V soils, but they have a greater need for good management to maintain production because of steep slopes or shallow soils. g. Class VII - Soils in this class have very severe limitations that restrict their use to grazing, woodland or wildlife. h. Class VIII - In this class are soils that have severe limitations (steep slopes, rocklands, swamps) that they can be used only for wildlife, recreation, watersheds, and esthetic appreciation. Examples of this time of land would be sandy beaches, river washes, and rock outcroppings. 7. Following is an abbreviated version of the eight classes of the U.S.D.A. Land Use Capability Classification System. LAND CAPABILITY CLASSES ____________________________________________________________________________ | NO CULTIVATION PASTURE, HAY, SUITABLE FOR CUTIVATION | WOODLAND, AND WILDLIFE ____________________________________________________________________________ | I. Requires good soil management | V. No restrictions in use. practices only. | II. Moderate conservation practices| VI. Moderate restrictions in necessary. | use. III. Intensive conservation. | VII. Severe restrictions in use. practices necessary. | IV. Perennial vegetation | VIII. Best suited for wildlife and infrequent cultivation. | recreation. __________________________________________________________________________ D. Information related to the following are likely to be found within a soil survey: clay hardpan porosity stoniness color horizons profile structure drainage moisture salts temperature erosion organic matter soil depth texture fertility pH soil horizons water table __________________________________________________________ ACTIVITY: 1. Use the soil survey of local county (or nearby county) and consider: soil properties, soil classification, land capability classification, land use interpretations and soil distribution on the landscape. 2. Have students locate a particular place on the soil maps and identify the soils, and capability classes of the map unit. __________________________________________________________ 7/25/90 sg #%&C