soil compaction

The most general category of the NRCS Soil Classification System recognizes eleven distinct soil orders: oxisols, aridsols, mollisols, alfisols, ultisols, spodsols, entisols, inceptisols, vertisols, histosols, and andisols. Inceptisols are young soils that are more developed than entisols. These soils are found in arctic tundra environments, glacial deposits, and relatively recent deposits of stream alluvium. Common characteristics of recognition include immature development of eluviation in the A horizon and illuviation in the B horizon, and evidence of the beginning of weathering processes on parent material sediments. Figure 15: Organic Soil Landscape (British Columbia). (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) Figure 7: Chernozemic Landscape (Prairies). (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) The first formal system of soil classification was introduced in the United States by Curtis F. Marbut in the 1930s. This system, however, had some serious limitations, and by the early 1950s the United States Soil Conservation Service (now the Natural Resources Conservation Service) began the development of a new method of soil classification. The process of development of the new system took nearly a decade to complete. By 1960, the review process was completed and the Seventh Approximation Soil Classification System was introduced. Since 1960, this soil classification system has undergone numerous minor modifications and is now under the control of Natural Resources Conservation Service (NRCS), which is a branch of the Department of Agriculture. The current version of the system has six levels of classification in its hierarchical structure. The major divisions in this classification system, from general to specific, are: orders, suborders, great groups, subgroups, families, and series. At its lowest level of organization, the U.S. system of soil classification recognizes approximately 15,000 different soil series.