preventing soil erosion

rganic Cryosol Profile. (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) Histosols are organic soils that form in areas of poor drainage. Their profile consists of thick accumulations of organic matter at various stages of decomposition.

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. Figure 10: organic Cryosol Profile. (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) 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. Canada's first independent taxonomic system of soil classification was first introduced in 1955. Prior to 1955, systems of classification used in Canada were strongly based on methods being applied in the United States. However, the U.S. system was based on environmental conditions common to the United States. Canadian soil scientists required a new method of soil classification that focused on pedogenic processes in cool climatic environments. Oxisols develop in tropical and subtropical latitudes that experience an environment with high precipitation and temperature. The profiles of oxisols contain mixtures of quartz, kaolin clay, iron and aluminum oxides, and organic matter. For the most part they have a nearly featureless soil profile without clearly marked horizons. The abundance of iron and aluminum oxides found in these soils results from strong chemical weathering and heavy leaching. Many oxisols contain laterite layers because of a seasonally fluctuating water table. Figure 12: Gleysol Profile. (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) Figure 17: Forested Podzolic Landscape (Ontario). (Source: Soil Landscapes of Canada, Version 2.2, Agriculture and Agri-Food Canada. 1996) Canadian System of Soil Classification