A limiting factor is any unfavorable soil property or characteristic that limits the land from intensive uses such as cropland (keeps it out of Class I land). Factors include limiting conditions of slope, erosion, texture, depth of soil, drainage, surface runoff, and flooding. An example of Class I land in West Virginia is land that is mapped as "Wheeling silt loam". It is a deep, well-drained, moderately permeable soil with a 0-3% slope, moderate runoff, slight erosion, and no flood hazard. However, the same soil with a 3-8% slope is placed in Class II because the slope imposes some land use limitations or hazards, and in this case is a limiting factor in land use. Mark all characteristics that limit this soil from being placed in Class I land.
Up to this point you have studied things that make one piece of land different from another because of differences in soil properties, degree of erosion, and slope. Now you must take what you have learned and determine the land use capability or land class.
These varying types of land are classified in eight Land Capability Classes, which relate to the most intensive use of the land without damaging it. The classification is used in agricultural land use planning by the Natural Resources Conservation Service and similar agencies around the world. (Note that Class I represents the best land and Class VIII the least favorable for farming.)
Class I Land - Soils in Class I have no limitations that restrict their use. They will grow practically any crop adapted to the locality. Class I land is nearly level, holds adequate supplies of plant-available water, is fertile, and is easy to work. Practically free from hazards, it is subject to little erosion, and is well-drained. It can be maintained with ordinary good farming practices such as the use of crop rotation, manure, fertilizer, and lime when needed.
Class II Land - Soils in Class II have limitations that require careful soil management and moderate conservation practices. Soils in this class are good, but certain physical characteristics keep them from being as good as Class I. Class II land may slope enough that runoff water may cause some erosion. It may tend to be a little droughty, or a little wet. Any of these conditions may limit the use of the land or require some easily applied conservation practice such as contouring, strip cropping, or protective cover crops.
Class III Land - Soils in Class III have moderate to severe limitations and require special conservation practices. Soils in this class have more restrictions than those in Class II. When used for cultivated crops, the conservation practices are usually more difficult to apply and maintain. Most crops will grow well but the soil needs a lot of protection and care. There are several variations in Class III land. Some of it is moderately sloping and needs intensive care to control erosion, especially when used for row crops. Poor drainage may place it in Class III if the necessary drainage is hard to maintain. Droughty land also may be in Class III. These features must be overcome or combated year after year if used for crops.
Class IV Land - Soils in Class IV have severe limitations that require management. The restrictions in the use of these soils are greater than those in Class III, and the choice of plants is more limited. Class IV land is not suited for regular cultivation, and should not grow a row crop more than once in five years. Often, it is too steep and badly eroded for cultivation. It may be too dry for regular crop production, or it may be wet and drainage systems are too hard to install and maintain.
Class V Land - Soils in Class V have little or no erosion hazard, but do have other faults that limit their use largely to pasture, woodland or wildlife food and cover. Soils in this class are frequently flooded, may be poorly drained, or have some combination of these limitations. Because of these limitations, cultivation of common crops is not feasible; but pastures may be improved with lime and fertilizer and proper management.
Class VI Land - Soils in Class VI have extreme limitations that make them generally unsuited for cultivation and limit their use to pasture. It is practical, however, to apply pasture improvements, such as seeding, liming, fertilizing, and water control.
Soils in class VI have limitations that cannot be corrected, such as (1) steep slope, (2) severe erosion hazard, (3) effects of past erosion, (4) stoniness (unremovable rocks and rock out crops), (5) shallow rooting zone, (6) excessive wetness or overflow, and (7) low moisture-holding capacity. Because of one or more limitations, these soils are not suited for cultivated crops, even though some of the soils in this class can be adapted to special crops such as sodded orchards.
Class VII Land - Soils in Class VII have severe limitations that make them unsuitable for cultivation and that restrict their use to permanent woodland. Physical conditions of soils are such that it is even impractical to apply pasture improvements. Soil restrictions are more severe than those in Class VI because of one or more limitations that cannot be corrected, such as steep slopes, erosion, shallow soils, stones, or wet soil. Lime and fertilizer applications are not practical on Class VII and VIII lands and should be so marked on the card (No. 28) even though the field sign may give recommendations.
Class VIII Land - Soils and land forms in Class VIII have limitations that prevent their use for commercial plant production and restrict their use to recreation, wildlife, or watershed development. Soils and land forms in this class will not produce crops, grasses or trees of much economic importance, although benefits from wildlife use, watershed protection, or recreation may be possible. Examples of Class VIII land are stream banks and rocky areas that will not grow trees. If Class VIII land is used in a contest, it must be given on the field sign. See comment concerning lime and fertilizer application under Class VII.
The following will be helpful in determining Land Capability Classes in agronomic land judging. These show the effect of an individual soil property or factor where it is the only limitation.
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