Agricultural fencing

In agriculture, fences are used to keep animals in or out of an area. They can be made from a wide variety of materials, depending on terrain, location and animals to be confined. Most agricultural fencing averages about 4 feet (1.2 m) high, and in some places, the height and construction of fences designed to hold livestock is mandated by law.

Historically throughout most of the world, domesticated livestock would roam freely and were fenced out of areas, such as gardens or fields of crops, where they were unwanted. Over time, especially where crop agriculture became dominant and population density of both humans and animals was significant, livestock owners were made to fence their animals in.

The earliest fences were made of available materials, usually stone or wood, and these materials are still used for some fences today. In areas where field stones are plentiful, fences have been built up over the years as the stones are removed from fields during tillage and planting of crops. The stones were placed on the field edge to get them out of the way. In time, the piles of stones grew high and wide.

In other areas, fences were constructed of timber. Log fences or split-rail fences were simple fences constructed in newly cleared areas by stacking log rails. Earth could also be used as a fence; an example was what is now called the sunken fence, or "ha-ha," a type of wall built by digging a ditch with one steep side (which animals cannot scale) and one sloped side (where the animals roam).

The tradition of fencing out unwanted livestock prevails even today in some sparsely populated areas. For example, until the mid-20th century, most states in the American West were called "open range" ("fence out") states, in contrast to Eastern and Midwestern states which long had "fence in" laws where livestock must be confined by their owners. Though the open range was part of the western tradition, over time, open range was limited long before it was eliminated completely; first came an obligation to keep cattle from roaming onto state and federal highways, where collisions with fast-moving cars and trucks created a public safety hazard. In addition, voters could voluntarily choose to make certain heavily farmed areas a "herd district," where livestock needed to be fenced in, a process that also became popular in areas where development of hobby farms created conflicts between large and small landowners. Over time, court cases steadily limited the application of open range law until the present day, where it is the exception rather than the rule in many parts of the American West.

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