AGRICULTURAL FENCES

In agriculture, fences are used to keep animals in or out of an area.

Early fences

In older times, livestock would roam and were fenced out of areas, such as gardens and fields of crops, where they were unwanted. This prevails yet today in sparsely populated areas. States in the American West that follow this tradition are called "fence out" states, in contrast to Midwestern states which have "fence in" laws where livestock must be confined by their owners.

The earliest fences were made of available materials, usually stone or wood. 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.

A later development was 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).

Barbed wire

The Industrial Revolution brought the first barbed wire fences, which were widely used after their introduction in the mid-19th century. This technology made it economically feasible to fence rangeland for the first time. The introduction of barbed wire contributed to the range wars of that century, as it exacerbated tensions between landowners seeking exclusive control over large tracts of land, and traditional transient users of that land.

Barbed wire was made by many manufacturers in an almost endless variety of styles. For the most part these were functionally identical. The differences reflected peculiarities of each manufacturing process rather than deliberate design of the end product. Sections of unusual barbed wire are collected by some enthusiasts.

The traditional barbed wire used from the late 19th through most of the 20th century was made from two mild steel wires, usually of about 12 or 14 gauge, with about 15-30 twists per metre. Steel barbs were attached every 10-20 cm. Barbs had either two or four points, with the two point design using somewhat heavier and longer barbs. The relative merits of two point vs. four point wire are the subject of deeply held views among many farmers and ranchers, to the extent that both types are still made today.

Barbed wire is typically run on wooden posts, either commercially grown in plantations or, particularly in the American West, often posts that have been cut from nearby trees. Wire is attached to the posts using fencing staples. Typically four or five strands of barbed wire make up a fence. Posts are usually spaced 3-6 m apart.

In areas where there is more rainfall, either rot-resistant wooden posts or steel posts are used. Wood with natural rot resistance, such as oak and juniper, was often used until it became in short supply in the 1950s. Then, chemically treated pine and spruce posts became prevalent. Creosote, pentachlorophenol, and chromated copper arsenate were all widely used.

In the 1970s, high-tensile barbed wire became available. It is lighter in gauge (usually 16 gauge) but, due to higher carbon content, just as strong as the traditional mild steel. Advantages include lighter weight and lower cost.

Barbed wire is effective for cattle and horses, but not for pigs, sheep, or goats. Where these animals are to be fenced, woven wire is used instead, often with one or several strands of barbed wire at the top. For swine, a ground-level barbed wire strand is used as well to prevent digging. Woven wire is costly to purchase and time-consuming to install.

Parts of this page retrieved from "http://en.wikipedia.org/wiki/Split-rail_fence" available under the terms of the GNU Free Documentation License.

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