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A plough (UK) or plow (US; both ) is a tool (or machine) used in farming for initial cultivation of soil in preparation for sowing seed or planting to loosen or turn the soil. Ploughs are traditionally drawn by working animals such as horses or cattle, but in modern times may be drawn by tractors. A plough may be made of wood, iron, or steel frame with an attached blade or stick used to cut the earth. It has been a basic instrument for most of recorded history, although written references to the plough do not appear in English until 1100 CE at which point it is referenced frequently. The plough represents one of the major advances in agriculture. The primary purpose of ploughing is to turn over the upper layer of the soil, bringing fresh nutrients to the surface, while burying weeds and the remains of previous crops and allowing them to break down. As the plough is drawn through the soil it creates long trenches of fertile soil called furrows. In modern use, a ploughed field is typically left to dry out, and is then harrowed before planting. Plowing and cultivating a soil homogenizes and modifies the upper 12 to 25 cm of the soil to form a plow layer. In many soils, the majority of fine plant feeder roots can be found in the topsoil or plow layer. Ploughs were initially human powered, but the process became considerably more efficient once animals were pressed into service. The first animal powered ploughs were undoubtedly pulled by oxen, and later in many areas by horses (generally draught horses) and mules, although various other animals have been used for this purpose. In industrialised countries, the first mechanical means of pulling a plough were steam-powered (ploughing engines or steam tractors), but these were gradually superseded by internal-combustion-powered tractors. Modern competitions take place for ploughing enthusiasts like the National Ploughing Championships in Ireland. Use of the plough has decreased in some areas, often those significantly threatened by soil damage and erosion, in favour of shallower ploughing and other less invasive conservation tillage techniques. Natural farming methods are emerging that do not involve any ploughing at all, unless an initial ploughing is necessary to break up hardpan on a new plot to be cultivated, so that the newly introduced soil life can penetrate and develop more quickly and deeply. By not ploughing, beneficial fungi and microbial life can develop that will eventually bring air into the soil, retain water and build up nutrients. A healthy soil full of active fungi and microbial life, combined with a diverse crop (making use of companion planting), suppresses weeds and pests naturally and retains rainwater. Thus the intensive use of water-, oil- and energy hungry irrigation, fertilizers and herbicides are avoided. Cultivated land becomes more fertile and productive over time, while tilled land tends to go down in productivity over time due to erosion and the removal of nutrients with every harvest. Proponents of permaculture claim that it is the only way of farming that can be maintained when fossil fuel runs out. On the other hand, the advantage of agricultural methods that require repeated ploughing are that they allow monocropping on a large scale at remote locations, using industrial machinery rather than human labor. == Etymology == In older English, as in other Germanic languages, the plough was traditionally known by other names, e.g. Old English ''sulh'', Old High German ''medela'', ''geiza'', ''huohilī(n)'', Old Norse ''arðr'' (Swedish ''årder''), and Gothic ''hōha'', all presumably referring to the ard (scratch plough). The term plough or plow, as used today, was not common until 1700 CE. The modern word ''plough'' comes from Old Norse ''plógr'', and therefore Germanic, but it appears relatively late (it is not attested in Gothic), and is thought to be a loanword from one of the north Italic languages. Words with the same root appeared with related meanings: in Raetic ''plaumorati'' "wheeled heavy plough" (Pliny, ''Nat. Hist.'' 18, 172), and in Latin ''plaustrum'' "farm cart", ''plōstrum, plōstellum'' "cart", and ''plōxenum, plōximum'' "cart box".〔C.T. Onions, ed., ''Oxford Dictionary of English Etymology'', s.v. "plough" (Oxford: Clarendon Press, 1996).〕〔''Webster's Encyclopedic Unabridged Dictionary of the English Language'', s.v. "plow" (NY: Gramercy Books, 1996).〕 The word must have originally referred to the wheeled heavy plough, which was common in Roman northwestern Europe by the 5th century.〔Dr. Judith A. Weller, "Agricultural Use", in ''Roman Traction Systems'': accessed 20 April 2012, available at ()〕 Orel (2003)〔Orel, Vladimir (2003). ''A Handbook of Germanic Etymology''. Leiden, Netherlands: Brill. s.v. " *plōȝuz".〕 tentatively attaches ''plough'' to a PIE stem *''blōkó-'', which gave Armenian ''peɫem'' "to dig" and Welsh ''bwlch'' "crack", though the word may not be of Indo-European origin. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「plough」の詳細全文を読む スポンサード リンク
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