The Plow

Ross Weller

The plow was technology essential to the development of agricultural surplus, and an advanced incarnation is still used today in modern, mechanized farming. Prior to the invention of the plow circa 2000 BC (Pryor, 1985), farmers used hand-tools such as hoes and picks to prepare soil for planting. It is easy to imagine a farmer discovering it takes less energy to drag a pick through the earth than to swing it. The next development would probably be a hand-tool specifically designed for this motion. Swarthmore professor Frederic Pryor notes, in The Invention of the Plow, that the human-drawn plow evolved from the animal-drawn plow, not visa-versa. Human-drawn plowing is an act of desperation or lack of draft animals. However, the earliest plows- animal-drawn or otherwise- were probably developments on hand-tools. The first plow designs were too light to do more than scratch the earth, earning them the moniker “scratch plows”. The lightness of the scratch plows evidences the likelihood that they evolved from hand held tools.

Use of the plow in agriculture would have spread rapidly behind the domesticated oxen and the associated development of the harness. Pryor notes that societies employ the plow at different stages in the preparation of a crop. Some cultures plow first and then sow seeds. Others sow first, then plow. The varying application of the plow seems to indicate that plowing developed independently in different locations or that plowing technique was altered to better suit the local crops. The employment of the animal-drawn plow would have greatly increased the efficiency of farmers, allowing more people to become engaged in other occupations. The degree of field preparation that plowing requires (e.g. clearing rocks) would have prompted farmers to replant the same fields rather than prepare others. The presence of the oxen on the fields would have presented a solution to the problem of keeping these fields fertile. The application of manure could have developed from observations of the presence of oxen “graced” patches of fields.

The scratch plow would have been very light and maneuverable. The limiting factor in the terrain that farmers could plow would have been the oxen and the hardness of the ground. Scratch-plowed furrows most likely followed the contours of more friable soils. This would not have made for less efficient harvesting compared to straight lines of crops. The plows would have initially been made of exclusively of wood or of wood with stone blades. The necessity of plowing harder ground, driving by factors like population pressure and exhaustion of older fields, led to the development of plows with blades of harder materials, eventually leading to plows of iron and steel. The addition of a moldboard to plow design increased the extent that plowing improved the fertility of the field. The moldboard, an angled section of the blade that folds furrows over and buries surface material, probably increased the plow’s weight and resistance through the soil significantly and would have therefore required more oxen be used in draft. A heavier plow and larger teams of oxen would also have made s maneuvering along contours and around obstacles more difficult. With the development of the moldboard plow, the blade of the plow no longer scratched the earth, but instead spread it to one side. This spreading action leads to the blade becoming known as the share- as in plowshare.

The next great advance in plow technology came in the middle ages with the development of the heavy wheeled plow. While light scratch plows only disturbed the uppermost levels of the soil, heavier plows could penetrate deep into the soil, allowing greater aeration and nutrient redistribution. The problems with heavier plows were that more draft animals were needed to pull them and they could bury themselves to too great a depth under their own weight. The addition of wheels onto the plow frame created a limit to how deep the plow could drive. The problem of pulling the plow was solved by communal draft animal sharing (Williams, 2003). This pooling of resources probably created a degree of farmer solidarity and encouraged farmers to live in closer proximity.

The heavy wheeled plow would have been very ungainly to turn, but the strength of the plow and the draft teams would have allowed farmers to plow long rows despite roughness of sections of ground. The plow featured a sharp disk or blade, called a coulter, which helped break apart hard soil and cut tree roots. Williams cites the prevalence of Waldhufendorf type villages in Germany characterized by their hufen- “long, narrow fields that were cut back into the forest behind each new holding”- as evidence of the widespread adoption of the heavy wheeled plow and of the form of farming that suited its use.

The invention of the horse collar had considerable impact on plowing. Previous harnesses had constricted the breathing, and thus power output, of horses. The new collar, which distributed pressure to the horse’s bone structure, allowed horses to take the place of oxen. Horses were faster and more maneuverable than oxen, allowing one team to cover a greater area and freeing more workers from farming. According to Pryor, humans are employed to pull plows only “in extremis”, so the natural tendency of plowing methods has always been to improve the efficiency and decrease the labor intensity of farmers.

Later advances to the draft-drawn plow mostly involve introduction of metal parts and improved metallurgy. All iron plows and all steel plows lead to increases in productivity. Once fields had been significantly smoothed by decades and centuries of plowing, it was possible for plows with multiple shares to be used. This would have created more uniform furrows and faster plowing, although likely required more energy to pull the plow. The problem of draft power was finally solved by motorized horse-power. Tractor drawn plows have replaced draft-animal plows on modern, Western farms. Modern plows are a series of cutting disks laid in parallel that produce many furrows with each pass.

Plowing has produced serious long term effects on the environment. Contour plowing reshaped the topography of farmlands over time. Earth overturned by plowing is susceptible to erosion, particularly by wind. The American Dust Bowl was the result of prolonged drought and the loosening of topsoil from plowing. It is important to remember that soil, particularly the uppermost layers such as the topsoil and humus, is involved in a delicate balance of nutrients and life, of water and air. Plowing, by definition, disturbs this balance.

Frederic L. Pryor. The Invention of the Plow (in Explanations in Economic History). Comparative Studies in Society and History, Vol. 27, No. 4. (Oct., 1985), pp. 727-743.

Michael Williams. Deforesting the Earth: From Prehistory to Global Crisis ( Univ. of Chicago Press, 2003), pp. 102-142.

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last updated 1/25/06