THE PLOW
Plows are the primary tools of farmers used to break up the soil. Plowing turns over a layer of earth so that the vegetation growing on top is buried beneath the layer. The are many reasons for plowing, such as opening the soil for aeration and to receive rain. Plowing can also pulverize the soil , making it easier to plant seeds.
The earliest plows date back 5,000 years in the Middle East. They were pulled by oxen while the farmer walked along behind and were made entirely of wood, using a tree limb with a branch attached for a “scratcher.” Later improvements involved adding stone or metal to the device. Once wheels were added, the farmer could ride along on a sulky, and teams of animals were hitched to the plow. The first real advancement came from the Dutch, who changed the moldboard to actually turn the soil instead of just loosening it. In 1720, the English patented a plow with an iron-sheathed moldboard. English plows were exported all over the world.
Thomas Jefferson designed an improved moldboard, which was patented by Jethro Wood in 1819. He made a cast-iron plow which became the standard of the times. These plows worked well in the abrasive soils of the Eastern U.S., but did not clean themselves well in the soft, loamy soils of the Midwest. A blacksmith from Chicago named John Lane, developed a wood base with metal strips cut from a saw blade in 1833. A few years later, a similar design was being built by John Deere. Those two developments turned the American Midwest into the greatest food producing area in the world.
The next advancement in plow bottoms was the disk. These plows use one or more rotating steel disks two feet in diameter. The rotational action reduces friction, preventing erosion, but must have extra weight pushing down on the disks to penetrate the soil. The disks work well in areas where soil would otherwise stick to moldboards.
Another development was the chisel plow, using a number of steel tines coming to a point at the end. Chisels are used where the farmer does not wish to turn the soil over. A fourth type is the rotary plow, consisting of either rotating blades or high-speed rotating tines. These plows leave the soil very smooth and ready for planting. In 1868, James Oliver invented chilled cast iron that revolutionized plow manufacturing.