Before the industrial revolution, machines did not assist humans with most tasks. Ancient farmers needed a better way of plowing fields than simply dragging the plow themselves. Hard ground is especially difficult for humans to plow on their own. With the invention of simple plows that attached to an animal such as a donkey or ox, humans saved time and energy. Animal-pulled plows allowed humans to plow more land faster and grow more crops.
Modern plows use various techniques to plow the soil. The moldboard plow uses multiple steps to turn soil as it is pulled across a field. The moldboard plow slices through the ground beneath it and cuts the ground into pieces. Then the moldboard plow turns the soil, flipping the slices over. The disk plow inverts soil using curved steel blades that cut through hard ground and shrubbery before the moldboard plow is used, if necessary.
When overturning the soil is not necessary or suitable, chisel plows allow farmers to penetrate the soil without overturning large areas of it. Long, curved shanks extend from the plow and slice into the soil. The plow stirs the soil as it passes through the field without causing soil displacement. In areas where usable soil is scarce or the soil is not deep, losing soil is damaging to farms. Chisel plows help conserve soil.
During the construction of wind farms at sea, as well as other at-sea construction sites, underwater plows are towed behind the vessel to locations where they are used. Underwater plows dig deep below the ocean into the Earth to lay cables. Displacement plows for underwater usage are similar to land displacement plows, overturning earth to install cables. Nondisplacement underwater plows create deep trenches to lay cables in without overturning much earth.