This handout accompanies a talk; there is no separate text article. The handout itself serves mostly to add flavor to the talk, and to provide references.
There are three general historic solutions to preparing fields for agriculture - the hoe, the light plow, and the heavy plow. All three destroy the competition (weeds) and demote it to fertilizer, and loosen and aerate the soil.
The class only dealt with the hoe in passing. It is effective, but does not scale well. Light plows enabled larger-scale farming of light, sandy soils - and were used in the ancient and classical worlds.
Much of Europe had heavy clay soil, which would defeat (read ‘break’) a light plow. By pre-medieval standards, it was not arable. The invention of the heavy plow increased the amount of land the could be farmed, and the yields from that land.
It also effected social change, because a farmer had to have access to a team of typically-eight oxen or horses in order to plow a field. (The changes were embedded in the language. Terms such as ‘acre’, ‘oxgang’, ‘knight’s fee’, ‘hide of land’ all stem, explicitly or implicitly, from the eight-ox plow team.)