Mould-board plow

I've talked before about growing crops in the Middle Ages.  But today I want to discuss one particular medieval invention that made it all possible, the mould-board plow.  (American farmers today call it the moldboard plow.  Historians stick with mould-board.  Our students get confused enough as it is without thinking this has something to do with that funny orange stuff you find when you forgot the cottage cheese in the back of the refrigerator.)

Let's start with plowing.  If you've driven through the countryside much you've doubtless seen farmers plowing and wondered vaguely what they were doing.  They were preparing the soil to grow crops, loosening it up, creating crevices in which seeds could lodge and sprout, turning it over so that whatever had been growing there before (say, weeds or grass) would be killed and turned under to rot and fertilize the soil.

Plows have been around as long as agriculture.  For millennia the plow was a basic pointed stick with handles.  The pointy part, the plow-share as it is called, was if possible made of metal.  (Think of the Old Testament hope for a better time, when people will "beat their swords into plow-shares.")  It could be pulled by an ox, a donkey, or even a person in a pinch, with another person walking behind to guide it.

This plow (the Romans called it an aratum, and it's the root of our word "arable," meaning land that can be cultivated) was not very efficient, because fields had to be cross-plowed.  That is, the plow-share would slice the soil, but you had to plow both end-to-end of a field and side-to-side to get the soil properly turned over.  It was however lightweight and cheap.

Medieval people (eleventh-twelfth century) came up with something much better, the mould-board plow, pictured below.

It was called this because it had a mould-board, a curved piece of wood or metal right behind the sharp plow-share.  This would turn the soil over as it was sliced into.  (The word is "mould," meaning soil or earth, not "mold.")  In the medieval image above, it's the dark, curved part of the plow, seen edge-on and hence somewhat cryptic looking (keep reading).

A mould-board plow was called a carruca in medieval Latin, related to "cart," because it was heavy enough that it normally needed wheels.  It also could be pulled a lot easier by a strong animal like an ox or two than by a donkey.

It was also more expensive (because of all the metal), so a lot of peasant families ended up having to club together.  But it was much more efficient, because you didn't have to cross-plow, meaning you could plow twice as many fields (more or less) in the same amount of time, leading to more food being grown.  The heavy, moist soils that could be plowed with the carruca were also generally richer, better for growing crops.  On the other hand, it was so effective at digging up heavy, moist soil that it was never adopted for thin, light soils, such as much of the land around the Mediterranean or on hilltops, where it would be unnecessarily cumbersome and the danger was drying out the soil.

The basic medieval design for a mould-board plow lives on.  Today they are pulled by tractors, not oxen, and often they will have multiple sets of cutter (plow-share) and mould-board side by side.  But if you look at the modern plow pictured below, you will see that the basic design is the same as the twelfth-century plow, even though there's a cutting wheel instead of a pointy plow-share.  There is still a plow-share, but it's now attached to the bottom of the mould-board (you can see it in the left-most of the three mould-boards pictured below), which is mounted horizontally rather than vertically (as in the medieval plow pictured above).  And of course there are three sets of cutters and mould-boards next to each other in this modern plow.

© C. Dale Brittain 2018

For more on medieval agriculture, see my new ebook, Positively Medieval: Life and Society in the Middle Ages.