The Heavy Plough and the Agricultural Revolution in Medieval Europe
By Thomas Barnebeck Andersen, Peter Sandholt Jensen and Christian Stejner Skovsgaard
Discussion Papers on Business and Economics No. 6 (2013)
Abstract: This research tests the long-standing hypothesis, put forth by Lynn White, Jr., that the adoption of the heavy plough in northern Europe led to increased population density and urbanization. White argued that it was impossible to take proper advantage of the fertile clay soils of northern Europe before the invention and widespread adoption of the heavy plough. We implement the test in a difference-in-difference set-up by exploiting regional variation in the presence of fertile clay soils. Consistent with the hypothesis, we find that regions with relatively more fertile clay soil experienced increased urbanization and population after the plough had its breakthrough, which was approximately around the closing of the first millennium AD. We find that the heavy plough accounts for more than 10% of the increase in population density and urbanization during the high middle ages.
Introduction: As of the 9th century to the end of the 13th century, the medieval European economy underwent unprecedented productivity growth. The period has been referred to as the most significant agricultural expansion since the Neolithic revolution . In his path-breaking book, “Medieval Technology and Social Change”, Lynn White, Jr. argues that the most important element in the “agricultural revolution” was the invention and widespread adoption of the heavy plough.
The earliest plough, commonly known as the ard or scratch-plough, was suitable for the soils and climate of the Mediterranean; it was, however, unsuitable for the heavy soils found in most of northern Europe, which “offer much more resistance to a plough than does light, dry earth”. The consequence was that north European settlement before the middle ages was limited to lighter soils, where the ard could be applied. The heavy plough and its attendant advantages may have been crucial in changing this. More specifically, heavy ploughs have three function parts that set them apart from primitive ards. The first part is an asymmetric ploughshare, which cuts the soil horizontally. The second part is a coulter, which cuts the soil vertically. The third part is a mouldboard, which turns the cut sods aside to create a deep furrow (Mokyr 1990; Richerson 2001). The mouldboard is the part of the heavy plough from which its principal advantages on heavy clay soils derive. The first advantage is that it turns the soil, which allows for both better weed control on heavy soil in damp climates and incorporation into the soil of crop residues, green manure, animal manure or other substances. The second advantage is that mouldboard ploughing produced high-backed ridges, which contributed to more efficient drainage of heavy clay soils. The ridges also allowed for better harvests in both wet and dry seasons. In the wettest season there would still be crops on the crest, and in the driest seasons there would still grow crops in the furrow. The third advantage is that the heavy plough handles the soil with such violence that cross-ploughing is not needed, thus freeing up labor time. Hence by allowing for better field drainage, access the most fertile soils, and saving of peasant labor time, the heavy plough stimulated food production and, as a consequence, “population growth, specialization of function, urbanization, and the growth of leisure”.