Economic Development and Urban Growth in the High Middle Ages 179field and a summer crop in another while leaving the
third free to regenerate itself.
The success of this scheme depended upon the
quality of the soil and the availability of adequate
rainfall. Northwestern Europe, though at the same
latitude as Newfoundland or Labrador, is mild and
moist. Its weather is moderated by the Atlantic Ocean
and, in particular, by the Gulf Stream, a warm water
current that rises in the Caribbean and washes the
shores of England and France. Pleasant summers with
temperatures that usually do not exceed 80 degrees
Fahrenheit follow long, wet winters in which pro-
longed freezes are rare. The prevailing winds are
westerly, bringing abundant rainfall even in the
summer months as Atlantic squalls, forced northward
by high pressure over the Iberian Peninsula, drop
their moisture on the land. In much of the Mediter-
ranean basin, where little or no rain falls to support
summer crops, the two-field system remained domi-
nant; in the harsh, dry tablelands of Castile, seven-
field systems in which only one-seventh of the land
was cultivated at a time was common.
Production was further increased by the introduc-
tion of the heavy iron plow, or carruca, and the complex
technology that surrounded it. This device was appar-
ently of Slavic origin. Mounted on wheels, it consisted
of a horizontal plowshare and an angled mould-board
that turned the sliced earth aside. Cutting a deeper fur-
row than its Roman predecessor (see illustration 10.2),
the iron plow made the seed less vulnerable to late frosts
and to the depredations of birds and rodents. This in-
creased yields and extended the limits of cultivation by
allowing the seed to survive in colder climates. Heavy
clay soils that were impervious to the scratchings of an-
cient plowmen could now be utilized for the first time,
and the clearing of virgin land was greatly simplified
(see illustration 10.3).
Iron plows were expensive. They also required the
increased use of draft animals if their full potential was
to be realized. The old Roman plow required, at the
most, a single team of oxen and in light soils could of-
ten be pulled by a pair of human beings. The heavy
plow might require as many as eight beasts. The in-
creasing use of three- and four-yoke teams from the
ninth century onward was responsible for a reorganiza-
tion of labor on more cooperative lines. It was also an
indication of greater prosperity, as was the innovation
of plowing with horses. Horses are not as strong in ab-
solute terms as draft oxen, but they are much faster.
Horse plowing increases the amount of land that can be
cultivated in a day by more than 30 percent. This rep-
resented a great increase in efficiency. However, horses
are more inclined to sickness and injury than oxen, and
their diet must be supplemented by feed grains. Oxen,
for the most part, need only to graze. The introduction
of horse plowing was therefore limited to those regionsThe chart shows the dramatic reductions in population
from A.D. 500 to 1450 that followed the collapse of the
Roman Empire, the equally dramatic increase during the
so-called agricultural revolution, and the precipitous drop
after 1340 in the wake of the Black Death. Estimates are
in millions.
Region 500 600 1000 1340 1450
British Isles 0.5 0.5 2 5 3
France-Low Countries 5 3 6 19 12
Germany-Scandinavia 3.5 2 4 11.5 7.5
Greece and the Balkans 5 3 5 6 4.5
Hungary 0.5 0.5 1.5 2 1.5
Iberia 4 3.5 7 9 7
Italy 4 2.5 5 10 7.5
Slavic lands 5 3
Poland-Lithuania 2 3 2
Russia 6 8 6
Total 27.5 18 38.5 73.5 51
Source: Adapted from: Carlo Cipolla, The Middle Ages,Fontana Eco-
nomic History of Europe (London: Colliers, 1973) p. 36. Used with per-
mission of HarperCollins Publishers Ltd.TABLE 10.1Population Changes in Medieval EuropeIllustration 10.2
The Mediterranean “Scratch” Plow.The Mediterranean
scratch plow preceded the heavy wheeled plow and had been
used throughout the Roman Empire. It remained popular in dry
regions until modern times because it did not turn over the fur-
rows and therefore helped to preserve moisture in the soil.