Additional question, if I may: what would the infrastructure of such a system look like? How was the food moved and stored? Who controlled that distribution and how?

Hello, there.

Thank you for this excellent question. This is a really good question, as it deals with sort of the fundamentals of the history of urbanization, namely, how to feed all the people living in a city. Cities produce little to non food of its own, and are dependent to have an abundance of food from its nearby territories. The quick answer to your question is: it depends on some different factors.

Just as a quick side note, even though you didn’t specify it, I have primarily been looking at agricultural output of European farms during the medieval time, even though you didn’t specify which area you meant. I did this primarily because most of my readily accessible books and articles on medieval agricultural output deals with Europe. You also did not state a particular year, and as the medieval period is long, and there are difference between the different medieval periods, it is very difficult to get an precise answer.

There are several factors that are important when discussing how much land is needed to feed an entire city. Some factors are more global and affect agriculture no matter where it is situated. This include environmental factors – did it rain enough this season; did it rain to much? Was the last winter long or short? Factors like this had a huge impact on the agriculture output of the farmlands. Other factors were more local; is the fertile land easy to access, or hard to reach? What kind of crops are you using? How fertile is the soil? The last factor - how fertile is the land? - was perhaps the most important, as it was an important factor in how much food a certain area of farmland produced. It is also import when we are talking about. Agricultur output was different throughout the middle ages. For example, in 800, the average yield ratio for grain was about 1:25, meaning for every kg of grain sown, you’d get about 2,5 kg back. This ratio increased to 1:4 in the 11th century. This cleary demonstrates that the agricultural output differentiated during the medieval period.

It is difficult to say an exact average agricultural output for a whole continent, but if we take a look at a local example, we might some answers. In their paper English Agricultural Output 1250-1450: Some Preliminary Estimates, Broadberry, Cambell and Leeuwen taken a look at the agricultural output in England during the late middle age period. There are differences between different crops and throughout the period. The agriculture output varies between 4 and 16 bushels per acre (I’m not entirely sure how much a “bushel” was during the late medieval period, but I’ve seen figures stating that a bushel is between 21 and 27 kg, depending on the type of crop). The average yield per acre of land for all types of crops was between 6 and 10 bushels of wheat. As you can see, average yield differentiated throughout the medieval period.

So, what do these figures mean? Even though there are difficulties in getting good, average numbers of farmlands needed, studies have shown that during the late middle ages, around 20 acres were needed to support a family of 5 people for a year. Some of the crops were used as seeds for the next season (Usually, 1/4 of the crop was needed in order to be able to replant the next season. This could also fluctuate between seasons, but 1/4 was the average throughout most of the medieval period). Some of the grain was also used for feeding livestock, but around 3/4 of the calorie intake during the medieval period was from the agricultural output from the farmlands. Meaning that if an average of 4 acres of land were needed to feed one person, if we extrapolate this to a city of 10,000, it means that during the late middle ages, we need about 40,000 acres (or little over 160 km2) just in order to feed the city (not counting the people working on the farmlands around the city). This is an area just about the size of the land area of Washington D.C. The area was most likely needed to be bigger, as a lot of the agricultural output of the farmlands around a city also were needed in order to feed the people working on the farms.

As I stated in the second paragraph, it is very difficult to get a precise answer for the whole of medieval period. One has to do some guessing in the research, but we can do some research that gives us some good estimates. I hope this answers your questions.

Sources:

Broadberry, S. Campbell, B. and Leeuwen, B. (2008) English Agricultural Output 1250-1450: Some Preliminary Estimates

Kümin, B. (ed.) (2018) The European World 1500–1800: An Introduction to Early Modern History

Bagge, S. (2004) Europa tar form. År 300 til 1350.

Additional questions how did italian cities feed themselves? Both Milan and Naples were among the biggest cities in medieval Europe with a population of over 100 000. Italy overall isn’t that big, and mostly mountainous.

Josiah Russell estimated that the leading city in a region usually had around 1.5% of the population of the region. (Josiah Russell, Medieval Regions and their Cities, page 38.)

He estimates that Dublin had about 11,000 people before the Black Death (page 137), compared with 675,000 people and 84,000 km2 in Ireland (page 235), as well as a certain share of western Britain. But this was far from typical.

Most of the other leading cities were much larger, and Venice had about 100,000 people, so most cities of 10,000 people would be local centers linked to the leading regional centers. I think the 1.5% rule would tend to overstate the local part of the regional population. So figure 60,000 people. Maybe 4,000 km2, supporting this local city of 10,000, and the leading regional centers.

(Note that this isn't just land to feed the city.)