The foundation of the Medieval economy was agriculture. Throughout Europe, 80-90 percent of the population struggled to coax a living, and perhaps a surplus, out of the soil. It wasn't easy, but using a wide variety of techniques it was done and often with marked success. While crops varied somewhat depending on the climate and soil quality, England and France saw mostly wheat, barley, peas and oats being grown, along with vegetables, vinyards and fruit orchards.
Medieval agriculture, like that still practiced in many Third World areas, got by without machines, hybrid seed or chemical fertilizer. A horse, an ox, or a wife, was used to pull the plow. Harvesting was done by hand. Crops available for export went a short distance by ox cart, and thence by river barge or sea going ship to market. For local consumption there were vegetable gardens and fruit trees. Fruit, however, was often turned into cider for export or winter use. Berrys, nuts and anything else eatable was also gathered when available. Bee hives were kept to produce honey . These subsidiary crops kept the farmers busy most of the time, for the main crops only required a few weeks intense labor at planting and harvesting time.
To compensate for the lack of modern fertilizer, the farmland was treated with animal (and sometimes human) manure, and allowed to remain fallow every second ot third year. When fallow, the field was sometimes planted with legumes (peas, beans) that restored the lost nitrogen in the soil. Medieval peasants didn't understand the chemistry of this, but had learned by trial and error over the centuries that it worked. The normal practice was to to leave a field fallow every other year, and more adept farmers would plant leguemes in the fallow year, which increased the nitrogen content of the soil. But if the land was particularly good, the climate right and the farmer particularly skillful, one could get away with fallowing a field every third year. Normally, however, farmers would switch beween the two methods depending on what they thought they could get away with. Too many "every third year" cycles would reduce the yields noticiably, at which point the farmer would have no choice but to use every other year fallowing in order to rebuild the fertility of the land.
The Romans had been avid students of agriculture, and much of that knowledge survived either in practice or in the collection of Roman era manuscripts preserved at monasteries. The Romans were enthusiastic letter writers and a favorite subject was food, how to produce it and how to prepare it. Many of these letters survived the fall of the empire and much knowledge was gained from them.
There were two major agricultural innovations that appeared after the Roman government fell. One was the mould-board plow. This elaborate metal and wood device was developed by Slavic tribes and spread west from the 6th century on. It's design allowed six ot more oxen to pull a plow and break up virgin ground, or the heavy, clay laden soils typical of northern Europe. As an example of the impact of this new plow, consider the huge population growth that occurred after its introduction. The area of France, Germany, Switzerland, Austria and the Low Countries had a population that flucturated between 10 and 15 million from 1 AD to 600 AD. In came the new plow and during the next six centuries the population grew to about 36 million (from a low of ten million, as a result of all the invasions and civil strife.) These areas now support a population of over 250 million, which gives you an idea of how sparsely populated the area was way back then.
The second innovation was the horse collar. Roman --and ancient-- horse tackle was rather inefficient, resulting in an underutilization of an animal's full strength. The horse collar did away allowed horses to be used for pulling a plow, or heavy loads in general. This created a big increase in the horse population, as the horse was more versatile a beast of burden than the ox. With horses more common on farms, more people learned to ride them, which led to English yeomen (who often used horses for their famrs) to be easily mounted on horseback (using captured or stolen French horses.) This made the English armies even more lethal because of their mobility, and the fact that the yeoman infantry didn't wear themselves out marching on foot all over France.
Farming was a matter of numbers. While most peasant farmers may have been illiterate, they knew how to count. They knew that wheat would yield 250 to 300 liters of grain per acre (modern famring methods, on the same land, yield over 1,500 liters of grain per acre.) Barley would bring 700-720 liters per acre. The higher yield for barley was partially the nature of the plant, plus the fact that you put 72 liters of seed into each acre of wheat and 144 liters per acre of barley. Oats yielded 360-400 liters an acre, for 108 liters of seed. Peas, an important diet suppllement and protien source, gave 300-340 liters per acre, for 108 liters of seed. Flax and hemp was also grown, to provide rawmaterial for linen and rope.
Depending on the nature of the land, the size of the farmers holdings, local weather conditions, and drinking habits, about half the land would be sown in barley. In ale drinking areas (most of England and large parts of France), barley would be needed for making ale. Barley was also a more productive grain, even though it produced a less tasty meal than wheat. A third (or more) of the land would be planted in wheat. The remainder would go for peas and oats. Grain yields of slightly under four times seed grain sown were the norm until the 18th century. There, another burst of innovation brought productivity to ten times seed sown.. In the 20th century, this rose to twenty times.
Oddly enough, agricultural experimentation did take place in Medieval times, often at abbeys under the superviion of monks (who were the Medieval scholars and scientists.) Consistant yields of eight times seed sown were reported. But the Medieval period was one of poor communications and strong traditions. The new techniques were not broadcast far and wide and, even if they were, most farmers would be reluctant to change their ancient (and reliable) methods. Moreover, some of the methods, such as using much higher doses of animal manure, were not always possible because there would not have been enough domestic animals available to produce the needed manure. But some of the new techniques, such as denser planting to crowd out weeds, would have worked widely. One could say that the agricultural "reforms" of the 18th century were basically a side effect of the "Age of Enlightenment," whereby the new was given equal opportunity with the traditional.
In England, the idea farm size for a family was a "yardland" (24-30 acres) in size. Only about a quarter of the English farm families had this much land (or a bit more) before the Bubonic Plague , most had ten or fewer. Those farmers possessing a yardland were able to work their land efficiently enough to feed themselves and prodice a surplus for sale. Wheat grain could be sold for about 40 ducats a bushel. Barley went for 25-30 ducats a bushel and peas for 15-20 ducats a bushel. In a good year, a yardland of crops could generate grain for sale that would bring 1,500-2,000 ducats. Another thousand ducats could be obtained by selling off cheese, wool, honey, sheep, eggs, fruit and vegetables. Some of this profit was saved, some was spent on repairing or replacing farm equipment and the some went for household neccessities (utensils, salt , furnishings) or luxuries. But a lot went to pay taxes and fees. There were a lot of these. The principal one was the land rent, which varied quite a lot. A rough annual average would be 10-50 ducats per acre. In addition to this there might be payments of a percentage of the main crop, as well as a percentage of the wool taken from sheep (that often grazed on the overlords land.). There were fees for taking over as a new tenant (as when the existing tenant died and his son took over) and fees for the use of the landlords meadows for grazing sheep and forests for taking wood, nuts and berrys. The miller charged 4-5 percent of the grain to grind it into flour.
A prudent farmer put aside grain and coin for hard times. While the overlords were supposed to keep reserves of grain for hard times, this was sometimes not the case or the reserves were not adequate.
Many farmers knew that for anywhere from a few hundred to a few thousand ducats per acre they could purchase better lease terms on their land, or buy the land outright.. Thus the farmer families that were efficient and frugal for generation after generation, eventually found themselves land owners, members of the minir gentry and, eventually, part of the nobility.
Medieval farmers did more than just grow grain and peas. Most farmers had one or more horses and oxen, two or more milk cows, a few pigs, several dozen sheep or goats, beehives and some chickens. Many farmers kept geese as well. The horses and/or oxen pulled the plow and did other heavy work. The cows supplied milk, most of which was turned into cheese. The pigs were fattened to supply the main course for major feasts. The sheep supplied wool, which was spun into cloth for the families clothes. The chickens supplied eggs and meat to liven up the diet of peas and porridge.
There would also be up to an acre or more in vegetables. During the Summer and Fall, the vegetable garden made meals most palatable. Hemp and flax were also grown, to provide materials for clothing, household goods and tools. There might also be apple or pear trees on the farm, that would yield fruit. In many parts of Europe, apples produced a potent cider, which made the dreary Winter weather more palatable. By Spring, however, food supplies would usually be low, which made Lent as much a virtue as a necessity.
The larger the farm, the more different activities there would be. These yardland farmers thus had need of additional labor and would hire farmers of smaller plots. The hired help would cost three to ten ducats a day (depending on the productivity of the worker) plus meals (a few more ducats a day). Specialized work, like re-thatching the farmers house, would run to about ten ducats a day for the thatcher, and 4-5 ducats a day for his assistant. And you had to feed them. Some well off farmers had one or more live in servants. These were relatively cheap, costing as little as 100-250 ducats a year (plus room and board, which could add up to more than the wages. Servants were often the older children of less well off farmers. Afther the Plague, servant's wages went up, as did their maintenance. The hired help demanded better food and lodging, and generally got it once the Plague had created a shortage of servants.
The farmer also had to deal with the church and he usually had to pay a title (ten percent) of all produce to the cleric (abbot or bishop) who presided over the manor, plus the usual land rents. The tithing was generally not resented, because the church tended to maintain reserves of grain. In times of need, the faithful to called on the church for relief and, if it was available, it was generally forthcoming. The church preached charity and, in times of need, tended to practice what it preached.
For the majority of farmers who had small holdings, life was much less secure. An acre of barley could, in an average year, produce about 500 liters of grain (after making allowances for taxes and seed for the next crop). This was enough to feed one adult for a year at a very basic level. A farmer with a wife and two children could get along with five acres. Everyone would have to work, especially for other sources of food like the vegetable garden and rummaging in the woods for mushrooms, nuts, and berries. But a five acre holding left little margin for bad weather. Several bad years in succession could lead to widespread famine: in England alone 10-15 percent of the population perished from starvation or the effects of malnutrition as a result of a series of unusually wet, cold years from 1315 through 1318.caused a succession of bad harvests. Most of the dead were the farmers with less land. Naturally, there was more land available for the survivors. After the Plague, there was plenty of land, and most European nations date their "national costumes" (from the "good old days") from the centuries following the Plague, when the peasantry prospered because there were many fewer people but the same amount of farmland.