In Medieval Europe, farming was based on a three-field system. In this system, there were three plots of land. One plot held spring crops, which were planted in the spring and harvested in the fall. Another plot held winter crops, which were planted in the fall and harvested in the spring. The third plot was left fallow. The following year, the plot left fallow would hold winter crops, the plot that held winter crops would hold spring crops, and the plot that held spring crops would be left fallow. This system helped prevent the soil from wearing out. This was essential because they did not have fertilizers.
In Charlemagne, water mills were used to grind grain. Water mills saved peasants from doing labor and provided a large profit for owners. But water mills were hard to build because they several skills. First, a dam was put on a running stream. Then the millstones had to be cut and moved to the mill site. Next a blacksmith or carpenter built the machinery to run the mill, and lastly, the mill needed to stay in good condition.