Final answer:
Crop rotation was crucial in the Middle Ages for increasing soil fertility, diversifying crops, and improving crop yields.
Step-by-step explanation:
Crop rotation was important to agriculture in the Middle Ages because it increased soil fertility and allowed for the diversification of crops. By planting different types of crops in a field each year, and sometimes letting the field lie fallow, farmers could replenish nutrients in the soil, which would otherwise be depleted by continuous planting of the same crops. This practice not only improved soil nutrient levels but also helped in breaking pest cycles, thus reducing the need for pesticides and enhancing overall crop yields. Crop rotation was a key aspect of the agricultural advancements in the Middle Ages that contributed to the increased productivity necessary to support a growing population.