1. The surplus population could leave for underpopulated areas.
It should be noted that villeins were not absolutely prohibited from leaving their manors. Rather, they were forbidden from leaving without permission from the lord, which was usually obtainable. For instance, manorial records often feature payments of chevage by landless sons who had left the ...
The main ways are through improved field management, clearing woodland, and adoption of dairy.
Crop rotation involves the evolution from two-field to three-field crop rotation starting in Charlemagne's time; followed by the adoption of four-field crop rotation starting in Belgium in the 18th century. The change to three-field crop rotation both reduces the ...
Just adding a little perspective: this question seems to originate along the lines of thinking in terms of the Malthusian catastrophe. But the "growing population" in the Middle Ages did not grow that much:
The population levels of Europe during the Middle Ages can be roughly categorized:
400–600 (Late Antiquity): population decline
A plan of Harlech Castle, built by Edward I between 1283 and 1295;
A modern view from the SSW (left-upper-left in plan above); and
A close-up of the Guard House itself.
As you can plainly see, the Guard House is more spacious than the other four towers combined, all five being three stories tall as well. The back half living quarters of one ...
As population grew, people starved. This is the Malthusian Trap.
As wealth increased, the population grew until people started starving again.
Most GDP growth was captured not in living standards, but in increased population density.
Most GDP in those days was in the form of food production; food was expensive and consumed most of most people's lives.