How did agricultural advances affect Chinese society during the Middle Ages?

It resulted in more people moving to rural areas.

Explanation:

Improvements in farming machinery included, for example, the moldboard plow and watermill. Later, cotton planting and weaving technology were adopted and improved.

While around 750, 75% of China's population lived north of the river Yangtze, by 1250, 75% of population lived south the river. This migration was possible due to the introduction of quick-ripening strains of rice  from Vietnam suitable for multi-cropping.

what are local authorities doing to fix the problem

explanation:

c, to compete