The medieval period is an extremely expansive length of time in European history (roughly 600–1500 CE), and farming techniques differed from century to century. Therefore, it is difficult to make generalizations. One correlation that can be pointed out is that more effective farming typically emerged along with the growth of towns in the countryside.
The driving force behind the agricultural revolution, which emerged in particular between 950 and 1100, was the use of the heavy-wheeled plow, fitted with an iron-tipped coulter and pulled by oxen or horses. Innovations in horse collars and horseshoes further facilitated the ease by which animals could be used to dig up the tougher soils on and around the Mediterranean. This was significant for many of Europe’s small towns, which had begun to appear in places like the Holy Roman Empire, France, the kingdom of Castile, Italy, and elsewhere, because surplus crops could now be cultivated on the town's agricultural frontier, brought into the city by peasant farmers, and sold at markets to foreigners. The capacity of towns and cities to harvest and store surplus grain and other crops greatly enhanced the wealth of the countryside and fostered the creation of new, trans-European trade routes.
Another important innovation in this period was the invention of the mill. Mills were a landmark achievement in peasant agriculture; they would remain the world’s only source of mechanical power until the emergence of the steam engine during the Industrial Revolution. Mills, often powered by a local water source such as a river, were important for grinding grain, driving saws for the production of lumber, pressing olive oil, powering forges, and crushing pulp for making paper. The constant stream of power provided by moving water from a river turned a series of gears that could be used to lift implements that could crush tough and difficult-to-work materials of all kinds. Mills, like the contemporaneous developments in plow and hand-tool technology, greatly increased the amount of products that peasants could produce from agriculture and forest-based products, enhancing the wealth of the towns they were sold to all the while.