I work in agriculture and would contend that a farmer from 1000 years ago would be able to understand what is happening on today's farms without much effort.

This link takes you to Cato The Elder's "DE AGRICULTURA"http://www.gutenberg.org/cache/epub/12140/pg12140.html

Much of which rings true today and reads a lot like some of the old farm management textbooks I have at home.

Cato's insistence on not working wet ground is a timeless truth of farming. If anything it is more correct today where we use heavy equipment that can cause larger compaction problems on wet ground than it was in his own time. His encouragement to use ditching and surface drainage is still relevant.

A quote from Cato's "DE AGRICULTURA" "Cut hay in season, and be careful not to wait too long. Harvest before the seed ripens, and store the best hay by itself for the oxen to eat during the spring ploughing, before you feed clover"

This is modern advice. As hay crops get old they develop more lignin which is indigestible.

There is another quote from him about plowing down lupines to increase next years crop. He didn't know that this provided Nitrogen for that crop, but it doesn't make his advice any less correct.

At it's most basic level growing a crop generally requires the following steps(give a take a few and not getting into the difference between modern till and no-till systems:

Preparing the ground. Controlling Weeds. Sowing Seeds. Controlling Pests. Providing Enough but not too much Water. Harvest.

Modern technology makes all of these actions faster, more precise, more repeatable and more efficient, but if you were to take a historical farmer have them watch the action and then show them the effects they would understand what happened. (ie. watch a planter go through a field, then show the farmer how seeds have been placed in rows with perfect spacing)