How did the three field system work?

The three-field-system worked when the farmer has three separate fields that he wanted to use to plant different crops on. Field 1 would have wheat, Field 2 barley, and Field 3 is left fallow. Then the farmer would rotate the crops the next year, planting wheat or barley in Field 3, then Field 1 would be planted with barley or wheat respectively and Field 2 left as fallow. Next year Field 1 would be left fallow and Fields 2 and 3 are planted with barley and wheat.

Ultimately this system allows each field to rest for one year out of being used for 2 years. Sometimes some farmers or producers would use that field that they are keeping fallow for some extra grazing for their cattle or their neighbor's cattle so that nutrients via manure can be incorporated back into the soil. For today's farming community, a field that is left alone for one year is a field that is making them loose money, so they have to make use of that field they are not using for cash crop production, be it for hay, or extended grazing.