These are 1st year or 2nd year numbers. The output per-acre will steadily decline afterwards unless you know to set some land aside to be fallow and grow someth

These are 1st year or 2nd year numbers. The output per-acre will steadily decline afterwards unless you know to set some land aside to be fallow and grow something that will return nitrogen to the soil. And like was mentioned by dghughes, rotation is important. From about the middle ages to the early 20th century, European farmers practiced the three-crop rotation scheme. Winter wheat or rye in one field, peas, lentils or beans in a second, and the third would be "resting". It got replaced in Britain and Belgium with the four-crop rotation plan, which produced more calories. https://en.wikipedia.org/wiki/Crop_rotation https://en.wikipedia.org/wiki/Crop_rotation