Brad DeLong and Turnip Townshend

Brad points to the Wikipedia article on this man here, and notes his connection to our Revolution as well.

Townshend introduced to England the four-field crop rotation pioneered by farmers in the Waasland region in the early 16th century. The system (wheat, barley, turnips and clover), opened up a fodder crop and grazing crop allowing livestock to be bred year-round, and increased productivity by avoiding leaving the soil uncultivated every third year. Previously, a three-year rotation was practiced by farmers in Europe with a rotation of rye or winter wheat, followed by spring oats or barley, then letting the soil rest (leaving it fallow) during the third stage. Crop rotation is necessary in order to avoid the build-up of crop-specific soil pests and diseases, and because different families of plant have varying nutritional requirements. The four-field crop rotation was a key development in the British Agricultural Revolution.

I should also note the Mark Overton, BBC series, who ties this into organic and industrial farming.