Norfolk four-course system

Wheat, then turnips, then barley, then a year of clover grazed or cut for feed. The Norfolk rotation dropped the fallow year altogether. Turnips and clover kept more cattle and sheep fed through the winter, clover is a nitrogen-fixing legume, and the extra animals returned manure to the fields, so the same farm grew more grain and more meat. Borrowed from Flemish practice and championed by Charles "Turnip" Townshend (pictured), it was central to the farming changes that fed an English population rising from 5.5 million in 1700 to over 9 million by 1801. The strict four-course pattern is unlikely to survive anywhere on a commercial scale today, yet the idea of a root break and a legume still shapes arable rotations.