Concept
The British Agricultural Revolution, or Second Agricultural Revolution, was an unprecedented increase in agricultural production in Britain arising from increases in labour and land productivity between the mid-17th and late 19th centuries. Agricultural output grew faster than the population over the hundred-year period ending in 1770, and thereafter productivity remained among the highest in the world. This increase in the food supply contributed to the rapid growth of population in England and Wales, from 5.5 million in 1700 to over 9 million by 1801, though domestic production gave way increasingly to food imports in the 19th century as the population more than tripled to over 35 million. Using 1700 as a base year (=100), agricultural output per agricultural worker in Britain steadily increased from about 50 in 1500, to around 65 in 1550, to 90 in 1600, to over 100 by 1650, to over 150 by 1750, rapidly increasing to over 250 by 1850. The rise in productivity accelerated the decline of the agricultural share of the labour force, adding to the urban workforce on which industrialization depended: the Agricultural Revolution has therefore been cited as a cause of the Industrial Revolution. However, historians continue to dispute when exactly such a "revolution" took place and of what it consisted. Rather than a single event, G. E. Mingay states that there were a "profusion of agricultural revolutions, one for two centuries before 1650, another emphasising the century after 1650, a third for the period 1750–1780, and a fourth for the middle decades of the nineteenth century". This has led more recent historians to argue that any general statements about "the Agricultural Revolution" are difficult to sustain. One important change in farming methods was the move in crop rotation to turnips and clover in place of fallow under the Norfolk four-course system. Turnips can be grown in winter and are deep-rooted, allowing them to gather minerals unavailable to shallow-rooted crops. Clover fixes nitrogen from the atmosphere into a form of fertiliser.
