Editing Plough (section)

===Heavy ploughs===
{{Main|Carruca}}
[[File:ChineseIronPlow1637.jpg|thumb|Chinese iron plough with curved mouldboard, 1637]]
In the basic mould-board plough, the depth of cut is adjusted by lifting against the runner in the furrow, which limited the weight of the plough to what a ploughman could easily lift. This limited the construction to a small amount of wood (although metal edges were possible). These ploughs were fairly fragile and unsuitable for the heavier soils of northern Europe. The introduction of wheels to replace the runner allowed the weight of the plough to increase, and in turn the use of a larger mould-board faced in metal. These ''heavy ploughs'' led to greater food production and eventually a marked population increase, beginning around AD 1000.<ref>{{Cite book |last1=Weber |first1=William |title=Production, Growth, and the Environment: An Economic Approach |date=2014 |publisher=CRC Press |isbn=9781482243062 |page=63 |url=https://books.google.com/books?id=59TMBQAAQBAJ&q=population+growth+and+food+production+1000AD&pg=PA2 |language=en}}</ref>

Before the [[Han dynasty]] (202 BC{{snd}}AD 220), Chinese ploughs were made almost wholly of wood except for the iron blade of the ploughshare. These were V-shaped iron pieces mounted on wooden blades and handles.{{r|temple|p=18}} By the Han period the entire ploughshare was made of [[cast iron]]. These are the earliest known heavy, mould-board iron ploughs.<ref name="greenberger 2006 11-12"/><ref>[[Wang Zhongshu]], trans. by K. C. Chang etc., ''Han Civilization'' (New Haven and London: Yale University Press, 1982).</ref> Several advancements such as the three-shared plow, the plow-and-sow implement, and the harrow were developed subsequently. By the end of the [[Song dynasty]] in 1279, Chinese ploughs had reached a state of development that would not be seen in [[Holland]] until the 17th century.{{r|temple|pp=18}}

The Romans achieved a heavy-wheeled mould-board plough in the late 3rd and 4th century AD, for which archaeological evidence appears, for instance, in [[Roman Britain]].<ref>Evi Margaritis and Martin K. Jones: "Greek and Roman Agriculture", [[John Peter Oleson|Oleson, John Peter]], ed.: ''The Oxford Handbook of Engineering and Technology in the Classical World'', Oxford University Press, 2008, {{ISBN|978-0-19-518731-1}}, pp. 158–174 (166, 170).</ref> The Greek and Roman mould-boards were usually tied to the bottom of the shaft with bits of rope, which made them more fragile than the Chinese ones, and iron mould-boards did not appear in Europe until the 10th century.{{r|temple|p=17}} The first indisputable appearance after the Roman period is in a northern Italian document of 643.{{r|Lynn White, Jr.|p=50}} Old words connected with the heavy plough and its use appear in [[Slavic languages|Slavic]], suggesting possible early use in that region.{{r|Lynn White, Jr.|p=49ff}} General adoption of the [[carruca]] heavy plough in Europe seems to have accompanied adoption of the [[three-field system]] in the later 8th and early 9th centuries, leading to improved agricultural productivity per unit of land in northern Europe.{{r|Lynn White, Jr.|pp=69–78}} This was accompanied by larger fields, known variously as [[carucate]]s, ploughlands, and plough gates.