page_title: Science and technology of the Han dynasty
section_title: Alternating fields
hierarchical_section_title: Science and technology of the Han dynasty / Agriculture / Alternating fields
caption_attribution_description: A pottery model of a cow from the Chinese Han Dynasty (202 BCE &#8211; 220 CE).
context_page_description: The Han dynasty of ancient China, divided between the eras of Western Han, Xin dynasty of Wang Mang, and Eastern Han, witnessed some of the most significant advancements in premodern Chinese science and technology.
  There were great innovations in metallurgy. In addition to Zhou-era China's previous inventions of the blast furnace and cupola furnace to make pig iron and cast iron, respectively, the Han period saw the development of steel and wrought iron by use of the finery forge and puddling process. With the drilling of deep boreholes into the earth, the Chinese used not only derricks to lift brine up to the surface to be boiled into salt, but also set up bamboo-crafted pipeline transport systems which brought natural gas as fuel to the furnaces. Smelting techniques were enhanced with inventions such as the waterwheel-powered bellows; the resulting widespread distribution of iron tools facilitated the growth of agriculture.
context_section_description: During Emperor Wu's (r. 141–87 BCE) reign, the Grain Intendant Zhao Guo (趙過) invented the alternating fields system (daitianfa 代田法). For every mou of land—i.e. a thin but elongated strip of land measuring 1.38 m (4.5 ft) wide and 331 m (1,086 ft) long, or an area of roughly 457 m² (0.113 acres)—three low-lying furrows (quan 甽) that were each 0.23 m (0.75 ft) wide were sowed in straight lines with crop seed. While weeding in the summer, the loose soil of the ridges (long 壟) on either side of the furrows would gradually fall into the furrows, covering the sprouting crops and protecting them from wind and drought. Since the position of the furrows and ridges were reversed by the next year, this process was called the alternating fields system.
  This system allowed crops to grow in straight lines from sowing to harvest, conserved moisture in the soil, and provided a stable annual yield for harvested crops. Zhao Guo first experimented with this system right outside the capital Chang'an, and once it proved successful, he sent out instructions for it to every commandery administrator, who were then responsible for disseminating these to the heads of every county, district, and hamlet in their commanderies. Sadao Nishijima speculates that the Imperial Counselor Sang Hongyang (d. 80 BCE) perhaps had a role in promoting this new system.
  Rich families who owned oxen and large heavy moldboard iron plows greatly benefited from this new system. However, poorer farmers who did not own oxen resorted to using teams of men to move a single plow, which was exhausting work. The author Cui Shi (催寔) (d. 170 CE) wrote in his Simin yueling (四民月令) that by the Eastern Han Era (25–220 CE) an improved plow was invented which needed only one man to control it, two oxen to pull it, had three plowshares, a seed box for the drills, a tool which turned down the soil, and could sow roughly 45,730 m² (11.30 acres) of land in a single day.
caption: A Han-dynasty pottery model of a standing cow
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