During Emperor Han Wudi's reign from 141-87 BCE, the Intendant of Grain Zhao Guo devised the alternating fields system. The system planned that for every mou (a strip of land 1.38 m wide and 331 m long) of land, three deep furrows, each 0.23 m wide were to be sowed in straight lines with crop seed. In the summer, the loose soil on either side of the furrows would eventually fall into the furrows, covering the sprouting crops while protecting them from wind and drought. In addition, the position of the furrows and ridges were switched every year, the process was named the alternating fields system. Crops could grow in straight lines from sowing to harvest, which conserved moisture in the soil and provided a stable annual yield for crops. Once the system proved to be successful Zhao Guo ordered every commandery administrator, who were responsible for a separate county, to implement the process in their fields. Prosperous families who owned oxen or had access to easy labor greatly benefited from the 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. Only until the plow was improved upon by the Eastern Han, where only one man was needed to control it and two oxen to pull it were peasants able to greatly benefit from the alternating fields system.