As far as production techniques are concerned, temperature is no threat to the growth of wheat, but insufficient water becomes a major factor to hinder the wheat production. Likewise, the preservation of soil moisture in the Hebei plain is historically exercised, and by Tang dynasty two wheat production regions are formed, i.e., the eastern foot of Taihang mountains, and lower stretch on the banks of the Yellow River, in addition to the southern foot of Yanshan mountains. During the Northern Song and Jin dynasties, wheat grows all on the Hebei plain as a major crop.