So far as grain supply in Chang’an in the Han and the Tang Dynasty is concerned, the Guanzhong Plains could provide only 2 million dan while the remaining 3 to 4 million dan had to depend on East and Southeast China by means of canal transportation. Several reasons contributed to the Guanzhong’s lack of capacity of grain production. First of all, the consumptive population in Chang’an increased gradually, such as the increasing number of imperial servants, officials in the capital, capital garrison troops, nominates and examinees of imperial officialdom, businessmen and Buddhist monks. Next, the Guanzhong’s agricultural productivity was weakened, for example, decrease of grainproducing cultivated land, of irrigated fields, and of dutycontributing farming households. Finally, the climate of the Guanzhong Plains went through transition to cold and dry respectively between the 2nd and 6th, and between the 9th and 11th century. Therefore, what was described in the folk song which said, “The imperial grain warehouse, supporting millions upon millions of mouths,” cited by Ban Gu, was not accurate.

Chang’an in the Han and the Tang Dynasty; the Zhengbai Canal; grain supply