Since the storage of rice in the husk and the placement of Fudoso warehouse were encouraged in the Daijokanpu (official documents issued by Daijokan, Grand Council of State) on September 2, 708, storage of rice in the husk had been carried out year after year nearly 30 years; existing records of rice tax suggest that there existed the storage approximately the same quantity of crop yields of more than 30 years from the rice field tax during the Tenpyo era.
和銅元年8月10日_(旧暦)の太政官符で、稲穀の貯蔵と不動倉設置が奨励されて以来、毎年備蓄が行われて、約30年近く後天平年間田租収入の30年分余りの（田地からの年間収穫量とほぼ同一）の貯蔵が存在していたことが現存する各令制国の正税帳から推測できる。