Tōhoku region
Tōhoku was traditionally considered the granary of Japan because it supplied Sendai and the Tokyo-Yokohama market with rice and other farming commodities. Tōhoku provided 20 percent of the nation's rice crop. The climate, however, is harsher than in other parts of Honshū due to the stronger effect of the Siberian High, and permits only one crop a year on paddy fields.
Koban (coin)
The Japanese economy before the mid-19th century was based largely on rice. The standard unit of measure was the koku, the amount of rice needed to feed one person for one year. Farmers made their tax payments of rice which eventually made its way into the coffers of the central government; and similarly, vassals were annually paid a specified "koku" of rice. The Portuguese who came to Japan in the 1550s, however, preferred gold to rice; and the koban, which was equal to three koku of rice, became the coin of choice in foreign trade.