Distribution of C. V. of Rice Yield per TAN in Japan

Abstract

In 1953, Section of Statistical Researches in the Ministry of Agriculture and Forestry published the account tables of annual variation of paddy rice & wheat yield per TAN of cities, towns and villages in Japan, which contain the mean yield per TAN, standard deviation and the C. C. V. (coefficient of variation.) of rice and wheat. Those were accounted by the statistics from 1926 to 1940. Based on these tables the writer has drawn up a map of distribution of C. V. of paddy rice yield per TAN (Fig. 1). The map points out the stability and the unstability of agricultural production in Japan, for daddy rice is the most important in every prefecture. Eastern Japan in comparison with western Japan, has a high unstability, almost all parts have the C. V. of 20 or more. Western Japan has a high stability, and its C. V. is less than 20 in most of the region. Centers of the unstable areas in eastern Japan are on the mountain-lands, plateaus of Kitakami and Abukuma, mountains of the central chain of Ou, and some mountains of Chubu. Generally, eastern Ou, which lies to the east of the central chain of Ou, is much less stable, where the low land facing the sea without shelter to the north-eastern or eastern cold wind, e. g. the coastal plain of Sanbongi-hara, and marginal Jow land of Soma, are also unstable. But western Ou, the western side of the central chain of Ou, is comparatively stable. Especially, basins and plains which lie on the western side of the mountains and plateaus are stable. The cold wind which blows from the east or north-east in summer brings a poor harvest in these regions. That wind is named YAMASE in the nothern part of eastern Ou, and disfavoured by the farmers. It is an interesting fact that the centers of the unstable areas in Ou correspond to the grazing regions. In western Japan, mountain-lands are rather stable, the plateau of Chugoku, is very stable. And some low lands are unstable. Especially in the so-called Setouchi, which includes the low lands of Sanyo, the islands in the inland-sea of Seto, north-eastern Kyushu, and northern Shikoku. In that region poor harvests by low temperature seldom occur, but droughts can cause them there. Some regions suffer from floods by typhoons. In north-western Kyushu, Hizen Peninsula, Iki Island Tsushima etc. are unstable. The farther westward the region is from the district of Kinki, and the farther northward it is from the same district, the greater is its C. V. accounted for each prefecture. It seems to me that the nearer it is to the dry limit of the rice culture region on south-eastern Asia, the more frequent and severe damages of drought occur, while the nearer to the poler limit of it, the more frequent and severe damages of low temperature occur in summer.