In Japan, where a dense population is crowded together on a few small plains, it is not surprising that the use of sloping land in the mountains, which comprise 67% of Japan's area, has been promoted in various ways. In some regions the cultivation of steep land is amazingly intense. In this essay, only upland fields of considerable slope are discussed. The categories treated are 1) the steep field as a special type of upland field, 2) the regional distribution of steep upland fields, and 3) the problems of their future development.1. Upland fields in general are subordinate in importance to paddy fields, but in some regions they are of first. importance. Broadly speaking, there are two sorts of upland fields, those on flat elevated land, and those on steep slopes. A survey was made in 1942 to classify upland fields by degree of slope, as follows : those with 5° of slope, those whith 5°-15°, and those with more than 15° of slope. Those in the latter category comprised about 50, 000 hectares, or nearly one-fifth of the total area of all upland fields. In fact, the greater part of these had a declivity of 20°-30°, and some reached 35° of slope. The soils of these fields, which comprise 2% of the mountain lands of Japan, are infertile lithosols.Figures 1 to 4 show the distribution of steep upland fields : Figure 1 ……the ratio of steep fields to all upland fields, by prefecture ;Figure 2 ……the ratio of upland fields to all cultivated fields ;Figure 3 ……the ratio of steep fields to all upland fields, by gun (district);Figure 4. ……the relative density of steep fielde to total area.The most important steep upland field regions are the mountainous regions in the Outer Zone of Southwest Japan, namely Shikoku and the Kii Peninsula ; the Inland Sea Region in the Inner Zone ; and peninsular regions of Kyushu. The mountainous regions of Central Japan are secondary to the above areas in importance.2. The development of steep upland fields has been mainly related to self-sufficient food crops both on intensively cultivated permanent fields and on the much less important extensively cultivated shifting fields. Two morphological types of land use are distinguished : a) use of the natural slope with no modification, a type prevalent in Central Japan, and d) modification by terracing, a type dominant in Southwest Japan.In the use of natural slopes, contour cultivation is strictly adhered to, and much organic material is added to maintain the soil fertility. The yield of crops such as barley, wheat and soy beans is higher on these fields than on terraced fields. Mulberry trees are grown in large areas, and in some localities the Konnyaku tuber (Amorphophallus konjac) is grown intercropped with barley. On terraced slope lands, bench terraces are constructed on the steeper slopes, an sloping terraces on the less steep slopes. Typical examples of these are seen in southwest Shikoku. The strong intensity of precipitation is one of the most important factors that make steep land cultivable only by making terraces. The main crops are barley and wheat in winter, and sweet potatoes in summer. These terraces are subject to soil erosion on the one hand, and to drought on the other, , resulting in meager yields of all crops except sweet potatoes.3. To improve the utilization of steep lands by agriculturists, it is necessary to plant profitable cash crops, such as sweet oranges, konnyaku tubers, and mulberry trees. The fundamental weakness, of steep upland field cultivation lies in the extensive cultivation of self-sufficient food crops, which require much labor per unit of area, and yield relatively little in return.
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