On the Tuka-dukuri (a type of land utilization) on the Suwa Basin, Nagano Prefecture

Abstract

The Tuka-dukuri(mound cultvation)shown in Fig. 2-10 is a charac-teristic landscape of the Suwa basin. It is a type of land utilization, that is, in the rice-fields are many small mounds (25-30cm high and 1.5-2m in diameter), on one of which is planted a fruit-tree, such as apple, pear, grape, quince, etc. The area of the mound increases with the growth of the tree roots, untill finally the mounds join. Surrounding this basin are many mountains (ranging from more than 100m to about 500m in height from the bottom of the basin), and a number of rivers flowing into the basin, which make a fertile but very, damp alluv al plain. This basin is visited by floods about once every two years, when the rice-fields, especially on the southern side of the lake, are seriously damaged in places. Since the volume of this basin is very small, it will easilly be seen the temperature changes in this basin between summer and winter, or between the days and nights, is large. Owing its topography, the wind that blows into the basin is. a sort of Fohn, the humidity of the air is also low. In this region, the silk-reeling industry florurishes, its most active centre being the city of Okaya. For this reason a large part of the population is engaged in it, and there being densely populated districts, and small volume of the basin limits agricultural development, so that there is almost no uncultivated land to be found. Under these conditions we find developed the “Tuka-dukuri” just mentioned. Quince tree cultivation produces the best results, owing to the dry weather during the season for fruit growing, largely because of the soil. The position, therefore, is as follows: 1) It is very fortunate that when the quince trees that are planted in the rice-fields require humidity in the soil for their growth (in June, July & Aug.), they have all they need of it, because just at that time, the rice-fields are irrigated; and, conversely, when they do not require it, the rice-fields are cry. The reason for the irrigation season being so short is that this basin is situated so high above sea level, that the rice plant has to be grown earlier in the season than under ordinary conditions. 2) As these trees are able to resist the consequence of flooding, the farmers are able to secure a fair income even when floods have caused much damage elsewhere. 3) On the otherhand, the fruit-trees planted on such mounds are, apt to have short roots, which fact is an advantage. 4) For the apple and the pear, this basin is also suited in the case of vegetables grown on these mounds, the “Tuka-dukuri” is intensively developed on the Suwa basin.