Studies on Tobacco Culture in the Subtropic Conditions I. Ecological study on the growth process of tobacco in the district of Okinawa

Abstract

The growth of tobacco in Miyako Is., the representative district of tobacco leaves-production area in Okinawa, was researched, as compared with that of tobacco in Kagoshima, for the establishment of the best manners of tobacco culture. These results were obtained as follows; 1. The air temperature in Miyako Is. was higher than that in Kagoshima at the early growth stage of tobacco, but in that duration, the daylength in this island was comparatively shorter than that in Kagoshima (Fig. 1, 3). Those environmental conditions made little difference between the total leaves of tobacco in Miyako Is. and those in Kagoshima (Table 6). 2. Owing to the rather strong wind and comparatively small amount of the precipitation in Miyako Is., the soil was apt to be a little dry to tobacco. So, it grew more slowly than tobacco in Kagoshima at the early growth stage (Fig. 5, 7, 8). 3. But, the development of root of tobacco in Miyako Is. was relatively superior to the growth of the top, as compared with that in Kagoshima. It seemed that tobacco in Miyako Is. had adapted itself to the droughty and windy environment (Fig. 11). 4. After topping, tobacco in Miyako Is. grew more vigorously than that in Kagoshima, of which rate of dry matter production slowed down. On account of the vigorous growth at the late growth stage, the harvested leaves on the middle and upper stalk positions seemed to remain a little immature. So, the external qualities of the flue-cured leaves from tobacco in Miyako Is. was a little inferior to those in Kagoshima (Fig. 5, 6. Table 6). 5. Because of a small diurnal range of temperature in Miyako Is., the consumption of the substance by the respiration seemed to be comparatively greater at night than that of tobacco in Kagoshima. So, the dry matter weight of tobacco in Miyako Is. per unit leaf area was smaller than that in Kagoshima. It indicates that tobacco in Miyako Is. was inferior to that in Kagoshima on the efficiency in the accumulation of dry matter produced in unit leaf area (Fig. 2, Table 5). 6. When tobacco was planed on the ridge mulched with polyethylenc film which had been pitched after rain in Miyako Is., it grew more vigorously than tobacco on the non-covered ridge (conventional culture in Miyako Is.) at the early growth stage (Fig. 5, 6). As the film over the ridge interfered the supply of the moisture from precipitation into the ridge, the growth of tobacco was a little depressed just after topping. (Fig. 5, 8) But, tobacco on the mulched ridge got vigorously again after the more expansion of root system at the late growth stage, and this contributed to much yield, spoiling the external qualities of the flue-cured leaves in comparison with those on the conventional culture (Table 6).