Studies on Tobacco Culture in the Subtropic Conditions II. The growth of tobacco as related to different planting times in the district of Okinawa

Abstract

In order to determine the best planting time for tobacco culture in the district of Okinawa, tobacco (flue-cured tobacco variety, SC72) was planted at three different days (on January 10, 30 and February 20), and investigated about number of total leaves, growth process, yield and price per kg of the flue-cured caves, etc. in Miyako Is., the representative district of tobacco leaves-production area in Okinawa in 1976. The results were obtained as follows; 1. There was a tendency for number of total leaves to decrease as the planting time was advanced; 27.6, 30.8 and 33.0 leaves on tobacco planted on January 10, 30 and February 20, respectively (Table 1). 2. The growth of tobacco planted on January 10 was depressed on account of slightly low temperature and small amount of precipitation in the early stage. In the later stage, this tobacco showed vigorous growth and its prosperous growth was prolonged to the harvesting time. Tobacco planted on February 20 grew vigorously in the early stage, and its rate of dry matter production increased again owing to much amount of precipitation in the harvesting time. The growth process of tobacco planted on January 30 was comparatively moderate (Fig. 3, 4 and Table 3). 3. Width/length ratio of the harvested leaves on lower stalk position decreased as the planting time was advanced (Fig. 7). 4. The area of the harvested leaves was greater on each stalk position of tobacco planted on February 20 than that on the comparable stalk position of tobacco planted on January 10 or January 30, though there was not such a difference between tobacco planted on January 10 and that planted on January 30 (Fig. 7). 5. But, in dry leaf weight per unit leaf area of harvested leaves, tobacco planted on February 20 was not superior to tobacco planted on other day. On the contrary, the upper leaves of this tobacco were apparently inferior to those of tobacco planted on January 30 in dry leaf weight per unit leaf area. There was similar difference at the upper leaves between tobacco planted on January 10 and that planted on January 30. These results may indicate that the upper leaves harvested from tobacco planted on January 10 or February 20 seemed to be a little immature, in comparison with those harvested from tobacco planted on January 30 (Fig. 8). 6. Yield of the flue-cured leaves per 10a increased as the planting time was retarded, i.e., 269.0 kg, 282.8 kg and 363.3 kg in the plots planted on January 10, 30 and February 20, respectively. However, in the price per kg of cured leaves, the plot planted on Fcbruary 20 was inferior to other plots. The highest price per kg of cured leaves was gained in the plot planted on January 30 (Table 4). Judging from the results mentioned above, it is concluded that the last 10 day-period of January seems to be the best planting time for tobacco culture in Miyako Is. and the district near this island.