Effect of Sowing Time on Growth and Yield Characteristics of Six Commercial Sunflower Cultivars in Okinawa

• Published in: Japanese Journal of Crop Science Vol. 87; no. 3; pp. 223 - 232
• Main Authors: Takaragawa, Hiroo, Yabuta, Shin, Watanabe, Kenta, Kawamitsu, Yoshinobu
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo CROP SCIENCE SOCIETY OF JAPAN 05.07.2018; Japan Science and Technology Agency
• Subjects: Autumn; Crop growth rate; Cultivars; Effective accumulated temperature; Flowering; Growth rate; Harvesting; Helianthus; High temperature; Lodging; Oil and gas production; Optimization; Petroleum production; Photosensitivity; Planting; Seeds; Sowing time; Spring (season); Subtropics; Summer; Sunflower; Sunflowers; Typhoons; Winter; Okinawa
• ISSN: 0011-1848; 1349-0990
• DOI: 10.1626/jcs.87.223

Sunflower has been cultivated as a decorative plant in subtropical Okinawa; however, the optimal sowing time and suitable cultivar for oil production have not yet been determined. In this study, six cultivars were grown in four seasons and the growth and yield characteristics were examined to determine the optimal sowing time and suitable cultivar in the region. The effective accumulated temperature from emergence to flowering was 1000–1100°C, and some cultivars showed lower values under short day conditions in autumn and winter sowings. Sunflower can be grown year round in Okinawa because the temperature in winter is above 10°C. However, it is important to consider lodging due to typhoons during the seed harvesting season in sunflower sown in spring or summer (July–October). The results revealed that high growth rates before and after flowering were important for obtaining high yields in sunflower sown in autumn and winter; however, the yield was lowered by decreased biomass at flowering and reduced number of seeds caused by high temperatures in spring and summer. Therefore, the optimum sowing time to harvest sunflower seed for oil production was considered to be from the beginning of October to the beginning of February. By using cultivars that are photosensitive and have a high growth rate after flowering, a high seed yield of 300 kg 10 a−1 and high oil yield of 110 kg 10 a−1 could be obtained.