Research Article

Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates

Volume: 31 Number: 2 August 30, 2026

Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates

Abstract

Growing degree days (GDD) are widely used to describe crop development, but information on how sowing date influences thermal requirements in safflower remains limited. This study evaluated phenological development, thermal requirements and seed yield in a twelve-year field experiment (2013–2024) under semi-arid conditions in central Türkiye. Three cultivars were sown on five dates (1 March, 15 March, 1 April, 15 April and 1 May) in a split-plot design with three replications. Daily GDD was calculated using a base temperature of 5 °C and an upper threshold of 30 °C, with both minimum and maximum temperatures constrained to the threshold range. Year, sowing date, cultivar and their interactions significantly affected developmental stages, corrected GDD and seed yield (P < 0.01). Delayed sowing markedly shortened calendar time to emergence, whereas corrected mean GDD to emergence remained comparatively stable across sowing dates (92.72–96.28 °C day). Mean seed yield declined from 2399 to 838 kg ha⁻¹ from the first to the last sowing date. Daily accumulation of photothermal units produced stage-dependent differences between the earliest and latest sowings, and leave-one-year-out validation did not support the superiority of air-temperature-based GDD over 5-cm soil-temperature-based GDD. Linear mixed-effects models accounting for the experimental hierarchy further showed that several pooled associations between thermal variables and seed yield were weaker than suggested by simple correlations. Overall, early March sowing provided the highest seed yield, while threshold-corrected GDD indicated comparatively stable thermal requirements across sowing dates.

Keywords

References

  1. Akyuz, F., & Ransom, J. K. (2015). Growing degree day calculation method comparison between two methods in the northern edge of the US Corn Belt. Journal of Service Climatology, 2015, 1–9.
  2. Bonhomme, R. (2000). Bases and limits to using 'degree.day' units. European Journal of Agronomy, 13(1), 1–10. https://doi.org/10.1016/S1161-0301(00)00058-7
  3. Chapman, M. A., Chang, J., Weisman, D., Kesseli, R. V., & Burke, J. M. (2007). Universal markers for comparative mapping and phylogenetic analysis in the Asteraceae (Compositae). Theoretical and Applied Genetics, 115(6), 747–755.
  4. Eisensmith, S., & Russel, D. (1989). MSTAT-C: a microcomputer program for the design, management, and analysis of agronomic research experiment. MSTAT development team, Michigan State University, East Lansing.
  5. Culpan, E. (2023). Effect of sowing dates on seed yield, yield traits and oil content of safflower in Northwest Turkey. Turkish Journal of Field Crops, 28(1), 87–93. https://doi.org/10.17557/tjfc.1194005
  6. El Bey, N., Göre, M., & Kurt, O. (2021). Effect of sowing date on some agronomic and technological traits of safflower (Carthamus tinctorius L.) in Northern Turkey. Turkish Journal of Field Crops, 26(2), 188–194. https://doi.org/10.17557/tjfc.941575
  7. Emami, T., Naseri, R., Falahi, H., & Kazemi, E. (2011). Response of yield, yield component and oil content of safflower (cv. Sina) to planting date and plant spacing on row in rainfed conditions of Western Iran. American-Eurasian Journal of Agricultural & Environmental Sciences, 10(6), 947–953.
  8. FAO. (2024). Crops and livestock products: Safflower seed, area harvested and production quantity by country. Food and Agriculture Organization of the United Nations. Retrieved 12.04.2026 from https://www.fao.org/faostat/en/#data/QCL

Details

Primary Language

English

Subjects

Industrial Crops

Journal Section

Research Article

Publication Date

August 30, 2026

Submission Date

July 19, 2026

Acceptance Date

August 30, 2026

Published in Issue

Year 2026 Volume: 31 Number: 2

APA
Demir, İ. (2026). Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. Turkish Journal Of Field Crops, 31(2). https://doi.org/10.17557/tjfc.1998413
AMA
1.Demir İ. Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. TJFC. 2026;31(2). doi:10.17557/tjfc.1998413
Chicago
Demir, İsmail. 2026. “Safflower Phenological Development, Thermal Requirements and Seed Yield As Affected by Sowing Dates”. Turkish Journal Of Field Crops 31 (2). https://doi.org/10.17557/tjfc.1998413.
EndNote
Demir İ (August 1, 2026) Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. Turkish Journal Of Field Crops 31 2
IEEE
[1]İ. Demir, “Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates”, TJFC, vol. 31, no. 2, Aug. 2026, doi: 10.17557/tjfc.1998413.
ISNAD
Demir, İsmail. “Safflower Phenological Development, Thermal Requirements and Seed Yield As Affected by Sowing Dates”. Turkish Journal Of Field Crops 31/2 (August 1, 2026). https://doi.org/10.17557/tjfc.1998413.
JAMA
1.Demir İ. Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. TJFC. 2026;31. doi:10.17557/tjfc.1998413.
MLA
Demir, İsmail. “Safflower Phenological Development, Thermal Requirements and Seed Yield As Affected by Sowing Dates”. Turkish Journal Of Field Crops, vol. 31, no. 2, Aug. 2026, doi:10.17557/tjfc.1998413.
Vancouver
1.İsmail Demir. Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. TJFC. 2026 Aug. 1;31(2). doi:10.17557/tjfc.1998413

Turkish Journal of Field Crops is published by the Society of Field Crops Science and issued twice a year.
Owner : Prof. Dr. Behçet KIR
Ege University, Faculty of Agriculture, Department of Field Crops
Editor in Chief : Prof. Dr. Emre ILKER
Address : 848 sok. 2. Beyler İşhanı No:72, Kat:3 D.313 35000 Konak-Izmir, TURKEY
Email :  turkishjournaloffieldcrops@gmail.com contact@field-crops.org