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Journals / Turkish Journal Of Field Crops / 2026 / Volume: 31 Issue: 2

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

İsmail Demir(AHİ EVRAN ÜNİVERSİTESİ)0000-0002-8950-5253
Pages
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Publication Date
2026-08-30
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AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

Overall, early March sowing provided the highest seed yield, while threshold-corrected GDD indicated comparatively stable thermal requirements across sowing dates.

📌 3 Key Takeaways

🎯
Objective & Hypothesis:Growing degree days (GDD) are widely used to describe crop development, but information on how sowing date influences thermal requirements in safflower remains limited.
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Key Findings & Data: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.
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Conclusion & Impact:Overall, early March sowing provided the highest seed yield, while threshold-corrected GDD indicated comparatively stable thermal requirements across sowing dates.
🔬Design:Lab & Field Experiment
📍Scope:2013–2024 Verileri
⚙️Variables:Carthamus tinctorius L · Growing degree days · Photothermal units

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.

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Cite This Article

Demir, İ. (2026). Safflower Phenological Development, Thermal Requirements and Seed Yield as Affected by Sowing Dates. Turkish Journal Of Field Crops, Volume: 31 Issue: 2. https://doi.org/10.17557/tjfc.1998413

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