Table 2.
Phenological stages of sunflower plants sown on different planting dates during the austral summer seasons (2020/2021 and 2021/2022) in Pretoria.
| Season 2020/2021 | Season 2021/2021} | ||||||
|---|---|---|---|---|---|---|---|
| Developmental stage | Planting dated | Days** | TT (∘Cd) * | Rain (mm)*** | Days** | TT (∘Cd) * | Rain (mm)*** |
| Emergence to 50% flowering | Nov | 70 | 1071.63 | 356.10 | 66 | 946.14 | 509.30 |
| Dec | 65 | 1013.67 | 261.90 | 65 | 976.07 | 363.90 | |
| Jan | 70 | 983.61 | 167.30 | 70 | 965.24 | 297.90 | |
| Feb | 76 | 989.61 | 113.20 | 74 | 947.07 | 231.90 | |
| Mar | 76 | 869.68 | 98.10 | 84 | 838.47 | 194.20 | |
| Emergence to 50% physiological maturity | Nov | 95 | 1446.61 | 373.40 | 119 | 1722.12 | 605.20 |
| Dec | 93 | 1401.20 | 321.10 | 119 | 1665.25 | 598.10 | |
| Jan | 117 | 1442.65 | 194.40 | 126 | 1454.09 | 341.20 | |
| Feb | 116 | 1320.81 | 115.70 | 129 | 1379.19 | 262.90 | |
| Mar | 126 | 1240.38 | 99.80 | 138 | 1221.99 | 212.10 | |
*Thermal time (TT) was calculated using Tbase = 6∘C (Kiniry et al., 1992). The upper threshold temperature limit applied or optimum temperature (Topt) of 28∘C (Gintsioudis et al., 2024).
**From sowing to 50% flowering or 50% physiological maturity.
***Total rainfall accumulated over the planting date for each developmental stage.
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