Response of phenological and agronomical attributes and thermal utilization efficiency of cotton cultivars to cumulative heat units under different sowing dates

PURPOSE: Rising temperatures resulting from climate change play a vital role in the development of crop phenological stages. Egyptian cotton (Gossypium barbadense L.) is an important industrial cash crop that requires optimal temperature for economic production. Extreme temperatures cause a sharp decline in cotton yield and quality via affecting plant growth and physiology. Sowing time is a fundamental practice for maximizing the crop's genetic potential by minimizing the deleterious impacts of abiotic stress, specifically during critical reproductive stages, thereby enhancing the key yield attributes that collectively construct the final economic yield. METHOD: To create discrepancies in environmental growth resources over crop life span, three cotton cultivars (super Giza 94, Extra Giza 96 and Super Giza 97) were sown at three sowing dates (25-April, 15-May and 25-May) during 2022 and 2023 seasons. The meteorological data were collected and accumulated growing degree days (AGDD) were computed. Growth and phenological traits and yield attributes were estimated. RESULTS: Findings exhibited that the lowest values of small boll shedding % and the highest values of earliness % were observed with Super Giza 94 when sown early on 25-April in both seasons. With sowing on 25-April, Super Giza 94 produced the maximum increases in all yield attributes. Super Giza 94 was the most efficient cultivar for exploiting the cumulative heat units under different sowing dates with a higher value at sowing on 25-April in both seasons. CONCLUSION: The proper choosing crop cultivar keeps one of the most serious decisions for cotton farmers, since it determines the ceiling of the potential return, upon which the other agricultural activities, such as sowing dates, can be tailored. Accordingly, the current work deduce that sowing Super Giza 94 cultivar on 25-april is regarded as a promising practice for efficient use of prevailing climatic factors, hence balanced vegetative growth with high cotton productivity.