Abstract

Determining the appropriate harvest date for fresh sweet corn is essential for maximizing both yield quantity and quality. Growing Degree Days (GDD) is one method that has been commonly used to evaluate growth stages of many crops. Therefore, this study evaluated the effects of cultivars and planting dates on growth stages and yield of five sweet corn, namely, Insee 2, Hibrix 72, SM1351, SM9573, and Q18420. The experiment was conducted under two planting dates: the first on December 2, 2024, and the second on January 11, 2025. Days after planting and accumulated GDD were recorded at anthesis, silking, and harvest stages, along with fresh ear yield. The results showed that both cultivar and planting date significant effected on GDD and yield. At all growth stages, the first planting date exhibited higher GDD values than the second planting date. Hibrix 72 recorded the highest GDD of 1,636–2,056 °C, whereas Q18420 showed the lowest GDD of 1,361–1,568 °C. The second planting date promoted earlier reproductive development and harvest, resulting in higher yield compared to the first planting date, particularly for SM1351, which produced the highest yield. However, yields of Insee 2 and Hibrix 72 did not differ significantly between planting dates. In this study, GDD alone may not be sufficient to accurately predict growth stages and harvest date of sweet corn.