Seed size effects on early‐season growth, yield, and fiber quality of cotton

Abstract Early‐planted cotton ( Gossypium hirsutum L.) in the US Southern High Plains often encounters suboptimal growing conditions, which can delay emergence and reduce seedling vigor. Seed size is frequently associated with stand establishment, but the difficulty of testing seed size independent of cultivar has limited the ability to test the effects of seed size alone. This study evaluated three cultivars using large‐ and small‐seeded seed lots within each genotype across two growing seasons (2024–2025) in Lubbock, TX. Water uptake tests showed that large seeds absorbed more total water, while smaller, denser seeds hydrated proportionally faster. Warm germination was uniformly high for both large‐ and small‐seeded seed lots (>85%), but cool germination and the cool–warm vigor index better differentiated seed lots and were more closely associated with field emergence. Severe early‐season stress in 2024 limited the establishment, and seed index more strongly predicted field emergence under stressful conditions ( R 2 = 0.89) than under favorable conditions in 2025 ( R 2 = 0.32). Large seeds consistently produced seedlings with greater root and shoot biomass, with strong linear relationships observed between seed index and seedling growth traits ( R 2 = 0.82–0.95), contributing to stronger early vigor. Lint yields were greater in 2025 than 2024, with cultivar‐specific gains indicating strong year × cultivar interactions. Seed size did not affect lint yield or major fiber quality traits. Overall, evaluating seed size within and across cultivars provides new insights into stand establishment, while environmental conditions and genetics remain the primary determinants of lint productivity and fiber quality.