Effect of Planting Date on Seedling Vigor of Peanut Cultivars.

Establishment of a uniform and vigorous stand is crucial to successful peanut (Arachis hypogaea L.) production. Seed germination and emergence are highly dependent on temperature and moisture. Planting peanut seeds early or late in the season may slow germination and decrease seedling vigor due to variation in temperature. As emergence in peanuts is intermediate between epigeal and hypogeal, the first pair of true leaves are the first photosynthetic tissues completely aboveground. Studies on other crops indicated that a rapid development of the first true leaf is an indication of seedling vigor. However, the importance and contribution of the first true leaf on initial growth development in peanut plants have not been fully investigated. We hypothesize that the development of the first true leaf and its photosynthetic efficiency is correlated to seedling vigor for peanut plants, and the cultivars studied would vary in seedling vigor to planting temperatures. Therefore, a field experiment is being conducted using three peanut cultivars, Georgia-06G, Georgia-14N, and TifNV-High O/L. Seeds were sown in April (for early season assessment) and will be also sown in two other dates (May and June for mid and late season assessment, respectively) 2017. The three planting dates will expose seeds to different temperature conditions for germination and emergence. Stand establishment will be evaluated by counting emergence in approximately 1.5 m at 7, 9, 11, and 14 days after planting (DAP) and first true leaf area at 21, 35, and 49 DAP. Crop growth analysis as well as gas exchange and fluorescence of the first true leaf will be assessed at 21 and 35 DAP. This research is expected to assist in understanding the physiological contribution of the first true leaf on early growth and development in peanut plants, and its relationship to seedling vigor.