2019 Degree-Day 50 (DD50) Thermal Unit Thresholds for New Rice Cultivars and Seeding Date Studies.

The Degree-Day 50 (DD50) computer program is one of the most successful management aids developed by the University of Arkansas System Division of Agriculture. This program predicts critical growth stages that assist in increasing the effectiveness of crop management operations. In order to maintain its relevance, the computer program must be updated continually as new rice cultivars become available to growers. To accomplish this goal, studies are conducted in a controlled research environment where developmental data and DD50 thermal unit thresholds for current and new cultivars are determined. Throughout the 2019 season, DD50 thermal unit accumulation, developmental data, and the effect of seeding date (SD) on grain and milling yield potential for 20 cultivars were evaluated over six SDs under a dry-seeded, delayed-flood management system commonly used in southern U.S. rice production. Significant differences in grain and milling yield were observed for all 20 cultivars at each location. [ABSTRACT FROM AUTHOR]