Following is the formula used to calculate GGD along with some sample calculations. Growing Degree Days or heat units are calculated for each day starting the day after planting. The GDD accumulations for the growing season in Ohio range from less than 2500 GDD in northeastern counties to more than 3000 GDD along the Ohio River in southwestern Ohio. Growing Degree Day accumulations for specific locations in the state may be found in the following table. Often GDD information on hybrids can be obtained from company information booklets and salesmen.
Most companies use the time from planting to maturity to rate hybrids.
If the rating is from emergence to maturity, add 150 to get the GDD from planting. Professor, Agronomy Dept. This publication was prepared and funded through a cooperative effort of the Ohio Department of Energy and Ohio State University Extension. All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status. Keith L. Smith, Associate Vice President for Ag.