degreehours

Degreehours, also known as growing degree days or GDD, is a concept used in agriculture and horticulture to measure the accumulation of heat units that are considered necessary for plant growth and development. It is calculated by taking the average daily temperature and subtracting a base temperature, which is the minimum temperature at which a particular plant species will grow. The resulting value is then summed up over a period of time.

The base temperature varies depending on the plant. For example, corn typically has a base temperature of 50 degrees Fahrenheit, while tomatoes may have a base temperature of 55 degrees Fahrenheit. When the average daily temperature is below the base temperature, the GDD for that day is considered zero. The calculation is often expressed in degree days (e.g., Fahrenheit days or Celsius days).

Degreehours are used to predict when crops will mature, when to plant seeds, and to determine the timing of pest and disease management. By tracking the accumulation of degreehours, growers can make more informed decisions about crop management, leading to potentially better yields and reduced losses. Different models and thresholds may exist for specific crops or regions, and the exact calculation can sometimes include upper thresholds to account for temperatures that are too high for optimal growth.