Growing degree day (GDD)

• Explains the relationship between growth duration and temperature.
• A degree day is the mean temperature above base temperature (minimum temp).

Where, Tmax is maximum temperature and Tmin is minimum temperature of the day and Tb is the lowest temperature at which there is no growth which is also called base temperature.

• The concept of degree days can be used to estimate the suitability of a crop for a given climatic region assuming water is available.
• This can also provide an index for comparing the thermal needs of plants as well as for indicating the suitability of a location for a particular crop.
• Calculation of GDD is useful for predicting harvesting dates and secondly, they are useful to select optimum date of planting.