Minimum Temperature for Growing Degree Day (GDD) Calculation: Should it be Based on Daytime or the Entire Day?

Growing Degree Day (GDD) is a widely used measure of plant growth and development. It is calculated by taking the average temperature of a day and subtracting a base temperature. The resulting value is then accumulated over time to determine the number of GDDs a plant has accumulated. However, there is an ongoing debate as to whether the minimum temperature used in GDD calculations should be based on the daytime or the entire day. In this article, we will examine both options and discuss their advantages and disadvantages.

Minimum Temperature Based on Daytime

When calculating GDD, some researchers argue that the minimum temperature should be based on daytime only. Daytime is defined as the period between sunrise and sunset, and it is typically the time when most plant growth occurs. Therefore, using the daytime minimum temperature would provide a more accurate measure of plant growth. This approach is particularly relevant in areas where there is a wide temperature range between day and night.
There are several advantages to using minimum daytime temperature. First, it provides a more accurate estimate of plant growth and development during the period when most growth occurs. Second, it is more appropriate for plants that are sensitive to low daytime temperatures. Finally, it avoids the problem of using the minimum temperature during the night, which can be misleading and not reflect the growth of the plant.

However, there are some disadvantages to using the minimum daytime temperature. First, it may not be appropriate for plants that grow primarily during the night. Secondly, it does not take into account the effects of low temperatures during the night, which can have a significant impact on plant growth and development.

Minimum temperature based on the whole day

Another approach to calculating the minimum temperature for GDD is to use the minimum temperature based on the whole day, including daytime and nighttime. This approach takes into account the effects of both daytime and nighttime temperatures on plant growth and development. It is particularly relevant in areas with a relatively stable temperature range.
There are several advantages to using the minimum temperature based on the entire day. First, it provides a more comprehensive measure of plant growth and development, taking into account the effects of both daytime and nighttime temperatures. Second, it is more appropriate for plants that grow mainly during the night. Finally, it avoids the problem of using the minimum daytime temperature, which may not reflect the growth of the plant.

However, there are some disadvantages to using the minimum temperature based on the whole day. First, it may not be suitable for plants that are sensitive to low temperatures during the day. Second, it may not provide an accurate measure of plant growth and development during the period when most growth occurs, which is typically during the day.

Conclusion

In summary, the choice of minimum temperature used in GDD calculations depends on several factors, including the type of plant being grown, the temperature range of the location, and the time of day when most growth occurs. In general, using a daytime-based minimum temperature is more appropriate for plants that are sensitive to low temperatures during the day, while using a daytime-based minimum temperature is more appropriate for plants that grow primarily during the night. Ultimately, the choice of approach should be based on the specific needs of the plant and the location where it is being grown.

FAQs

1. What is Growing Degree Day (GDD)?

Growing Degree Day (GDD) is a measure of the heat energy available for plant growth. It is calculated by taking the average temperature of a day and subtracting a base temperature. The resulting value is then accumulated over time to determine the number of GDD a plant has accumulated.

2. What is the minimum temperature used in GDD calculations?

The minimum temperature used in GDD calculations is the temperature below which plant growth does not occur. This temperature is called the base temperature and is typically set to 10°C (50°F) for most crops.

3. Should the minimum temperature in GDD calculations be based on daytime or the whole day?

There is an ongoing debate about whether the minimum temperature used in GDD calculations should be based on daytime or the entire day. Both approaches have their advantages and disadvantages, and the choice depends on several factors, including the type of plant being grown and the temperature range of the location.

4. What are the advantages of using the minimum daytime temperature in GDD calculations?

Using the minimum daytime temperature provides a more accurate estimate of the plant’s growth and development during the period when most of the growth occurs. It is also more appropriate for plants that are sensitive to low temperatures during the daytime and avoids the problem of using the minimum temperature during the nighttime, which can be misleading and not reflective of the plant’s growth.

5. What are the advantages of using the minimum temperature based on the whole day in GDD calculations?

Using the minimum temperature based on the whole day provides a more comprehensive measure of the plant’s growth and development, taking into account the effects of both daytime and nighttime temperatures. It is also more appropriate for plants that grow mainly during the nighttime and avoids the problem of using the minimum temperature during the daytime, which may not be reflective of the plant’s growth.

6. What are the disadvantages of using the minimum daytime temperature in GDD calculations?

Using the minimum daytime temperature may not be suitable for plants that grow mainly during the nighttime and does not take into account the effects of low temperatures during the nighttime, which can have a significant impact on the plant’s growth and development.

7. What are the disadvantages of using the minimum temperature based on the whole day in GDD calculations?

Using the minimum temperature based on the whole day may not be suitable for plants that are sensitive to low temperatures during the daytime and may not provide an accurate measure of the plant’s growth and development during the period when most of the growth occurs, which is typically during the daytime.