Growing degree-day
Growing degree days are a heuristic concept in phenology. They are used by farmers and gardeners to predict the date when a plant flowers or grain matures.
If no extreme conditions such as unseasonal drought or diseases occur, grow plants in a cumulative manner that is strongly influenced by the ambient temperature. Growing degree days take into account aspects of local weather and allow gardeners to predict or control it in greenhouses even the arrival of plant maturity.
Calculation of growing degree days
There is no standardized way of growing degree days calculation (see ¹). Most common are three calculation methods: - The calculation of the simple average - The modified calculation of the simple average - The Baskerville - Emin (BE) calculation method
The period of summation is also not standardized. Depending on the application of the growing degree days different time periods and calculation methods are used.
Application growth and maturation history of annual plants: If you want to predict the growth and maturation history of annual plants with the growing degree days then the time of sowing is considered the beginning of summation commonly used. The last day of the summation is usually the first frost day. Here usually the growth degree days calculation method "modified calculating the simple average " or is "Baskerville - Emin method" used as this allows the spring and early summer day result with lower minimum temperatures higher heat sums.
Application growth and maturation history of perennial plants; usually wine, oranges, peaches, etc.: In predicting the full maturity of perennial plants or fruits with the growing degree days is considered the beginning of summation usually the first month of the year with a monthly average temperature of min. 10 ° C used. Alternatively, the first three consecutive days are used with a daily average temperature of 10 ° C as the start of the summation. The summation ends with the last day of the last month with a monthly average temperature of min. 10 ° C. Alternatively, is summed up to the first frost day. Here usually the growth degree days calculation method " of calculating the arithmetical average " used as this allows the fruit to maturity less important spring and early summer days are rated lower.
Growing degree days (WGT ) according to the calculation method "modified calculating the simple average " are calculated by taking the average of the daily minimum (Tmin ) and maximum temperature ( Tmax) and him with a threshold ( Tz) compares (usually 10 ° C ). As equation is used:
Prior to the calculation of the average is any temperature that is below the threshold is changed to the threshold value. Similarly, maximum temperatures are normally capped at 30 ° C, because most plants and insects grow and multiply if this temperature is not exceeded faster. However, some require hot temperate and tropical plants above 30 ° C to ripen fruits or seeds to days.
For example, provides a day with a maximum temperature of 23 ° C and a minimum temperature of 12 ° C a contribution of 7.5 growing degree days. A day with a maximum temperature of 13 ° C and minimum temperature of 7 ° C contributes 1.5 growing degree days.
Growing degree days (WGT ) according to the calculation method " of calculating the arithmetical average " are calculated by taking the average of the daily minimum (Tmin ) and maximum temperature ( Tmax) and him with a threshold ( Tz) compares (usually 10 ° C). As equation is used:
Maximum temperatures usually also capped at 30 ° C.
This provides an example tag with a maximum temperature of 23 ° C and a minimum temperature of 12 ° C and a contribution of 7.5 growing degree days. A day with a maximum temperature of 13 ° C and minimum temperature of 7 ° C but contributes 0 growth degree days.
Growing degree days (WGT ) to the Baskerville - Emin (BE) calculation method:
WGT = (( W * cos (A)) - (( threshold - day average ) * ( (3.14 / 2) A) )) / 3.14 (See ¹)