Strawberry: cold hours and growing degree hours

Strawberry: cold hours and growing degree hours

The Strawberry Cold Hours and Growing Degree Hours calculation in LetsGrow.com helps monitor cold hours and growing degree hours in strawberry cultivation. 

What are cold hours?

Cold hours are the number of hours during which the temperature is below a certain threshold. You can choose between two calculation methods:
  1. Standard cold hours calculation
  2. Cold hours according to the Philip Lieten model, which more specifically looks at how far below the threshold temperature is

What are growing degree hours?

Growing degree hours indicate how much warmth a plant has received. This is calculated by multiplying the number of degrees above a set temperature threshold by the number of hours this occurs. For example: if it is 3°C above the threshold for 5 hours = 15 growing degree hours.

Settings for the calculations (via Data Entry)

Via Data Entry you set threshold values, summations, and target values for cold hours and growing degree hours. Enter these on the correct date.

Threshold values

Enter the temperature threshold for cold hours and growing degree hours at the start of the cultivation
  1. For cold hours: temperature threshold below which an hour counts as cold hour
  2. For growing degree hours: temperature threshold above which an hour counts as growth time

Cold hours summation

Enter the correct date when the summation starts, stops, or resets, this is done via a drop-down menu:
  1. Start: from this date counting cold hours begins
  2. Reset: from this date a new count starts (this day counts)
  3. End: counting stops on this date
  4. Start & Reset: counting begins and is automatically reset when the set target is reached
    With Start & Reset, after reaching the cold hour target, the growing degree hour counting is also automatically started or reset. This is shown with the status "reset due to cold hours target".

Cold hours (Philip Lieten) summation target

  1. This is the number of cold hours you want to reach before the plant comes out of dormancy
  2. It is best to enter the target at the start of the summation period, but if a new value is set later in the period, this will be considered valid
  3. When setting a summation with "start & reset", the reset is executed when the first target value is reached.

Growing degree hours summation

The growing degree hour summation setting works the same way as the cold hours summation setting. Use the drop-down menu to set:
  1. Start: from this date counting begins
  2. Reset: from this date a new count starts
  3. End: counting stops here

If you chose Start & Reset for cold hours, then the growing degree hour counting can automatically start or reset at the moment the cold hour target is reached.

Entering an end date is important for determining an advice temperature (see explanation below).

Growing degree hours target

  1. This is the number of growing degree hours you want to reach to achieve a development phase (such as flowering or fruit setting)
  2. Set this value at the start of the growth phase/cultivation
  3. You can also adjust your target values later in the cultivation.
  4. Combined with an entered end date, an advice temperature is automatically calculated: the average daily temperature needed to reach the target on the end date

Automatic functions of the module

  1. Simple control: you only need to enter target values and one-time settings; the module does the rest (calculating cold hours and growing degree hours (sum))
  2. Advice temperature calculation to help steer toward the growing degree hour target (based on end date)
  3. Graphs can be made to show the progress of cold hours and growing degree hours toward the goals.