PAR Plant calculated
1 Introduction
PAR stands for Photosynthetic Active Radiation. This is
radiation with a wavelength between 400 to 700 nanometers. Plants are provided with
specialized receptor pigments that are able to receive the energy of PAR light and use it for the photosynthesis process, hence why PAR is also called growth light. The amount of
PAR light that the plant receives can be used to measure the growth potential of the plant.
The module PAR plant calculated can give you a good indication of the amount of PAR light reaching the
plant, if based on the correct parameters.
The amount of light in the greenhouse can be measured by using of a PAR meter. The
measurement of an indoor PAR meter can support you in determining your screening strategy
to steer towards the optimal light level and light sum. However, the measurement of the PAR
light sensor can deviate, for example due to shade from greenhouse structure in between the
meter and the light source. For this, LetsGrow.com has developed the PAR Plant Calculated. It is
calculated by correcting the radiation in W/m² with the light transmission of the greenhouse,
screens, and then supplementing it with the artificial lighting. This filters out external influences
and can provide a reference value for your PAR light sensor measurement. If you do not have a
PAR sensor, you can use the PAR Plant Calculated as an indicator of the amount of PAR light
that you are currently receiving.
2 The Module
The PAR Plant Calculated module is made up of various components. You can find the contents
of the module in the table below.
2.1 Calculations
Radiation sun plant calculated - W/m²
The calculated amount of radiation that reaches the plant. This is calculated by reducing the radiation in W/m² with the light transmission of the greenhouse roof and fabrics (when closed).
Assimalation lighting on
Indicates whether the artificial lighting in the greenhouse is on. All configured types of lighting are included here.
Assimalation lights part - %
The percentage of “Assimilation lighting on” relative to the total configured lighting systems.
Plant: PAR - µmol/m²/s
The calculated amount of PAR light in µmol/m²/s that reaches the plant. This is calculated by adding PAR sun calculated to the radiation sun plant calculated.
PAR lighting calculated - µmol/m²/s
The supplied artificial PAR light in µmol/m²/s.
PAR sum plant - mol/m²
The daily sum of caculated PAR light in mol/m². This sum resets at midnight.
3 Setting up the Module
To calculate the light on the plant, several parameters must be entered. The module requires manual input of parameters for setup. Manual input can be found under the module button (orange box). Click on the correct module "PAR Plant Calculated" (green box). Then select the specific module you want to modify, typically named after the corresponding location or compartment.
Once in the correct module, navigate to ‘Data entry’ (orange box):
The parameter values must be entered on the first active day of the module or crop cycle. You can navigate to the desired week using the arrows (orange box). Parameters can be entered on a specific day and will continue to apply in the following weeks (green box) until a new value is entered, at which point the value will be updated . You can check when a value was last entered by hovering your mouse over the parameter value (blue box). If you’ve made any changes in this overview, click Save to apply the changes (red box).
Light transmission of greenhouse
How much light is let through the glass? Is there chalk on it? Then the light transmission
decreases. If a coating is being applied or removed, you must adjust this parameter, on the right date to maintain
the correct calculated value. This value is typically around 70%.
Light transmission of screens
Which screens are connected to the module and how much light do these screens let through?
PAR installed 1 t/m 6 and PAR LED Installed 1 t/m 3:
Only necessary when lighting is installed in the greenhouse. How much PAR light do these lamps add? Pay attention; if your
lighting installation can be switched on and off in several phases, then you need to enter the
power of PAR light per phase (installed light). For example: PAR installed 1 is at 25%, then the
total capacity is also at 25%.