Posted on by Jason G

 Conversion - Instantaneous PPFD to Integrated PPFD

Note: To be able to read PPFD or instantaneous PPFD will require an accurate quantum meter to take the readings, such as the Apogee MQ-500.

Most light meters measure the instantaneous photosynthetic photon flux density in µmol m-2 s-1 and yet plant growth is determined by the integrated daily photosynthetic photon flux density in mol m-2 d-1.

Here is how to convert from µmol m-2 s-1 to mol m-2 d-1 when using electric lights.

There are 3600 seconds in an hour. If the electric light output is constant, the instantaneous PPFD can be added up (integrated) over an hour.

Therefore 1 µmol m-2 s-1 = 3600 µmol m-2 h-1.

This must be divided by a million (1,000,000) to convert from micromoles to moles: 3600 µmol m-2 h-1 = 0.0036 mol m-2 h-1.

If the electric lights are on continuously (24 hours), the hourly PPFD must be multiplied by 24 to get the daily PPFD: 0.0036 mol m-2 h-1 = 0.0864 mol m-2 d-1.

There are 86,400 seconds in a day (3600 x 24 hours) so the daily PPFD can be calculated directly from the instantaneous PPFD from the following equation: µmol m-2 s-1 multiplied by 86,400 and divided by 1,000,000 = mol m-2 d-1.

So: 1 µmol m-2 s-1 = 0.0864 mol m-2 d-1 with continuous light

 

These conversions are accurate only under electric lights. The integrated daily PPFD from sunlight changes during the day so a single measurement cannot be used to estimate daily PPFD.

 

Daily PPFD Reference Table

24-Hour Photoperiod

Instantaneous PPFD
(µmol m
-2 s-1)

Daily PPFD
(mol m
-2 d-1)

10

0.864

100

8.64

200

17.28

300

25.92

*600

*51.84

1000

86.40

2000

172.80

 

16-Hour Photoperiod

Instantaneous PPFD
(µmol m
-2 s-1)

Daily PPFD
(mol m
-2 d-1)

10

0.567

100

5.67

200

11.52

300

17.28

600

34.58

*1000

*57.60

2000

115.20

   

12-Hour Photoperiod

Instantaneous PPFD
(µmol m
-2 s-1)

Daily PPFD
(mol m
-2 d-1)

10

0.432

100

4.32

200

8.64

300

12.96

600

25.92

1000

43.20

*1300

*56.23

2000

86.40

*There are 50 to 60 moles per m2 day on sunny summer days in outside areas without any shade.

 

Reference: https://www.apogeeinstruments.com/conversion-instantaneous-ppfd-to-integrated-ppfd/

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