Photoperiod Blackout and Night Interruption
Computes the uninterrupted dark period a blackout schedule produces, checks it against the crop's critical period.
Example
You enter
- Blackout pulled at (0-23) 17
- Blackout opened at (0-23) 8
- Crop critical dark period (hours) 13
- Long photoperiod to compare (hours) 16
- Short photoperiod to compare (hours) 11
- PPFD during the photoperiod (micromol/m^2/s) 400
- Night interruption (hours) 4
- Night interruption PPFD (micromol/m^2/s) 2
You get
- Uninterrupted darkness 15.0 h dark, 9.0 h light
- Light hours 9
- Against the critical period CLEARS it with 2.0 h of margin
- DLI at the long photoperiod 23.04 mol/m^2/day
- DLI at the short photoperiod 15.84 mol/m^2/day
- Light given up for the signal 7.2
- Dli given up (%) 31.25
- A night interruption contributes 0.0288
- Interruption share of long (%) 0.125
Checked against published worked examples from: UMass Extension.
Details, formula, and sources
ScopeComputes the uninterrupted dark period a blackout schedule produces, checks it against the crop's critical period, and prices the light given up. A night interruption at 2 micromol contributes 0.125% of the light budget for a complete reversal of flowering, which is also the warning about stray light.
Formula or tablethe uninterrupted dark period from the pull and open times, against the crop's critical dark period; DLI at each photoperiod = PPFD x hours x 3,600 / 1,000,000.
Source and editionShort-day crops generally need 12 to 13 hours of uninterrupted darkness. The crop's own published critical photoperiod and the cultivar's response group govern.
Free accessPublic arithmetic; critical photoperiods are published per crop and cultivar.
What governsEstimate. AHJ and licensed professional govern.
API field namesblackout_pull_hour, blackout_open_hour, critical_dark_hours, long_photoperiod_hours, short_photoperiod_hours, ppfd_umol_m2_s, interruption_hours, interruption_ppfd_umol_m2_s, dark_hours, light_hours, dark_margin_hours, long_dli, short_dli, dli_given_up, dli_given_up_pct, interruption_dli, interruption_share_of_long_pct
- Light leaks not modelled; any stray light during the dark period can break itsite survey
- Response group cultivar-specific; the critical period is not a species constantbreeder data