DLI (Daily Light Integral)
The cumulative amount of photosynthetically active light received per unit area over 24 hours, measured in mol/m²/day.
Daily Light Integral (DLI) is the total amount of photosynthetically active radiation (PAR, 400-700 nm) received per unit area over a 24-hour period. It is expressed in moles of photons per square metre per day (mol/m²/day).
DLI is calculated from PPFD (Photosynthetic Photon Flux Density) and the duration of the light period:
DLI = PPFD (μmol/m²/s) × Hours × 3600 ÷ 1,000,000
Understanding DLI allows growers to optimise their light periods, choose appropriate fixtures, and compare natural and artificial lighting conditions.
Typical DLI requirements:
- Propagation / low-light plants: 4-10 mol/m²/day
- Leafy greens / herbs: 12-20 mol/m²/day
- Vegetative cannabis / tomatoes: 20-35 mol/m²/day
- Flowering cannabis / fruiting crops: 35-50 mol/m²/day
- High-intensity crops: 50-65 mol/m²/day
DLI can be increased by raising light intensity (PPFD), extending the photoperiod, or both.
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