Daily Light Integral (DLI)
DLI = PPFD × hours × 0.0864 (mol/m²/day). Low-light 5–10, medium 10–20, high 20+ mol/m²/day. Drives photosynthesis.
Why This Biology Metric Matters
Why: DLI determines photosynthesis capacity. Too low = slow growth. Too high = light stress.
How: DLI = PPFD (µmol/m²/s) × hours × 0.0864. PPFD from PAR meter or light specs.
- ●Low-light plants 5–10, medium 10–20, high-light 20+ mol/m²/day.
- ●1 µmol/m²/s for 1 hour ≈ 0.0036 mol/m². Factor 0.0864.
- ●Supplement when natural light insufficient. DLI additive.
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For educational use only. Always confirm dosages and care with a licensed veterinarian.
🧬 Biology Facts
DLI = total photons per m² per day. Drives photosynthesis rate.
— Purdue
PPFD in µmol/m²/s. PAR range 400–700 nm. LED efficiency varies.
— Extension
Daily Light Integral (DLI) measures total cumulative PAR that plants receive over 24 hours in mol/m²/day. Formula: DLI = PPFD × hours × 0.0864. Low-light plants need 5-10, medium 10-20, high-light 20+ mol/m²/day.
Sources: USDA, Purdue Extension, PAR meter manufacturers.
Key Takeaways
- • DLI = PPFD × hours × 0.0864 (mol/m²/day)
- • Low-light plants: 5-10, medium: 10-20, high: 20-30+ mol/m²/day
- • Light source efficiency affects effective DLI (LED 95%, HPS 85%, fluorescent 75%)
- • Seasonal light varies; winter may need supplemental lighting
Did You Know?
How Does DLI Work?
PPFD vs DLI
PPFD is instantaneous intensity; DLI is cumulative daily total. DLI = PPFD × hours × 0.0864.
Plant Requirements
Different plants need different DLI. Low-light houseplants (5-10), herbs (10-20), fruiting vegetables (20-30+).
Light Source Efficiency
Sunlight 100%, LED 95%, HPS 85%, fluorescent 75%. Effective PPFD = PPFD × efficiency × seasonal factor.
Expert Tips
Plant DLI Requirements
| Category | DLI Range | Optimal |
|---|---|---|
| low light | 5-10 | 7.5 |
| medium | 10-20 | 15 |
| high | 20-30 | 25 |
Frequently Asked Questions
What is the difference between PPFD and DLI?
PPFD measures instantaneous light intensity in µmol/m²/s at a specific moment. DLI measures total cumulative light energy over 24 hours in mol/m²/day. DLI = PPFD × hours × 0.0864.
How do I measure PPFD?
Use a quantum PAR meter (photosynthetically active radiation meter) measuring 400-700 nm. Place the sensor at plant canopy height for accurate readings.
What DLI do tomatoes need?
Tomatoes are high-light plants requiring 20-30 mol/m²/day DLI for optimal growth. Seedlings need 12-18, vegetative 20-25, flowering/fruiting 25-35 mol/m²/day.
Can I use DLI for all plants?
Yes. Low-light plants need 5-10, medium 10-20, high-light 20-30+ mol/m²/day. Requirements vary by species and growth stage.
How does light source affect DLI?
Different sources have efficiency factors: sunlight 100%, LED 95%, HPS 85%, fluorescent 75%. The calculator accounts for these when computing effective DLI.
What happens if DLI is too low or too high?
Too low: slow growth, leggy plants, poor flowering. Too high: photoinhibition, leaf bleaching, heat stress. Adjust duration or intensity accordingly.
Key Statistics
Official Data Sources
⚠️ Disclaimer: This calculator is for educational purposes only. Actual light received may vary due to distance, reflectivity, and distribution. Verify with a PAR meter at plant canopy height. Plant requirements are general guidelines.
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