Scientific Guide: Setting Grow Light Height & Spacing

Key Factors: Plant Type, Growth Stage, Light Intensity (PPFD), and Coverage

1. Core Principles

Light Intensity Rule: Intensity decreases by the inverse square law (e.g., doubling distance = ¼ intensity).

PPFD Matters: Target Photosynthetic Photon Flux Density (PPFD) in μmol/m²/s:

Seedlings: 100–300

Vegging: 300–600

Flowering/Fruiting: 600–1000+

DLI Check: Ensure Daily Light Integral (DLI) matches plant needs (e.g., tomatoes need 20–30 mol/m²/day).

2. Setting Height by Growth Stage

Notes:

Adjust based on heat output: If leaves curl/yellow, raise lights.

Use a PAR meter for precise PPFD measurements at canopy level.

3. Calculating Spacing

Beam Angle: Narrow beams (60°) need closer spacing; wide beams (120°) can be spaced farther.

Formula:

Spacing = Light Width × 0.7–1.0

Example: For a 2ft-wide fixture, space lights 1.4–2 ft apart.

Uniformity Goal: Aim for ≤20% PPFD variation across the canopy.

4. Plant-Specific Tips

Leafy Greens (Low Light):

Height: 12–18″ (LED)

PPFD: 200–400

Spacing: 2–3 ft between fixtures.

Tomatoes/Peppers (High Light):

Height: 12–14″ (LED)

PPFD: 600–900

Spacing: 1–2 ft (ensure 100% canopy overlap).

5. Calibration Steps

Measure PPFD at canopy level with a meter (e.g., Apogee MQ-500).

Check Coverage: Use manufacturer’s footprint map or a light distribution app.

Monitor Plants:

Leggy growth → Lower lights or increase intensity.

Bleaching/curling → Raise lights.

Adjust Weekly: Raise lights as plants grow (maintain consistent PPFD).

6. Advanced Tools

Light Meters: Quantify PPFD/DLI.

Lux Apps (e.g., Photone): Estimate PPFD (calibrate against a real meter).

Light Movers: For HID lights to improve uniformity.

To purchase our grow lights, pls contact tadiran@tatalux.com

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