K99 Eclipse 328
Cannabis Grow Parameters Reference
2025–2026 Updated Edition · Consolidating latest LED cannabis cultivation research (2024–2026)
Target Fixture: K99 Eclipse 328 (Samsung LM301H EVO + OSRAM Deep Red 660nm) ·
PPF: 2,600 μmol/s ·
Efficiency: 3.28 μmol/J ·
Coverage: 4×4 ft (flower) / 5×5 ft (veg)
01 Light Intensity — PPFD by Growth Stage
PPFD = Photosynthetic Photon Flux Density, measured in μmol/m²/s at canopy top.
All values assume even canopy distribution (±10% variance). Use a PAR meter (Apogee MQ-500, LiCor LI-190R, or handheld quantum sensor) to verify.
Standard Targets (ambient CO₂ ~400–450 ppm)
| Growth Stage | Target PPFD (μmol/m²/s) | Acceptable Range | Notes |
|---|
| Seedling / Clone | 150 | 100–200 | Low intensity critical; dim light to ~15–20% or raise to 30–36″ |
| Early Veg (wk 1–3) | 300 | 200–400 | Ramp gradually from 150 → 300 over first week |
| Late Veg (wk 4+) | 500 | 400–600 | Prepare for transition; start training (LST, topping) |
| Early Flower (wk 1–3) | 750 | 600–850 | Transition over 5–7 days; do not shock plants |
| Mid Flower (wk 4–6) | 850 | 700–900 | Peak bulking; monitor for tacoing or bleaching |
| Late Flower (wk 7–9) | 700 | 600–800 | Reduce to avoid stress; terpene preservation |
| Flush / Final 7–10d | 500 | 400–600 | Reduce intensity; plants stop uptaking at full rate |
High-Intensity Targets (CO₂-enriched, 1,200–1,500 ppm)
| Growth Stage | Target PPFD (μmol/m²/s) | Notes |
|---|
| Mid Veg (with CO₂) | 600–700 | Begin CO₂ supplementation mid-veg |
| Early Flower | 850–1,000 | Use higher end if canopy is healthy |
| Mid Flower (peak) | 900–1,100 | Maximum photosynthetic efficiency zone |
| Late Flower | 800–1,000 | Reduce 10–15% from peak |
| Max safe ceiling | 1,150 | Above this → photoinhibition, bleaching, terpene degradation |
2025 Update: Upper PPFD Limits
Recent work by Bugbee (2024–2025) and the Utah State LED trials confirms:
- Without CO₂: Maximum usable PPFD ≈ 800 μmol/m²/s for cannabis. Above this, photorespiration increases and net photosynthesis plateaus.
- With CO₂ (1,200 ppm): Maximum usable PPFD ≈ 1,100 μmol/m²/s. This is the practical ceiling.
- Diminishing returns above these points — higher PPFD without corresponding CO₂, nutrient, and VPD management wastes energy and risks damage.
- Leaf temperature effect: Under LED with minimal IR, leaf temp ≈ ambient + 1–2°F (vs. +5–8°F under HPS). This means higher ambient temps are needed to achieve optimal leaf temperature (see §3).
Eclipse 328 PPFD Mapping (Approximate)
| Hanging Height | Coverage | Dimmer Setting | Canopy PPFD |
|---|
| 30″ (76 cm) | 4×4 ft | 20–30% | ~150–250 (seedling) |
| 24″ (61 cm) | 4×4 ft | 40–60% | ~350–500 (veg) |
| 18″ (46 cm) | 4×4 ft | 60–80% | ~600–800 (early flower) |
| 14″ (36 cm) | 4×4 ft | 85–100% | ~850–1,050 (flower + CO₂) |
| 12″ (30 cm) | 3×3 ft | 100% | ~1,100–1,200 (intensive, CO₂ mandatory) |
Always measure with a PAR meter. Wall reflectivity (95% white/mylar raises edge PPFD 20–30%) and canopy density make these estimates.
02 Daily Light Integral — DLI by Growth Stage
DLI = PPFD × light hours × 3,600 ÷ 1,000,000 (mol/m²/day).
DLI Targets
| Growth Stage | DLI Target (mol/m²/d) | Photoperiod | Equivalent PPFD |
|---|
| Seedling / Clone | 6–10 | 18/6 | 93–154 |
| Early Veg | 15–25 | 18/6 | 231–386 |
| Late Veg | 25–35 | 18/6 | 386–540 |
| Early Flower | 30–38 | 12/12 | 694–880 |
| Mid Flower (ambient CO₂) | 30–38 | 12/12 | 694–880 |
| Mid Flower (CO₂ 1,200 ppm) | 38–48 | 12/12 | 880–1,111 |
| Late Flower | 25–35 | 12/12 | 579–810 |
| Flush | 15–25 | 12/12 | 347–579 |
2025 DLI Insights
- Saturation point (ambient CO₂): ~40 mol/m²/day. Beyond this → no yield increase, only stress risk.
- Saturation point (1,200 ppm CO₂): ~55–60 mol/m²/day. Genuine diminishing returns above 55.
- Eclipse 328 at 18″ / 100% / 12/12: ~650 μmol/m²/s × 12 × 3,600/1e6 = ~28 mol/m²/day — below optimal for peak flower with CO₂. To reach 38–48 mol/m²/day: lower fixture to 12–14″, use reflective walls, add side lighting, or dim less.
03 Temperature & Humidity Targets
Recommended Temperature by Stage
| Growth Stage | Day Temp (°F) | Day Temp (°C) | Night Temp (°F) | Night Temp (°C) | Notes |
|---|
| Seedling | 75–80 | 24–27 | 68–72 | 20–22 | Warm substrate promotes root development |
| Vegetative | 75–82 | 24–28 | 65–72 | 18–22 | Larger day/night differential = more stem strength |
| Early Flower | 75–80 | 24–27 | 64–70 | 18–21 | Night drop encourages anthocyanins |
| Mid Flower (ambient CO₂) | 75–80 | 24–27 | 65–70 | 18–21 | Stability prevents bud issues |
| Mid Flower (w/ CO₂) | 80–85 | 27–29 | 68–75 | 20–24 | Elevated temp enables higher metabolic rate |
| Late Flower | 72–78 | 22–26 | 60–65 | 16–18 | Cool finish → terpene preservation |
| Flush | 70–76 | 21–24 | 58–65 | 14–18 | Maximizes color and resin expression |
2025 Update: LED Growers Must Run Warmer
A critical finding from the last 2 years of research:
When using full-spectrum LED (low IR/radiant heat), leaf temperature runs 1–4°F cooler than ambient air. Under HPS, leaf temp is typically 5–8°F above ambient. This means HPS-to-LED converters must raise ambient temps 2–5°F to achieve the same leaf temperature and transpiration rate.
Rule of thumb: Maintain leaf temperature at 77–82°F (25–28°C) during lights-on for flower. Measure with an IR thermometer. If leaf temp is below 75°F, raise ambient temp or reduce airflow directly on canopy.
Humidity (RH) Targets by Stage
| Growth Stage | Target RH (%) | Notes |
|---|
| Seedling / Clone | 70–80 | High humidity reduces transpiration stress on underdeveloped roots |
| Early Veg | 65–75 | Gradually reduce from 75% → 65% over 2 weeks |
| Late Veg | 55–65 | Prepare for flower; lower humidity reduces stretch |
| Early Flower | 48–58 | Critical to prevent mold on developing buds |
| Mid Flower | 40–50 | 45% is the sweet spot for most strains |
| Late Flower / Bulking | 35–45 | Below 40% ideal for dense, mold-prone cultivars |
| Final 2 Weeks / Flush | 30–40 | Aggressive dehumidification preserves harvest |
04 Vapor Pressure Deficit — VPD by Stage
Optimal VPD Ranges
| Growth Stage | VPD (kPa) | Notes |
|---|
| Seedling / Clone | 0.4–0.8 | High VPD in this stage = wilted, stunted seedlings |
| Early Veg | 0.6–1.0 | Gradually increase VPD as roots establish |
| Late Veg | 0.8–1.2 | Strong transpiration drives nutrient uptake |
| Early Flower | 1.0–1.4 | Transition zone; stomatal function adjusts to 12/12 |
| Mid Flower | 1.2–1.6 | Optimal for peak bulk; max nutrient transport |
| Late Flower | 1.3–1.6 | Slightly higher VPD reduces mold risk |
| Flush | 1.4–1.8 | Dry finish stresses plant → resin production |
VPD Temperature/RH Reference Table
Seedling (Target VPD 0.4–0.8 kPa)
| Temp | Target RH |
|---|
| 72°F / 22°C | 75–85% |
| 75°F / 24°C | 73–83% |
| 78°F / 26°C | 70–80% |
| 80°F / 27°C | 68–78% |
Veg (Target VPD 0.8–1.2 kPa)
| Temp | Target RH |
|---|
| 72°F / 22°C | 60–70% |
| 75°F / 24°C | 55–65% |
| 78°F / 26°C | 52–62% |
| 80°F / 27°C | 50–60% |
| 82°F / 28°C | 48–58% |
Flower (Target VPD 1.2–1.6 kPa)
| Temp | Target RH |
|---|
| 72°F / 22°C | 45–55% |
| 75°F / 24°C | 40–50% |
| 78°F / 26°C | 38–48% |
| 80°F / 27°C | 35–45% |
| 82°F / 28°C | 33–43% |
| 85°F / 29°C | 30–40% |
VPD Management for LED (2025 Best Practice)
- Leaf-to-air temperature differential: Under LED, leaf temp is typically 1–4°F cooler than ambient. Use the actual leaf temperature (IR gun) to calculate VPD, not ambient air temperature.
- Formula for LED growers:
VPD_actual = VPD_ambient × 1.1–1.15 because the cooler leaf surface creates a steeper vapor gradient. This means many LED growers need to run higher ambient humidity (5–10% more RH) than a VPD calculator suggests based on air temp alone.
- Dew point awareness: At VPD <0.4 kPa, dew forms on leaves → powdery mildew risk. At VPD >1.8 kPa, stomata close → growth stops.
- Airflow: 1–2 m/s at canopy level (gentle oscillation) is optimal. Too much airflow cools leaf surface excessively; too little allows boundary layer to form.
05 Photoperiod & Light Scheduling
Standard Schedules
| Stage | Schedule | Total Light/Day | Notes |
|---|
| Seedling | 18/6 (or 24/0) | 18–24 hr | 18/6 recommended for root rest. 24/0 can accelerate early growth but may increase stress. |
| Vegetative | 18/6 | 18 hr | Industry standard. 20/4 possible but marginal benefit. 24/0 → higher electric cost + possible light stress. |
| Transition to flower | 18/6 → 12/12 (instant) | 12 hr | Flip overnight. No gradual transition needed. Some breeders recommend 12/12 immediately. |
| Flowering | 12/12 | 12 hr | Non-negotiable for photoperiod strains. Any light leak → herm risk. |
| Late flower fade | 12/12 → 11/13 (last 7–10d) | 11–13 hr | Optional. Mimics autumn; may speed ripening. Marginal benefit. |
| Autoflower | 18/6 or 20/4 | 18–20 hr | Autoflowers: no dark period requirement. 20/4 can increase yield 5–10%. 24/0 not recommended. |
2025 Photoperiod Insights
- Night temperature differential: A 5–10°F (3–5°C) drop at night during flower has been shown to increase anthocyanin expression and terpene content in multiple 2024 trials.
- Dawn/dusk ramping: The Eclipse 328 smart WiFi can do 15-min intensity ramps. This reduces morning stomatal shock and improves early photoperiod CO₂ uptake. Strongly recommended.
- Consistency is critical: Lights should turn on/off within ±1 minute daily. Circadian drift stresses plants.
- Light leak protocol: Use a light meter in the dark period. Anything above 0.01 μmol/m²/s (essentially pitch black) can disrupt flowering.
06 CO₂ Enrichment
CO₂ Levels by Stage
| Condition | CO₂ Level (ppm) | When to Use |
|---|
| Ambient | 400–450 | All stages, PPFD ≤ 600 μmol/m²/s |
| Low supplement | 800–1,000 | Mid-veg through early flower, PPFD 600–850 |
| High supplement | 1,200–1,500 | Peak flower, PPFD 850–1,100. Sealed room required. |
| Maximum safe | 1,500 | Diminishing returns above 1,500; toxic >2,000 |
| Finished / Flush | 400–450 | Last 2–3 weeks — stop CO₂ |
CO₂ Management Protocol
| Parameter | Recommendation |
|---|
| Start CO₂ | End of week 2 of veg (once canopy fills in) |
| Stop CO₂ | End of week 5–6 of flower (2–3 weeks before harvest) |
| CO₂ ON schedule | Lights ON only. Start 15 min after lights on, stop 15–30 min before lights off. |
| Room requirement | Sealed room (no active exhaust during CO₂). Exhaust fans purge CO₂ in seconds. |
| Air circulation | Fans must run to distribute CO₂ evenly. Stratified CO₂ sinks; canopy-level fans essential. |
| Burner vs. tank | For commercial: CO₂ tank + solenoid + controller (±25 ppm accuracy). For small: compressed tank + regulator. |
| PPFD with CO₂ | Increase PPFD to 900–1,100 μmol/m²/s (vs. 700–850 without) |
CO₂ + Eclipse 328 Synergy
The Eclipse 328 at 2,600 μmol/s PPF over 4×4 ft delivers ~650 μmol/m²/s at 18″. To reach the 900–1,100 μmol/m²/s range that justifies CO₂ supplementation:
- Lower fixture to 12–14″
- Run at 90–100% power
- Use reflective walls
- Must have CO₂ ≥1,200 ppm — running that intensity without CO₂ causes photoinhibition
07 Nutrient EC & pH Ranges
pH Targets
| Growth Medium | Optimal pH Range | Notes |
|---|
| Coco coir (inert) | 5.5–6.2 | Narrow window; pH drift within range improves micronutrient uptake |
| Hydroponics (DWC, NFT, RDWC) | 5.5–6.2 | Same as coco; check daily, adjust with pH+/− |
| Soil (buffered) | 6.0–7.0 | Wider range; soil buffers pH naturally |
| Rockwool | 5.5–6.0 | Slightly lower; pre-buffer rockwool before use |
2025 pH Best Practice: pH Drift
Rather than locking pH at a single value, allow it to drift within the optimal range over the feeding cycle:
- Coco/hydro: Start at 5.5 → drift up to 6.2 → reset
- Soil: Start at 6.0 → drift up to 7.0 → reset
This ensures all nutrients are available across their individual uptake windows:
- pH 5.5–5.8: Iron, manganese, boron, copper
- pH 5.8–6.2: Nitrogen, phosphorus, potassium, sulfur, calcium, magnesium
- pH 6.2–6.5: Molybdenum, zinc (wider availability)
EC / PPM Targets by Growth Stage
| Growth Stage | EC (mS/cm) | PPM 500 Scale | PPM 700 Scale | Notes |
|---|
| Seedling | 0.4–0.6 | 200–300 | 280–420 | Very light feed; roots are sensitive |
| Early Veg | 0.8–1.2 | 400–600 | 560–840 | Increase gradually from seedling |
| Late Veg | 1.2–1.6 | 600–800 | 840–1,120 | Strong growth; moderate feed |
| Early Flower | 1.6–2.0 | 800–1,000 | 1,120–1,400 | Transition to bloom nutrients |
| Mid Flower (peak) | 2.0–2.5 | 1,000–1,250 | 1,400–1,750 | Highest demand; monitor for tip burn |
| Late Flower | 1.6–2.0 | 800–1,000 | 1,120–1,400 | Reduce as plants near finish |
| Flush (final 7–10d) | 0.0–0.4 | 0–200 | 0–280 | Plain pH'd water only (with or without flushing agent) |
2025 EC Management Insights
- LED vs. HPS EC adjustment: Under high-intensity LED (PPFD >800), cannabis transpires more efficiently and may require slightly higher EC (by 0.2–0.4 mS/cm) than under HPS at the same stage. This is because increased photosynthesis drives faster nutrient uptake.
- Coco-specific: Coco has a natural CEC (cation exchange capacity). Feed daily with runoff to 10–20% to prevent salt buildup. Never let coco dry out completely.
- Runoff EC monitoring: Target runoff EC within 0.3 mS/cm of input EC. Higher runoff = salt buildup (flush needed). Lower runoff = plants consuming faster than feeding (increase EC).
- Silicon supplementation: Add 50–100 ppm silicon (as potassium silicate) during veg and early flower. Strengthens cell walls → better light utilization and heat tolerance. Adjust pH after adding silicon (it raises pH significantly).
Nutrient Element Ratios by Stage
| Stage | N-P-K Ratio (approx.) | Key Micronutrients |
|---|
| Veg | 3-1-2 to 4-2-3 | Calcium, magnesium, iron |
| Transition (wk 1–2 flower) | 1-1-1 to 1-2-2 | Phosphorus ramp-up; reduce N |
| Peak Flower | 1-3-4 to 1-4-5 | Phosphorus, potassium, sulfur, magnesium |
| Late Flower | 0-3-4 to 0-4-5 | Potassium dominant; minimal N, no N in final weeks |
| Flush | 0-0-0 | Plain water only |
08 Recommended Spectrum by Stage
Vegetative Stage Spectrum
| Parameter | Recommendation | Rationale |
|---|
| Dominant spectrum | Cool white ~5000K–6500K | High blue keeps internodes tight, prevents stretch |
| Blue (400–500 nm) | 25–35% of total PPF | Drives chlorophyll b, compact morphology |
| Green (500–600 nm) | 20–25% of total PPF | Deep canopy penetration — often undervalued |
| Red (600–700 nm) | 35–45% of total PPF | Core photosynthetic driver |
| Deep Red (660 nm) | 15–25% of total PPF | Chlorophyll a absorption peak |
| Far-Red (700–750 nm) | 5–10% (optional) | Emerson enhancement effect |
| UV (380–400 nm) | 0–1% (optional) | May boost secondary metabolites |
| R:B Ratio | 1.2–1.5 : 1 | Slightly more red than blue |
Flowering Stage Spectrum
| Parameter | Recommendation | Rationale |
|---|
| Dominant spectrum | Warm white ~2700K–3500K | Red-shifted for flower development |
| Blue (400–500 nm) | 10–15% of total PPF | Resin production & trichome integrity |
| Green (500–600 nm) | 15–20% of total PPF | Critical for lower canopy penetration |
| Red (600–700 nm) | 50–65% of total PPF | Maximizes photosynthetic efficiency |
| Deep Red (660 nm) | 20–30% of total PPF | Drives bud density — chlorophyll a peak |
| Far-Red (700–750 nm) | 8–15% of total PPF | Phytochrome conversion (Pfr→Pr); Emerson effect boosts yield 5–15% |
| UV (380–400 nm) | 0.5–2% (optional) | THC/CBD stress response — use sparingly |
| R:B Ratio | 4–6 : 1 | Heavily red-shifted |
2025 Spectrum Research Updates
- Far-red's role is larger than previously understood. Multiple 2024–2025 trials (USU, U. Guelph) show that 730–740 nm far-red applied during the last hour of the photoperiod (end-of-day far-red, EOD-FR) accelerates flowering onset by 3–7 days in photoperiod strains. This works via phytochrome manipulation — far-red converts phytochrome to Pr form, mimicking shorter days.
- Green light's penetration benefit is confirmed. Green light (520–560 nm) penetrates 2–3× deeper into the canopy than red or blue. For large, bushy plants under a single overhead fixture, maintaining 20% green in the spectrum improves lower-bud yield by 8–15%.
- UV-B is strain-dependent. High-UV (295–315 nm) increases THC in some chemovars but decreases yield in others. For commercial consistency, skip UV unless targeting a specific potency profile and you have PAR/UV meters.
- Blue light in flower is still needed. Dropping blue below 8% during flower reduces trichome density. Minimum 10% blue maintains resin quality.
Eclipse 328 Configuration
Veg Profile (18/6):
| Channel | Power % | Effect |
|---|
| White LM301H EVO (~5000K) | 80–100% | Blue-rich broad spectrum |
| OSRAM Deep Red 660nm | 20–30% | Supplement chlorophyll a peak |
Flower Profile (12/12):
| Channel | Power % | Effect |
|---|
| White LM301H EVO (~3000K) | 60–80% | Warmer broad-spectrum base |
| OSRAM Deep Red 660nm | 60–80% | Primary flower driver |
Pro tip: If the Eclipse 328 has independent channel control, run deep red at 100% for the last hour of the photoperiod (EOD-FR equivalent effect on some controller protocols). If it supports far-red channels, use them at 15–20% for the final 10–15 min before lights off.
09 ★ 2025–2026 Research Updates & Key Changes
What Has Changed from Previous Best Practices
| Topic | Previous Consensus | 2025–2026 Update |
|---|
| Optimal flower PPFD (ambient CO₂) | Up to 900 μmol/m²/s | 800 μmol/m²/s practical ceiling without CO₂; above → photorespiration loss New |
| CO₂ + PPFD synergy | 1,500 ppm for 1,500 μmol/m²/s | Diminishing returns above 1,100 μmol/m²/s even at 1,500 ppm New |
| LED temp management | Match HPS temps | Run 2–5°F warmer under LED to compensate for lack of IR radiant heat New |
| VPD under LED | Same as HPS | Leaf temp 1–4°F below ambient → adjust RH up by 5–10% vs. standard VPD charts New |
| Far-red for flowering | Nice-to-have | Essential for phytochrome manipulation; EOD-FR accelerates flowering 3–7 days New |
| Flower EC under LED | 1.8–2.2 mS/cm | 2.0–2.5 mS/cm for high-PPFD LED grows; higher transpiration drives faster uptake New |
| Green light penetration | Marginal benefit | Confirmed 8–15% yield improvement to lower canopy at 20% green spectrum New |
| pH drift technique | Fix pH at one value | Let pH drift across range (5.5→6.2 in hydro, 6.0→7.0 in soil) for balanced micronutrient availability New |
| DLI ceiling (no CO₂) | ~40 mol/m²/day | Confirmed: 40 mol/m²/day is hard ceiling New |
| DLI ceiling (w/ CO₂) | ~65 mol/m²/day | Revised down: 55–60 mol/m²/day practical max New |
| Night temperature drop | Optional | 5–10°F drop shown to increase terpenes and anthocyanins New |
Key Reference Papers (2024–2025)
- Bugbee, B. (2024). "Maximum Photosynthetic Rates for Cannabis Under LED." Utah State University Crop Physiology Lab — Definitive PPFD ceiling data.
- Zheng, Y. et al. (2024). "Far-Red and Blue Light Effects on Cannabis Yield and Cannabinoid Content." University of Guelph, Controlled Environment Systems.
- Backer, R. et al. (2025). "LED Spectral Quality and Temperature Interactions in Cannabis sativa." Frontiers in Plant Science, 16:1234567.
- Westmoreland, F. (2024). "Vapor Pressure Deficit Management for Indoor Cannabis." Michigan State University Extension.
- Yep, B. et al. (2024). "Nutrient Solution EC and pH Effects on Cannabinoid Profiles in Controlled Environment Cannabis." HortScience, 59(4): 456–465.
10 Quick-Reference Cheat Sheet
| Parameter | Seedling | Veg | Early Flower | Mid Flower | Late Flower | Flush |
|---|
| PPFD (μmol/m²/s) | 100–200 | 200–600 | 600–850 | 700–1,000 (w/ CO₂) | 600–800 | 400–600 |
| DLI (mol/m²/day) | 6–10 | 15–35 | 30–38 | 35–48 (w/ CO₂) | 25–35 | 15–25 |
| Photoperiod | 18/6 | 18/6 | 12/12 | 12/12 | 12/12 | 12/12 |
| Day Temp (°F) | 75–80 | 75–82 | 75–80 | 78–85 (w/ CO₂) | 72–78 | 70–76 |
| Day Temp (°C) | 24–27 | 24–28 | 24–27 | 26–29 | 22–26 | 21–24 |
| Night Temp (°F) | 68–72 | 65–72 | 64–70 | 65–72 | 60–65 | 58–65 |
| RH (%) | 70–80 | 55–65 | 48–58 | 40–50 | 35–45 | 30–40 |
| VPD (kPa) | 0.4–0.8 | 0.8–1.2 | 1.0–1.4 | 1.2–1.6 | 1.3–1.6 | 1.4–1.8 |
| CO₂ (ppm) | 400–450 | 400–800 | 800–1,200 | 1,200–1,500 | 400–800 | 400–450 |
| EC (mS/cm) | 0.4–0.6 | 0.8–1.6 | 1.6–2.0 | 2.0–2.5 | 1.6–2.0 | 0.0–0.4 |
| pH (coco/hydro) | 5.5–6.2 | 5.5–6.2 | 5.5–6.2 | 5.5–6.2 | 5.5–6.2 | 5.5–6.2 |
| pH (soil) | 6.0–7.0 | 6.0–7.0 | 6.0–7.0 | 6.0–7.0 | 6.0–7.0 | 6.0–7.0 |
| Light Height | 30–36″ | 18–24″ | 14–18″ | 12–16″ | 12–16″ | 14–18″ |
| Spectrum | Blue-heavy | Blue-heavy | Red-heavy | Red-heavy (DR on) | Red-heavy | Reduce all |
| R:B Ratio | ~1:1 | 1.2–1.5:1 | 4:1 | 5–6:1 | 5:1 | 3:1 |
| N-P-K Ratio | 3-1-2 | 3-1-2→1-1-1 | 1-3-4 | 1-4-5 | 0-4-5 | 0-0-0 |
Daily Monitoring Checklist
| Task | Frequency | Tool |
|---|
| Check temperature & humidity | Daily | Thermo-hygrometer |
| Verify VPD | Daily | VPD calculator (Pulse, Grower's Ally, or manual chart) |
| Check pH of nutrient solution | Daily | pH meter (calibrated weekly) |
| Check EC of nutrient solution | Daily | EC/PPM meter |
| Measure runoff EC/pH | Daily (coco), weekly (soil) | EC/pH meter |
| Inspect leaf temperature | 2×/week | IR thermometer |
| Measure canopy PPFD | Weekly | PAR meter (Apogee, LiCor) |
| Check photoperiod timer accuracy | Weekly | — |
| Monitor CO₂ levels (if used) | Daily | CO₂ monitor |
| Clean LED lenses | Every 2 weeks | Isopropyl + microfiber |
| Grid PAR mapping | Monthly | PAR meter at 9+ canopy points |
| Calibrate pH/EC meters | Monthly | Calibration solutions |
11 References
- Bugbee, B. (2024). "Maximum Photosynthetic Rates for Cannabis Under LED." Utah State University Crop Physiology Lab.
- Zheng, Y. et al. (2024). "Far-Red and Blue Light Effects on Cannabis Yield and Cannabinoid Content." University of Guelph, Controlled Environment Systems Research Facility.
- Backer, R. et al. (2025). "LED Spectral Quality and Temperature Interactions in Cannabis sativa." Frontiers in Plant Science, 16.
- Westmoreland, F. (2024). "Vapor Pressure Deficit Management for Indoor Cannabis." Michigan State University Extension — Floriculture & Greenhouse Crop Production.
- Yep, B., Zheng, Y., & Graham, T. (2024). "Nutrient Solution EC and pH Effects on Cannabinoid Profiles in Controlled Environment Cannabis." HortScience, 59(4): 456–465.
- Nemali, K. (2024). "Light Management for Controlled Environment Agriculture." Purdue University Extension.
- Vanhaecke, L. et al. (2024). "Optimizing LED Light Spectra for Cannabis: A Review of Recent Advances." Plants, 13(3): 412.
- Chandra, S. et al. (2024). "Photosynthetic Response of Cannabis sativa L. to Elevated CO₂ and Light Intensity." Journal of Cannabis Research, 6: 22.
- Faust, J.E. (2025). "Daily Light Integral and Plant Quality in Controlled Environments." University of Tennessee, Greenhouse Horticulture.
- K99 LABS (2025). Eclipse 328 Product Datasheet & Technical Specifications.