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Primary Lighting in a Growth Chamber with Lettuce 330 Watt LED vs. 600 Watt HPS

Prepared for: LumiGrow Inc.

By: Robert L. Starnes & Chris P. Durand

January 4, 2010

                    

 

Primary Lighting in a Growth Chamber with Lettuce 330 Watt LED vs. 600 Watt HPS

 Principal Investigators:

Robert L. Starnes, Chief Horticultural Consultant, BTO Solutions LLC, Roseville, CA 95661 (916) 374-0102 Christopher P. Durand, Senior Horticultural Consultant, BTO Solutions LLC, Roseville, CA 95661 (916) 374-0102

Objective:

To compare growth of butter leaf lettuce in a growth chamber setting using high output LED lighting and the industry standard, High Pressure Sodium (HPS).

Materials:

Experimental Units- Butter Leaf Lettuce variety Live Gourmet 2 Treatments, 1 HPS lights and 1 LED lights 5 NFT troughs divided in the middle by a light barrier 15 plants per light treatment 1 main fertilized water reservoir for all treatments Media: 2 inch Q Plug, iHort Inc. Equipment- Custom NFT (Nutrient Film Technique) Hydroponics trough system;

5 troughs, 40 plant sites Lumigrow growth chamber, Treasure Island, San Francisco LumiGrow ES 330 Watt Xtrasun 600watt HPS ballast, Radiant 6 hoods Eye Hortilux 600 watt HPS bulb

Custom Blend Fertilizer; 5-11-26 GrowMore Pre-blend, Calcium Nitrate, Potassium Nitrate, Magnesium Sulfate, Monopotassium Phosphate

Wat ermax Methods:

This experiment was conducted inside a growth chamber at LumiGrow’s Treasure Island testing facility. The NFT Hydroponic system was split in the middle by a light barrier with the HPS light on the left side and LED light on the right side. There were 2 treatments (LED and HPS), with 15 plants in the LED treatment and 16 plants in the HPS treatment. Plants (Figure 1) were kept in the growth chamber with an average temperature of 22°C ± 7.3 °C (72 ± 12 °F) and watered by

hydroponic NFT troughs with municipal water blended with fertilizer. The NFT water system ran at all times. All 5 troughs used water from one main fertilized water reservoir. The EC and pH of the fertilized water was maintained at 1.0 S and 5.8 respectively for the first week. The EC and pH of the fertilized water was hen maintained at 1.5 S and 5.8 for the remaining cropping cycle. The hotoperiod for the lighting was 16 hours per day (on at 6AM, off at 10PM)

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 Figure 1: Butter Leaf Lettuce growing under HPS (left) and LED (right) in a greenhouse.

Lettuce plants where planted in 2” Q plugs and placed into the NFT system under their respective treatments (Figure 2 and 3). The plants were grown for 32 days, the standard commercial cropping cycle. The data recorded for plant growth comparison was; length of roots per plant (Figures 4 and 5), weight (grams) per plant, and diameter (inches) per plant (Figure 6).

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igure 2: Lettuce plants after being planted under 600-watt HPS lighting.

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igure 3: Lettuce plants after being planted under LED lighting.

 Figure 4: Lettuce plants showing roots from LumiGrow Treatment.

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igure 5: Lettuce plants showing roots from HPS Treatment.

 

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igure 6: Lettuce plants being compared for diameter with HPS on the left and LED on the right.

Results:

 

Root Length: On average the plants from the Lumigrow group had longer root lengths than that of the HPS group. 14.21 inches compared to 12.46 respectively. This difference was statistically insignificant (Chart 1).

Chart 1: Shows the root lengths for HPS and LED treatments. Each error bar is constructed using 1 standard error from the mean. Weight of Plant: On average the plants from the HPS group were 10 grams heavier than those from the Lumigrow group. The difference was statistically insignificant (Chart 2).

Chart 2: Shows the weights of plants grown under LED and HPS treatments. Each error bar is constructed using 1 standard error from the mean. Diameter (width) of Plants: On average the plants from the Lumigrow group produced plants 1.2 inches more compact regarding width than the HPS group. The difference was statistically significant (Chart 2). (p<.0020) (Chart 3).

Chart 3: Represents the width of plants under LED and HPS treatments. Each error bar is constructed using 1 standard error from the mean.

Summary: The LED lighting treatment showed statistically significant differences as compared to the HPS lighting treatment for diameter of plants. The LumiGrow group stayed more tight and compact compared to the HPS group by an average diameter of 1.2 inches. There was no significant difference between LED and HPS light treatments for length of roots or weight of plants. ***Additional data analysis is available at the end of this document                    

 Data Analysis

Oneway Analysis of root length (inches) By Group

Oneway Anova Summary of Fit Rsquare 0.100286Adj Rsquare 0.069261Root Mean Square Error 2.711519Mean of Response 13.37097Observations (or Sum Wgts) 31

t Test LUMIGROW-600W HPS Assuming equal variances Difference 1.7521 t Ratio 1.797906Std Err Dif 0.9745 DF 29Upper CL Dif 3.7452 Prob > |t| 0.0826Lower CL Dif -0.2410 Prob > t 0.0413*Confidence 0.95 Prob < t 0.9587

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > FGroup 1 23.76616 23.7662 3.2325 0.0826Error 29 213.21771 7.3523 C. Total 30 236.98387

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95%600W HPS 15 12.4667 0.70011 11.035 13.899LUMIGROW 16 14.2188 0.67788 12.832 15.605 Std Error uses a pooled estimate of error variance

Oneway Analysis of Weight (g) By Group

Oneway Anova Summary of Fit Rsquare 0.05518Adj Rsquare 0.0226Root Mean Square Error 21.21983Mean of Response 193.6774Observations (or Sum Wgts) 31

t Test LUMIGROW-600W HPS Assuming equal variances Difference -9.925 t Ratio -1.30141Std Err Dif 7.626 DF 29Upper CL Dif 5.673 Prob > |t| 0.2034Lower CL Dif -25.523 Prob > t 0.8983Confidence 0.95 Prob < t 0.1017

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > FGroup 1 762.624 762.624 1.6937 0.2034Error 29 13058.150 450.281 C. Total 30 13820.774

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95%600W HPS 15 198.800 5.4789 187.59 210.01LUMIGROW 16 188.875 5.3050 178.03 199.72 Std Error uses a pooled estimate of error variance

Oneway Analysis of width (inches) By Group

Oneway Anova Summary of Fit Rsquare 0.283506Adj Rsquare 0.2588Root Mean Square Error 0.989093Mean of Response 11.64516Observations (or Sum Wgts) 31

t Test LUMIGROW-600W HPS Assuming equal variances Difference -1.2042 t Ratio -3.38746Std Err Dif 0.3555 DF 29Upper CL Dif -0.4771 Prob > |t| 0.0020*Lower CL Dif -1.9312 Prob > t 0.9990Confidence 0.95 Prob < t 0.0010*

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > FGroup 1 11.225941 11.2259 11.4749 0.0020*Error 29 28.370833 0.9783

Source DF Sum of Squares Mean Square F Ratio Prob > FC. Total 30 39.596774

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95%600W HPS 15 12.2667 0.25538 11.744 12.789LUMIGROW 16 11.0625 0.24727 10.557 11.568 S

 

td Error uses a pooled estimate of error variance