The Effects of LED Lighting on
Winter Greenhouse Grown Sugar
Snap Peas
Masters of Professional Studies in Horticulture
Integrated Project
Karen M. Weiss
December, 2011
Background
• Student -turned grower- turned farmer
• Sustainability at Little Foot Farm
– Thrifty use of available resources and assets
– Experiment with new ideas + ‘old school’ methods
– management strategy that safeguards environment ,inhabitants, well
being of family
– adherence to economically viable methods of enterprise management
• SARE Project
– utilization of a bedding plant production greenhouse year-round
– cropping schedule that minimizes non-renewable energy inputs and
seasonal work stress.
– Recycling/cycling of farm by products-straw
– promising new technology- LED
– additional revenue stream
Introduction
• Small Farm Strategy-Product for niche market• “First to Market”- weather protection
• High Value Crop-Pisum sativum- Sugar snap peas
– Temperature needs in winter
– Day-length/light needs in winter
• Supplemental heat
• Supplemental lighting
– Light emitting diodes- LEDs
• Light wavelength/spectrum
• Economic viability
Introduction-Winter HarvestProtection Components
• Winter temps and day-light limiting but not
prohibitive- Eliot Coleman
• Covered structures- row covers, cold frames,
greenhouses, multiple layers
• No energy use- in-ground, ‘held’, greens
(maché, spinach, arugula
• Additional heat in MN
Introduction-Sugar Snap peas
High Value Attributes of Edible pea pods
• Sweet- 3 year-old like them
• String-less varieties
• Uses- fresh, cooked, frozen
• Self life- 2 weeks
• Convenience- ‘pre-packaged’
• Limited locally grown supply
• Cool season
Introduction-Sugar Snap Peas
• Plant Characteristics
– temperature range
• Germination above 40° F
• 50-75°F, but can withstand below freezing temps
(Slinkard et al. 1994)
– Grown year-round
• California, Oregon
– Self pollinating
– Crop time -55-70 days
– Taller varieties need trellising
Sugar Snap Peas
Previous Research- specifics are limited
• Oregon State
– Links heat units to harvest times
• UCCE- Season differences-not attributed
specifically to day length/light or
temperature (Gaskell, 1997)
• Edible pea shoots- Wash. State (Miles and Sonde,
2003)
– benefit from supplemental light Nov-Mar
Introduction-Lighting
• High pressure Sodium, Low pressure Sodium,
Metal halide, Florescent- well studied
– Proven effective in greenhouse use- improves yield in
lettuce by up to 150% (Koontz et al. 1987; Cathey and Campbell
1979), (Wittwer ,1965 in Miles and Sonde, 2003)
– High energy requirements- (exception: florescent)
• LED
– Low energy required, durable, long- life, cool
temperature, specific wavelength spectrums (Massa,
2001)
– Expensive initial cost
Introduction-LEDs
Previous Research- LEDS
• NASA – 1990’s (Morrow, 2001).
• Red Spectrum– Blue spectrum 1-20%
(Yorio, 1998)
• Sole light source
• Supplemental light source
– Blue spectrum?
• Influx of research dollars – USDA (GPN, 2010)
– Sustainability
– ‘Green’ (Ouzounis , 2011)
Introduction-Economics
•
•
•
•
Initial cost – 2010- $6-7/watt, 2011 20%
Long-term cost- low energy use 70-80%
Watt per sq. ft ?
Management requirements
– Small coverage area
– Distance from plants
Methods and Materials
• Preliminary Experiment- establish protocol for
Primary Experiment
– Greenhouse Layout
– Cultivar
– Growing medium
– Planting dates
– Set-up
– Lighting treatments
Materials and Methods- Preliminary
Experiment
• “Cascadia”
• Straw-bales
• 2 growing mediums
– Compost + worm castings
– Sunshine organic potting soil+ Suståne
• Direct seeded and transplanted
• 6 hours supplemental light
– 100% Red, 80% red + 20% full/8%blue
• 40° F
Materials and Methods-Primary
Experiment- Growing method
• Johnny’s ‘Super’ Sugar snap peas
– Taller, higher yielding
•
•
•
•
•
•
2-3” Sunshine organic potting mix
Suståne 8 oz./ 36”
Transplants
2” spacing
42° F
Watered as needed
Materials and Methods- Greenhouse Layout
XX
4 Red LED Lights*
Full Spectrum**
3 Red LED Lights
2 Blue LED Lights
No LED Lights
XX
Bale Not Used
Chicken Wire
C2
XX
C4
B1
C2
B1
B2
B3
C1
B2
B3
C1
A3
A1
A3
B4
A1
C3
B4
A2
C3
A4
C4
XX
A4
A2
North
1 Bale = 18” x 36”
*Each red LED bulb has 200 diodes and is 10 watts
*Each blue LED bulb = 60 diodes and is 4 watts
Woven Wire
Figure 1. Greenhouse Layout - Sugar Snap Pea LED Lighting Evaluation - Jan. 8,
2011- May 4, 2011
Materials and Methods-LED Lighting
Treatments
• 20 Hours
– Treatment A-40 watts - 100% Red spectrum
– Treatment B- 38 watts
• 30 watts Red spectrum
• 8 watts Full spectrum
– Treatment C- no light
• Lights clamped to woven
wire 14-18” above plants
• Moved weekly
Materials and Methods- Data
Collection
• Time to First Blossom -TFB
• Average Shoot length – 30 and 60 day- ASL
• Harvest Dates
– Time to First Harvest - TFH
– Length of harvest -LH
• Yields
– Total Yield by Block -TYB
– Total Yield by Treatment -TYT
Results-TFB
• Treatment A and B
– 67 days post 1st transplant date
• Treatment C
– 71 days post 1st transplant date
Results- ASL
Average Shoot Length in Inches
•ASL was recorded
60
at 30 and 60 days
50
post transplant
40
A-100% Red
(Figure 2).
30
•The ASL for
B-80% Red+ 20% Full
Spectrum
Treatment A was
20
C-None
27" and 53.2",
10
•Treatment B was
0
27.8"and 55" and
30
60
Days from 2nd Transplant
•Treatment C 14.2"
and 26.2".
Figure 2. Average shoot length (ASL) (inches) at day 30 and day 60 of LED
lighting experiment on Sugar Snap peas
Results- Harvest
•Harvest began April 8- 81 day
post 1st transplant
•Both treatments A and B- 27
days
•Treatment C- 7 days later
•A and B -24.5 days/block
•Treatment C- 20 days
•Averaged only 13 days/block
Results- TFH and LH
20
18
16
Yield in Ounces
14
12
A-100% Red
10
8
6
B-80% Red+ 20%
Full Spectrum
4
C-None
2
0
Harvest Dates- Day 1-Day 26
Figure3. Yield in Ounces by Harvest Date for 'Super' Sugar Snap Peas grown
using LED Lighting
Results- Yield
• TYT for Treatments A and B and C were
57.57 oz and 63.10 oz, and 21.45 oz.
respectively.
• The highest and lowest TYB of the
lighted blocks were both from Treatment
A at 20.87 and 7.95 oz respectively.
• Yield was more consistent with
Treatment B
Results- TYB
25.0
Block 1
Block 2
20.0
Total Yield (Oz)
Block 3
15.0
Block 4
Mean
10.0
Standard
Deviation
standard
Error of the Mean
5.0
0.0
Treatment A-100% Red Treatment B-80% Red+
light
20% Full Spectrum
Treatment C-No
Supplemental light
Lighting Treatment, each with 4 Blocks of sample data.
Mean and Standar Error of the Mean are also plotted.
Figure 4. Total Yield (ounces) Per Block- TYB for Sugar Snap peas grown using
LED Lighting
Results- TYT
70
Total Yield in Ounces
60
50
Treatment A-100% Red2
40
Treatment B-80%Red
+20% Full
30
Treatment C-No Light
20
10
0
Lighting Treatment
Figure 5. Total Yield (Ounces) Per Treatment-TYT for Sugar Snap peas grown
with LED lighting
Discussion
• TFH reduced by 15-20% with both LED
treatments,
• TY was improved with both LED lighting
treatments by approx. 200%
• 8% better yield in full spectrum than red
spectrum with 5% less wattage
• More consistent harvest by date with full
spectrum despite lower wattage
Discussion
• Small sample size limiting
• Based on mean and difference in the mean,
no statistically significant difference in lighted
treatments.
• There was a statistically significant benefit
with the 2 lighting treatments over no lighting
• Control for more variables
Discussion-Contributing FactorsDisease Pressure
Necrosis
developed
approximately 10
days after first
transplants
No tissue
analysis
Wilt?
mildew?
Virus?
Abiotic?
Discussion-Contributing FactorsDisease Pressure
• Power Outage? Minimum
temp reading week of Feb 7
• 22° F
Discussion-Contributing Factors
• Lighting Set-up
– difficult to move
• Low side walls
• Spacing
– keeping blocks
separate- reduced # of plants by 20%
– Harvesting individual blocks difficult
Economic Analysis-Budget
Expense Item
Number of Units
Cost /unit
Total Cost
Cost/Crop
Bales
Soil
Seeds
Fertilizer
Electricity
Nat. Gas
LED 60 diode Full Spectrum
LED 200 diode Red Spectrum
Labor
24
(6 )2.8 cu ft bags
1/2 lb/1000 sds
6 lbs
468 kWh
180 therms
8
28
16 hrs
$
$
$
$
$
$
$
$
$
$ 60.00
$ 66.00
$
3.25
$
7.20
$ 49.00
$ 127.80
$ 192.00
$ 1,904.00
$ 128.00
Total
$ 30.00 $
$ 49.50 $
$
3.25 $
$
7.20 $
$ 49.00 $
$ 127.80 $
$
6.00 $
$ 60.00 $
$ 128.00 $
$ 460.75 $
0.13
0.21
0.01
0.03
0.20
0.53
0.03
0.25
0.53
1.91
9lbs
$ 6.00 $
54.00 $ 54.00 $
$ (406.75) $
0.23
(1.68)
2.50
11.00
6.50
1.20
0.10
0.71
24.00
68.00
8.00
Cost/Sq Ft/Crop
Income
Suga r Sna p Pea s Ha rves ted
Net Profit (Loss)
Table 1. Expense Report- Winter Grown Sugar Snap Peas 2011- 224 sq Ft
Greenhouse Space
Economic Analysis-Budget
Expense Breakdown
by Percent
growing
components
28%
19%
25%
lighting
heating
28%
labor
Economic Analysis
• 9 lbs/30 LF
• 4 best yielding blocks - .5 lb/ LF
• Expected yield varies greatly
– Utah State-garden grown- 30 lb/100 ft (Drost, 2010).
– UCCE- field grown- .2 lb/ plant (Gaskell, 2010)
• .5lbs x 30LF= 15lbs
• If field grown yield could be achieved 57 lb for
this 224’ space would be possible
• Still a $114 loss
Results-Economic Viability
• Results suggest LED improve yield and viability of
growing Sugar snap peas in winter greenhouse
• Economic viability very much in question
• Raises a number of questions
–
–
–
–
Minimum time and amount of LED
Effect of a change in planting date
Reduction in labor- Lighting set-up and management
Ideal temperature setting
Future Work
• Later spring planting date – 30 days
supplemental light and heat
• Early fall planting- 30 days supplemental light
and heat
• Change bale spacing= 60LF for 224 sq. ft space
• Lighting to 4.3watt/ft
Future Work- Budget
Hypothetical
Expense Breakdown
by Percent
growing
components
25%
38%
18%
19%
lighting
heating
labor
Future Work
Expense Item
Bales
Seeds
Soil + Compost
Fertilizer
Electricity
Nat. Gas
LED 90 diode Full Spectrum-2011
LED 200 diode Red Spectrum-2011
Labor
Number of Units
24
1/2 lb/1000 sds
(6 )2.8 cu ft bags
6 lbs
116 kWh
80 therms
10
20
14 hrs
Cost / unitTotal Cost
$ 2.50 $ 60.00
$ 6.50 $
4.87
$ 11.00 $ 66.00
$ 1.20 $
7.20
$ 0.10 $ 12.06
$ 0.71 $ 56.80
$ 20.00 $ 200.00
$ 54.00 $ 1,080.00
$ 8.00 $ 112.00
Total
Cost Per Crop
Cost/Sq Ft/Crop
$ 30.00 $
0.13
$
4.87 $
0.02
$ 33.00 $
0.14
$
7.20 $
0.03
$ 12.06 $
0.05
$ 56.80 $
0.24
$
6.25 $
0.03
$ 33.75 $
0.14
$ 112.00 $
0.47
$ 295.93 $
1.24
.5lb/ft =30lbs
$
$ 180.00 $
$ (114.31) $
$ 864.99
$570.68
Income
Suga r Sna p Pea s Ha rves ted-Scena ri o #1
6.00
$ 180.00
Net Profit /Loss
Suga r Sna p Pea s Ha rves ted-Scena ri o #2
Net Profit /Loss
.2lb/plant=144lbs $
6.00
$ 864.00
Table 2. Hypothetical Expense Report- Winter Grown Sugar Snap Peas 2012224 sq. ft Greenhouse
0.75
(0.49)
$3.60
$2.36
Key Observations and Conclusions
• The use of energy efficient LED lighting is gaining traction
– The improvements in spectrum availability,
– influx of research dollars
– improving price
• cost necessitates their application be in 'high value' crop situations
• Their effectiveness as a supplemental lighting was demonstrated
• The addition of 38-40 watts per 2.5 LF of peas increased yield by
200%
• reduced time to harvest by 15-20%.
• LEDs with 8% blue spectrum produce better yields and more
consistent harvest but was not statistically significant
• The economic viability of using LEDs as a supplemental light source
remains in question and requires further evaluation.
Literature Cited
•
•
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•
•
•
•
•
•
•
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•
Cathey, H. M., and L. E. Campbell. 1979. Relative Efficiency of high- and low-pressure sodium and incandescent filament lamps used to
supplement natural winter light in greenhouses. J. Amer. Soc. Hort. Sci. 104(6):812–825.
Coleman, Eliot. 1998. The Winter Harvest Manual: Farming the Back Side of the Calendar. Four Seasons Farm, Harborside ME. pg. 1-2.
Drost, Dan. 2010. Peas in the Garden. Utah State University Cooperative Extension.
Duke, J.A. 1981. Handbook of Legumes of World Economic Importance. Plenum Press, New York. p. 199-265
Gaskell, Mark. 1997. Edible Pea-Pod Production in California. Vegetable Research and Information Center. University of California
Cooperative Extension.
Greenhouse Product News . Purdue Receives Grant to Study LED Lighting November 1, 2010
Koontz, H. V., R. P. Prince, and R. F. Koontz. 1987. Comparison of fluorescent and high pressure sodium lamps on growth of leaf lettuce
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Miles, C.A. and M. Sonde, 2003. Pea Shoots. PNW567 A Pacific Northwest Cooperative Extension Publication. Washington State
University. pg. 5.
Morrow, Robert C. 2008. LED Lighting in Horticulture. Hort Science 43:1947-1950.
Morrow, Robert C., R. J. Bulb, and T.J. Tibbits. 2001. Light Emitting Diodes as an Irradiance Source for Plants. ASGSB Bulletin vol 3.
Slinkard, A. E., G. Bascur, and G. Hernandez-Bravo. 1994. Biotic and Abiotic Stresses of Cool Season Food Legumes in the Wester
n Hemisphere. 195-203. In: Muehlbauer F. J. and Kaiser W. J. (Eds.) Expanding the production and use of cool season food
legumes. Kluwer Academic Publishers. Dordrecht, The Netherlands.
Yorioi, N. C., R. M. Wheeler, G.D. Goins, and G.W. Stutttie. 1998. Blue Light Requirements for Crop Plants in
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