The Effects of LED Lighting on Winter Greenhouse Grown Sugar

Snap Peas

Masters of Professional Studies in Horticulture Integrated Project

Karen M. WeissDecember, 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 Harvest-Protection 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

• 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)

Previous Research- LEDS

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

A4

B3

B4

B4

XX

B3

A4

C4

C4

A3

C2

C3

C3

A3

B2

B2

C2

A2

C1

A1

A1

C1

A2

B1

B1XX XX

4 Red LED Lights*

Full Spectrum**3 Red LED Lights2 Blue LED Lights

Bale Not Used

XX

No LED Lights

Chicken Wire

Woven Wire

*Each red LED bulb has 200 diodes and is 10 watts*Each blue LED bulb = 60 diodes and is 4 watts

1 Bale = 18” x 36” North

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

Figure 2. Average shoot length (ASL) (inches) at day 30 and day 60 of LED lighting experiment on Sugar Snap peas

0

10

20

30

40

50

60

30 60

Aver

age S

hoot

Leng

th in

Inch

es

Days from 2nd Transplant

A-100% Red

B-80% Red+ 20% Full Spectrum

C-None

•ASL was recorded at 30 and 60 days post transplant (Figure 2). •The ASL for Treatment A was 27" and 53.2",•Treatment B was 27.8"and 55" and •Treatment C 14.2" and 26.2".

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

0

2

4

6

8

10

12

14

16

18

20

Yie

ld in

Ou

nce

s

Harvest Dates- Day 1-Day 26

A-100% Red

B-80% Red+ 20% Full Spectrum

C-None

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

Figure 4. Total Yield (ounces) Per Block- TYB for Sugar Snap peas grown using LED Lighting

0.0

5.0

10.0

15.0

20.0

25.0

Treatment A-100% Red light

Treatment B-80% Red+ 20% Full Spectrum

Treatment C-No Supplemental light

Tota

l Yie

ld (

Oz)

Lighting Treatment, each with 4 Blocks of sample data.Mean and Standar Error of the Mean are also plotted.

Block 1

Block 2

Block 3

Block 4

Mean

Standard DeviationstandardError of the Mean

Results- TYT

0

10

20

30

40

50

60

70

Tota

l Yie

ld in

Oun

ces

Lighting Treatment

Treatment A-100% Red2

Treatment B-80%Red +20% Full

Treatment C-No Light

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 Factors-Disease Pressure

Necrosis developed approximately 10 days after first transplants

No tissue analysisWilt? mildew?Virus?Abiotic?

Discussion-Contributing Factors-Disease 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 Cost/Sq Ft/Crop

Bales 24 2.50$ 60.00$ 30.00$ 0.13$ Soil (6 )2.8 cu ft bags 11.00$ 66.00$ 49.50$ 0.21$ Seeds 1/2 lb/1000 sds 6.50$ 3.25$ 3.25$ 0.01$ Fertilizer 6 lbs 1.20$ 7.20$ 7.20$ 0.03$ Electricity 468 kWh 0.10$ 49.00$ 49.00$ 0.20$ Nat. Gas 180 therms 0.71$ 127.80$ 127.80$ 0.53$ LED 60 diode Full Spectrum 8 24.00$ 192.00$ 6.00$ 0.03$ LED 200 diode Red Spectrum 28 68.00$ 1,904.00$ 60.00$ 0.25$ Labor 16 hrs 8.00$ 128.00$ 128.00$ 0.53$

Total 460.75$ 1.91$ IncomeSugar Snap Peas Harvested 9lbs 6.00$ 54.00$ 54.00$ 0.23$ Net Profit (Loss) (406.75)$ (1.68)$

Table 1. Expense Report- Winter Grown Sugar Snap Peas 2011- 224 sq Ft Greenhouse Space

19%

25%28%

28%

Expense Breakdown by Percent

growing components

lighting

heating

labor

Economic Analysis-Budget

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

25%

18%

19%

38%

Hypothetical Expense Breakdown

by Percentgrowing components

lighting

heating

labor

Future Work

Table 2. Hypothetical Expense Report- Winter Grown Sugar Snap Peas 2012- 224 sq. ft Greenhouse

Expense Item Number of Units Cost / unitTotal Cost Cost Per CropCost/Sq Ft/CropBales 24 2.50$ 60.00$ 30.00$ 0.13$ Seeds 1/2 lb/1000 sds 6.50$ 4.87$ 4.87$ 0.02$ Soil + Compost (6 )2.8 cu ft bags 11.00$ 66.00$ 33.00$ 0.14$ Fertilizer 6 lbs 1.20$ 7.20$ 7.20$ 0.03$ Electricity 116 kWh 0.10$ 12.06$ 12.06$ 0.05$ Nat. Gas 80 therms 0.71$ 56.80$ 56.80$ 0.24$ LED 90 diode Full Spectrum-2011 10 20.00$ 200.00$ 6.25$ 0.03$ LED 200 diode Red Spectrum-2011 20 54.00$ 1,080.00$ 33.75$ 0.14$ Labor 14 hrs 8.00$ 112.00$ 112.00$ 0.47$

Total 295.93$ 1.24$ IncomeSugar Snap Peas Harvested-Scenario #1 .5lb/ft =30lbs 6.00$ 180.00$ 180.00$ 0.75$ Net Profit /Loss (114.31)$ (0.49)$ Sugar Snap Peas Harvested-Scenario #2 .2lb/plant=144lbs 6.00$ 864.00$ 864.99$ $3.60Net Profit /Loss $570.68 $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• 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

Hort. Sci. 22:424–425.• Massa, Gioa G., H.H. Kim, R.M. Wheeler, and C.A. Mitchell. 2008. Plant Productivity in Response to LED Lighting. Hort. Science

43:1951-1955.• 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 Bioregenerative Life

Support Systems. Life Support Bioseph. Science. 5:119-128