Greenhouse Supplemental Light Quality for Vegetable Nurseries

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1 Greenhouse Supplemental Light Quality for Vegetable Nurseries Chieri Kubota and Ricardo Hernández The University of Arizona LED Symposium (Feb 20, 2015) Supplemental lighting from late fall to early spring Large commercial greenhouse nurseries are located in Canada (BC and Ontario) Typical practices 18 hour illumination from midnight to 6 pm at around mol m 2 s 1 PPF. No or limited illumination over pepper seedlings Overhead HPS lamps 1

biologically active radiation (300-800 nm) Light quality effect on plant growth can be

2 Leaf photosynthesis (quantum efficiency) After McCree (1972) and Sager (1988) Photosynthetically Active Radiation (PAR, nm) UV Blue Green Red Far red Plant biologically active radiation ( nm) Light quality effect on plant growth can be photosynthetic or photomorphogenic. Plant Growth Rate Plant Photosynthetic Rate = Leaf Photosynthetic Rate x Leaf Area 2

Supplemental FR Lighting for Baby Leaf Lettuce under Artificial Lighting Supplemental far red light (700 800 nm) significantly increased the biomass of baby lettuce plants by 28%.

3 Supplemental FR Lighting for Baby Leaf Lettuce under Artificial Lighting Supplemental far red light ( nm) significantly increased the biomass of baby lettuce plants by 28%. This was due to the increased light interception caused by enhanced leaf elongation. Similar observation by Stutte et al. (2009). 28% in dry mass (Li and Kubota, 2009) LED Research Objectives at UA 1. To conduct research necessary for vegetable nurseries to adopt LED lighting technology Phase I: Light quality requirement for LED lighting Phase II: Side by side comparison with the conventional HPS lighting 2. To explore new LED applications beneficial to vegetable nurseries Low intensity applications of red and far red LEDs for controlling plant morphology Pulsed lighting 3

4 Blue vs. Red light Red light has the highest quantum efficiency (for single leaf) (e.g., McCree, 1972) Blue light increases stomatal opening (conductance) and thereby photosynthetic gas diffusion (e.g., Hogewoning et al., 2010) Some species/cultivars (e.g., lettuce) cannot grow under red light (small % of blue light needs to be added) (e.g., Dougher and Bugbee, 2001) Blue light reduces leaf size and internode length, making plants more compact. This possibly reduces whole plant photosynthetic rate by reducing the light interception or increases canopy photosynthetic rate by increasing light penetration in the plant canopy. Phase I: Supplemental LED blue:red photon flux ratios for vegetable transplants Objective To examine different supplemental LED Blue:Red photon flux ratios for growth and development of vegetable transplants. Hypothesis Blue photon flux requirement is depending on the background solar DLI (high DLI vs. low DLI). DLI: daily light integral, moles per sq meter per day (mol m 2 d 1 ) 4

2/19/2015 Phase I: Materials & Methods Supplemental PPF: 55 μmol m 2 s 1 for 18 hours (2am to 8pm)

Plant materials: Cumlaude cucumber, Komeett and Aloha tomato, and Fascinato pepper [young seedling stage]

wavelength: Blue = 455 nm, Red = 661 nm Side by side comparisons of supplemental LED lighting under

5 2/19/2015 Phase I: Materials & Methods Supplemental PPF: 55 μmol m 2 s 1 for 18 hours (2am to 8pm) Supplemental DLI: 3.5 mol m 2 d 1 by LED light. Plant materials: Cumlaude cucumber, Komeett and Aloha tomato, and Fascinato pepper [young seedling stage] R treatment B4:R96 treatment B16:R84 treatment 4% 16% 96% 84% Control NO SUPPLEMENTAL N LIGHT Peak wavelength: Blue = 455 nm, Red = 661 nm Side by side comparisons of supplemental LED lighting under different background solar DLIs Minimum DLI for vegetable High solar DLI: mol m 2 d 1 transplants: 13 mol m 2 d Low solar DLI: 5 9 mol m d Phase I: Materials & Methods 5

2/19/2015 Phase I: Results Effects of supplemental LED light Cucumber seedlings

7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 LED supplement P < 0.0001 P < 0.

I: Results Effects of B:R ratios of supplemental LED light 55 μmol m 2 s 1

tomato and pepper seedlings (both DLIs) & cucumber seedlings (high DLI) 4% = 96% =

low solar DLI conditions dry mass, leaf count, and leaf area decreased with the

6 2/19/2015 Phase I: Results Effects of supplemental LED light Cucumber seedlings shoot dry wt DRY RESPONSE (16MASS days after seeding) Shoot dry mass (g) control LED supplement P < P < High DLI Low DLI SOLAR DAILY LIGHT INTEGRAL Hernández and Kubota (2014) Phase I: Results Effects of B:R ratios of supplemental LED light 55 μmol m 2 s 1 supplemental lighting, high DLI = and low DLI = 5 9 mol m 2 d 1 Growth of tomato and pepper seedlings (both DLIs) & cucumber seedlings (high DLI) 4% = 96% = 16% 84% Growth of cucumber seedlings (low DLI) 4% > 96% > 16% Cucumber 84% Under low solar DLI conditions dry mass, leaf count, and leaf area decreased with the increase of blue photon flux for cucumber seedlings. Blue photon flux Hernández and Kubota (2014) 6

7 Conclusion Phase I LED supplemental lighting enhanced plant growth even under high background solar DLI conditions. red supplemental LED lighting is recommended for cucumber seedlings and is acceptable for tomato and pepper seedlings. [No need to consider including blue light under the range of solar DLI examined (5 23 mol m 2 d 1 )]. Under much lower solar DLI (0 5 mol m 2 d 1 ) or when LED lighting contributes to the majority of DLI, addition of blue light is expected to become more critical. Responses to LED light quality are species specific. Phase II: Comparison between LED and HPS supplemental lighting Objective To find plant responses of vegetable transplants (mature seedlings) grown side by side under LED and HPS supplemental lighting Compared electrical efficiencies between HPS and LED supplemental lighting 7

2/19/2015 Materials & methods: treatments Supplemental PPF: 55 60 μmol m 2 s 1 for 18 hours (2am to 8pm)

Plant materials: Cumlaude cucumber, Komeett tomato, and Fascinato, Orangela, PP0710 and Viper pepper Treatment

8 2/19/2015 Materials & methods: treatments Supplemental PPF: μmol m 2 s 1 for 18 hours (2am to 8pm) Supplemental DLI: mol m 2 d 1 by LED light. Plant materials: Cumlaude cucumber, Komeett tomato, and Fascinato, Orangela, PP0710 and Viper pepper Treatment Red LED Treatment Blue LED Treatment 600W HPS 5% Red = 632 nm peak Blue = 443 nm peak 53% 42% Background solar DLIs Low solar DLI: mol m 2 d 1 Phase III: Materials & methods 8

9 Unfair comparison of energy consumption of LEDs vs. HPS in small scale research settings Traditional electric lighting (eg, HPS) LED light 9

10 2/19/2015 Phase II: Results Growth and Energy LED vs. HPS supplemental lighting Plant growth (biomass) for tomato, cucumber, and pepper (except some cultivars): 20 30% increase under HPS (due to increase in leaf temperature (+1.0 C) 5% = < Red LEDs 53% 42% HPS Blue LEDs Supplemental lighting efficiency (plant grams dry mass per kwh used for lighting): 6 17% increase under HPS 5% < < Red LEDs 53% 42% HPS Blue LEDs (Hernandez and Kubota 2014; 2015) Estimation of energy use (LEDs and HPS with reported light conversion efficiency for a 1 ha commercial scale use at 57 mol m 2 s 1) Areal Power Consumption (W m 2) Fixture Growth Efficiency (g kwh 1) Lamp type Areal Power Consumptionx (W m 2) (Cucumber, sdli = 4) Fixture Growth Efficiency (g kwh 1) Red LEDs 85% 1.7z Blue LEDs 85% 1.9z W HPS 81% 1.6y z Nelson x Effective PAR conversion photons efficiency (% over total) ( mol J 1) y Manufacturer and Bugbee (2014); catalogue value Aldrich and Bartock (1994) with some modifications Hernández and Kubota (2015) 10

LEDs Degree of leaf curling was mitigated significantly by blue suppl. LEDs for pepper (four cultivars) Hernández et al.

11 Phase II: Results Morphology LED vs. HPS supplemental lighting Hypocotyl length for tomato: significant reduction under blue or red suppl. LEDs Hypocotyl length for cucumber: 38% reduction under red suppl. LEDs Hypocotyl length for pepper: Significant reduction under blue suppl. LEDs Degree of leaf curling was mitigated significantly by blue suppl. LEDs for pepper (four cultivars) Hernández et al. (2014); Hernández and Kubota (2015) Blue LEDs HPS Red LEDs Pepper leaf curling index Conclusion Phase II Growth enhancement under HPS lighting was observed for all species examined, mainly due to the increased radiative heat transfer between the lamp and plants. Responses to LED light quality were species and cultivar specific. red and blue supplemental lighting might have unique applications for controlling morphology of cucumber and pepper, respectively. 11

New LED Application End of Day Far red Light Treatment Classic

(photoperiod) determines stem elongation during the successive night

chemical control of stem or hypocotyl elongation EOD FR Application for

12 New LED Application End of Day Far red Light Treatment Classic photobiology (phytochrome response) Light quality at the end of day (photoperiod) determines stem elongation during the successive night (dark period) EOD far red light >> taller plants Effective at VERY low light intensity Responses are light quality dependent (i.e., P fr /P total ) Potential non chemical control of stem or hypocotyl elongation EOD FR Application for Vegetable Rootstock Longer hypocotyls are needed in vegetable grafting (rootstock) Greater grafting speed Keeping grafted unions above the soil line when they are transplanted. Suitable for production of grafted cuttings Adequate hypocotyl length for grafting cucurbit rootstock is ~7 cm. 12

End of day light quality treatment for controlling

Far red Dose (0 9000 mol/m 2 /d) Tomato rootstock

Squash hypocotyl (mm) ~3 mol/m 2 /s for 24 min

2 /d) (Chia and Kubota, 2010; Kubota et al.

13 End of day light quality treatment for controlling morphology of vegetable seedlings in greenhouse EOD Far red Dose ( mol/m 2 /d) Tomato rootstock seedlings EOD Far red Dose ( mol/m 2 /d) Squash hypocotyl (mm) ~3 mol/m 2 /s for 24 min Squash rootstock seedlings EOD Far red Dose ( mol/m 2 /d) (Chia and Kubota, 2010; Kubota et al., 2011) Moving Far Red Lighting New application method High power FR LEDs?? m/s 13

Moving Far Red Lighting New application method LED bar Speed = (Average PF) x (Effective length) (Target Dose) Average PF was found by the FR photon flux distribution at the horizontal

8 mm/s or slower in order to meet the target dose of 4000 mol m 2. (Yang et al., 2012) End of Day FR Treatment with Moving fixture vs.

14 Moving Far Red Lighting New application method LED bar Speed = (Average PF) x (Effective length) (Target Dose) Average PF was found by the FR photon flux distribution at the horizontal plane 5 cm below the FR LED bar. Under the following conditions: Average PF = 4.5 mol m 2 s 1 Effective length = 700 mm The LED bar s traveling speed must be 0.8 mm/s or slower in order to meet the target dose of 4000 mol m 2. (Yang et al., 2012) End of Day FR Treatment with Moving fixture vs. Stationary fixture (A proof of concept) Main factor Hypocotyl (mm) EOD FR treatment and LED fixture type (dose = 4000 mol/m 2 /d) Moving fixture (0.8 mm/s) Stationary fixture (11 min at 6.2 mol/m 2 /s) Non treated control 82.2 a 89.6 a 53.0 b (Yang et al., 2012) 14

End of day red lighting? Using a similar approach, EOD red light treatment has been evaluated as a nonchemical means to prevent stem elongation of vegetable seedlings.

15 End of day red lighting? Using a similar approach, EOD red light treatment has been evaluated as a nonchemical means to prevent stem elongation of vegetable seedlings. So far, no clear impact on hypocotyls was found. Acknowledgements Jose Pablo Santana Polung Chia Mark Kroggel Neal Barto Zhenchao Yang Murat Kacira CCS, Inc. (Kyoto, Japan) ORBITEC (WI, USA) Bevo Farms USDA SCRI 15

Developing LED Lighting Technologies and Practices for Greenhouse Crop Production

Developing LED Lighting Technologies and Practices for Greenhouse Crop Production C.A. Mitchell 1, A.J. Both 2, C.M. Bourget 3, J.F. Burr 1, C. Kubota 4, R.G. Lopez 1, G.D. Massa 1, R.C. Morrow 3, E.S.