Applications of supplemental LED lighting in vegetable propagation - PowerPoint PPT Presentation

Applications of supplemental LED lighting in vegetable propagation Chieri Kubota and Ricardo Hernandez The University of Arizona SCRI LED Stakeholders Meeting (2/2/2012)

www.ag.arizona.edu/ceac School of Plant Sciences Department of Ag. and Biosystems Engineering Dr. Gene Giacomelli Dr. Pat Dr. Chieri Kubota Dr. Murat Kacira Dr. Merle Dr. Roger Huber (ABE/PLS) Rorabaugh (PLS/ABE) (ABE) Jensen (ENTO) (PLS) (PLS)

Kubota Research Areas • Value added crop production – Enhancing health promoting characteristics by controlled environment • Sustainable crop production technology – Vegetable grafting – Soilless strawberry culture • New Controlled Environment technology development – LED lighting in greenhouse – In vitro controlled environment

Greenhouse vegetable nurseries • Greenhouse vegetable seedlings for hydroponics are high ‐ value products – Crop value (e.g., $1.00 to $1.50 per grafted tomato seedling) • Making a scheduled delivery of high quality seedlings is the highest priority in propagation. • Supplemental lighting as a key winter CE technology • Even in the sunny Southwest, supplemental lighting has been used in winter Photo from Bevofarms.com

UA LED Research Objectives 1. To conduct research necessary for vegetable propagators to adopt LED lighting technology – Light quality requirement for LED lighting – Side ‐ by ‐ side comparison with the conventional HID lighting – Testing new fixture designs and application methods 2. To explore new LED applications beneficial to vegetable propagators – Low intensity applications of red and far ‐ red LEDs for controlling plant morphology

LED light quality requirement for vegetable seedlings under different solar light intensities (DLIs) • Tomato, cucumber and bell pepper • Plug seedlings stage (except cucumber) • 18 hours supplemental lighting photoperiod • 55  mol m ‐ 2 s ‐ 1 PPF on average over canopy • Red and blue LEDs – 660 and 455 nm LED with 20 nm FWHM – 0, 4, and 16% blue/PAR photon flux ratios – 0, 2, and 9  mol m ‐ 2 s ‐ 1 blue photon flux (400 ‐ 500 nm) • Two different background solar DLIs (compared side ‐ by ‐ side) – 25% shade (high DLIs) vs. 52%+52% shade (low DLIs)

Light quality (solar + LEDs) 16%B treatment under high DLI 16%B treatment under low DLI Solar PPF = 1064  mol m ‐ 2 s ‐ 1 Solar PPF = 345  mol m ‐ 2 s ‐ 1 LED PPF = 55  mol m ‐ 2 s ‐ 1 LED PPF = 55  mol m ‐ 2 s ‐ 1 (Composed from multiple scans inside greenhouse at around noon)

Tomato responses High DLI = 19.4 ± 1.9 mol m ‐ 2 d ‐ 1 Low DLI = 8.9 ± 0.9 mol m ‐ 2 d ‐ 1 (Hernandez and Kubota, 2012)

Cucumber experiment

Objective 1. Research necessary for vegetable propagators to adopt LED lighting technology Next step • Complete our “phase I” by testing bell pepper response to varied blue PF rates under different DLIs • Move to Phase II – Using a commercially applicable LED design – Compare the LED light with the conventional HPS light • Plant responses (growth and flowering response) • Electric power use

UA LED Research Objectives 1. To conduct research necessary for vegetable propagators to adopt LED lighting technology – Light quality requirement for LED lighting – Side ‐ by ‐ side comparison with the conventional HID lighting – Testing new fixture designs and application methods 2. To explore new LED applications beneficial to vegetable propagators – Low intensity applications of red and far ‐ red LEDs for controlling plant morphology

Supplemental Far ‐ Red Light Potential Applications • Far ‐ Red (700 ‐ 800 nm) LEDs are a unique light source for plant applications • Applications in greenhouse – Extending stem/hypocotyl of plants (cut flower and seedlings) – Expanding leaf and enhancing growth rate (leafy greens) – Photoperiodic lighting (studied at MSU) • Applications in growth chamber (plant factory) – Extending stem/hypocotyl of plants (seedlings) – Expanding leaf and enhancing growth rate (leafy greens)

End ‐ of ‐ Day Light Treatment • Classic photobiology (phytochrome response) • Light quality at the end of day (photoperiod) determines stem elongation during the successive night (dark period) – EOD red light >> shorter plants – EOD far ‐ red light >> taller plants • Effective at VERY low light intensity • Responses are light quality dependent (i.e., P fr /P total ) • EOD ‐ FR: Limited applications in the past (there was no pure FR light source). • EOD ‐ FR: Potential non ‐ chemical control of stem or hypocotyl elongation

EOD ‐ FR Application for Vegetable Rootstock • Longer hypocotyls are needed in vegetable grafting – Greater grafting speed – Keeping grafted unions above the soil line when they are transplanted. Adequate hypocotyl length for grafting cucurbit rootstock is ~7 cm.

End ‐ of ‐ day light quality treatment for controlling morphology of vegetable seedlings in greenhouse EOD Far ‐ red Dose (0 – 9000  mol/m 2 /d) Squash hypocotyl (mm) Tomato rootstock seedlings EOD Far ‐ red Dose (0 – 9000  mol/m 2 /d) ~3  mol/m 2 /s ~3  mol/m 2 /s for 24 min for 24 min EOD Far ‐ red Dose (  mol/m 2 /d) Squash rootstock seedlings (Chia and Kubota, 2010; Kubota et al., 2011)

Moving Far ‐ Red Lighting New application method High power FR LEDs ?? m/s

Moving Far ‐ Red Lighting New application method LED bar (Average PF) x (Effective length) Speed = (Target Dose) 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 . FR photon flux distribution at the horizontal plane 5 cm below the FR LED bar.

End ‐ of ‐ Day FR Treatment with Moving fixture vs. Stationary fixture (proof of concept study) Test unit for moving fixture with programmable speed control (designed by Murat Kacira)

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) 82.2 a Stationary fixture 89.6 a (11 min at 6.2  mol/m 2 /s) Non ‐ treated control 53.0 b Traveling speed (application times) of moving fixture 0.8 mm/s (one application per EOD) 73.6 a 3.1 mm/s (four applications per EOD) 90.9 a

Irrigation boom used in greenhouse

Objective 2. To explore new LED applications beneficial to vegetable propagators • We successfully demonstrated the applications of EOD far ‐ red LED lighting to elongate the stem of vegetable rootstock seedlings. • Next step: Using a similar approach, EOD red light treatment will be evaluated as a non ‐ chemical means to prevent stem elongation of vegetable seedlings.

Acknowledgements • Mark Kroggel (UA, • CCS, Inc. (Kyoto, Japan) CEAC) • ORBITEC (WI, USA) • Polung Chia (UA, CEAC) • USDA SCRI • Zhenchao Yang (NW A&F, China) • Murat Kacira (UA, CEAC) • Neal Barto (UA, CEAC) Greensys 2011, Greece