Developing LED LightingTechnologies and Practices for Greenhouse Crop Production

A USDA NIFA Specialty Crops Research Initiative (SCRI) project began experimentally during the second quarter of 2011 involving collaborations among the University of Arizona, Michigan State University, Purdue University, and Rutgers University, as well as the Orbital Technologies Corporation (ORBITEC), CCS, Inc. in Japan, commercial greenhouse growers, and energy industries throughout the United States.  The focus of the project is to develop hardware, practices, and standards for economically viable, energy-efficient use of light-emitting diodes (LEDs) for diverse applications in the greenhouse industry. LEDs are solid state, physically robust, very long-lived, and selectable to emit narrow-spectrum wavelengths matching pigment absorption for desired plant responses. Waste heat is removed separately from photon-emitting surfaces, so emitters can be placed close to crop surfaces without risk of overheating plant tissues. The hypothesis being tested is that significantly less electrical energy is needed to achieve the same or better plant responses using LEDs than with traditional greenhouse lighting systems, and that LED lighting systems will be economically viable within reasonable break-even times over the long term.  New LED system designs being tested minimize shading of crops from solar irradiation as the sun tracks across greenhouses. LED systems will be used to control photoperiodic floral initiation and development as well as photomorphogenic development of a variety of bedding-plant and vegetable-transplant species, to promote rooting of cuttings and root development of grafted vegetable and ornamental transplants, and to provide side and intracanopy supplemental lighting for high-wire greebhouse tomato production.  Metrics of performance related to flowering, transplant vigor, and fruit yield using LED lighting will be compared with controls using traditional lighting technologies and correlated with metrics of electrical energy utilization and daily light integral.  Following preliminary testing at the academic institutions, commercial partners will field test LED prototype hardware in production settings. Each laboratory and commercial stakeholder will contribute data and information for economic and life-cycle analyses, and best practices will be developed to improve LED hardware design prototypes and operation.  Procedures will be established for comparative, standardized testing of LED lighting arrays for the greenhouse industry.  A robust education / outreach program is being developed for stakeholders and the general public, and an academic training program is being developed at the Universities for future academic leaders in applied horticultural lighting.