Controlled environment agriculture, including greenhouses, vertical farms, and plant factories, has existed in the US for decades, especially for production of environmental horticultural crops like potted plants and bedding plants. As technologies advance, interest in controlled environment agriculture has risen. This option is now being considered as a viable method of producing other high value crops as well, such as vegetables and herbs. However, growers haven’t widely adopted these new technologies yet out of a concern over the expense. Supplemental lighting, and light-emitting diodes (LEDs) in particular, is one such technology where great advances have been made, but growers are slow to adopt.

With all the benefits that come from supplemental lighting, a set of researchers set out to help growers exploring controlled environment agriculture make educated decisions. This multi-disciplinary group of researchers was awarded a Specialty Crop Research Initiative (SCRI) grant from USDA NIFA in 2018 to study supplemental lighting in greenhouses. Lighting Approaches to Maximize Profits, or LAMP, is the title of this multi-state, collaborative project aimed at optimizing supplemental lighting needs in greenhouse applications.

Their mission statement reads:  We will help growers get more value out of their lighting systems by providing horticultural and economical information and tools to manage the lights for optimal crop growth and quality and to maximize the return on investment.

Jessica Tatro, Production Research and Development Manager at Pleasant View Gardens and one of the industry representatives on the LAMP advisory panel, commented, “Pleasant View Gardens utilizes supplemental and photoperiodic lighting to provide high-quality liners to the floriculture industry. We recognize the benefits of crop lighting but are continually looking for ways to maximize our current lighting systems to increase quality and/or reduce energy costs through different lighting strategies. As our lighting systems age, we are also interested in new lighting technology that could produce similar quality crops with reduced input costs.”

She added, “We are excited to be a member of Project LAMP and look forward to the research coming out of this group, specifically the decision-support programs and modeling software being developed around the economics of lighting, and the development of software and controllers to regulate how/when lights are run.”

Dr. Marc van Iersel from the University of Georgia leads the team and is accompanied by a cadre of agricultural economists, engineers, horticulturalists, extension specialists, and industry representatives. Many aspects of supplemental lighting will be evaluated, including energy informatics (improving efficiency by collecting, analyzing, and acting on information), photobiology (the effect of light on living organisms, in this case plants), engineering (optimal control algorithms, hardware to implement them, and imaging technologies to monitor growth) and even impact evaluation of the team’s efforts.

While supplemental lighting advancements have stimulated greater interest in food production in controlled environments, traditional crops grown in greenhouses (potted plants, bedding plants) stand to benefit from this research as well. Production time could be shortened and higher quality plants could result with the optimization of lighting. With that in mind, the LAMP team selected various annual and perennial ornamentals, such as rudbeckia, verbena, pansy and petunia, in addition to lettuce as the model crops for testing.

The team focuses strongly on the impacts of far red light. Previous research has confirmed that far red light triggers an elongation response in plants, such as stem elongation and leaf expansion. Newer research shows that a combination of red and far red light can be synergistic and may further enhance plant growth by stimulating a higher rate of photosynthesis – a total amount greater than applying each wavelength independently. These two phenomena are more apparent in small, young plants. So, one key objective of the LAMP project is to optimize red and far red wavelengths to encourage young seedlings to grow bigger faster to increase leaf area, since larger leaves enhance light capture. This allows the canopy to close sooner, and light waste is minimized.

Another lighting strategy to enhance growth is the employment of LEDs. For example, supplementing sunlight with LEDs can cut the rooting time of many crops, leading to a significant decrease in the production schedule. For those nervous about trying LEDs, propagation and young plant operations are a good place to start experimenting with them. Finished production, too, can benefit from supplemental lighting, with a two- to three-week shortened finish time. In this case, lighting can be cost effective if the producer is doing two or more crop turns in a production space, with the potential to get more turns.

The cost of lighting is a major concern to any operation. A large part of the LAMP project is dedicated to understanding the costs and benefits of LEDs, including lamp efficiency and efficacy and the amount of heat generated by LEDs vs. high-pressure sodium (HPS) lamps. The LAMP team plans to quantify this information and incorporate these calculations into a decision support tool to help growers decide which supplemental lighting system (LEDs, HPS, or no lights) is best for them. This should be available in the coming months on the LAMP home page.

For example, the heat generated by LEDs vs HPS lights is an important consideration and is being compared. High-pressure sodium lights generate a fair amount of radiant heat that is directed downward, towards the leaf surface, leading to an increase in the leaf surface temperature. LEDs, on the other hand, do not emit as much radiant heat; therefore, will more ambient heat be required?

Furthermore, the team is considering how a new cost calculator can be integrated into the current USDA ARS Virtual Grower software tool. This decision-support tool was developed many years ago to help growers estimate heating costs under various scenarios. It has since undergone several updates and revisions to increase its capacity and utility, including the addition of lighting systems. Members of the LAMP team include USDA-ARS researchers who plan to spearhead the next Virtual Grower update and incorporate a range of different lighting options.

This is just a sampling of the key objectives of the LAMP project. AmericanHort and its affiliate, HRI, in conjunction with like-minded organizations such as the American Floral Endowment, supported funding of this research through the USDA NIFA Specialty Crop Research Initiative (SCRI) granting program.

For more information, please visit the LAMP team website or follow the project on Facebook.