Source: UNIVERSITY OF GEORGIA submitted to NRP
INCREASING THE COST-EFFECTIVENESS OF LED LIGHTING IN CONTROLLED ENVIRONMENT AGRICULTURE
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1011550
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 28, 2016
Project End Date
Sep 30, 2021
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
Horticulture
Non Technical Summary
Light emitting diodes (LEDs) have received a great deal of attention in recent years. Whether LEDs are economically feasible for supplemental lighting in greenhouses is still under debate. Economic benefits of LEDs can be increased by taking advantage of some of their unique properties. One of those properties is that the brightness of LEDs can be precisely and quickly adjusted. This characteristic is unique to LEDs and can be used to adjust the light output in real-time and based on the crop's ability to use that light. We want to use this capability to help growers reduce their electricity costs, while producing high quality crops. Another unique property of LEDs is that they can provide specific wavelengths (colors) of light. We want to take advantage of this by using far-red LEDs to induce flowering in short-day plants, even when grown under long-day conditions. Our overarching goal is to use the unique properties of LEDs to develop new production methods that will increase their cost-effectiveness. Our work will 1) give growers better control over crop growth, 2) lower the costs of supplemental lighting, and 3) allow growers to precisely control flowering of short-day crops.
Animal Health Component
40%
Research Effort Categories
Basic
40%
Applied
40%
Developmental
20%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2031430102030%
2032199102070%
Knowledge Area
203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1430 - Greens and leafy vegetables; 2199 - Ornamentals and turf, general/other;

Field Of Science
1020 - Physiology;
Goals / Objectives
Goal 1: Control of LED lighting using an adaptive control system that provides supplemental light based on the crop's ability to use that light. Giving plants only the amount of light they can use efficiently will greatly reduce electricity costs.Goal 2: We will use red and/or far-red LEDs to control flower initiation in short-day plants, giving growers better control over crop timing and reducing production costs.
Project Methods
Objective 1: Adaptive control of supplemental lighting. Monitoring quantum yield and electron transport rate of different bedding plant species exposed to a wide range of different light levels. These studies will allow us to determine the relationship between light level and quantum yield. That relationship will allow us to predict how efficiently different species will be able to use supplemental light, depending on the amount of sunlight.Adaptive lighting of greenhouse crops. We will conduct greenhouse trials with different bedding plant species (petunia, geranium, salvia) to develop optimal production protocols that minimize required LED lighting, while producing high quality crops. In these studies, we will compare plant growth and quality of crops grown with three different lighting treatments: 1) no supplemental light, 2) supplemental light from LEDs, and 3) supplemental light from LEDs controlled using an adaptive lighting controller. Power consumption by the LEDs will be continuously monitored. Plant growth and quality will be determined based on dry weight, plant height, compactness (weight/height), flower number, and flower density (no. of flowers/weight). We expect that adaptive control of lighting can greatly reduce the electricity costs of supplemental lighting, without a negative impact on plant quality.Objective 2. Controlling flowering of short-day plants. Flowering of short-day plants is controlled by a plant chemical called phytochrome, which is used to 'measure' the night duration. Phytochrome can exist in two forms: red-light absorbing phytochrome (Pr) and far-red light absorbing phytochrome (Pfr). When Pr receives red light, it is converted to Pfr. Pfr can be converted back to Pr in by exposure to far-red light or by prolonged periods of darkness. The conversion of Pfr to Pr in the dark is a slow process: the longer a plant has been in the dark, the less Pfr is left. Plants determine the duration of the night based on how much Pfr is left. For short day plants to flower, the level of Pfr in the plants needs to drop below a particular threshold, something that normally only happens when the nights are long. However, by giving plants far-red light (730 nm), we can greatly speed up the conversion of Pfr into Pr, which should trigger a flowering response in short-day plants without the need for black cloth.We will use far-red LEDs to control flowering of short-day plants. An unwanted side effect of far-red light may be stretching of the plants, so it is critical to determine the lowest effective dose of far-red light. We will determine the required intensity and duration of far-red light required to trigger flowering in multiple short-day species (African marigold, chrysanthemum, and poinsettia) under long day conditions. We will also determine the minimum number of nights with far-red light needed to induce flowering. To conduct these studies, we have built an indoor crop production system, where we can control the photoperiod, as well as the intensity and duration of supplemental far-red light. We plan to include red light in this system as well. We currently have a total of 48 growing sections (30 x 60 cm2) available for these studies. We will collect data on the number of days to flowering, number of flowers, plant height, and dry weight. These data will be used to quantify compactness and flower density.These studies will be used to develop guidelines to make optimal use of far-red LEDs for controlling flowering of short-day plants, giving growers better control over their short-day crops. If this technology is shown to be effective, we expect that future LED grow lights will have far-red LEDs built-in. PhytoSynthetix, one of our industry collaborators, is already planning to incorporate far-red LEDs into their grow lights. Those far-red LEDs can be controlled separately from the LEDs used to provide photosynthetic lighting.

Progress 10/28/16 to 09/30/21

Outputs
Target Audience:Commercial greenhouse and controlled environment agriculture industry, as well as researchers who work in controlled environment agriculture. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Seven graduate students, three undergraduates, and one technician participated in this project and were exposed to the latest in LED technology and had the opportunity to study plant responses to different lighting strategies. The undergraduate got hands-on research experience. All graduate students had the opportunity to present their research at the Annual Conference of the American Society for Horticultural Science, as well as LightSym 2021, an international symposium. How have the results been disseminated to communities of interest?Results have been published in peer-reviewed journal articles, trade journal articles, and have been presented at multiple scientific and grower meetings, as well as webinars. An update was provided to the USDA-NIFA-SCRI advisory council. Research updates also are available on the website www.hortlamp.org. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We were able to determine suppplemental lighting needed for individudal crops based on their ability to use that lighting in order to reduce electricity costs, as well as determined best crop timing for reduction in production costs. An online lighting cost calculator tool was developed to allow greenhouse growers to estimate the cost of supplemental lighting, based on their specific conditions.

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Jayalath, T.C. and M.W. van Iersel. 2021. Canopy size and light use efficiency explain growth differences between lettuce and mizuna in vertical farms. Plants 10(4): 704. (In special issue on The effects of LED light spectra and intensities on plant growth). https://doi.org/10.3390/plants10040704.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Legendre, R., N. Basinger, and M.W. van Iersel. 2021. Low-cost chlorophyll fluorescence imaging for stress detection in plants. Sensors 21(6): 2055 (in special Issue on Fluorescence Biosensing). https://doi.org/10.3390/s21062055.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Casamali, B., M. van Iersel, and D. Chavez. 2021. Plant growth and physiological responses to improved irrigation and fertilization management for young peach trees in the Southeastern United States. HortScience 55:336-346. https://doi.org/10.21273/HORTSCI15505-20.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Liu, J. and M.W. van Iersel. 2021. Photosynthetic physiology of blue, green, and red light: light intensity effects and underlying mechanisms. Frontiers in Plant Science 12: 619987. (In special Issue on Crop Physiology under LED LIghting) https://doi.org/10.3389/fpls.2021.619987.


Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Commercial greenhouse and controlled environment agriculture industry, as well as researchers who work in controlled environment agriculture. Changes/Problems:Some research delays due to Covid-19. However, this freed up time for student to prepare manuscript, which helped them make progress towards graduation. What opportunities for training and professional development has the project provided?In 2020, seven graduate students, oneundergraduate, and one technician particpated in this project and were exposed to the latest in LED technology and had the opportunity to study plant responses to different lighting strategies. The undergraduategot hands-on research experience. All graduate students had the opportunity to present their research at the on-line nnual Conference of the American Society for Horticultural Science. How have the results been disseminated to communities of interest?Results have been published in peer-reviewed journal articles and have been presented at a scientific meeting (American Society for Horticultural Science). Research updates also areavailable on a the website www.hortlamp.org. What do you plan to do during the next reporting period to accomplish the goals?We are working on improved algorithms to control lighting and will develop both hardware and software to do so. We will also focus on two key metrics for optimal crop production: 1) light interception by crops and its dependence on lighting and 2) light use efficiency (how much biomass is produced per mol of light hitting the canopy).

Impacts
What was accomplished under these goals? The main accomplishment in 2020 was our workfocused on exposing plants to eitehr short- or long-term fluctuations in light levels. We have shown that lettuce can tolerate short-term fluctuations in light very well. The practical implication of this is that it allows growers to provide supplewmental light preferentially when electricty costs are low. In addition, lettuce tolrates day-to-day fluctuations in the daily light integral quite well. That means that greenhouse growersdon not necessarily need to strivve for the same daily light integral each dauy. A relatively high DLI one, followed by a lower DLI the next day does not have negative impacts on growth.

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Elkins, C. and M.W. van Iersel. 2020. Longer photoperiods with the same daily light integral increase daily electron transport through photosystem II in lettuce. Plants 9, 1172 (in Special Issue on Applications and Advances in Artificial Light for Horticulture and Crop Production). https://doi.org/10.3390/plants9091172
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Elkins, C. and M.W. van Iersel. 2020. Longer photoperiods with the same daily light integral improve growth of Rudbeckia seedlings in a greenhouse. HortScience 55, 16761682. https://doi.org/10.21273/HORTSCI14902-20
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Elkins, C. and M.W. van Iersel. 2020. Supplemental far-red LED light increases growth of Digitalis purpurea seedlings under sole-source lighting. HortTechnology 30, 564569. https://doi.org/10.21273/HORTTECH04661-20
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Palmer, S. and M.W van Iersel. 2020. Longer photoperiods with the same daily light integral increase growth of lettuce and mizuna under sole-source LED lighting. Agronomy 10, 1659 (in Special Issue on Role of Vertical Farming in Modern Horticultural Crop Production). https://doi.org/10.3390/agronomy10111659
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Mosharafian, S., S. Afzali, J.M. Velni, and M.W. van Iersel. 2020. Development and implementation of a new optimal supplemental lighting control strategy in greenhouses. Proceedings of the ASME Dynamic Systems and Control Conference, 8 p


Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Commercial greenhouse and controlled environment agriculture industry, as well as researchers who work in controlled environment agriculture. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?In 2019, seven graduatestudents, two undergraduates, and one technician particpated in this project and were exposed to the latest in LED technology and had the opportunity to study plant responses to different lighting strategies. The two undergraduates got hands on research experience. One of these students has since joined my lab as a MS student. How have the results been disseminated to communities of interest?Results have been published in peer-reviewed journal articles and have been presented at a scientific meeting(American Society for Horticultural Science) and grower meeting(Cultivate). Information also is availab;le on a new website www.hortlamp.org. What do you plan to do during the next reporting period to accomplish the goals?We are working on improved algorithms to control lighting and will develop both hardware and software to do so. We will also focus on two key metrics for optimal crop production: 1) light interception by crops and its dependence on lighting and 2) light use efficiency (how much biomass is produced per mol of light hitting the canopy).

Impacts
What was accomplished under these goals? Goal 1: Control of LED lighting using an adaptive controlsystem that provides supplemental light based on the crop's ability to use that light.We have tested a range of different lighting strategies, including extending the photoperiod and providing lower instantaneous light levels. We have found that this can increase growth of both leafy greens and some ornamental species. The underlying rewason is that plants can use light more efficiently when provided at lower intensities. Goal 2: We will use red and/or far-red LEDs to control flower initiation in short-day plants: No progress, this doesn't appear to work in a way that produces crops of acceptable quality. We did find that far-red light can be used to enhance growth of leafy greens.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Weaver, G.M., M.W. van Iersel, and J. Mohammadpour Velni. 2019. A photochemistry-based method for optimising greenhouse supplemental light intensity. BioSystems Engineering 128:123-137.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Weaver, G. and M.W. van Iersel. 2019. Photochemical characterization of greenhouse-grown lettuce (Lactuca sativa L. Green towers) with applications for supplemental lighting control. HortScience 54:317-322.
  • Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Weaver, G. and M.W. van Iersel. 2020. Longer photoperiods with adaptive lighting control can improve growth of greenhouse-grown Little Gem lettuce (Lactuca sativa). HortScience
  • Type: Theses/Dissertations Status: Published Year Published: 2019 Citation: Weaver, G. and M.W. van Iersel. 2019. Lighting control strategies for improved photochemical efficiency in controlled-environment agriculture.


Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Commercial greenhouse and controlled environment agriculture industry, as well as researchers who work in controlled environment agriculture. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?During 2018, six graduates students, four undergraduates, and one technician particpated in this project and were exposed to the latest in LED technology and had the opportunity to study plant responses to different lighting strategies. Two of the undergraduates got hands on research experience. How have the results been disseminated to communities of interest?Results have been published in peer-reviewed journal articles and conference proceedings and have been presented at scientific meetings (Controlled Environment Technology and Use, American Society for Horticultural Science) and grower meetings (Cultivate). What do you plan to do during the next reporting period to accomplish the goals?We will continue to investigate plant morphological and physiuological response to light spectrum, specifically the addition of far-red light. We will also model plant responses to different supplemental lighting strategies, followed by trials to evaluate those models. We will increasingly collaborate with engineers and economists to faciltiate adoiption of the most cost-effective supplemental lighting methods by the controlled environment agriculture industry.

Impacts
What was accomplished under these goals? Goal 1: Control of LED lighting using an adaptive controlsystem that provides supplemental light based on the crop's ability to use that light. We have tested the adaptive lghting control system for the production of both leafy greens (lettuce) and ornamental seedlings (rudbeckia and snapdragon). Both types of crops perform well under the adaptive lighting system, which can provide consistent light levels to the crop, both on a short-term basis and from day-to-day. We have shown the supplemental lighting can be controlled accurately either based on levels of incident sunlight or based on physiuologocal parameters of the crop (specifically linear electron transport through photosystem II, a measure of the rate of the light reactions of photosyntheisis. We have laos shown that providing the same total amount of light, but spread out over longer photoperiods (the period each day that the palnts receive light) can increase cropo growth by up to 30%. This has important practical implications: growers can increase crop growth without using more electricity. At the same time, because instantaneous amounts of supplemental light are lower with longer photoperiods, growers can install fewer lights, reducing the capital expenses of supplemental lighting systems. Goal 2: We will use red and/or far-red LEDs to control flower initiation in short-day plants Chrysanthemum morifolium (chrysanthemum) is a popular short-day plant grown in summer months for fall markets. Although often grown in summer, chrysanthemum requires long nights for flowering. Using narrow bandwidth far-red (730 nm) light emitting diodes (LEDs) to induce flowering mediated through phytochrome photoreceptors, instead of physical darkening with opaque black cloth, could reduce production costs and increase profits for growers. We tested whether200 min of night interuptionat three different times (beginning, middle, or end) during skotoperiods with a range of red:far-red ratios, resulting in a range phytochrome-photoequilibriums (PPE) of 0.3 to 0.8.Plants receiving night interuptionin the middle of the night flowered faster, had more inflorescences, and higher flowering percentages compared to plants receiving night iinteruptionat the beginning or end of the night.

Publications

  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Zhen, S. and M.W. van Iersel. 2018. Far-red light enhances photochemical efficiency in a wavelength-dependent manner. Physiologia Plantarum https://doi.org/10.1111/ppl.12834.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Weaver, G.M. and M.W. van Iersel. 2018. Modeling energy-efficient lighting strategies for petunia and impatiens using chlorophyll fluorescence and historical weather data. Proceedings of the SNA research conference 62:29-34.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Watson, R., M.-C. Boudreau, and M.W. van Iersel. 2018. Simulation of greenhouse energy use: an application of energy informatics. Energy Informatics 1:1.
  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Weaver, G. and M.W. van Iersel. 2019. Photochemical characterization of greenhouse-grown lettuce (Lactuca sativa L. Green towers) with applications for supplemental lighting control. HortScience (in press).
  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Weaver, G.M., M.W. van Iersel, and J. Mohammadpour Velni. 2019. A photochemistry-based method for optimizing greenhouse supplemental light intensity. Submitted to BioSystems Engineering.


Progress 10/28/16 to 09/30/17

Outputs
Target Audience:The target audience consists of fellow scientists, extension personnel, as well as greenhouse growers and indoor farming operations. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Results have been published in book chapters, peer-reviewed journal articles, and have been presented at scientific meetings (Controlled Environment Technology and Use, American Society for Horticultural Science) and grower meetings (Cultivate, PhotoX). What do you plan to do during the next reporting period to accomplish the goals?In the coming year we will quantify the impact of adaptive LED lighting control on growth growth and light use efficiency. We will laso test the use of LED lights to induce flowering in ornamantal plants.

Impacts
What was accomplished under these goals? Goal 1 has been achieved. We have developed a fully functional lightin g control system that is capable of either maintaining user-specified light levels at the top of the canopy or providing a tootal amount of light (daily light integral) by the end of the user-specified photoperiod. This system provides supplemental light when plants can use it most efficiently. Thesi lower reduce energy use anbd increase the cost-effectiveness of supplemental lighting.

Publications

  • Type: Book Chapters Status: Published Year Published: 2017 Citation: van Iersel, M. 2017. Light, photosynthesis and plant growth. In: R. Lopez and E. Runkle (eds.) Light management in controlled environments. p. 31-42. Meister Media Worldwide, Willoughby, Ohio (ISBN-13: 978-1544254494).
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: van Iersel, M.W. 2017. Optimizing LED lighting in controlled environment agriculture. In: S.D. Gupta (ed.). Light emitting diodes for agriculture. Smart lighting. p. 59-80. Springer Verlag, Singapore. (ISBN 978-981-10-5807-3) DOI: http://dx.doi.org/10.1007/978-981-10-5807-3_4
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Zhen, S. and M.W. van Iersel. 2017. Photochemical acclimation of three contrasting species to different light levels: Implications for supplemental lighting. Journal of the American Society for Horticultural Science 142:346-354. http://dx.doi.org/10.21273/JASHS04188-17.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Zhen, S. and M.W. van Iersel. 2017. Far-red light is needed for efficient photochemistry and photosynthesis. Journal of Plant Physiology 209:115-222. https://doi.org/10.1016/j.jplph.2016.12.004.