Progress 10/01/15 to 09/30/20
Outputs
Target Audience:Members of the controlled-environment agriculture community of the American Society for Horticultural Science (ASHS), through presentations at the virtual 2020 ASHS annual conference. Members of the NCERA-101 Committee on Controlled-Environment Technology and Use, via the 2020 Purdue University Station Report. Members of the global space life science community, through Elsevier electronic and print peer-reviewed publication. Members of the Dean's advisory council, via lab tours and demonstration lecture. Members of the indoor-agriculture stakeholder advisory board of sponsored research projects, via Zoom virtual progress reports and Indoor Ag Science Café webinars. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Throughout the project, three graduate students have had opportunities to become scientists, to travel to national conferences and present their thesis/dissertation works, to meet and network with other scientists in the CEA field, to publish their work, and to take next steps in their professional career development. Many undergraduate students have had opportunities to assist with the work of the graduate students, and in some cases, develop their own special research or senior capstone projects, for academic credit, or for hourly employment, and to intern with federal agencies, such as NASA. Electrical and mechanical engineering technology students have had opportunities to help fabricate the controlled-environment systems, to program monitoring and control software, and in one case to start up their own company after graduation that is now developing and marketing LED/hydroponic growth systems for home owners to grow some of their own produce in the kitchen. How have the results been disseminated to communities of interest?Peer-reviewed publications are submitted to refereed journals as soon after grad students graduate as possible. However, every year of a grad student's tenure, they participate in national conferences and give posters or oral presentations of their thesis or dissertation work as a progress report. Undergraduate students who have assisted in the work are typically included as co-authors on progress reports. The PI also submits an annual report to the NCERA-101 Committee on Controlled Environment Technology and Use, both as a written report that gets posted on the NCERA-101 website, as well as an oral report typically delivered at the in-person annual conference. Lab presentations (posters, talks, invited presentations) also are made at annual conferences of the American Society for Horticultural Science (ASHS). These organizations typically are diverse and inclusive, and increasingly so. The PI also is an organizing member of the Indoor Ag Science Café, a monthly webinar series dedicated to increasing communications about controlled-environment agriculture with CEA stakeholder industries, and makes at least one formal presentation per year to this outreach organization, which typically logs in at a rate of 40 to 80 participants per month. One of our projects also includes semi-annual reports to an advisory board, involving either remote or in-person meetings including progress-report presentations, followed by advisor feedback and suggestions. There are numerous yearly ad hoc local outreach opportunities through the PI's college, department, and university, to communicate knowledge about CEA in general as well as our research projects specifically, to campus visitors as well as part of formal programs. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
One controlled-environment crop-production project evaluated the capability of different slow-release fertilizer formulations incorporated into an arcillite calcined-clay growth medium to provide adequate plant nutrition for red-romaine lettuce cultivar 'Outredgeous' and Mizuna mustard to grow with "cut-and-come again" harvest strategies using ground-based analogues of the "Veggie"plant-growth unit being used to grow leafy vegetables in micro-gravity for "pick-and-eat" scenarios on the International Space Station (ISS) by the astronaut crew. Leaves were harvested at 28 days, 48 days, and at 56 days after planting in six Biomass-for-education (BPSe) plant-growth units lighted by light-emitting diodes (LEDs) located in a temperature-and-humidity-controlled walk-in growth room. Deionized water was delivered by passive capillary wicking into containers within the BPSEs hydrating crop roots, and subsequently fertigating arcillite rootzones. It was discovered that, for lettuce, edible yield increased at each subsequent harvest for the faster-releasing fertilizer formulation, but at the expense of leaf nitrogen content, which tapered off at each harvest. Plants yielded least using the slowest-release fertilizer, but leachates from rhizospheres at the end of the experiment indicated that nutrient-solution electro-conductivity (EC) was not limiting for any fertilizer treatment. It is possible that one-way capillary wicking without rinsing or leaching may result in a root-zone environment less-than-optimal in terms of residual nutrient composition and amount, or oxygen content for cut-and-come-again lettuce yield in BPSEs or Veggie. Rootzone pH remained within nominal limits. Mizuna mustard responded differently from lettuce to different controlled-release fertilizer proportions, decreasing in yield at each subsequent harvest, for both fertilizer formulations tested, but decreasing the most with the slowest-releasing formulation. The impact of these treatments was to provide NASA with guidance regarding how to change recommendations from the manufacturer regarding how to modify amounts and proportions of controlled-release fertilizer treatments into the rootzones of each of these crops, as well as insights regarding how future water and fertilizer-delivery systems to roots of plants growing in space likely should be modified. Two other controlled-environment projects involving extensive technical setup, including hardware fabrication and software creation, were completed during the reporting period in preparation for highly-controlled-environment studies with leafy greens and baby greens that are now underway. One of those projects involved completing system fabrication and programming control & monitoring software for a crop cuvette that grows a hydroponic crop stand (up to 48 plants) within a height-and-volume-adjustable cuvette space that allows CO2 gas exchange to be monitored continuously throughout entire production cycles of leafy-green crops (e.g., 28-30 days). During that period, day/night temperature, CO2 concentration, and several LED lighting parameters (adjustable intensity, spectrum, photoperiod) are controlled, and rootzone pH and EC are monitored and adjusted as needed. Flow-through atmospheres are humidified during early seedling growth. Photosynthetic and transpiration rates are monitored as a function of environmental growth conditions throughout cropping cycles. This "Minitron III" controlled-environment crop-growth/gas-exchange system located in a large, walk-in growth chamber is being used to co-optimize different CO2 and lighting conditions for different stages of the cropping cycle to promote rapid, efficient crop growth while minimizing energy inputs and resource utilization. Crop photosynthetic rate is being used as a real-time response to current environmental conditions. The dimmable, selectively switchable lighting system self-monitors electrical-energy utilization, and after a crop-production cycle, crop yield and productivity parameters are measured and expressed as a function of energy cost for lighting. The Minitron system is being used to minimize energy costs during close-canopy lighting, targeted lighting when photons are not allowed to fall on spaces not populated by photosynthetic tissues, and to phasically co-optimize light intensity, spectral composition, daily light integral, and CO2 concentration throughout the cropping cycle, using real-time gas exchange as well as growth parameters and electrical-energy use to determine when to make changes, what changes to make, and by how much. The other controlled-environment growth system consists of four metallic structural frameworks to support three stationary standard plant-growth trays and height-adjustable LED fixtures mounted above the trays. Once again, the lighting fixtures are equipped to self-monitor electrical-energy consumption during periods when LEDs are energized. These frameworks are located within a large controlled-environment, walk-in growth room with its own temperature, humidity, and CO2-control capabilities. A control and monitoring computer is located just outside the growth chamber with cables to/from the fixtures going through a port in the chamber wall. Baby greens are grown in soilless medium with bottom fertigation until canopy closure, which typically is 15-17 days from seeding, depending on species and cultivar. LED arrays are located at variable lamp/plant-separation distances to create different "close-canopy" lighting treatments, with or without dimming of LEDs to the same reference light intensity at different lamp-plant separation distances. Although this "OptimIA" growth system does not include capability to continuously monitor crop gas exchange throughout cropping, it accommodates greater flexibility for treatment replication, simultaneous species/cultivar screening, and/or simultaneous application of different experimental treatments related to lighting. Opportunities for training and professional development Throughout the project, three graduate students have had opportunities to become scientists, to travel to national conferences and present their thesis/dissertation works, to meet and network with other scientists in the CEA field, to publish their work, and to take next steps in their professional career development. Many undergraduate students have had opportunities to assist with the work of the graduate students, and in some cases, develop their own special research or senior capstone projects, for academic credit, or for hourly employment, and to intern with federal agencies, such as NASA. Electrical and mechanical engineering technology students have had opportunities to help fabricate the controlled-environment systems, to program monitoring and control software, and in one case to start up their own company after graduation that is now developing and marketing LED/hydroponic growth systems for home owners to grow some of their own produce in the kitchen.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Burgner, S.E., K. Nemali, G.D. Massa, R.M. wheeler, R.C. morrow, and C.A. Mitchell. 2020. Growth and photosynthetic responses of Chinese cabbage (Brassica rapa L. cv. Tokyo Bekana) to continuously elevated carbon dioxide in a simulated Space Station Veggie crop-production environment. Life Sciences in Space Research 27: 83-88. doi.org/10.1016/j.lssr.2020.07.007
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Sheibani, F., Z. Yu, A. Clemente, C. McDonnel. and C. Mitchell. 2020. monitoring the dynamics of leafy vegetable production in real time with the Minitron III crop-growth/gas-exchange system. American Society for Horticultural Science (ASHS) conference. Poster presentation.
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:International Space Station astronaut "pick-and-eat" program and the Indoor Agriculture commercuial and scientific communities Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student working on the NASA project has just completed a master's degree and will prepare one or more manuscripts from the thesis for submission for publication in a refereed scientific journal.During the present reporting period, that graduate student had a chance to travel to a national scientific conference and make an oral presentation.A PhD student working on the AFRI project is gaining valuable experience supervising a team of engineering technology students helping to activate and make routinely operational the Minitron system.Data collected with that system will be presented by the PhD student at several scientific conferences during the forthcoming reporting period. Biology, horticultural science, mechanical, and electrical engineering technology undergraduate students work on the AFRI and startup SCRI project on an hourly-paid basis assisting the graduate student and PI to make the technical aspects of these projects operational.These students routinely ask the PI and grad students to serve as references for them for summer internships, as well as for their first professional positions after graduation.Two of them formed a company, developed a kitchen hydroponic growth system with LED lighting for growing fresh vegetables in the home, and are marketing that system nationally.An undergraduate assistant to the NASA project was able to compete for a research internship at the NASA Kennedy Space Center and will spend the spring semester there assisting space scientists. How have the results been disseminated to communities of interest?Outputs and outcomes from all of the projects are presented by graduate students and the PI at the annual conference of the NCERA-101 Committee on Controlled-Environment Technology and Use, at the American Society for Horticultural Science, at The American Society for Gravitational and Space research, as oral and/or poster presentations, and the International Conference on Environmental Systems.The PI made illustrated oral presentations during the reporting period on "The Early History of Indoor Agriculture" as well as the Indoor Ag Science Café.The communities of interest included the commercial indoor Ag industry as well as the scientific, academic horticultural science community interseted in development of controlledenvironment agriculture. What do you plan to do during the next reporting period to accomplish the goals?The focus of the finishing NASA project will emphasizepreparation and submission of manuscripts for publication of the work.One manuscript may be submitted to a space life-support journal, while the other may be submitted to a horticultural science journal. For the energy-reduction-for-CEA project, baseline data will be obtained correlating crop response to close-canopy (15 to 20 cm) lighting while measuring energy consumption by the lighting array.Efficiency will be expressed as fresh and dry biomass per kilowatt-hourof energy expended for crop lighting throughout the cropping cycle.This will be contrasted with similar measurements conducted at the same light intensity but at a light-crop separation distance of 40 to 50 cm.For stakeholders who cannot dim their LED lighting arrays, the reciprocal experiment will be conducted not dimming the LEDS at close separation, but rather contrast the biomass of leafy greens obtained at the intensity obtained by moving undimmed LEDs closer to crop surfaces.Once an optimum close-canopy distance and productivity rate are selected, targeted lighting will be tested, with concurrent energy measurement, compared to full-coverage lighting under the same conditions of separation, intensity, etc.The most efficient approach to combined close-canopy, targeted lighting then will be determined using the same metrics.Phasic optimization then will be investigated separating the growth curve into lag phase, exponential phase, and plateau phase, and testing different combinations of light spectrum, light intensity, and CO2that give the best biomass/energy cost metric for that phase. For the startup SCRI project, the experiments will be conducted in a highly controlled growth chamber comparing up to 4 leafy-species concomitantly, growing them initially to baby-green maturity (dense stand of plants / tray to first true leaf fully expanded).Because plants will be grown as a "lawn", targeted lighting will be a non-issue, but close-canopy and phasic optimization could be very important for the short production cycle (15 to 17 days).Later, the same plants will be grown to leafy-green maturity (28 to 30 days).Phasic optimization capability of the OSRAM SCRI arrays will have even more flexibility than the OSRAM AFRI array, including UV-A, blue, green, red, far-red, and warm-white LEDs.The AFRI and SCRI projects are anticipated to synergistically inform each other.
Impacts
What was accomplished under these goals?
NASA project.During the present reporting period red leaf lettuce and mizuna were grown in ground-based analogs of the Veggie pant growth units that are being used to grow those crops for repeated pick and eat by astronauts on the International Space Station.The ground-based units provided adjustable overhead LED lighting and utilized capillary wicking of water from a closed reservoir into contained baked clay growth media incorporating controlled release fertilizer (CRF) pellets.We compared two different CRF mixtures, one that releases fertilizer more rapidly and the other more slowly, into arcillite plant growth substrate.The strategy was to harvest leafy shoots at three different times during a 56 day crop production period, take comparative yield data, and do mineral analysis of the tissue for each harvest.For lettuce the faster releasing fertilizer promoted more biomass production over the entire cropping cycle.All mineral contents were within normal range, except for manganese, which accumulated to high levels in lettuce leaf tissues.For mizuna, leaf fresh weight and area were higher for the finest particle size arcillite (Profile) compared with a mix of Profile and coarser Turface.The combination of fine arcillite and faster releasing fertilizer not only led to the highest yield but also the highest tissue mineral content over the three harvest periods.Manganes accumulated to very high levels in mizuna, but was not toxic to the plants.The arcillite growth substrate was the source of high manganese.Even though tissue nitrogen content declined with successive mizuna harvests, it remained within normal ranges.Thus, it is likely that the CRF formulations could be reduced somewhat for both ISS crops without running out of fertilizer during the three-harvest cut and cone again cropping periods. Energy reduction for CEA.This part of the overall project supported by AFRI focused on technical completion of the powerful Minitron III combined plant-growth gas-exchange analytical system.The early part of the reporting period involved installation and testing of a new LED lighting system custom-designed and assembled by OSRAM for the Minitron system.The combined Minitron-lighting system enables close-canopy lighting with dimmable LEDs allowing reduction of input power even as reduced separation distance between lights and plants increases light intensity, thereby enabling reduced power input for the same light intensity.Removable secondary optics for each LED cluster on the array also allows targeted lighting that avoids waste of photons between plants until the foliar canopy closes.The new LED array has 4 individually dimmable channels including blue, green, red, and far-red light.The PAR quantum sensor of the Minitron was replaced by a combined PAR-FR sensor that adds sensitivity to far-red light that the previous PAR sensor did not have, but also adjusts to photon energies of all PAR wavebands, giving integrated readouts in yield photon flux density without requiring spectroradiometer re-calibrations every time that spectral blends are adjusted.Addition of the LED array software to the original command & control computer led to the decision to replace the original computer with a newer, faster computer, as well as the decision to translate the original programming language, C#, into Python, thereby greatly reducing the risk of control-program crashes during plant experiments with streams of sensor and plant data being collected continuously.Crop-stand photosynthetic rates corrected for humidity differential between sample outlet port and cuvette bypass line due to transpiration were re-programmed in Phython, as was keyboard control of mass-flow-valve apertures controlling both injection of pure CO2 into the bulk air stream directed into the cuvette inlet port as well as the inlet rate of the air-CO2mixture into the cuvette.Both a humidifier tower as well as a CO2scrubber for the cuvette inlet air stream using soda-lime pellets were designed, constructed, and integrated into the Minitron system.An adjustable-rate aerator has been added to the rootzone hydroponics container, as well as a passive vent, and an adjustable-rate peristaltic pump for delivering cuvette outlet air to a gas-routing board while venting excess cuvette outlet atmosphere that doesn't need to go through the infrared gas analyzer for CO2analysis.Preliminary crop experiments with leaf lettuce indicated a need to change closed-cell-foam hydroponic plant-support plugs to ones that are completely non-toxic to plants.Alternate sources and kinds of foam materials for hydroponic plant support have been investigated and tested. Other CEA.Late in the reporting period, a multi-institutional SCRI project was approved that this lab will be involved in.Although funding has not yet begun, we have received from OSRAM 12LED fixtures that will be mounted in a walk-in controlled-environment growth room as part of 4 separate light arrays.A desktop computer has been ordered that will be dedicated to controlling and scheduling operation of the arrays. OSRAM software to control and schedule the arrays has been obtained and will be installed on that control computer.Four adjustable-height aluminum frames for mounting lamps and shelves housing hydroponic trays are being constructed and assembled.The height of lamps will be continuously adjustable above hydroponic trays growing baby greens between 50-cm separation distance and whatever separation when photon-beam colors become unblended.Fiber mats (bamboo, hemp) lining holy trays nested within unholy trays containing nutrient solution are being tested as a growing system for baby greens of several different leafy species.Growth space on shelving beneath LED fixtures can accommodate up to four 20" x 10" trays simultaneously.Electrical power/energy meters have been obtained for measuring energy consumption for each light array separately. NASA project.During the present reporting period red leaf lettuce and mizuna were grown in ground-based analogs of the Veggie pant growth units that are being used to grow those crops for repeated pick and eat by astronauts on the International Space Station.The ground-based units provided adjustable overhead LED lighting and utilized capillary wicking of water from a closed reservoir into contained baked clay growth media incorporating controlled release fertilizer (CRF) pellets.We compared two different CRF mixtures, one that releases fertilizer more rapidly and the other more slowly, into arcillite plant growth substrate.The strategy was to harvest leafy shoots at three different times during a 56 day crop production period, take comparative yield data, and do mineral analysis of the tissue for each harvest.For lettuce the faster releasing fertilizer promoted more biomass production over the entire cropping cycle.All mineral contents were within normal range, except for manganese, which accumulated to high levels in lettuce leaf tissues.For mizuna, leaf fresh weight and area were higher for the finest particle size arcillite (Profile) compared with a mix of Profile and coarser Turface.The combination of fine arcillite and faster releasing fertilizer not only led to the highest yield but also the highest tissue mineral content over the three harvest periods.Manganes accumulated to very high levels in mizuna, but was not toxic to the plants.The arcillite growth substrate was the source of high manganese.Even though tissue nitrogen content declined with successive mizuna harvests, it remained within normal ranges.Thus, it is likely that the CRF formulations could be reduced somewhat for both ISS crops without running out of fertilizer during the three-harvest cut and cone again cropping periods.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Mitchell, C. 2019. Purdue Station Report, NCERA-101 Committee on Controlled-Environment Technology and Use, Montreal, CA, April 15-17.
- Type:
Other
Status:
Published
Year Published:
2019
Citation:
Mitchell,, C. 2019. Early history of Indoor Farming. Indoor Ag Science Cafe webinars presentation o-sponsored by Ohio State, Michigan State, and Purdue, October 15.
- Type:
Book Chapters
Status:
Published
Year Published:
2019
Citation:
Mitchell, C. and F. Sheibani. 2019. LED advancements for Plant-Factory Artificial Lighting. In:
T. Kozai, ed., Plant Factory, Second Ed., Academic Press.I SBN: 9780128166918
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Kong, Y., A. Nemali, C. Mitchell, and K. Nemali. 2019. Spectral quality of light can affect energy consumption and energy-use efficiency of electrical lighting in indoor lettuce farming. HortScience 54(5): 865-872.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2020
Citation:
Burgner, S., K. Nemali, G. Massa, R. Wheeler, R. Morrow, and C. Mitchell. 2020. Growth and photosynthetic responses of Chinese cabbage (Brassica rapa L. cv. Tokyo Bekana) to
elevated carbon dioxide in a simulated Space Station Veggie crop-production
environment. Life Sciences in Space Research (In review).
- Type:
Conference Papers and Presentations
Status:
Awaiting Publication
Year Published:
2020
Citation:
Mitchell, C. 2019. History of of indoor agriculture and vertical farming. In History of Controlled-Environment Agriculture Workshop, American Society for Horticultural Science, Las Vegas, NV, July 22-24.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Morsi, A., G. Massa, and C. Mitchell. 2019. Optimizing controlled-release fertilizer for leafy greens grown on the International Space Station. Controlled Environments session, American Society for Horticultural Science, Las Vegas, NV, July 22-24.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:Both controlled-environment agriculture (CEA) projects continue to reach out to the CEA community at large. The PI is the official representative of Purdue University to the NCERA-101 Committee on Controlled-Environment Technology and Use, and reported progress for both CEA projects at the annual conference that met in Raleigh, North Carolina during the reporting period.The CEA project related to the ILSRA International Space Station (ISS) astronaut"pick-and-eat" scenario for growing and eating vegetables grown in the Veggie plant-growth unit also waspresented by one of the graduate students at the annual conference of the American Society for Horticultural Science during the reporting period. The PI presented development of the AFRI-sponsored experimental system to maximize energy savings in indoor agriculture as part of the online Indoor Ag Science Cafe webinar series to an audience composed primarily of commercial stakeholders. The PI also targets undergraduatw and graduate students in CEA-related courses that he teaches or lectures in throughout the year. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? A second graduate student came into the NASA ILSRA project during the reporting period and beganto optimize environmental conditions for vegetable production in space. The graduate student had an opportunity to travel to a national conference and present initial findings of her degree research, was able to network with other students and professionals in CEA from around the country. An undergraduate assistant to this projectreceived valuable laboratory experience assisting in all aspects of the research process and is becoming interested in future training in graduate school as well. Mechanical and electrical engineering technology students assisted a PhD studet with upgrades to the Minitron IIIcuvette system being developed to monitor and control all aspects of crop-stand development in controlled environments,New engineering technology students came into the Minitron III project during the reporting project and are gaining valuableinsights regarding interdisciplinary research projects applying theirhands-on engineering experience to advance controlled-environment agriculture. The PhD student also is gaining valuable experience working with a powerful new analytical research tool. How have the results been disseminated to communities of interest?An oral presentation was made at the annual conference of the NCERA-101 committee on controlled environment technology and use.A manuscript was submitted to the journal Life Sciences and Space Research and is in review at the time of reporting.A poster presentation was made at the annual conference of the American Society for Horticultural Science.An oral presentation related to controlled- environment agriculture was made at the annual Indiana Horticultural Congress.? What do you plan to do during the next reporting period to accomplish the goals?NASA Project.Comprehensive mineral analysis of leaves from each Mizuna cut-and-come-again harvest will indicate whether nutrient content becomes increasingly limiting to plant growth with successive harvests, suggesting that either the ratio of different controlled-release fertilizers or total dose of controlled-release fertilizer is not adequate to support continuing growth at the same high level as for the first harvest.If decreases in specific mineral content of leaves do not support the interpretation of mineral deficiency, then EC and pH in the arcillite growth medium after final harvest will be measured by the pour-through method.If pH is out of bounds for this non-rinsing, capillary-wicking method of plant growth, then introduction of buffering material into the original arcillite-fertilizer mix will be investigated.If EC is rapidly depleted, the possibility of reverse wicking of solubilized fertilizer out of the growth medium down the capillary wicking material into the sponge material lining the water reservoir will be investigated.At the end of the experiment, residual water will be collected, EC measured, the residual water dried, and the residue re-solubilized in a measured volume of solvent for mineral analysis.Findings of the study will be used to help interpret results of Mizuna growth performance on ISS in microgravity.Adaptation of culture and/or fertilization in microgravity will be investigated depending the outcome of ground-based findings. Energy Reduction for CEA.The new OSRAM LED array will be integrated with the Minitron III cuvette system at the beginning of the next reporting period and the integrated system will be checked out for nominal functioning of all components and control functions following interface with the control computer.Following the checkout period, a hydroponic leafy-green lettuce crop will be grown for an entire 30-day cropping cycle checking out all important control functions of the Minitron III system, including CO2control, temperature control, spectral and light-intensity control and atmosphere flow control, automatically monitoring photosynthetic/respiratory (CO2) gas exchange at all stages of crop production.Light and CO2dose-response (saturation) curves will be determined for all stages of the cropping cycle for which the crop stand will respond.Following this checkout period, a crop will be grown at a constant low light intensity with the height-adjustable walls of the cuvette initially fully extended (50 cm above the crop stand).The self-monitoring power/energy expenditure of the LED array for the reference light intensity will be recorded for several days, then the array will be incrementally moved closer to the crop stand in 10-cm increments every 3 days, each time readjusting power to the array (downward) to maintain the same reference light intensity at the closer separation distance.This procedure will be repeated for increasingly closer LED-crop separation distances until the blended light beam separates into individual waveband colors, meaning the separation distance is too close.The anticipated energy savings over an entire cropping cycle are expected to be large, and will determine the best close-canopy lighting separation distance to maintain for future experiments.The next step will be to engage the targeted lighting function of the new OSRAM array to avoid loss of photons between plants when they are small with discreet spaces between them.Selective LED on/off switching will be controlled from the command & Control computer using overhead images from an RGB camera mounted at the center of the LED array.Each day that plants in the array increase in diameter, switching adjustments will be made so that photons continue to fall directly on plants but not on spaces between plants that are not populated by plant tissue.Non-invasive, non-destructive measures of crop growth (cumulative growth curves) will be determined by image analysis of the entire crop stand daily.Upon final harvest, destructive growth analysis will be paired with integrated energy analysis over the entire cropping cycle to determine kWh energy expenditure / g DW plant biomass harvested.Once close-canopy / targeted-lighting parameters are optimized for excellent cumulative energy savings over the life of a lettuce crop, lighting spectrum and intensity will be optimized for each phase of a cropping cycle.During lag phase, when crops are relatively non-responsive to light and CO2, manipulation of waveband ratios and total light intensity will be used to maximize energy savings while maintaining seedlings in a normal developmental state.Crop-stand photosynthetic gas exchange will be used to determine when the lag phase ends and when exponential growth begins.Light intensity and spectrum, plus CO2, will be optimized in combination to maximize productivity during exponential growth, but then to back off optimizing conditions if growth starts to taper off toward the plateau phase before harvest.Ratios of red, blue, green, and far-red radiation will be varied at each growth stage for height control, maximizing leaf expansion, CO2assimilation rate, and maintaining responsiveness to CO2.Anticipated energy savings from phasic optimization of the lettuce lag phase, from not wasting resources beyond the anticipated brief exponential growth phase, and post-exponential growth, if any, will be accumulated along with those for close-canopy and targeted lighting.The grand total of electrical-energy savings for lighting is anticipated to exceed an order of magnitude less than that presently expended for indoor farming methods using LEDs.
Impacts
What was accomplished under these goals?
NASA Project.Impact of the ground-based NASA ILSRA project to optimize environments for production of leafy vegetables in space is that environmental conditions on the international Space Station (ISS) must be closely mimicked in a ground-based growth chamber.Screening of candidate species for the "Veggie" plant-growth unit suggested thatBrassica rapacv. Tokyo Bekana (Chinese cabbage) was the best-growing vegetable with excellent nutrient composition for ISS crew consumption.However, when grown under ISS-like environments, Chinese cabbage grew poorly and developed leaf chlorosis and necrosis.Investigation revealed that it does not tolerate ambient ISS CO2levels (2800 ppm).Chinese cabbage has been de-selected in favor of leafy greens that tolerate ISS CO2.During the present reporting period, anotherBrassica rapacultivar, 'Japonica', that also performed well during initial leafy-greens screening, did not show stress symptoms in the presence of high CO2like 'Tokyo Bekana' did.Known as Mizuna, thisB. rapacultivar is being optimized in preparation for ISS pick-and-eat scenarios.Studies focus on effects of light and fertilizer treatments, which are the only variables that can be controlled on ISS.Treatments were applied in conjunction with "cut-and-come-again" experiments for multiple harvests from the same plants.Plants were grown for 56 days under one of three LED lighting treatments:90% red: 10% blue; 70% red : 30% blue; or 50% red: 50%blue. Large and medium-sized leaves from each treatment were harvested two times during the experiment: The first harvest occurred 28 days from planting, and the second harvest at 38 days. Whole plants were harvested at 56 days.Data suggest that the more red light, the higher the yield: 90% red gave the highest yield followed by 70% red, and then 50% red.Increasing blue light decreased Mizuna yield.Red light enhances leaf expansion while blue light inhibits leaf expansion but increasesleaf number.Fresh weight yield decreased over time, with yield from the first harvest almost double that from both second and final harvests.These decreases may relate to depletion of mineral nutrients incorporated into the growth medium.All plants developed mineral-deficiency symptoms.Proportions and rates of controlled-release fertilizer were varied during cut-and-come-again experiments.Leaf samples are being analyzed to determine if mineral deficiency is what decreases leaf yield during cut-and-come-again harvests. Energy Reduction for CEA.Activity focused onmaking environmental control of the Minitron III system fully operational, and working with OSRAM Innovations to develop an LED array to realize energy-saving benefits by integrating it with the Minitron gas-exchange / hydroponics growth system.The Minitron System is being readied for analytical work in connection with an AFRI-sponsored projectto improve efficiency and reduce cost of LED lighting for leafy-greens production.This system enables researchers to simultaneously monitor gas exchange of up to 48 leafy-green plants growing as a hydroponic crop stand from seed to harvest under environments controlling temperature, light intensity, light spectrum, and CO2concentration.Additionally, separation distance between the lights and crop surface can be adjusted to create opportunities to test different close-canopy-lighting distances.Minitron III includes various off-the-shelf components along with those of unique design and function. During the reporting period, existing components were modified and new elements added to create a more accurate, more powerful analytical device.Several test runs of the system were conducted with the cuvette containing leafy-green plants at different stages of development to assure that all mechanical and electronic components worked properly to monitor gas exchange by those plants, thereby also allowing assessment of the accuracy of custom-written software.Programming in the language C# was tweaked in several cases based upon data streams from sensors and plant responses to environmental growth conditions.Several components of the open gas-exchange system were upgraded or added for additional accuracy of photosynthetic gas-exchange analysis.A gas-routing board (GRB) was reconstructed replacing copper components with non-CO2-absorbing Bev-A-Line tubing and plastic valves. The GRB is a "switching station" including all flowing-gas lines for calibration (zero and calibration gases) as well as sample and bypass (reference) lines coming from the crop cuvette.A cylinder of ultra-zero gas with less than 2 ppm CO2concentration and less than 6 ppm of H2Ovconcentration was added to the system to help calibrate Infrared Gas Analyzer (IRGA) at zero levels of CO2and H2Ov.The IRGA measures photosynthetic gas exchange of crop stands continuously and automatically as the difference in CO2concentration between an air stream flowing through a lighted cuvette containing photosynthesizing plant tissue (corrected for H2Ovmole fraction) vs. an identical stream that bypasses the cuvette. A CO2scrubber is a new component of the Minitron gas-exchange system added during the reporting period to assure accurate control of CO2concentration being introduced into the cuvette for crop photosynthesis measurement. Previously, ambient air was injected with pure CO2(through a mass-flow-control valve)and used as the reference to measure differential CO2concentration, but uncontrolled variation in baseline CO2concentration often made work with "ambient" CO2levels impossible. In order to remove room CO2and inject pure CO2back into the CO2-free air at controlled levels, several CO2-scrubbing cannisters (containing color-indicating soda lime) have been installed upstream of the branch-point between the mass-flow valve controlling air-flow rate into the crop cuvette and the cuvette bypass line.As well, an optional (switchable) humidifier column has been added to the gas-flow component of the Minitron system to ensure adequate humidification of cuvette inlet (and bypass) air to accommodate stages of crop development when plants have not yet developed enough leaf surface area for adequate transpiration. Another major effort of the Mitchell lab during the reporting period has been working with OSRAM Innovations to develop a new LED array with properties and capabilities unique for conducting powerful research with the Minitron system.This LED array includes four channels of red, blue, green, and far-red wavebands of radiation.This LED array is wavelength tunable and dimmable, and separate LED clusters are individually on/off switchable.Self-monitoring and logging of power (kW) and energy (kWh) consumption have been designed into this lighting array, which will greatly assist in determining energy-use efficiency of different spectral and close-canopy-lighting treatments to be experimentally determined during the next reporting period.The new lighting component of Minitron also will enable researches to monitor and perform quantitative image analysis of crop growth with an installed RGB camera looking down at the crop stand from the center of the LED array.Complying with University Radiological and Environmental Management safety regulations also was an important activity during assembly of Minitron system components during the past year.Ongoing updates and documentation to the Minitron III Operations & Instruction manual constitute yet another important task that has been accomplished during the past year. Other CEA.AProposal related to energy savings was submitted to the NIFA SCRI program.That proposal was not funded but will be revised for 2018-2019.A proposal for use of renewable energy from food waste to reduce CEA energy costs was submitted to the NSF INFEWS Program with multi-disciplinary colleagues.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Morsi, Asmaa H., Massa, Gioia, Mitchell, Cary. Optmizing spectra for Mizuna grown on international space station. 2018 Annual Conference of the American Society for Horticultural Science, Washington DC.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2018
Citation:
Burgner, Samuel, Massa, Gioia, Wheeler, Raymond, Mitchell, Cary. Photosynthetic and growth response of Brassica rap to elevated carbon dioxide in a spaceflight production environment. Life Support & Space Research
- Type:
Journal Articles
Status:
Accepted
Year Published:
2018
Citation:
Kim H-Ji, Lin M-Yang, Mitchell CA, Light spectral and thermal properties govern biomass allocation in tomato through morphological and physiological changes, Environmental and Experimental Botany (2018), https://doi.org/10.1016/j.envexpbot.2018.10.019
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:International Space Station astronaut "pick-and-eat" program directly and the controlled-environment agriculture scientific community generally Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student working on the NASA project to optimize environmental conditions for vegetable production in space completed degree requirements during the project period, and is preparing a paper for publication in a peer-reviewed scientific journal. The graduate student also had an opportunity to travel to a national conference and present the findings of his degree research, as well as to interview with several industrial companies for a professional position in the controlled-environment agriculture industry. Several undergraduate assistants received valuable laboratory experience assisting in all aspects of the research process and are becoming interested in future training in graduate school themselves. Mechanical and electrical engineering technology students did special projects on the cuvette system being developed to monitor and control all aspects of crop-stand development in controlled environments, and two of them became so interested in environmental control of plant growth themselves that they formed a company to develop kitchen hydroponic systems for the home. Since graduation, they have been obtaining grants and gaining valuable business experience to complement their engineering technology skills. New engineering technology students continuing to help develop and evolve the cuvette system are gaining insightful hands-onexperience to complement their theoretical training. How have the results been disseminated to communities of interest?Oral and poster presentations were made at the annual conference of the NCERA-101 committee on controlled environment technology and use, a televised piece on space agriculture was broadcast live and distributed to schools nationally as part of Purdue University's annual "Dawn or Doom" series of technology presentations. Oral presentations related to controlled-environment agriculture also were made at several extension events during the reporting period. What do you plan to do during the next reporting period to accomplish the goals?For the NASA project, a second graduate student will begin work to optimize light and fertilizer environments for cultivation of Mizuna in the Veggie plant-growth units that currently are used on the International Space Station (ISS) for plant growth. The findings of the first grad student who finished during the present reporting period have caused NASA to re-evaluate growing Chinese cabbage on ISS in the presence of chronically high CO2 that cannot be controlled in Veggie. It also helps NASA justify the need for an advanced plant growth habitat for ISS that will provide complete control of the plant-growth environment, including CO2. Mizuna seems not to be adversely affected by elevated CO2 during its growth, so optimization of the light/fertilizer environment seems feasible. Cultural protocols for "cut-and-come-again" types of vegetative harvest will be tested during the forthcoming budget period. Several major proposals to federal agencies will be submitted or revised and re-submitted during the next reporting period. Common themes of the proposals will include major energy savings for CEA by leveraging the unique properties of LEDs, developing new energy-saving best practices for controlled-environment crop production, and leveraging of renewable energy sources.
Impacts
What was accomplished under these goals?
NASA Project. The NASA-funded ILSRA project to optimize fertility and lighting environments for pick-and-eat salad crops growing on the International Space Station (ISS) for astronaut consumption dominated research activities over the course of the reporting period because of current funding and staffing. One task involved growing 'Red Robin' dwarf tomato for 98 days in the growth chamber under ISS cabin environmental conditions using three different controlled-release fertilizer protocols and four different lighting treatments. Vegetative growth and fruit number tended to be higher under higher proportions of red light, but fruit mass was more under higher proportions of blue light. Plant stature also was shorter and more compact under elevated blue light. Most plants were productive and produced a considerable number of well-developed fruit regardless of fertilizer or light treatment. However, all plants exhibited stress symptoms, especially leaf epinasty and some stunted growth and tissue necrosis. Additional experiments during the reporting period focused on Chinese cabbage (Brassica rapa cv. Tokyo Bekana) with a production cycle of only 28 days. As for tomato, Chinese cabbage had stress symptoms including chlorosis, necrosis, and leaf rolling. Many potential stressors were investigated during the reporting period, including micronutrient toxicities of the growth medium, arcillite (such as manganese), intolerance of high red light, controlled-release fertilizer ratios, possible calcium deficiencies, and even root restriction and root hypoxia due to the small capillary wicking "pillows" the plants were originally grown in. A number of follow-up, preliminary experiments were conducted in the growth chamber under ISS-like environmental conditions investigating each possibility and imposing treatments designed to alleviate the candidate stress. The arcillite growth medium was rinsed, larger root-volume pots were used instead of plastic pillows, and plants were even grown in the greenhouse instead of in the growth chamber to see if the plants would grow better under broad-band solar light than under narrow-spectrum LED light. In every case except one, Chinese cabbage exhibited the same chlorosis, necrosis, stunting, and twisting that it did initially, unless it was planted in the greenhouse. Chinese cabbage grown in the greenhouse under ambient solar and environmental conditions showed no stress symptoms. At that point, we began to review ISS cabin environmental conditions that we were mimicking in the growth chamber that were not present in the greenhouse. The ISS cabin environment included 24/21.5 C (D/N) temperatures, 45/50% (D/N) relative humidity, a 16:8 (D/N) photoperiod, and an ambient CO2 concentration averaging 2800 ppm continuously. The one factor that really stood out was the very high CO2 level that the plants were exposed to continuously. Thus, we conducted a series of experiments using multiple growth chambers set to different CO2 levels ranging from much lower ambient CO2 (600 ppm) to ISS-normal CO2 (2800 ppm). Simultaneously, we switched from root-restrictive pillow culture to larger cylindrical pots that were a precursor to a new hydroponics system called "PoNDS" that NASA was switching over to for the ISS Veggie system. Capillary wicking still is used to deliver water to the root system incorporating arcillite containing controlled-release fertilizer. We also investigated phasic growth sensitivity of Chinese cabbage to CO2 enrichment by swapping plants between different growth chambers at different CO2 concentrations and at different stages of crop production. There was a dramatic reduction in leaf chlorosis and necrosis when plants were grown at 600 ppm CO2. Subsequent experiments comparing growth of Chinese cabbage at 450, 900, or 1350 ppm CO2 indicated that plant growth at 450 ppm was significantly higher than at 900 or at 1350 ppm, suggesting that this cultivar of Chinese cabbage, at least, is quite sensitive to chronic exposure to elevated levels of CO2. Photosynthetic rate also was lower at the two higher CO2 levels, as was mesophyll conductance. Since other salad species such as leaf lettuce that have been grown on the ISS did not experience the same stress symptoms as 'Tokyo Bekana' to CO2 enrichment, it is important to screen candidate crop species for space under the same environmental conditions as exist on the ISS. As well, alternative plant-growth facilities need to be developed on spacecraft with completely separate climate-control capabilities that do not allow off-nominal environmental conditions that will interfere with the crew or its food. Energy reduction for CEA.Activity was focused during the reporting period on upgrading and improvingthe functionality of a combinedcrop-growth / gas-exchange cuvette system incorporating recirculating hydroponics and a height-adjustable light cap consisting of light-emitting diodes that are individually switchable and dimmable by waveband (color). All electrical lines and interfaces were modified for maximum safety, all copper and brass plumbing was replaced with CO2-impermeable plastic tubing and fittings, and infrared gas analyzer calibration and operational protocols were completed and protocols documented for routine operation. Two grant proposals to NIFA regarding energy reduction for controlled-environment agriculture related to close-canopy LED lighting, targeted LED lighting, and phasic optimization of the light & CO2environment were prepared and submitted during the reporting period. A third proposal related to the harnessing renewable energy for CEA was submitted to the joint NSF/NIFA INFEWS program relevant to the nexus of food, energy, and water. Funding has not yet been secured for this important emphasis area. Other CEA.Support was provided during the reporting period for two aquaponics proposals lead by colleagues in the areas of hydroponics, LED lighting, and specialty-crop culture. Meetings were held with representatives of the CEA industry to establish partnerships that could result in apilot-scale research facility that would help to attract federal grants.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Both, A.-J., B. Bugbee, C. Kubota, R. Lopez, C. Mitchell, E. Runkle, and C. Wallace. 2017. Proposed product label for electric lamps used in the plant sciences. HortTechnology 27(4): 544-549.
- Type:
Book Chapters
Status:
Published
Year Published:
2017
Citation:
Dorais, M., C. Mitchell, and C. Kubota. 2017. Lighting greenhouse fruiting vegetables. In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments, Meister Media, publ., Willoughby, OH., pp. 159-165.
- Type:
Book Chapters
Status:
Published
Year Published:
2017
Citation:
Mitchell, C. 2017. From the Earth to the Moon-and back again! In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments. Meister Media, publ., Willoughby, OH. pp. 166-168.
- Type:
Book Chapters
Status:
Published
Year Published:
2017
Citation:
Mitchell, C. and G. Stutte. 2016. Sole-source lighting for controlled-environment agriculture. In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments. Meister Media, publ., Willoughby, OH, pp. 48-54.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2018
Citation:
Dzakovich, M., C. Gomez, M. Ferruzzi, and C. Mitchell. 2018. Chemical properties and flavor of greenhouse tomatoes remain unchanged in response to red, blue, and far-red supplemental light from light-emitting diodes. HortScience (in review).
- Type:
Journal Articles
Status:
Submitted
Year Published:
2018
Citation:
Burgner, S., K. Nemali, G. Massa, R. Wheeler, and C. Mitchell. 2018. Photosynthetic characteristics of Brassica rapa cv. Tokyo Bekana under chronically elevated CO2 environments. J. Adv. Life Support. (Submitted for publication)
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:International Space Station astronaut "pick-and-eat" program directly and the controlled-environment agriculture scientific community generally Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A Master's graduate student and several undergraduate assistants are assigned to the NASA project to optimize environmental conditions for vegetable production in space and to trouble shoot stress responses occurring in the growth chamber on the ground mimicking ISS-like conditions on orbit, except for microgravity. The experience being gained by all students involved in the project is giving them training in the research process, including hypothesis testing, data collection and analysis, and data interpretation. The graduate student is receiving experience in advanced degree thesis preparation and the undergraduates are being exposed to the graduate-degree process. As the controlled-environment field continues to expand, all students involved in the project are earning valuable credentials as potential future employees and professionals in the CEA growth industry. Undergraduate engineering technology students (electrical and mechanical) working in the lab making a crop gas-exchange cuvette system operational through computer programming, system assembly, and trouble shooting are gaining valuable experience working in a multi-disciplinary environment. Some have become interested in hydroponics and other aspects of the indoor agriculture industry that they never would have known about otherwise. Some may end up in engineering-support roles in the controlled-environment agriculture industry. How have the results been disseminated to communities of interest?Oral and poster progress reports were made during the reporting period at the annual conference of the American Society for Horticultural Science, to the NCERA-101 committee on Controlled-Environment Technology and Use, and at the annual conference of the American Society for Gravitational and Space Research. What do you plan to do during the next reporting period to accomplish the goals?For the NASA project, efforts will continue to minimize or eliminate cultural or environmental stresses that may interact with elevated CO2 and aggravate observed stress responses of the test crops. Root-volume restriction that is built into the pillows used to grow the plants in space will be evaluated by comparing growth with that of plants gown in the same media and fertilizer but in containers of larger root volume. Because tissue analysis indicates that some mineral elements are present in excess, possibly at toxic levels, and that others are deficient in tissues, adjustments will be made both to the controlled-release fertilizer formulation as well as its dose incorporated into the calcined-clay growth medium. Once stress factors have been identified and mitigated, red : blue ratios and total photon flux will be optimized for test-crop growth responses. For the cuvette project, baseline tests of the fully operational system will be run, first without plants, then with 49-plant stands of leafy greens, measuring gas exchange continuously throughout their 30-day life cycle, measuring crop response to CO2 enrichment at different stages of growth, and light intensity and spectrum to same. Several different species and cultivars of greens and herb crops will be tested, including leaf lettuce, Chinese cabbage, kale, arugula, and basil, noting difference in tolerance to various parameters, including high CO2. Several major proposals related to the CEA sustainability theme of this overall project will be written and submitted next year. All will be team efforts, including multi-disciplinary, multi-institutional inputs.
Impacts
What was accomplished under these goals?
Effort during the reporting period was distributed across all three overall project goals, with the NASA sub-project receiving most attention with federal funding in hand and reporting deadlines as drivers. The Energy Reduction for CEA sub-project did receive additional major attention in terms of grant-proposal writing for a multi-institutional, multi-disciplinary project to secure funding for that sector of the overall project. Similarly, contributions were made to the Other CEA sector by providing support for proposals submitted for funding of aquaponics and solar-splitting-for-agriculture research. For the NASA "pick-and-eat" project for the International Space Station (ISS), "Veggie" plant-growth hardware has been developed for NASA to grow vegetables, including height-adjustable overhead arrays of light-emitting diodes (LEDs) with water and nutrients supplied through plastic "pillows" that contain water within the micro-gravity environment of the ISS. Temperature and humidity of Veggie float with ambient conditions of the ISS crew cabin. Environmental and cultural conditions used on ISS (except for microgravity) were mimicked on the ground in growth chambers to grow Chinese cabbage and dwarf tomato using ground-based mock-ups of the ISS Veggie units. A number of stress factors have been identified, and effort is underway to minimize or eliminate stressors as well as their potential interactions. Plants were grown mimicking ISS-like environmental conditions of temperature (24.5 C days / 21 C nights), humidity (45% days / 55% nights), and CO2 concentration (2800 ppm average). Initial trials on ISS conducted by astronauts involving a single cultivar of leaf lettuce resulted in plant growth looking normal and similar to ground-controls. Trials of a promising cultivar of Chinese cabbage conducted on the ground in our growth chamber varied combinations of growth-substrate composition, incorporated timed-release fertilizer concentrations, LED spectral composition, and total light intensity using Biomass-Production-Systems-for-Education (BPSe) growth units under ISS environmental conditions resulted in inferior plant growth compared to greenhouse controls. Similar poor growth was found for a promising dwarf tomato cultivar under ISS conditions. Although multiple cultural and / or environmental stressor combinations are suspected to be causal, attempts to eliminate them one by one failed to improve growth of Chinese cabbage, until CO2 was reduced from 2800 PPM to near Earth-normal ambient. Since modification of ambient crew-cabin CO2 concentration is not an option for plant growth in Veggie on ISS, investigations are underway at Purdue to alleviate other-CO2 environmental / cultural stressors in effort to determine if eliminating those interactions can significantly reduce plant response to supra-optimal CO2. Parallel efforts are investigating whether genetics and / or genetics x environment interactions are responsible for the negative response of the Chinese cabbage cultivar thus far tested to supraoptimal CO2 in combination with other ISS plant-growth conditions. A team of electrical and mechanical engineering technology students has teamed up with a horticulture graduate student and undergraduate researcher to put the finishing touches on a crop gas-exchange cuvette system that includes environmental control (temperature, light intensity and spectrum, CO2 concentration) as well as hydroponic culture. As this system becomes fully operational, it will become a powerful tool defining phasic optimization of growth environments for leafy greens at all stages of their growth cycle. This tool is being featured in proposals for which funding is being sought.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Dzakovich, M., M. Feruzzi, and C. Mitchell. 2016. Manipulating sensory and phytochemical profiles of greenhouse tomatoes using environmentally relevant doses of ultraviolet radiation. J. Agr. & Food Chem. DOI: 10.1021/acs.jafc.6b02983.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Gomez, C. and C. Mitchell. 2016. Physiological and productivity responses of high-wire tomato as affected by supplemental light source and distribution within the canopy. J. Amer. Soc. Hort. Sci. 141 (2): 196-208.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Dzakovich, M., C. Gomez, and C. Mitchell. 2015. Tomatoes grown with light-emitting diodes (LEDs) or high-pressure sodium (HPS) vs. HPS supplemental lighting are of comparable quality. HortScience 50 (10): 1-5.
- Type:
Book Chapters
Status:
Published
Year Published:
2015
Citation:
Mitchell, C., J. Burr, M. Dzakovich, C. Gomez, R. Lopez, R. Hernandez, C. Kubota, C. Currey, Q. Meng, E. Runkle, C. Bourget, R. Morrow, and A.J. Both. 2015. LEDs in Horticulture. Horticultural Reviews 43: 1-87.
- Type:
Book Chapters
Status:
Published
Year Published:
2016
Citation:
Lu, N. and C.A. Mitchell. 2016. Supplemental lighting for greenhouse-grown fruiting vegetables. In T. Kozai et al. (eds.), LED Lighting for Urban Agriculture. DOI 10.1007/978-981-10-1848-0_16.
- Type:
Book Chapters
Status:
Awaiting Publication
Year Published:
2017
Citation:
Dorais, M., C. Mitchell, and C. Kubota. 2017. Lighting greenhouse vegetables. In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments, Meister Media, publ. (In press).
- Type:
Book Chapters
Status:
Awaiting Publication
Year Published:
2017
Citation:
Mitchell, C. 2017. From the Earth to the Moon-and back again! In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments. Meister Media, publ. (In press).
- Type:
Book Chapters
Status:
Awaiting Publication
Year Published:
2017
Citation:
Mitchell, C. and G. Stutte. 2016. Sole-source lighting for controlled-environment agriculture. In: R. Lopez and E. Runkle (eds.). Light Management in Controlled Environments. Meister Media, publ. (In press).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Mitchell, C. 2016. LEDs for plant research and controlled-environment agriculture. Horticultural lighting conference. PenWell Corp., The Palmer House, Chicago, IL, October 12. hlc_2016_conference_proceedings.pdf.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Mitchell, C. 2016. LED lighting as a plant-growth regulator: an historical perspective. 43rd annual conference of The Plant-Growth Regulator Society of America (PGRSA), Raleigh, NC, Mitchell, C. 2016. July 18. http://pgrsa.org/conference/2016-conference.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Gomez, C. and C. Mitchell. 2016. In search of an optimized supplemental lighting spectrum for greenhouse tomato production with intracanopy lighting. Acta Hortic. 1134. ISHS 2016. DOI 10.17660/ActaHortic.2016.1134.8. Proc. VIII Int. Symp. on Light in Horticulture, C.J. Currey et al., Eds.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Gomez, C., M. Clark, and C. Mitchell. 2016. Effect of intracanopy lighting and/or root-zone temperature on high-wire tomato production under sub-optimal air temperature. Acta Hortic. 1134. ISHS 2016. DOI 10.17660/ActaHortic.2016.1134.9
Proc. VIII Int. Symp. on Light in Horticulture C.J. Currey et al., Eds.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Mitchell, C. 2015. Academic research perspective of LEDs for the horticulture industry. HortScience 50(9): 1293-1296.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Burgner, S. and C. Mitchell. 2016. Optimized light quality and fertilizer composition for crop production on the International Space Station. American Society for Gravitational and Space Research, 32nd annual meeting, Cleveland, OH, October 26-29.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Kim, H-J, C. Gomez, and C. Mitchell. 2016. Comparison of LED and HPS supplemental light quality on greenhouse tomato production in northern states during winter months. American Society for Horticultural Science, 113th annual conference, Atlanta, GA, August 8-11.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Burgner, S. and C. Mitchell. 2016. Optimized light quality and fertilizer composition for crop production on the International Space Station. American Society for Horticultural Science, 113th annual conference, Atlanta, GA, August 8-11.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Mitchell, C. 2016. Peri-urban agriculture in greenhouses and warehouses using LEDs and renewable energy. Workshop on Energy from renewables: confronting global collapse . University of Minnesota, Minneapolis, October 1.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Mitchell, C. 2016. Reducing energy for plant-growth lighting in space and on Earth. Plants-in-Space Symposium, Australian Academy of Sciences, The Shine Dome, Canberra, Australia, September, 21.
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