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What is the impact of LED grow lights on indoor horticulture crops?

Michigan State University researchers are studying the effects of sole source LED grow lights on edible and ornamental crops.

Michigan State University opened its Controlled-Environment Lighting Laboratory (CELL) in 2017. The 400-square-foot vertical farm research facility is being used to study the indoor production of high-value specialty crops, including edibles and ornamentals with LED grow lights.

Continue reading What is the impact of LED grow lights on indoor horticulture crops?

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Updated daily light integral (DLI) maps now available

New DLI maps have been created from an updated database that includes data from 1998 to 2009.

Daily light integral (DLI) is the amount of photosynthetically active radiation (PAR) received each day as a function of light intensity and duration. DLI maps display the ambient light delivered daily during each month across the entire United States. The original maps released in 2002 were researched and developed by Jim Faust at Clemson University and Joanne Logan at the University of Tennessee.

Continue reading Updated daily light integral (DLI) maps now available

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Current, Powered by GE and Stockbridge Technology Centre Partner to Research the Farm of the Future

This article was originally posted on currentbyge.com

  • Stockbridge Technology Centre’s Vertical Farming Development Facility to enable growers to test and model their individual urban farm setup prior to investment
  • Aims to propel the success of the vertical farming industry, projected to be worth $13.9 billion USD in 20241 and generate more “farmable land” to address future global food production pressures
  • Current by GE’s Arize LED horticulture solution will help researchers test growth of crops such as leafy greens and herbs in different conditions

Continue reading Current, Powered by GE and Stockbridge Technology Centre Partner to Research the Farm of the Future

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Does it make economic sense for you to install grow lights?

The Lighting Approaches to Maximize Profits (LAMP) project aims to determine how growers can maximize their return on investment when considering installing grow lights.

As light emitting diodes (LEDs) become more efficient and more affordable, an increasing number of greenhouse and plant factory growers will consider installing LED luminaires to light their crops. In the case of greenhouse growers, these luminaires would provide light to supplement natural sunlight. For plant factory growers, production depends entirely on the light provided by an artificial light source including LEDs, high pressure sodium or metal halide luminaires.

Continue reading Does it make economic sense for you to install grow lights?

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Controlling basil downy mildew might be as simple as turning on a light

The use of supplemental light to control downy mildew on food and ornamental crops could be integrated into current disease management practices.

Downy mildew is a major disease on both ornamental and food crops. Whether these crops are grown outdoors or in a controlled environment, environmental conditions, generally cool to moderate temperatures and high humidity, are favorable to downy mildew development. Warm temperatures and high humidity are conducive to powdery mildew development.

Continue reading Controlling basil downy mildew might be as simple as turning on a light

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NASA developing LED light recipes that astronauts and growers can use

The LED light recipes that NASA scientists are developing on Earth could eventually be used by astronauts in space and growers on the ground to optimize the production of food crops.

National Aeronautics and Space Administration (NASA) has been growing plants in space for research since the early 1980s. Within the last five years, NASA has been focusing on growing plants in space primarily for food production and as an astronaut life support system.

Continue reading NASA developing LED light recipes that astronauts and growers can use

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NASA Taps Osram to Support Its Food Production Research

Osram’s smart horticulture lighting system prototype used in NASA ground research to help provide space crews with a reliable source of fresh food

WILMINGTON, Mass. & KENNEDY SPACE CENTER, Fla.–Osram, a global high-tech lighting company, today announced it is providing the National Aeronautics and Space Administration (NASA) with a customized version of its proprietary connected horticulture research lighting system, Phytofy RL. The smart lighting software, coupled with a unique setup of connected grow light fixtures, will supplement the lighting technology used in NASA’s Food Production Research focused on production of salad-type crops for crews during space travel. All software, hardware and LEDs in Phytofy were developed by Osram. Osram has developed a broad portfolio of horticulture LEDs that irradiate the specific wavelengths needed for optimum growth of a wide variety of plants and flowers, allowing the light to be adapted specifically for the needs of various crops.

Continue reading NASA Taps Osram to Support Its Food Production Research

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Growing microgreens with LED grow lights in Sonora, Mexico

(Español abajo.)

Urban grower Karla Garcia is proud to announce the creation of her new company, Microgreens FLN based in Sonora, Mexico. Karla is a recent graduate with honors and a master’s degree in plant science from the University of Arizona. She is proud of her company’s commitment specializing in microgreens production using an indoor vertical farming strategy. Microgreens are an emerging class of specialty leafy greens and herbs. The crops are harvested when the cotyledons are fully developed and in some cases when the young plants have one true leaf.

Continue reading Growing microgreens with LED grow lights in Sonora, Mexico

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Local by Atta rebuilds vertical farm with GE LEDs after devastating fire

Case File Facts

COMPANY: Local by Atta

LOCATION: Moncton, New Brunswick, Canada

CROPS: Local by Atta produces a variety of lettuces, basil, kale, Swiss chard, bok choy, cilantro and microgreens. Products are sold at farmers markets, health food stores, grocery stores, restaurants and through a weekly basket  program. The basket program is expected to increase sales as the company looks to expand with pick up at local businesses, municipal buildings and its new production facility.

TECHNOLOGY: GE Arize Lynk LED Growing System

The Local by Atta team (from left to right) includes: Brandon Petitpas, assistant farmer; Jesse Howatt, co-founder and farmer; Nick Barron, assistant farmer; Julian Howatt, co-founder and farmer, and Svitlana Rastovska, assistant farmer.

Background

Local by Atta was founded by Julian and Jesse Howatt. The two brothers, who grew up on a farm, have professional backgrounds in urban planning.

“Even though we grew up on a farm we have an interest in cities,” said Julian Howatt. “In 2012-2013 we reached a point in our careers that we wanted to start an urban farm together. I had been growing lettuce hydroponically in my apartment. We scaled it up to a shed in my brother’s backyard. In late 2013 we started a small-scale commercial farm and in March 2014 we began selling at a local farmers market.”

Julian said one of the reasons that they chose to do indoor hydroponics was the limitations of an outdoor urban farm.

“With an outdoor urban farm there are limitations with the land that is available and it is more difficult to do very intensive farming,” he said. “Also, our climate is not conducive to long growing seasons because of the short summers.

“An indoor farm provides a major competitive advantage for leafy greens. Except for the summer when there is a local supply, for most of the year the majority of leafy greens are coming from California and other parts of the West Coast. We saw the biggest potential starting to sell our products from September through June. It made more sense given the constraints of trying to produce high yields on a small land-based urban farm to go year-round with an indoor farm using a hydroponic production system.”

When the Howatts started growing hydroponically in their backyard shed they were looking to trial a couple of LED lights.

“We wanted a horticultural quality LED fixture and not just some random LED from a hydroponic store where we weren’t sure about the quality of the lights,” Julian said. “I googled horticultural LEDs and found Hort Americas online. I contacted Chris Higgins and I explained that we were setting up a small hydroponic production facility growing lettuce. I spoke to Chris for about an hour and talked about LEDs and lighting issues and ended up purchasing a couple of LEDs. I also read the Hort Americas case study article on Jeffrey Orkin at Greener Roots Farm in Nashville, Tenn. We eventually contacted Jeffrey because we were looking for other hydroponic farmers to exchange notes with and get some advice.”

Challenge

In late 2013 the Howatts began growing in a commercial building renting 1,500 square feet of space.

“We started off with a nutrient film technique system with PVC channels,” Julian said. “We figured out very quickly that the plumbing for this type of system is much more complex resulting in more issues including leaks, flooding and clogging. We eventually switched over to a raft system.

“Our raft system was five levels high. It was 12 feet high about 24 feet long and 4 feet wide. We had two of these systems. These were our major production systems.”

When the Howatts moved into the building they had limited funds to set up the production facility.

“At the very beginning we started with more fluorescent than LED lights,” Julian said. “We didn’t have a lot of money and LEDs were more expensive. We weren’t willing to make the jump to just LEDs at that point.”

A fire in January 2016 destroyed the interior of the building including $10,000 worth of crops that had just been planted.

Solution

“We lost the entire farm to the fire and had to restart,” Julian said. “We had maxed out the space in the building and had already started considering options of expanding, relocating and scaling up our production before the fire occurred. We restarted the business in June 2016 and started selling greens again in September 2016.”

The company’s new location consists of 7,000 square feet with 1,000 square feet of that space used for office, storage and cold storage.

“Our set up is basically a big rectangular space,” Julian said. “We have the space for six large towers. We have the frames built and are currently using three of them. Each tower measures 16 feet tall, 50 feet long and 4½ feet wide and has six production levels. Each level has two ponds measuring 4- by 24-feet. As we expand we are filling in the frames with the ponds, rafts, plumbing, lighting and wiring. The water reservoir is at the bottom of the tower and the water is pumped up to each level and then drains down to the bottom.

“Of the nearly 6,000 square feet of production area we currently are only using half of that space. By next summer we expect to be using all of it. We have about 4,000 square feet under lights. That will double as we expand. It will be close to 8,000 square feet under lights once we are at full production.”

For the new facility the Howatts chose GE LEDs which they have been using since January 2017.

“After the fire we began looking at rebuilding and we only considered installing LEDs,” said Julian. “We didn’t even consider fluorescents. It was mostly because of power constraints. The fluorescent lamps were consuming too much power and generating too much heat. It wasn’t feasible to add more fluorescents.

“Because of the exchange rates we shopped around for price quotes and even though Hort Americas wasn’t the lowest, what we really liked was the customer service that the company offered and the industry knowledge that Chris had that most of the other lighting suppliers didn’t. The other suppliers we contacted had experience related to greenhouse production, but they weren’t as knowledgeable in regards to indoor farming.”

Local by Atta produces a variety of lettuces, basil, kale, Swiss chard, bok choy, cilantro and microgreens. Products are sold at farmers markets, health food stores, grocery stores, restaurants and through a weekly basket program.

Benefits

Julian said one of the advantages of using the GE LEDs is their energy efficiency.

“The biggest constraint for us besides money is the power constraint,” he said. “How much power do we have access to in the building can be an issue. It’s not as simple as just getting more power from the utility company.

“The GE LEDs are more efficient so we can get more light for the same amount of power, which is a nice bonus for us. Most of our crops grow better under the GE lights when they have the same light intensity or when we can give them more light because we can afford the power. Generally for most crops the yields are better and the quality of the product is better. This is especially true for red lettuces. We get better red pigmentation.”

For more: Local by Atta, (506) 233-0393; moncton@atta.ca; http://www.atta.ca; https://www.facebook.com/LocalByAtta.

Click here for additional Case Studies and Horti-Facts.

Prepared by Hort Americas 2017©          Photos courtesy of Local by Atta

Current powered by GE Hort Americas

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LEDs have the potential to change how crops are grown

The use of LED grow lights to provide specific light wavelengths could allow growers to increase nutritional values of edible crops, enhance the intensity of foliage and flower color and improve the postharvest longevity of ornamental and edible crops.

Improvement in the light intensity delivered by light emitting diodes (LEDs) is helping to expand their use for the production of both edible and ornamental crops. Research with LEDs has been going on for about 30 years. Only within the last 10 years have increases in the light
intensities of LEDs allowed researchers to study the direct effects of narrow wave bands of light on plant physiology.

 

“LEDs are now available to deliver all blue, all red, all green, all yellow light or mixtures,” said University of Tennessee plant sciences professor Dean Kopsell. “White LEDs are almost a broad spectrum light source. White LEDs are actually mostly blue light with a little bit of red, yellow and green light with a white phosphor over them.”

Kopsell and his colleagues at the University of Tennessee are studying the impact individual types of light can have on the nutritional qualities of edible crops. Their work is focusing on crops that can be produced relatively quickly in 25-35 days, including microgreens and baby greens. They have also begun looking at some herbal crops including basil, tarragon and chives.

Researchers at the University of Tennessee are finding that exposing plants like brassicas to blue light is having a significant effect on their nutritional values. Photos courtesy of Dean Kopsell, Univ. of Tenn.

 

“Some of the unique things we are finding are when we change the light quality environment, going away from broad band light sources like fluorescent, incandescent and HIDs, and exposing plants to narrow band wavelengths of red and blue light, many things are changing in the plants. These narrow bands of light are having an effect on several plant quality parameters from a metabolic standpoint.”

 

Potential of specific light wavelengths

 

University of Tennessee researchers have found that exposing plants to narrow wavelengths of the light spectrum has resulted in the increased production of antioxidants and anti-carcinogenic compounds within the plants.

“What is even more interesting is some of the primary metabolites like the mineral nutrients are also increasing,” Kopsell said. “We are shifting the light ratios and putting more blue light into the mix. Blue light is close to the ultraviolet (UV) range and has higher energy values than red light. Because of the higher energy level associated with blue light, the more blue light we are exposing the plants to, it seems the more significant the results are on nutritional values.

“We haven’t got hard data yet, but everything that we can see, smell and taste, these blue lights not only affect nutrient uptake, and anti-oxidant metabolism, but they also affect aromatic compounds and flavor compounds. They make them more intense.”

Although researchers have only recently begun to study the impact of narrow light wavelengths on plant physiology, Kopsell said this will be the major use of LEDs in future applications.

“Not only is a grower going to be able to select the type of light and intensity from the LED manufacturer, but eventually the grower will know when is the critical time to apply a specific amount of light to a crop. One of the things that we have seen with these short term crops is using the light as a finishing-off treatment. The crops are grown under regular light conditions like any grower would have the ability to do and then just before harvest the plants would receive a specific type of light for a certain period of time. This light treatment would stimulate the plant physiology uptake and metabolism right before the plants go to the retail market.”

Kopsell said research exposing leafy brassicas to blue light prior to harvest has intensified pigments and green leaf color.

“We increased the green pigments in the leaves so that they looked more vibrant,” he said. “Other research has shown that UV light increases the anthocyanin compounds in leaf lettuce. Providing a little UV light, which is blocked out in most greenhouse environments, at the right time, a grower can get a crop to color up quickly before the plants are shipped out. What we have done with leafy greens to intensify the color of the leaves can also be done with petal tissue. By changing the light quality a grower could get more vibrant flower colors.”

Need for fine tune management

Kopsell said whether plants are grown outdoors, in a greenhouse or in a closed controlled environment with artificial light, the plants are using specific wavelengths from the available light source.

“Horticulture, floriculture and agronomic researchers know how much light is needed in order to produce crops with broad spectrum light,” he said. “The million dollar question that hasn’t been answered is how much light is needed from LEDs to achieve that same level of production? It is going to be less than the daily light integral (DLI) from a broad spectrum light source. But, right now we can’t tell you how much less it’s going to be.

“Applying specific light wavelengths when the plants need them, whether it’s for juvenile growth, flowering or fruiting, we don’t have a good grasp on the amount of light that the plants actually need. If a grower is only going to supply his plants with red and blue light, how much less light can a grower use in that production system?”
One of the reasons that plants will not require as much light from LEDs is because of the reduction in light stresses.
University of Tennessee studies have shown LED grow lights provide  a less stressful light environment for plants.

“Providing specific types of red and blue light, the amount of stress on plants is reduced because the plants don’t have to tolerate the light not being used for metabolism and physiology,” he said. “We have data that shows LEDs provide a less stressful light environment for plants. So we have to determine how much less light is needed. It is going to require an extra level of management to know what kind of light, how much light and when to apply it. Growers are going to be able to use LEDs to fine tune the light environment. It’s going to depend on the crop, how it’s being grown, where it’s being grown and how the crop will be used. Is it an ornamental, edible or medicinal crop? It’s not going to be as easy as sticking a seed or cutting into a substrate and letting Mother Nature take control. It’s really going to take some fine tune management. But the future looks bright so far.”

 


For more: Dean Kopsell, University of Tennessee, Plant Sciences Department, Institute of Agriculture, Knoxville, TN 37996-4561; (865) 974-1145; dkopsell@utk.edu.

 

David Kuack is a freelance technical writer in Fort
Worth, Texas; dkuack@gmail.com.Visit our corporate website at https://www.hortamericas.com
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Hort Americas visits Plant Factories (Vertical Farms), Tokyo and Chiba University

Hort Americas had the opportunity of the year this past week.  Hort Americas was able to visit commercial horticulture businesses (including but not limited to greenhouses, garden centers, vertical farms and plant factories) in Tokyo and Yokohama and then head to an International Meetings on Plant Factory at Chiba University.

We know pictures are worth a thousand words, so please enjoy.

Small garden centers and poinsettias were everywhere.
Plus we had a chance to visit the Sakata Garden Center.

Japanese consumers are definitely willing to pay for quality.

Vertical farming concepts at Farming Frontier 2012

Plant factory research was one of the many reasons for our trip.

Local farmers market in downtown Tokyo.

We will save the details of this one for later.

Green walls on high-end jewelry stores on Ginza St.

Just one display of some of the amazing orchids we saw.

Chiba University is, in our opinion, providing students with an amazing opportunity to innovate  in the green world.
Dr. Kozai – nothing more needs to be said.

Climate-controlled propagation of tomatoes for the greenhouse.

Chiba University branded tomatoes.

Mirai’s Plant Factory at Chiba University.

“Green-Innovation”

Plant factories in the mall – Mirai.

University of Wageningen and Chiba University working together to innovate the horticulture industry.

A very nice reception at Chiba – International Meeting of Plant Factory 2012.

Chiba University

New technology from Mebiol – Greenhouse-grown tomatoes

One final garden center photo.

Should you have additional questions on any of the images, please email us at infohortamericas@gmail.com.

We look forward to hearing from you.

Visit our corporate website at https://www.hortamericas.com

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Algae Production Using LEDs at the University of Kentucky

Algae production could help reduce greenhouse gases

Researchers at the University of Kentucky are using a greenhouse and LED lights to study the feasibility of growing algae with flue gas from coal-burning power plants to reduce greenhouse gas emissions.

By David Kuack

Algae are considered a nuisance by commercial greenhouse growers. The warm, moist conditions that occur in greenhouses provide the ideal environment for algae growth.
Algae can be found anywhere these conditions exist, including floors, walkways, under and on benches, on greenhouse glazings and walls, in irrigation pipes and emitters and misting lines, on the surface of evaporative cooling pads and on the surface of growing media in containers and ground beds. Algae can also be a food source for fungus gnats and shore flies. But algae also hold great potential in the production of value-added products.
Even though algae are a problem for growers, these simple green plants hold great potential in the production of biofuels, fertilizers, cosmetics, fish and animal feed and other value-added products. Members of the algae program at the University of Kentucky in Lexington are looking at the potential of algae production to help lower the emission of greenhouse gases, primarily carbon dioxide, from the burning of fossil fuels, particularly coal.
Andy Placido, an engineer associate with the university’s Center for Applied Energy Research, said the restrictions on greenhouse gas emissions will only increase as environmental issues gain in importance among the public and government and regulatory officials.
Kentucky’s Department of Energy Development and Independence is always looking for ways to make coal cleaner because it is a big part of the state’s economy,” said Placido. “State officials know that there is eventually going to be some type of restrictions or tax on greenhouse gas emissions. Coal produces more carbon dioxide per energy unit than natural gas and other fuels. So officials are trying to evaluate the technology that is available to reduce greenhouse gas emissions.”

Algae Production with LEDs
This culture closet is equipped with LED lights and temperature
control. It is used to grow algae from a few milliliters up to
15-20 liters. The algae is then moved into a greenhouse for further
production under  higher light levels and warmer temperatures.

An ample source of carbon dioxide
While most coal-burning power plants in Kentucky have been equipped with scrubbers to remove sulfur dioxide and nitrogen oxides, Placido said little has been done to restrict the amount of carbon dioxide that is generated in the flue gas.
“We are going to be using post-scrubbed flue gas, which is going to contain about 12 percent carbon dioxide and not a whole lot more,” he said. “There is a minimal amount of sulfur and nitrogen. That is the reason we are looking at using the carbon dioxide because there aren’t any mature technologies for the capture of this gas. Right now, we are basically following the same route that occurred during the 1980s when these power plants were looking for the technology to capture the sulfur and nitrogen.”
If the research is successful in capturing and using the carbon dioxide, there is the potential to use some of the sulfur and nitrogen currently being removed from the flue gas by the scrubbers.
“We know that algae use sulfur and nitrogen in addition to carbon dioxide,” he said. “Algae might eventually allow for the scrubbers to be eliminated altogether.”

LED lights and a greenhouse
Placido said the algae culturing system starts in the laboratory where the algae are allowed to multiply.
“We work with the university’s Department of Biosystems and Agricultural Engineering which maintains the algae strains in beakers,” he said. “The algae are purchased in small vials and then cultured up to a few hundred milliliters.”
Placido said this is when he and the other researchers start to work with the algae in an in-house designed culture closet equipped with Philips LED lights.
“We are growing algae indoors with temperature control,” he said. “We are starting to bubble in 5 percent carbon dioxide to allow the algae to acclimate to a higher percentage of carbon dioxide along with the LED lighting as we prepare to move the algae into the sunlight. When there is enough algae that have acclimated (0.05-0.1 gram of algae per liter of water), they will be taken from the culture closet to the greenhouse. In the greenhouse, it will still be a temperature-controlled environment. We’ll allow the algae to grow in the greenhouse and once they become accustomed to the higher light levels and change in temperature, we will take the algae out to the power plant where it will be exposed to outdoor conditions along with the flue gas. That is our algae process chain.”

Maximizing algae growth
LED lights are being used 24 hours a day in the culture room to provide constant light. Placido said they are also looking at using the LEDs outside as a supplement at night and possibly during winter at the power plant so the algae continue to grow.
“During the night algae start to respire during which they release carbon dioxide and take in oxygen,” he said. “This is the reverse process of what happens during the day. By using the LEDs we can keep the algae growing for 24 hours or at least reduce the respiration process. Because the LEDs are very efficient, we expect more algae will be produced than the energy needed to operate the lights.”
Placido said algae split when they grow so production is judged on doubling time. Under optimum light and temperatures in the lab a doubling time of 12-24 hours is achievable.
“With the outdoor conditions we will have with the flue gas, we are hoping to have a doubling time of two to three days,” he said. “We would like to increase the growth rate, but that is going to take some nutrient work along with optimizing the light and temperature levels. Outside we’re at the mercy of Mother Nature.”
Placido said algae growth is much better with the LEDs in a controlled environment than outside under natural conditions. He said the difference in growth comparing inside and outdoor conditions has not been quantified.
“We have gotten much greater algae growth rates inside in the culture closet equipped with LEDs than outside or in the greenhouse even under the best days in regards to light and temperature,” he said.



Algae Production in Photo Reactors
Algae is produced in photo-reactors that can be placed inside or outside  of a  greenhouse.
 The ultimate goal is to build a large reactor adjacent to a coal-burning  power plant
that  will use the carbon dioxide given off in the plant’s flue gas.

Real world use
Placido said when the system is set up at the power plant, more flue gas will be produced than can be used to grow the algae. The flue gas will be pulled into the photo-reactor, which is a series of glass tubes on a steel frame, as carbon dioxide gas is needed.
“Once the system is saturated with carbon dioxide, the algae will be allowed to grow and then will be harvested. More carbon dioxide will be added as it is needed,” he said. “We know that our reactor isn’t nearly big enough to capture all of the carbon dioxide. The reactor we are using only holds about 2,000 gallons of water. That’s a good size, but nowhere near the size we would need to capture all of the carbon dioxide. We have estimated to capture all of the carbon dioxide from this one power plant would require a reactor that would cover 100 acres and take millions of gallons of water.
Placido said the power plant can provide an unlimited amount of steam to keep the water in the reactor tubes from freezing during the winter.
“During the winter with the sun’s heat during day the water temperature would stay above freezing,” he said. “With the steam from the power plant to heat the water along with keeping the water circulating continuously, that should be enough to keep the system from freezing. Then we would supplement the natural light with the LEDs if it was needed.”

Grower potential
Placido said there are some possibilities for commercial growers to produce algae and use algae in the future.
“That is our goal, to find out how we can improve the process for making fuel and how does that compare with other algae-derived products, such as fertilizers, animal feed, etc.,” he said. “Our end goal is to make biofuel. In the future the ideal situation would be for growers to produce their own energy source.”

For more: Andy Placido is Engineer Associate II, University of Kentucky, Center for Applied Energy Research, (859) 257-0223; andy.placido@uky.edu.
David Kuack is a freelance technical writer in Fort Worth, Texas, dkuack@gmail.com.

Visit our corporate website at https://www.hortamericas.com

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Improving Greenhouse Production with LED Lights

U.S. researchers are looking at the potential benefits to
the propagation and production of greenhouse ornamental and vegetable crops
using LED lights.

By David Kuack
Although U.S. researchers have started studying the
effects of LED lights on the production of greenhouse ornamental and vegetable
crops, much of the data being used by American growers comes from studies done
in Europe. Purdue University horticulture professor Cary Mitchell said that studies
currently being done in the United States will provide growers with information
that is relevant to their production and climatic conditions.
Mitchell is leading a team of university researchers who
have received a $4.9 million grant, including $2.4 million from USDA, to study
LED lighting for greenhouse applications. Mitchell along with Purdue
horticulture professor Roberto Lopez is working with scientists and engineers at
the University of Arizona, Michigan State University, Rutgers University and
Orbital Technologies Corp. Mitchell is working with graduate student Celina
Gomez to study the impact of LED lights on the propagation and production of
high-wire tomatoes. Lopez and graduate students Christopher
Currey and Michael Ortiz are studying the use of LED lights on bedding plant
cuttings and plugs.
Propagation trials
Due to limited greenhouse research space, Gomez is using
one bench to compare the effect of providing supplemental light from a high
intensity discharge lamp or from LED lights with control plants that receive
only natural daylight. During the first year of the propagation study, Gomez is
conducting an experiment every month. The experiment includes a control group
of tomato seedlings that receive no supplemental light, an overhead HID lamp
that provides the industry standard and overhead LED arrays that provide three
different ratios of red to blue light.
“The propagation experiment is repeated for three weeks
every month,” Mitchell said. “We are measuring the differences in plant growth
from one month to the next. As we enter spring, the ambient light levels are
increasing. Gomez will measure the daily light integral (DLI) that is occurring
and the different red/blue ratios and what the plants prefer and determine what
they need. In addition to the plant metrics being collected, we are also
measuring the amount of electricity used for supplemental lighting.”
After the tomato seedlings reach the stage at which they
would be grafted onto the rootstock, data is being collected including plant
dry weight, height, stem diameter, leaf span and leaf area.
Mitchell said the propagation area that is equipped with
the lights receives 5 moles per square meter per day of supplemental light in
addition to the natural solar daily light integral that varies throughout the
year.
“Since we have only done the experiment a couple of times
so far this year, we’ve yet to see what kind of plant response pattern emerges,”
he said. The supplemental light we are providing now might not be enough light
during the dead of winter. Any benefits of supplemental light that occur during
the winter should disappear as the trials move later into spring. Once we have
obtained a full year profile of seedling response, we will be able to determine
the optimum amount of supplemental light to apply each month.
“One of the best management practices that we hope comes
of this long term study is to determine at what point it is important to use
supplemental lighting, as well as when it is no longer useful to do so.”
For the propagation study the tomato seedlings are
receiving supplemental light for 23 hours a day in order to achieve a daily
light integral of 5 moles per square meter per day.
Tomato seeds are being germinated in a substrate called
steadyGROWpro plugs. Six different tomato varieties are being tested: ‘Success’,
‘Komeett’, ‘Maxifort’, ‘Sheva-sheva’, ‘Liberty’ and ‘Felicity’. Seedlings of ‘Success’
and ‘Komeett’ are used for the production study after being grafted onto ‘Maxifort’.
These varieties were recommended by Marco de Bruin at Bushel Boy Farms in Owatonna, Minn., because they have
different growth habits.

Production trials
In the production experiments the grafted seedlings are
being transplanted into Coco Agro coir slabs.
“The lighting treatments containing both test cultivars
are blocked into separate half rows in order to determine if there are position
effects within the greenhouse that could affect yields,” Mitchell said.
The plants are being provided with supplemental light
twice a day. He said they are applying a daily light integral of 9 moles per
square meter per day.
“In early March we were lighting for 12 hours per day,”
Mitchell said. “Lighting usually starts well before sunrise and begins again
before the sun goes down.”
The first production study in 2012 began at the end of
January. Mitchell said the tomato plants that had received supplemental light
treatments were already setting fruit in early March.
“The control plants that didn’t receive any supplemental
light were way behind,” he said. “They were barely setting fruit. That’s what
you would expect in a cloudy region like Indiana.”
The first production experiment of 2012 will be
terminated after six months and a second will begin immediately. Mitchell said
the second experiment will be the exact opposite of the first in terms of solar
daily light integral changes.
“We want to see what challenges there are both with the
propagation and the production starting in the summer and going into the winter,”
he said. “If production is started in the greenhouse in July, the plants are
going to be receiving a lot of sunlight. As the photoperiod starts to shorten going
into fall that is when supplemental lighting will be more valuable.
“We are hoping to come up with recommendations for
growers in this region or in any other northern region that has cloudy weather regarding
when is the best time to start lighting their crops. We are also looking at
timing the production so that growers are not competing with home-grown or
field-grown tomatoes. That way the greenhouse growers are not competing with
availability and price for what’s being grown in backyards or in the field.”

Priming the ornamentals
propagation pump
Purdue horticulture professor
Roberto Lopez and graduate students Christopher Currey and Michael Ortiz are
studying the effect of supplemental light on the propagation of ornamental
vegetative cuttings and plugs.
“We’re looking at the top three
flowering crops that are produced from vegetative cuttings, which are
geraniums, petunias and New Guinea impatiens,” Lopez said. Currey and Ortiz are
comparing rooting, dry mass accumulation and other quality parameters under red
and blue LED lights to high pressure sodium lamps. Initial trials with cuttings
have shown that there are not a lot differences in terms of rooting time and
quality between the two light sources. Additionally, preliminary data is
showing no differences in the time to flower or quality of cuttings propagated
under the various LED lights and high pressure sodium lamps for the three
annual crops.
“Initially, the results
are very similar for
both rooted cuttings and finished plants,” Lopez said. “But this is very
preliminary. There were really no differences seen for these three crops. What
we were mainly trying to achieve was a certain daily light integral with both
the high pressure sodium and red and blue LEDs. With the additional trials that
we will be doing we will also be looking to quantify the amount of electricity
used by the high pressure sodium lights and the LEDs.”
Best timing,
amount of light
Lopez said none of the vegetative cuttings received
supplemental light during the first seven days of propagation because that is
when the cuttings are forming callus.
“A grower typically wouldn’t use lights during this
period unless the light level was really low,” he said. “During that period the
grower is trying to baby the cuttings to get them to form callus. If the light
level is too high during this period the cuttings could be stressed. After a
week the cuttings begin to form roots and start to photosynthesize. A grower
can maximize photosynthesis during rooting by increasing the daily light integral.”
Currey’s research and studies
Lopez performed at Michigan State University indicate growers should
provide a daily light integral of between 8-10 moles per square meter
per day to be able to increase rooting and the overall quality of the cutting.
Lopez and Ortiz are also
testing LED lights during plug propagation of celosia, cosmos, impatiens,
geranium, marigold, pansy and petunia.
“One of the biggest challenges with
plug production of annual bedding plants is keeping the plugs compact,” Ortiz
said. “Compact plugs ease transport in boxes and allow for a higher volume of
plugs to be transported at one time. This is definitely something to consider
as fuel prices continue to rise.
“Plugs are often grown in dense
288- or 504-cell trays that promote rapid stem elongation. We are using red and
far red LEDs in end-of-day treatments in an attempt to manipulate the
phytochrome-mediated genes that are responsible for stem elongation under dense
planting conditions. If LEDs can be used to control seedling height, the
industry can decrease its reliance on plant growth regulators.”
Lopez and Ortiz are also
investigating red and blue LEDs as a supplemental lighting source during winter
bedding plant plug production.
“The goal behind this
experiment is to quantify root development under different ratios of red and
blue LED light and high pressure sodium light,” Ortiz said. “We also are also
trying to determine if supplemental light from LEDs can offer more rapid root
development than light from high pressure sodium lamps. This can make a big
impact on energy use in the industry.”
Lopez said producing cuttings is much different than producing
plugs.
“With plugs a grower is starting out with plants that
have roots,” Lopez said. “A grower may end up being able to delay the sowing of
the plugs if he is using lights. We may find that the LEDs might prove to be
even more beneficial with plugs than with cuttings.”
For more: Cary Mitchell, Purdue
University, Department: Horticulture and Landscape Architecture, (765) 494-1347;
cmitchel@purdue.edu.
Roberto Lopez, Purdue University, Department of Horticulture
and Landscape Architecture, (765) 496-3425; rglopez@purdue.edu;

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