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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.

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

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  • 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

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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.

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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.


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

We look forward to hearing from you.

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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;
David Kuack is a freelance technical writer in Fort Worth, Texas,

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AJ Both of Rutgers discusses LED Lights for Horticulture and Greenhouses

Best management practices for selecting LED lights

Development of testing guidelines will make it easier for light manufacturers and growers to compare LED systems.

By David Kuack

Growers are always looking at new technology for growing their plants faster, better and cheaper. One of the relatively new technologies that is gaining interest among growers and researchers is light emitting diode (LED) lighting.
So far, much of the research that has been done on LED lighting for plant production has occurred in Europe and Japan. More recently an increasing number of researchers and growers in the United States have begun to look at what benefits the use of LED lighting may have on both vegetable and ornamental plants. This research is focusing on different phases of the production cycle, including seed germination, vegetative propagation, the impact on flowering and increased photosynthesis.
Much of the LED research in the United States is being conducted by plant scientists. One research project, which has received funding from USDA, is a cooperative effort between researchers at Purdue University, Michigan State University, University of Arizona and Rutgers University. While some of this project’s studies are examining plant growth and development, one part of the project is focused on developing best management practices and guidelines for testing and selecting LED lighting.

LED Grow Lights
LED Grow Lights used in Cut Roses

Measuring LED performance
A.J. Both, an agricultural engineer in Rutgers University’s Department of Environmental Sciences, said his part of the research project addresses the challenges that any grower or consumer encounters when they look at LED lighting.
“There are many companies with products on the market today and they all have claims about lifespan, light quality and benefits,” Both said. “It’s very difficult to verify these claims independently. So every manufacturer can pretty much claim what it wants. There is no real standard or baseline that we can relate these statements to and say this makes sense or no this is too outlandish to even consider.”
Both said he and the other project researchers thought it would be worthwhile to come up with a standardized approach or procedure to measure LED lighting systems for greenhouse applications.
“This would be an experimental setup in a controlled environment where measurements would be made of electricity consumption, light output, light intensity and light spectral qualities,” he said. “We would develop a testing procedure to compare manufacturers’ products. We would then come up with some guidelines that would be provided to the industry. This would then enable both manufacturers and greenhouse growers to make comparisons between the lighting systems that are available.”

Making light comparisons easier
Both said the testing design that he is developing will allow manufacturers and growers to bring in light systems on which specific tests can be conducted related to energy consumption and other performance parameters. The tests will enable Both to evaluate the entire product.
He said all of the project’s researchers are planning to do tests on some manufacturers’ lights.
“It’s not going to be feasible to test every single unit that is available,” he said. “We are not like “Consumer Reports” that can do testing on a large scale and publish a lot of data. We will be selective in the number of systems that we will evaluate. We probably won’t test more than a couple dozen lights per year. We’re not planning to be in the business of running a commercial testing lab.”
Both’s goal is to develop a testing bank or testing set up within the next year and to start some initial testing as soon as the components are available.
“We will trial a limited number of lamps because the tests will require some time and some consideration as to what environmental conditions we want to test the lights under and the type of measurements we need to take,” he said. “Initially it will take more time and then as we get used to the testing procedures it will go more quickly.
“The testing that will be done is mostly for our own understanding and the ultimate development of guidelines or standardized measurement procedures. The industry, both manufacturers and growers, can use these standards to verify claims independently. Providing a set of guidelines the industry can follow and base their claims on will make it easier for growers to compare the different systems available.”

LED Interlighting Modules used in Greenhouse Tomatoes
LED Grow Lights used as Interlighting in Greenhouse Tomatoes

Looking at other industries
Both said the project researchers are looking at the lighting industry to see if there have been other guidelines or procedures developed. He said standards are being used in the architectural lighting industry and these will be looked at to determine if they have application to the guidelines being developed for the greenhouse industry.
“Of course, we want to take a look to see how much of those other industries’ standards apply to this particular application and to determine what changes we may have to make to really make it worthwhile for our industry,” he said. “Because we are an independent entity in this whole testing process, whatever we develop is going to be scientifically sound,” he said. “Hopefully the testing process will convince the industry, particularly the manufacturers, to voluntarily adopt these guidelines in their design and manufacturing procedures. They can also be used as a marketing tool for the purpose of gaining the acceptance of growers.”

Combining research results
Both said that by combining the information he collects with the findings of the plant scientists he is working with should provide growers with specific crop information.
“Determining which LED lighting is best for a particular crop is part of what the other project researchers are doing,” he said. “They are looking at it more from a quality aspect. What light wavelengths to provide, where to locate the lights in the crop canopy, what duration, and things like that. I’m looking at it from the standpoint of what type of lights need to be evaluated to make it clear to growers what choices they have and what system might be better for them depending on their operation.”
Both said the researchers plan to trial some of the systems that have potential at several grower operations. He expects to be involved with the grower installations for testing purposes and will likely be taking some measurements at these locations.

A learning process
Both said the history of using LEDs is relatively short and the challenges and benefits associated with their use are not yet fully understood.
“It is going to take some time to figure out for a particular crop what are the benefits and challenges of using LED lighting for photoperiod control or for photosynthesis lighting,” he said. “To expect our four-year project to discover everything there is to know about LED lighting is not realistic. We are going to need a lot more time as a research community to investigate all the issues related to LED lighting before the implementation can be complete.”
For more: A.J. Both, Rutgers University, Department of Environmental Sciences, Bioresource Engineering, (732) 932-9534;
David Kuack is a freelance technical writer in Fort Worth, Texas,

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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
“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
“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;
Roberto Lopez, Purdue University, Department of Horticulture
and Landscape Architecture, (765) 496-3425;;

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