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GLASE consortium aims to improve greenhouse energy efficiency

Even though the Greenhouse Lighting and Systems Engineering (GLASE) consortium is New York-based, the research it is doing has the potential to impact controlled environment agriculture worldwide.

The Greenhouse Lighting and Systems Engineering (GLASE) consortium is a partnership between Cornell University in Ithaca, N.Y., and Rensselaer Polytechnic Institute (RPI) in Albany, N.Y. The consortium will be conducting research to improve controlled environment agriculture (CEA) operations including reducing energy consumption.



The goal of the consortium is to create a more sustainable and profitable greenhouse industry. Although the focus of the research will be on greenhouse production, the findings should also have application to indoor CEA production including vertical farms and warehouses. Greenhouses, which can be electricity-intensive depending on the level of automation, cover 720 acres in New York State. The consortium is looking to reduce greenhouse electricity use and concomitant carbon emission by 70 percent and to increase crop yields by 2030.

Erico Mattos, who was appointed executive director of GLASE in June, said he has been hired as a subcontractor by Cornell University and will be working to recruit industry members to join the consortium.

“Currently I have a 50 percent time appointment with GLASE,” Mattos said. “My time with GLASE will increase as we bring in industry members. I am living in Georgia, but will be moving to upstate New York over the next year and will be located between RPI in Albany and Cornell University in Ithaca.”

Mattos said GLASE is a seven-year project which has received $5 million from the New York State Energy Research and Development Authority (NYSERDA). The money will be used to sponsor research between Cornell and RPI.

“The team leaders who will be doing the research are Neil Mattson at Cornell University and Tessa Pocock at RPI,” said Mattos. “They have a set of more than 300 milestones that their teams have to reach. They have already achieved some of these milestones.”

The research activities include improving lighting fixtures and systems that synergistically control lighting, ventilation, humidity and carbon dioxide, improving CEA operations and reducing energy consumption to create a more sustainable and profitable greenhouse industry.

“The teams at Cornell and RPI are well equipped with the resources they need to achieve the milestones of the core research proposal that has been sponsored by NYSERDA,” he said. “Even though the teams led by Neil and Tessa are completely self-sustainable, they may require some outside partnerships to achieve some of the goals.”

The GLASE consortium is headed by researchers Tessa Pocock at Rensselaer Polytechnic Institute and Neil Mattson at Cornell University and GLASE executive director Erico Mattos.
Photo courtesy of GLASE

Mattos said in his role as executive director he will act as an intermediary between Cornell, RPI and NYSERDA making sure that the research is proceeding and that milestones are being completed on time.

“The most important part of my position is to create a consortium with industry members,” Mattos said. “The goal over the next seven years will be for the project to receive less money from NYSERDA and more money from industry members. We want to establish a consortium that is self-sustaining. By bringing in industry members we will have money to do our own-sponsored research, technology transfer, outreach, and market research, all these types of things and GLASE will be self-financing.

“My role as executive director is to ensure that the team moves in this direction. By bringing in industry members, offering them the project and making sure that we provide them with access to the technology that is developed by Cornell and RPI.”


Complementary research

Mattos said the research that will be done at Cornell and RPI is complementary and will not overlap.

“RPI will be doing more engineering-related research, such as looking at light fixtures and components including the drivers and controllers,” he said. “They are also looking at photobiology—how plants respond to different spectra as they grow and produce different nutritional compounds and changes in plant metabolism and morphology. The RPI research work is more engineering-related.

“The research at Cornell is going to be more applied in the greenhouse, such as interactions of carbon dioxide enrichment and lighting control studies. Cornell will implement some of the systems that have already been developed at Cornell. Cornell will also be looking at different systems and different crops. Initially the studies will be done with tomatoes, lettuce and strawberries and then will be extended as necessary.”


The research conducted at Cornell University will be more applied in the greenhouse, including carbon dioxide enrichment and lighting control studies.
Photo by Chris Kitchen, Cornel Univ. Marketing

Mattos said the research will be expanded to commercial size greenhouses in New York, which will be 6,000 square feet for a small scale greenhouse and 20,000 square feet for a large scale greenhouse.

“RPI will develop new systems and Cornell will implement the greenhouse tests and then move forward to a final demonstration,” he said.

Mattos said the researchers will also be working in partnership with A.J. Both at Rutgers University, who will be doing some of the energy efficacy and radiometric studies of the light fixtures.

“One of the milestones Cornell research associate Kale Harbick will be working on is modeling,” Mattos said. “This will involve trying to calculate in advance how much energy in a greenhouse is consumed and what happens if some of the variables are changed. The research will look at how these changes affect the general energy consumption of the greenhouse.”


Seeking industry support

Mattos said when GLASE was developed over 30 industry companies provided letters of support indicating they wanted to become part of the consortium as industry members. Since the consortium was started, many other companies have expressed their interest in becoming part of the consortium.

“Even though these companies signed letters of support that doesn’t mean they will all become consortium members,” he said. “Cornell and RPI are both already working in partnership with some companies to develop the core research. There is nothing official as industry members yet. We are looking to bring in other industry members and really make them a part of this consortium. We want to reach a broad range of industry members so this support could be both financial or it could be providing equipment to conduct the research. But the primary goal is to bring in financial support.”

Mattos said there will be a series of benefits that come with industry membership.

“They would pay for a membership and then they would get a series of benefits. We are now working with a marketing media company to promote the consortium and the opportunity for membership.

“We want to bring in large manufacturing companies, but we also want to address the other end of the spectrum and work with small growers. The growers will benefit the most from this research.”


Academic collaborators, information hub

Mattos said it is the intension of the consortium to expand with researchers from outside New York.

“We intend to establish future academic collaborations to develop new research projects partially funded by GLASE through industry membership funds and new research grants,” he said.

Another goal of GLASE is to create a hub for greenhouse lighting and systems engineering which includes the centralization of information.

“We will create a central database to indicate the academic research currently on-going in the U.S. (what, where and who) to facilitate the interaction between the industry and academia,” he said.


Impact on greenhouse, plant systems

The crops that are to be studied initially by Cornell and RPI researchers are tomatoes, lettuce and strawberries.

“These are commercially relevant crops,” Mattos said “I went to Ithaca and met some of the members of Neil’s team, including graduate students Jonathan Allred and Erica Hernandez and research technician Matthew Moghaddam, who have been working with tomatoes and strawberries. Lettuce is also one of the most commonly produced greenhouse crops.

“Part of the milestones that Tessa will be working on will be done in environmentally controlled growth chambers and growth rooms. Tessa does not have a greenhouse. Most of the research that she will be doing is related to photobiology. Everything that she will be doing has application to warehouse production even though she is not doing the research in a warehouse. This research will look at nutritional compounds and pigment production. The research in the growth chambers will be compared with greenhouse studies.”

The research conducted at RPI will be done in growth chambers and growth rooms, which should have application to commercial warehouse production.
Photo courtesy of GLASE

Although the RPI research is not targeted for commercial indoor farms, Mattos said the results could be used to support that type of production.

“The proposal is to reduce greenhouse crop production energy consumption by 70 percent in seven years,” he said. “The economic factor and the majority of the research will be looking at greenhouse systems and how to integrate them. Economically we are focused on greenhouses. But we will be doing studies in growth chambers that may have application to support indoor farm production.

“Tessa will be looking especially at biological efficacy. Everybody talks about the efficacy of the light fixtures themselves. A lot of people are looking at that. Getting less attention is the biological efficacy, which is if there is a different spectrum, the same amount of photons or micromoles, can have a different impact on plants. Not only the morphology, but also the pigments, the chemical pathways. This is the biological efficacy.”


For more: Erico Mattos, Greenhouse Lighting and Systems Engineering (GLASE) consortium; (302) 290-1560;;


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

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Webinar on “Managing Nutrient Solutions for Hydroponic Leafy Greens and Herbs”

If you missed the e-GRO webinar “Managing Nutrient Solutions for Hydroponic Leafy Greens and Herbs” on Jan. 22, 2016, which was sponsored by Hort Americas, you can still view the webinar on YouTube.

Hydroponic greens and herbs are produced in systems with recirculating nutrient solutions. In order to maintain productive and quality crops, it is important to know how to properly maintain the nutrient solutions. Dr. Chris Currey at Iowa State University and Dr. Neil Mattson at Cornell University discuss strategies for managing pH and EC, formulating nutrient solutions and identifying common nutrient disorders.

Part 1: Common production systems, pH and EC management

Presented by Dr. Chris Currey, Iowa State University


Part 2: Nutrient solution recipes, common nutrient disorders

Present by Dr. Neil Mattson, Cornell University

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Meeting the fertilization needs of greenhouse lettuce

Greenhouse lettuce can be a successful container or
hydroponic crop for ornamental plant growers looking to give edibles a try.

By David Kuack
Ornamental plant growers considering producing an edible
greenhouse crop may want to try lettuce. Neil Mattson, associate horticulture
professor at Cornell University, said lettuce is a plant with moderate
fertility needs.
“Grown hydroponically, lettuce has somewhat lower
fertility needs than a greenhouse tomato crop,”

Ornamental plant growers interested in growing edible
crops may want to try lettuce. It can be produced in
containers with a growing medium or hydroponically
in troughs or a float system (pictured).
Photos courtesy of Cornell University

Mattson said. “Grown as a
container crop, lettuce is relatively similar to petunia. However, lettuce has somewhat
greater calcium needs. Growers can produce a relatively good crop of lettuce in
containers, if they use a complete fertilizer at a moderate strength of 150
parts per million nitrogen.”

Mattson said head lettuce can be produced in containers similar
to a bedding plant crop. The seed would be planted into a plug tray for three
to four weeks. Transplanting the plugs into larger containers, the crop could
be finished in four to six weeks depending on light and temperature levels.
He said baby leaf lettuce can be grown in flats. The seed
is directly sown into the growing medium and grown for three to four weeks
until plants reach suitable size.
Calcium deficiency

Leaf tipburn is a physiological disorder that can occur
when growing greenhouse lettuce. It can greatly impact the salability of a

“The main reason that tipburn occurs is the lettuce is
growing too fast under high light,” Mattson said. “For lettuce, the target
daily light integral is 17 moles per square meter per day. The light level should
be lower if there is poor air flow. If the light level goes higher than 17
moles, the rapid growth of young leaves is affected. There may be an inadequate
calcium supply, especially as the lettuce heads begin to mature and close. If
there is not enough air flow and not enough transpiration by the young leaves,
then not enough calcium can reach the leaves through the xylem sap. This can
cause tipburn to occur. It’s a case of pushing the plants too fast.”
tipburn in lettuce is not a result of a lack of calcium
supplied to the plants,
but an inability of the plants to
transport enough calcium to the young leaves.
Mattson said in many cases, tipburn is not a result of a
lack of calcium supplied to the plants, but an inability of the plants to
transport enough calcium to the young leaves.
“For container-grown lettuce, there is typically enough
calcium if the growing medium has a lime charge and if the fertilizer water
solution contains more than 50 ppm calcium,” he said. “Many common bedding
plant fertilizers, including 20-20-20, 20-20-20 and 21-5-20, do not contain
calcium. These fertilizers are typically used with tap water sources that
contain moderate alkalinity. In many cases, these tap water sources also
contain sufficient calcium.”
Mattson said it is important for growers to test their
water sources to make sure adequate calcium is being supplied, either from the
water source or added into the fertility program. If calcium needs to be added,
calcium nitrate is most commonly used. However, calcium nitrate is not
compatible with most complete fertilizers.
“Usually if a grower has to add calcium, it can be done
using a separate stock tank or a separate injector,” Mattson said. “One
strategy is to use a separate injector for the calcium nitrate in a series with
a 20-10-20 fertilizer that is being added with a second injector. Adding 50 ppm
calcium from calcium nitrate should be sufficient.
“An alternative method of calcium application, if a
grower has only one injector is to rotate between two separate stock tanks, one
for calcium nitrate and one for the bedding plant fertilizer. A grower would then
rotate between the two fertilizers. For example, for two days he would use the
20-10-20 fertilizer and on the third day he would use the calcium nitrate
applied at 150 ppm.”
Production with
organic fertilizers

Mattson has been able to grow a relatively good crop of
container-grown lettuce using granular organic fertilizers incorporated into
the growing medium.

“We incorporated poultry-based organic fertilizer (Sustane
8-4-4) into the growing medium at a rate of 8 pounds per cubic yard for both
the seed germination and transplant growing mixes,” he said. “That provided
good fertility, but for optimum yields I would also suggest making some liquid
organic fertilizer applications, maybe two to three times a week as the plants
get older.”
Mattson said the organic granular fertilizer he used is
temperature-dependent and is broken down by soil microbes. Sustane 8-4-4 has a
45-day release period, but under very warm greenhouse temperatures Mattson has
noticed quicker release rates. He said there are other slow release organic
fertilizers with different release periods. For example, Verdanta EcoVita lists
a 75-100 day release period.
electrical conductivity and pH

One strategy that Mattson recommends growers do periodically
is to monitor the electrical conductivity (EC) and pH levels.

“Monitoring EC will help growers determine if the plants
are receiving sufficient fertility,” he said. “If a grower is incorporating a
slow release fertilizer, this is a good indicator of when additional fertilizer
needs to be added. An under-fertilized plant will show yellow lower leaves from
nitrogen deficiency.”

electrical conductivity (EC) can help avoid
under fertilizing lettuce plants,
which show yellow
lower leaves caused by nitrogen deficiency.

Mattson said monitoring pH is important as it impacts
nutrient availability. He said lettuce isn’t commonly susceptible to iron
deficiency, but it will start to show up when the pH starts to increase above
“Monitoring EC and pH is especially important in
hydroponics,” he said. “A good grower who is producing his crop in a growing
medium in containers will monitor the pH every week or two. The pH may change
over the course of a week by maybe one unit.
“Growing hydroponically, a grower should be monitoring
the pH every day and make adjustments. Depending on the type of fertilizer and
the quality of the water, the pH in a hydroponic set up could change two units
in a day.”
Optimizing lettuce

Mattson said light and temperature are going to be the
drivers for how long it takes to finish a lettuce crop. Whether a grower is
producing the crop in containers with growing medium or hydroponically
shouldn’t have any effect on the length of production.

He said plant spacing can also impact the size of the
lettuce head. If plants are grown in small containers and spaced pot-to-pot,
the lettuce heads may not reach full size.
For greenhouse lettuce, Cornell University researchers
developed a hydroponic production model that enables growers to produce a
lettuce crop from seeding to harvest in 35 days if temperature and light
intensity are at optimum levels.
“When the light level isn’t optimized, a lettuce crop can
take more than 100 days from seeding to harvest,” Mattson said. “High pressure
sodium lamps would be the best lamps to use if a grower is looking to provide
supplemental light in a greenhouse to increase the daily light integral. For
the Cornell model we adjust the amount of light in the greenhouse based on the
amount of outdoor light. Seventeen moles per square meter per day is the daily
light integral we are aiming for with the model. The optimum temperature for
plant development is about 75ºF
during the day and 65ºF
at night.”

For more: Neil
Mattson, Cornell University, School of Integrative Plant Science; (607)

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

Visit our corporate website at

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Using Supplemental Lighting in Greenhouse Vegetable Crops

Why you should consider lighting greenhouse vegetable crops.

Can’t decide if it would be worth installing supplemental lights for your greenhouse vegetables? A combination of supplemental light and carbon dioxide can ensure that you are maximizing plant growth.

Melissa Brechner, director of the Controlled Environment Agriculture Center for Technology Transfer at Cornell University, usually tells greenhouse vegetable growers that supplemental lighting is worth the investment.

“It depends a little on the scale of the greenhouse facility,” Brechner said. “It also depends on the crop and what’s the market. If you are growing in November, December, January and February in some of the darker locations in the country, which covers a sizable area, you absolutely need supplemental lighting, if you want to have maximum production.”

Brechner said a greenhouse vegetable grower is going to need a minimum of 15 moles of photosynthetically active radiation (PAR) per day in order to produce a crop.

“For Ithaca, N.Y., and for many other places, the light levels range from a high of 15 moles per day in January up to about 65 moles per day in July,” she said. “Those levels are not going to change drastically whether a grower is in Arizona or in Ithaca. What is going to change is that in Arizona there aren’t the really dark 0 and 1 mole days that occur in Ithaca.

“For tomatoes and cucumbers I tell growers that they should have more than 20 moles per day to produce a good crop. I don’t know how different production would be if the light level was 30 moles per day. Is it worth the extra 10 moles for the grower to put in supplemental lighting? I’m not sure. But it is certainly worth it for a grower to go from 1 to 10 moles and from 10 to 20 moles.”

High, low light issues

Although greenhouse vegetable growers associate more problems with low light levels, Brechner said high light levels can also cause problems with some crops.

“Growers can have problems with both high and low light levels depending on the season in which the grower is trying to grow and where in the country he is located,” she said. “If a greenhouse lettuce grower is trying to grow in Georgia in August or even October, he is going to have a problem with too much light. The grower better have a shade curtain in the greenhouse or he is going to have tip burn problems.

“In Massachusetts in December the issue is going to be not having enough light. I have talked to growers in the Northeast who have told me that they don’t use any supplemental light and they don’t use much heat, but it take them three months to produce a crop. If they were lighting and heating, they could finish that crop in 35 days. Also, in the Northeast the growers are going to have less than 15 moles per day outside light. And depending on the glazing the greenhouse is covered with is going to determine what percentage of light will make it into the greenhouse. It is going to be somewhere between 65 percent on the low end and 90 percent on the high end depending on a number of factors.”

Brechner said the amount of PAR light that reaches the plants is a function of:
1. the angle of the sun in relation to the glazing,
2. what the glazing material is made of,
3. the cleanliness and condition/age of the glazing,
4. shading from greenhouse structure components, and
5. type of light (direct or indirect).

<style=”text-align: center;”>A greenhouse vegetable grower is going to need a minimum of 15 moles of photosynthetically active radiation (PAR) per square meter per day in order to produce a crop.
(Photo courtesy of Cornell University)

Optimum light levels

Brechner said that growth is directly correlated to the amount of light the plants receive, especially when they are in a vegetative state.

“I think lettuce is a less forgiving crop. Tomatoes and cucumbers if you don’t give them as much light they will still grow,” she said.“Lettuce should have 17 moles of PAR per square meter per day. This refers to the combination of natural light that is transmitted through the glazing as well as any artificial light that is used.

Our research has shown that an average of 17 moles gives optimal growth while minimizing tip burn. Brechner said there are some differences in the amount of light that different types of lettuce will tolerate.

“We’ve found for Boston (bibb) lettuce that a daily light integral of 17 moles of light per day used with vertical airflow to increase the rate of transpiration in order to increase calcium uptake prevents leaf tip burn,” she said. “Romaine lettuce can’t take as much light before it gets tip burn. And it certainly can’t take as much light without having vertical airflow.

“Lettuce grown outside receives more than 17 moles of light per day, but it is windier outside. Lettuce, especially romaine, grown outside will get tip burn if there is too much light. Even during December you can find field-grown lettuce coming from California that is tip burned.”

Greenhouse vegetable growers can have problems with both high and low light levels depending on the season and where in the country an operation is located.
(Photo courtesy of Cornell University)

Controlling light, CO2 levels

Cornell researchers have developed a light control algorithm that controls for daily light integrals. It’s called LASSI (Light and Shade System Implementation). The software interfaces with the greenhouse environmental control computer to turn on the supplemental lighting or to pull the shade curtains.

“Every hour of the day LASSI goes through a series of rules and makes the decision to turn the lights on or to pull the shade,” Brechner said. “It seeks to optimize the use of off-peak power. Most greenhouse operations have off-peak power rates which are usually from 11 p.m. until 5-6 a.m. The power at that time is significantly cheaper.

“This program can get a little tricky with tomatoes because they need four hours of darkness every day or they don’t grow well. Lettuce does not need this dark period.”

Brechner said LASSI can be used with any crop as long as the grower knows the appropriate target daily light integral. “We have used it (LASSI) with tomatoes that need a 4 hour dark period to grow normally,” she said. “Optimum DLIs have not been published in peer-reviewed literature. We have investigated a range of DLIs for lettuce from very low (8 moles) to high (22 moles). A similar set of DLI vs. production curves would be useful for all typical greenhouse vegetable crops, but I am not aware that they exist.”

Brechner said growers have the option of using supplementing carbon dioxide to substitute for a certain amount of light.

Table 1. Cost of supplemental lighting with and without the use of supplemental carbon dioxide.
With CO2     Without

Annual cost, supplemental lighting     $8,638          $17,151
Annual cost, supplemental CO2               $1,426           $0
Annual cost, total                                $10,064         $17,151
Hours using lights                               1,361             2,665
Off-peak %                                         75                  72
kWh electricity for light                      135,120         264,581

“For example if a grower supplements with 1,600 parts per million carbon dioxide, he can use half the amount of light and get the full amount of growth,” she said. “Adding carbon dioxide makes photosynthesis more efficient allowing the plants to fix more carbon with less light.”
Cornell has developed two versions of the LASSI program:
the original LASSI and CO2 LASSI, which take into account whether it’s cheaper for a grower to supplement with carbon dioxide or with light.

“For our fifth of an acre CEA greenhouse growing lettuce with supplemental carbon dioxide, the lighting cost would be $8,600 (see Table 1). The lighting costs would increase to $17,000 without the carbon dioxide,” she said. “The supplemental carbon dioxide costs are about $1,400 a year. Total cost for the supplemental lighting and CO2 for the CEA greenhouse simulation is $10,000 with supplemental carbon dioxide vs. $17,000 for supplemental lighting without carbon dioxide. Supplementing with carbon dioxide enables a grower to use half the supplemental light and still hit the daily light integral target every day. This enables the grower to achieve a consistent harvest every day of the year. The grower is basically pushing the plants as hard as he can without getting tip burn.”

Research at Cornell University has shown that an average of 17 moles of PAR per square meter per day gives optimal growth of lettuce while minimizing tip burn.
(Photo courtesy of Cornell University)


For more:
Melissa Brechner, Cornell University, Controlled Environment Agriculture Center for Technology Transfer; (607) 255-8146;;

David Kuack is a freelance technical writer in Fort Worth, Texas;
Visit our corporate website at