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Hort Americas looks to be a connecter of products and knowledge for the horticulture industry

Whether growers are producing vegetables, ornamentals or other hydroponic crops, Hort Americas is working to provide its customers with the products and knowledge they need to be successful.

When Hort Americas in Bedford, Texas, started operating as a wholesale horticulture distributor in March 2009, the company had no existing customer base.

“We would sell anything we could to anyone who would buy from us,” said general manager Chris Higgins. “That is not uncommon for new companies starting out, especially those that are doing wholesale supplies.

“When Hort Americas first started, the partnership we had with horticulture distributor and cooperative Horticoop in the Netherlands allowed us access to a lot of products that the company was already selling in Europe. Initially our focus was European products that were well suited for commercial vegetable hydroponic growers in North America. Most of the products we offered were not available from U.S. manufacturers.”

Even though the North American hydroponic vegetable industry is not as large as the Dutch industry, Higgins said U.S. growers have been interested in European technology.

“We looked to build off of our partnership with Horticoop which enabled us to consolidate orders in Europe on co-loaded containers. The products were shipped to the United States, unloaded in Dallas, and then shipped to our customers. The North American market is sophisticated enough to use the products shipped from Europe. But it does not always mean that the European manufacturers completely understand all of the needs of our customers.”

Higgins said the North American customers differ widely depending on geography, market demand and opportunity.

“These differences create opportunities for both low and high technology production methods and products,” he said. “It became glaringly important that our vendor partnerships needed to allow us to address each customer’s specific needs and level of technical expertise.”


Maintaining the right product inventory

When Hort Americas first started operating its product inventory was very limited.

“If we didn’t have a product in inventory then we were looking at eight to 12 weeks to deliver a customer’s order,” Higgins said. “Both our customers and Hort Americas had to be very good at planning in advance. This also meant we had to be even better at communication. Something we admittedly struggled with early on and continue to always improve at.”

“We focused on providing our smaller customers with the insight to what the most high tech growers in the world were doing. It was our job to figure out how to take what sophisticated Dutch operations were using and then find a way to fit parts of that into modified U.S. production systems.”


Chris Higgins, general manager at Hort Americas, said his company’s North American customers differ widely depending on geography, market demand and opportunity. He said these differences create opportunities for both low and high technology production methods and products.

One key difference is that unlike many Dutch greenhouse ornamental plant and vegetable growers who specialize in one crop, growers in the United States produce multiple crops in the same greenhouse.

“One of the biggest challenges for us was working with U.S. hydroponic leafy greens and herb growers, who grow a wide variety of crops in the same greenhouse,” Higgins said. “We work with growers and researchers on how to take the best products, equipment and knowledge that were built for monocrops and market them to U.S. growers who produce the variety their markets demand.

“Hort Americas also realizes it cannot do this for all products and technologies. Instead it has chosen to focus many of its resources on lighting, substrates and nutrients, including the products needed to make these categories ultimately successful.”


Evolving customer base, product mix, focus

As Hort Americas evolved so did its customers. Its product offerings have evolved with its customers’ needs.

“We listened, learned and then changed so that we could continue to add value to our customers and help them continue to grow,” Higgins said. “As we listened to our customers, better understood their needs and learned more about our competition, we found the areas where we were able to evaluate our capabilities and find ways where we could excel.”



Hort Americas listened to its customers and chose to focus on three specific categories: lighting, substrates and nutrients.

Photo courtesy of Farmbox Greens

Even though Hort Americas chose to focus on three product categories (lighting, substrates and nutrients), it didn’t abandon the other products it was selling.

“We took what our customers were asking for and tried to develop more expertise in those categories,” Higgins said. “This is where Hort Americas has really worked to add value. We do our best to share information and answer the technical questions consistently and as unbiasedly as possible.”


Filling the lighting knowledge gap

Hort Americas was a very early adopter of light emitting diode (LED) technology.

“We tackled LED technology much like we do everything else, we started visiting growers,” Higgins said. “We heard their concerns, questions and comments regarding light. This forced us to go back and do a lot of research. We found the gaps between the growers, the lighting companies and the horticulture lighting researchers. After that it was simple, fill the gaps.”

Higgins said there still might be a gap in lighting knowledge, but the industry continues to grow, learn and improve on the way it communicates.

“Early on our value came from focusing on the basics,” he said. “This started with helping growers gain the knowledge they needed to make a lighting decision. When we first started, 90 percent of our customers only spoke in terms of footcandles, lux, lumens and joules. Our goal was to get everyone communicating exclusively in micromoles and moles.”

To better advise its customers on managing light, Hort Americas has initiated new business partnerships and added more products including advanced shading products and other reflective materials to enable growers to make the most of natural light levels.


Clean, consistent substrates

Hort Americas is focusing on engineered substrates.

“These are substrates where we are either working with the manufacturers or we are the substrate manufacturer focusing on engineering certain physical traits based on what our customers require,” Higgins said. “This may be guided by the crop, the production/irrigation system or the regions of the country in which the growers are located. We want to offer engineered substrates that are very clean and consistent.

“For growers producing ornamental crops there is a lot of attention paid to weight, consistency and aesthetics. For growers of edible crops there is a lot of focus on consistency and yields. Since the substrate is an important part of the foundation of the plants, we make sure the substrates are as consistent and precise as we can possibly make them.”

Hort Americas has begun to look at how substrates best fit into each grower’s production system. This has led to the addition of a variety of products including containers which assist growers in making the root zone more controllable and manageable.


Simplifying fertilizer numbers

Hort Americas is selling both traditional and organic fertilizers to all size growers.

“What we learned with nutrients is that there is a big part of the U.S. hydroponic market that struggles with understanding nutrients,” Higgins said. “Some growers were also finding it difficult to get answers that they could relate to. We created tools like the online hydroponic fertilizer video series that makes it easier for growers to plug in their numbers. That also extends to working on problems that didn’t, and in some cases, don’t have any simple answers like organic fertilizers for hydroponic production systems.

“There are more growers trying organic fertilizers. This combined with the increasing demand for locally-grown produce, is creating a need for “systems” that don’t sacrifice yield. Hort Americas continues to work with growers to find the answers.”


Supporting industry events, research

Hort Americas has also made the choice to reinvest in the industry through education by supporting and sponsoring research and events. This includes supporting events like the International Congress on Controlled Environment Agriculture in Panama, the Lighting Solutions open house at Michigan State, the East Meets West conference in November 2016 and Ag Tech Worlds Collide in February 2018. The company is also supporting the horticulture research programs at Cornell University and Michigan State University.

“That is our way of reinvesting in the industry and helping to educate the industry,” Higgins said. “We are investing our profits to make the industry stronger and we are doing that through education.”


Demo greenhouse expands product, customer knowledge

In 2016 Hort Americas retrofitted a 12,000-square-foot greenhouse in Dallas for the purpose of demonstrating and researching new and existing products. Tyler Baras was hired as special projects manager to oversee the trialing of crops in different production systems along with the testing of existing and potential products for the company’s online catalog. Baras conducted studies on substrates and fertilizers.


Hort Americas retrofitted a greenhouse in Dallas in order to demonstrate and research new and existing products.
Photo courtesy of Tyler Baras

“We are focusing on better understanding the trials and tribulations growers go through when making decisions on what products to use,” Higgins said. “For example, we want to make sure we clearly understand how different irrigation regimes or different irrigation methods impact the substrates or the fertilizers we are recommending.”


For more: Hort Americas, (469) 532-2383;;


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

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What are the benefits of maintaining the optimum substrate oxygen level?

Increasing the oxygen level in the root zone can ensure healthy root growth and can impact crop yields.

Low oxygen levels in the growing substrate can play havoc with the health of both vegetable and ornamental plants. Shalin Khosla, greenhouse vegetable specialist at Ontario Ministry of Agriculture, Food and Rural Affairs in Harrow, Ontario, said a substrate oxygen level below 5 parts per million can have a negative effect on plant growth.

“Below 5 ppm oxygen, plants are going to suffer and at 2 ppm the roots are going to die off,” Khosla said. “The optimum substrate oxygen level is 6-8 ppm. If the oxygen level can be increased to 10 ppm is even better.”

Khosla said the temperature of the water can affect the level of oxygen.

“As irrigation water warms up it holds less oxygen,” he said. “Cold water holds more oxygen. Between 6-8 ppm of oxygen is the normal level at a water temperature of 68ºF-77ºF (20ºC-25ºC). As the water warms up to between 82ºF-86ºF (28ºC-30ºC), the oxygen level can drop to 5 ppm or lower because the plant roots are taking up some of the oxygen. Summer tap water, which is usually warmer, will have less oxygen in it.”


Impact of the irrigation system

The method of irrigation can also have a major impact on the level of oxygen received by the plants roots. In a hydroponic system such as nutrient film technique (NFT) or deep float technique (DFT) all the oxygen for the roots is supplied through the nutrient solution.

Greenhouse vegetable specialist Shalin Khosla (left) and research scientist Dr. Xiuming Hao at the Harrow Research and Development Centre, were part of a team of researchers that studied the impact that high levels of oxygen had on greenhouse tomato production.
Photo courtesy of Shalin Khosla, Ontario Ministry of Agriculture, Food and Rural Affairs

“The level of oxygen should remain high and more consistent if a grower is using a well-designed NFT or DFT system,” Khosla said. “Most NFT systems are fairly open and the level of oxygen can be maintained further down the line.”

Khosla said under warmer temperatures in NFT and DFT systems adding oxygen can help improve plant growth.

“Usually from the top of the NFT trough to the bottom is generally a 22.8 meter (75 feet) run,” he said. “The water that reaches the plants at the bottom of the trough is warmer and has less oxygen as the plants have used up most of the oxygen.

“Plants at the end of the trough can experience root tip die off which leads to a decrease in iron uptake resulting in the plants displaying iron deficiency symptoms. Maintaining a higher oxygen level in the water at the end of the trough prevents the loss of the root tips and iron deficiency.”

As the solution temperature increases some of the oxygen will be lost, but a higher level can be maintained by injecting oxygen into the water.

Khosla said for growers using a drip irrigation system with containers or grow bags, the level of oxygen in a normal nutrient solution is adequate because the solution can absorb oxygen once it reaches the open air. In some cases, the oxygen level may be reduced if the irrigation lines contain microbes and biofilm that can use up some of the dissolved oxygen. The oxygen level in the containers or bags of substrate is not as high as the oxygen level in the water coming out of the drippers because the plants are actively using the oxygen and root zone microbes are also using the oxygen.

“If cool water is being supplied through drip irrigation, then there will be a benefit because oxygen will be added to the substrate as cool water holds more oxygen,” he said. “If the temperature in the irrigation lines is warm and the water temperature in the substrate is warm, then the oxygen level will be lower and the roots will be under stress. Adding cool water with more dissolved oxygen will help maintain the health of the roots.”


Incorporating high levels of oxygen

Khosla and a group of Agriculture and Agri-Food Canada (AAFC) researchers at the Harrow Research and Development Centre in Harrow, Ontario, studied the impact of applying an oxygen super-saturated nutrient solution to greenhouse tomatoes. A super-saturated rate of oxygen was delivered from a cylinder of pure oxygen into the nutrient solution tank. Using a drip irrigation system, the oxygen super-saturated nutrient solution was delivered to tomatoes grown in grow bags filled with rockwool, coir or perlite.

A super-saturated rate of oxygen was provided by a cylinder of pure oxygen into the nutrient solution tank and delivered to the growing substrate through a drip irrigation system.
Photo courtesy of Tyler Baras

“A super-saturated level of oxygen would be between 35-75 ppm oxygen,” Khosla said. “The super-saturated level is five to 10 times more oxygen than is found in tap water. As the water is delivered from the drip tube to the substrate the oxygen level is reduced. The oxygen level in the grow bags, regardless of the substrate, was not as high as the level of oxygen in the water coming out of the drippers.”

Khosla said that if growers want to apply a super-saturated level of oxygen through drip irrigation they would need to deliver a higher rate into the nutrient solution.

“Growers need to make sure that they are maintaining a high enough level in the irrigation lines to ensure that a higher level of oxygen is reaching the plants,” he said. “If 30 ppm of oxygen is incorporated at the tank, there is going to be a drop in the level through the irrigation lines because of biofilm, bacteria and fungi growing in the lines that remove some of the oxygen. As the water drips down from the irrigation line into the substrate additional oxygen is lost.

“It is very difficult to measure exactly how much oxygen ends up in the substrate. Providing 32-60 ppm oxygen ensures that a super-saturated level is being maintained in the substrate.”

All three substrates worked well with the super-saturated level of oxygen.

“As long as enough oxygen was delivered to the substrate they all performed well,” Khosla said. “As the water drips from the irrigation tube to the substrate some of the oxygen is lost in the air so growers just need to be sure that a higher oxygen level is maintained in order to reach a higher level in the substrate, regardless of which one is used.”


Benefits of higher oxygen levels

The super-saturated oxygen levels had an impact on tomato fruit size and yields.

“The increase in fruit yield in relation to an increase in oxygen level was not linear,” Khosla said. “There was an increase in yields, the quality of the fruit was better and the size of the fruit was larger.

“In addition to the super-saturated oxygen levels we also studied the normal nutrient solution without any additional air and compressed air treatments. The plants receiving the super-saturated level of oxygen outperformed the compressed air and normal oxygen levels.”

The researchers also looked at when during the production cycle the incorporation of the super-saturated oxygen nutrient solution had the biggest impact on fruit production.

“In the earlier stages when the plants are young and growing, if a super-saturated level of oxygen is incorporated, there was a benefit,” Khosla said. “Once the plants are mature and growing it doesn’t seem to show the benefit. When the plants are older and stressed out there was an improvement in fruit production with the super-saturated oxygen level.”

Benefits of applying oxygen super-saturated nutrient solutions to greenhouse tomatoes included increases in yields and larger fruit.

Photo courtesy of Houweling’s Tomatoes

The researchers also attempted to see if there were any benefits to the plant root systems from the higher oxygen levels.

“We weren’t able to determine the impact of different oxygen levels on root growth because there were other factors involved,” he said. “In the case of growing in a substrate, there is an application component. There is the factor of timing the water applications, how often the plants are irrigated and the amount of water applied. In NFT and DFT systems where there is a continuous application of higher oxygen levels, growers are going to see the effects on the root system. Maintaining a healthy root system also reduces the chances of disease. Growers are seeing less disease outbreaks by adding oxygen.”


Raising oxygen levels

Although the researchers only studied the impact of super-saturated oxygen levels on tomato, Khosla said most crops will benefit from higher oxygen levels.

“If there is a depletion of oxygen in the root zone the plants are going to suffer,” he said. “

“Not a lot of growers that I know are using super-saturated oxygen solutions, but they are incorporating oxygen to increase the level,” he said. “Lettuce growers who have incorporated oxygen and then removed it have seen a drop in production.

“Some growers are using hydrogen peroxide or ozone to increase oxygen levels. Other growers are making sure that the water in the nutrient solution tanks is being agitated. Growers with NFT and DFT systems are bubbling oxygen or air into the systems. However, sometimes the air they are bubbling in is not enough to raise the oxygen level in the water.”


For more: Shalin Khosla, Ontario Ministry of Agriculture, Food and Rural Affairs, Harrow Research and Development Centre, Harrow, Ontario, Canada; (519) 738-1257;


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

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What are the benefits of applying greenhouse shading products?

Sudlac shading products give greenhouse growers of flowers and vegetables the ability to increase and extend production during periods of warm temperatures and high light levels.

High temperatures and high light levels, especially during the summer can have negative effects on ornamental and vegetable crops produced in protected structures, including greenhouses. An economical way for growers to reduce light and temperature levels is by applying shading products to greenhouse glazing materials.

“The application of shading products is related to maximizing the production capacity of the greenhouse,” said Ruben Lensing, area export manager at Sudlac. “Shading products can allow a grower to optimize the climate in the greenhouse, therefore increasing yields without having to invest in more structures. Warm temperatures can impact crop yields, whether a grower is producing flowers or vegetables. If it is too warm, a grower can bring down the temperature by applying a shading product, which can improve crop yields as well as extending production during warmer periods.

“Typically in July and August the greenhouse environment is much too warm in many parts of the U.S. During this time if the grower doesn’t reduce the temperature there will be some crop loss. If the temperature is reduced with shading, a grower may not be able to produce as much as in the spring, but the crop will survive and produce during these warmer months as well as into September and October. The use of shading is all about increasing crop productivity and extending the time of production.”


Application for all types of crops

Lensing said all types of growers are using Sudlac shading products.

“Sudlac products are used on all types of greenhouse crops including cut flowers, potted plants and vegetables,” he said. “Sudlac products are also now being used on the production of the newest greenhouse crop—cannabis. “I am visiting some greenhouse growers in the U.S. who are looking to change their crop from flowers to cannabis.

“Since there are more vegetables grown worldwide in greenhouse and protected structures, Sudlac products are used more with vegetable production. That is only because of the size of the worldwide vegetable market.”



Ruben Lensing, area export manager at Sudlac, said growers can lower greenhouse temperatures by applying a shading product, which can improve crop yields as well as extending production during warmer periods.


Lensing said Sudlac products are being used to increase production of both flowers and vegetables.

“With cut flowers, such as freesias, alstroemeria and gerbera, there are more shoots produced,” he said. “This means more flowers are produced per plant. Also, there is less fading of the flower color so the color is more intense.”

For potted plants, Lensing said certain kinds of shading can create more compact plants.

“Using a shade product can lower temperature at high light levels,” he said. “This allows a grower to produce a sturdy compact plant that is higher quality. This may also allow a grower to eliminate or reduce the amount of plant growth regulators that are needed. Applying shade can lower production costs and increase a grower’s return on investment.”

Lensing said the benefit of applying shade for vegetables like tomatoes, peppers and cucumbers, can result in more fruit produced per plant. Also, with some crops the fruit are also heavier.

“Applying a shade product translates to more flowers and fruit per plant which means a higher return for the grower,” he said.


Different products for different needs

Sudlac offers six different products for the U.S. market, including three shading products, two light diffusing coatings and one shade removing cleaner. Sudlac shading products can be used on all types of glazing material, including polyethylene, rigid materials including acrylic and polycarbonate, and glass.


Eclipse LD

Eclipse LD was the first Sudlac product sold in the United States and is the most widely sold product. LD stands for long duration. It is a protective coating against heat and light.

“When Eclipse LD is applied to the greenhouse it lowers the temperature and reduces the amount of light entering the greenhouse,” Lensing said. “Since Eclipse LD lowers the temperature when it is applied on where a greenhouse is located in the U.S. If the greenhouse is in the southern U.S., it might be applied as early as the end of February or beginning of March. In a more northern climate like Minnesota, Eclipse LD probably would be applied in April. Eclipse LD should be taken off when natural light levels decline, which is usually from September to November in most of the U.S. depending on location. It depends on where the greenhouse is located and climate conditions.”



Transpar is also a removable protective coating that maintains photosynthetically active radiation (PAR) light levels.

“Transpar is a coating that reflects infrared radiation, which is the light that produces the heat in the greenhouse,” Lensing said. “The PAR light is allowed into the greenhouse.”


Warm temperatures can impact crop yields, whether a grower is producing flowers or vegetables.




Optifuse is a removable coating that lets all the light into the greenhouse, but spreads the light.

“Optifuse diffuses the light,” Lensing said. “It spreads the light in the greenhouse so plants won’t burn. This is very important for flowers, lettuce and other vegetables.

“The advantage of using Optifuse is to allow as much light into the greenhouse as possible. Optifuse can be used in dark areas where there isn’t a lot of sunlight. When the light comes into the greenhouse all of it comes in, but it is spread throughout the greenhouse.

“There is one application exception with Optifuse shading product,” Lensing said. “Optifuse cannot be used on polyethylene film, but it can be used on every other type of glazing.


Optifuse IR

Optifuse IR is combines and properties of Optifuse and Transpar.

“Optifuse IR lowers the temperature by reflecting infrared radiation,” Lensing said. “It diffuses the light into the greenhouse like Optifuse and lowers the temperature like Transpar.”



Sombrero is an economical whitewash liquid. Like Eclipse it lowers the temperature. It is commonly used in warmer climates including southern California, Florida and Texas. Sombrero is removed by rain or water and no special product has to be applied to remove it from the greenhouse glazing.



Topclear is a shade removing product used to take off Eclipse LD, Transpar, Optifuse and Optifuse IR.

“It is important to use Topclear to remove these shading compounds,” Lensing said. “In most parts of the U.S. from September through November all of the shade should be removed from the greenhouse so that the glazing is completely clean to optimize plant production during the winter months.”


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

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Dissolved oxygen improves plant growth, reduces crop time

Incorporating dissolved oxygen into hydroponic production systems during warmer temperatures can help improve plant growth and reduce crop time.

Trying to grow hydroponic crops like leafy greens can be a real challenge during warmer times of the year. Growers have few options to lower temperatures, including cooling the greenhouse and/or water temperature. Another production technique that is being used by hydroponic growers in the United States and Australia is to introduce dissolved oxygen into the fertilizer tank solution.

“We’ve heard anecdotal reports that increasing dissolved oxygen levels can help prevent some root diseases like Pythium and other root rots,” said Tyler Baras, special projects manager at Hort Americas in Bedford, Texas. “We’ve also heard that increasing dissolved oxygen can possibly improve nutrient uptake and improve overall growth. Another possible benefit with using dissolved oxygen is reducing tip burn on leafy greens.

“These are some of the main issues with growing in warm climates like Texas during the summer. With an increase in water temperature comes a higher disease pressure and chances for tip burn. This has occurred in both nutrient film technique and deep water culture systems.”

Hort Americas conducted trials growing butterhead lettuce, basil and arugula in deep water culture systems at three different levels of dissolved oxygen.
Photos courtesy of Tyler Baras

The optimum water temperature for lettuce is between 65ºF-70ºF. For basil the optimum water temperature is around 75ºF.

Baras said most of the references he has read for adding dissolved oxygen suggest incorporating 4-10 parts per million for leafy greens.

“Most growers that I know are adding between 6-7.5 ppm for leafy greens,” he said. “When growers start to go beyond that rate to reach a higher level they have to use something like compressed oxygen or ozone. These are the main two methods, which are more expensive, for achieving a higher dissolved oxygen rate. Most growers I know are using a less expensive Venturi system or an air pump with air stones to add dissolved oxygen.”


Trialing different levels of dissolved oxygen

Baras has been studying the impact different dissolved oxygen levels can have on butterhead lettuce, basil and arugula grown in deep water culture systems. He set up deep water culture systems with three different levels of dissolved oxygen: 2 ppm, 7.5 ppm and 29 ppm.

“We have been tracking growth and how it affects the morphology of the plants,” he said. “The 2 ppm dissolved oxygen rate is what we were able to achieve without doing any type of aeration. This was our control.”

In another system Baras used a Venturi attachment to a small submersible pump that drew in atmospheric air.

“The highest rate of dissolved oxygen that we could achieve using atmospheric air was a maximum of 8.5 ppm,” he said. “The rate hovers between 7.5 to 8.2 ppm, with it usually averaging 7.5 ppm.”

The third system is a high rate of dissolved oxygen that uses compressed oxygen tanks to deliver 29 ppm.

“This system uses nanobubble technology,” he said. “We were using a prototype device that forces oxygen into a solution in really small bubbles so that the oxygen stays in suspension longer instead of falling out. The lowest rate that we could set was 29 ppm. This level of dissolved oxygen is much higher than what most leafy greens growers are targeting.

“A lot of the flowering crop and cannabis growers who are incorporating dissolved oxygen are actually targeting these higher rates. These growers are achieving 20-40 ppm dissolved oxygen. The flower and cannabis crops tend to prefer to be grown on the dry side. With this type of nanobubble dissolved oxygen technology it opens up this production method to crops beyond leafy greens.”


Some dramatic results

Baras said he has seen some dramatic effects on plant growth with higher dissolved oxygen rates. At the beginning of the trials during the first month the water temperature in the fertilizer tanks was 80ºF. During the second month the water temperature was between 75ºF-80ºF.

“At 2 ppm the arugula plants were severely stunted and were unsalable,” he said. “At this low rate there were also some severe nutrient deficiencies. At 7.5 ppm the arugula looked normal with slight deficiencies. There weren’t any nutrient issues at the 29 ppm rate and the plants almost doubled in size.”

Baras said even at the low rate of 2 ppm some crops could still be marketable.

“The basil and butterhead lettuce could still pass as marketable at the low 2 ppm rate,” he said. “The plants were very small and it would take several more weeks of production to reach the target weights we were aiming for. At the 7.5 ppm dissolved oxygen rate the plants had fairly normal growth as to what we are used to seeing.

For butterhead lettuce at the 2 ppm rate the heads were smaller and compact. The core of the heads were tighter, but actually had a good shape. At the 7.5 ppm and 29 ppm rates, the heads had similar shapes.

Butterhead lettuce (left to right) grown in 29 ppm, 7.5 ppm and 2 ppm of dissolved oxygen.

For the basil there was an increase in height as the dissolved oxygen level increased. Overall the plant height and size increased at higher dissolved oxygen rates.

“At the 29 ppm rate, the plants looked like the plants at the 7.5 ppm rate, but they were about a week ahead,” Baras said. “Both of these rates produced plants with healthy looking morphology, but the plants receiving 29 ppm dissolved oxygen developed faster. On average all of the crops grown with 29 ppm were at least a week faster to finish to a marketable size.”


Differences in root growth

Baras said the roots for the crops in the three rates of dissolved oxygen had different growth patterns.

“The roots in the 2 ppm dissolved oxygen systems were very short and stubby and almost seemed to be retreating from the water,” he said. “The roots remained mostly in the stone wool rooting cubes.”

At the 7.5 ppm dissolved oxygen rate the roots were long and had a lot of lateral branching. Baras said they looked like standard hydroponic roots.

“At the high 29 ppm rate the roots actually had less lateral branching, but they were really white, long and thick,” he said. “But there was less lateral branching. It almost seemed like since there was so much oxygen in the water the plants didn’t need to have as much lateral branching.”


Arugula (left to right) grown in 29 ppm, 7.5 ppm and 2 ppm of dissolved oxygen.

Even though there were differences in the root morphology, there was no significant difference in the root weight for all three dissolved oxygen levels. The average root weight for both the 7.5 ppm and 29 ppm rates was 0.8 ounces. The root weight for the 2 ppm rate was about 0.7 ounces.

For more: Hort Americas, (469) 532-2383;;

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

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What are the optimum nutrient levels for hydroponic edible crops?

Trials with organic and conventional fertilizers in hydroponic production systems are showing it’s possible to produce edible crops at much lower nutrient levels.

How much different is it growing edible crops organically than it is with conventional production inputs? Hort Americas special projects manager Tyler Baras is studying the differences in trying to grow organically versus using conventional production methods.

Baras has been doing organic production research in a 12,000-square-foot greenhouse in Dallas, Texas, using four deep water culture ponds and a nutrient film technique system. The ponds measure 4-foot by 8-foot and are 10 inches deep. Baras said the ponds are smaller than what would be found in many commercial greenhouse operations, but said the pond size is common in vertical farm setups. Baras has been trialing commercial organic fertilizers including Pre-Empt and an experimental organic fertilizer. The organic fertilizers are being compared with crops grown with Hort Americas 9-7-37 hydroponic fertilizer with calcium nitrate and magnesium sulfate. All of the production systems have also been incorporated with the commercial microbial inoculant TerraBella. Crops being grown in the production systems include Italian basil, green butterhead and red butterhead lettuce.

Trials in Hort Americas demonstration greenhouse are comparing the growth of butterhead lettuce and Italian basil using organic and conventional fertilizers in hydroponic production systems.
Photos courtesy of Tyler Baras

Rethinking optimum nutrient levels

Baras said the deep water culture production results he has gotten with Pre-Empt organic fertilizer have been comparable to the crops grown with the conventional Hort Americas hydroponic fertilizer.

“With Pre-Empt we have been able to match the growth rates of the conventional salt fertilizer,” Baras said. “As a result of the growth rates we have gotten with the organic fertilizer, we have started to question the nutrient recipes that have been recommended for hydroponic edible crop production. Many of the traditional recipes for hydroponic production have a target level of 200 parts per million nitrogen. But we are seeing the same growth rates in the organic fertilizer ponds with 10 ppm nitrogen as the 200 ppm nitrogen conventional fertilizer pond.”

Baras said the electrical conductivity level in the organic fertilizer ponds has been as a low as 0.5 compared to 2.5 in the conventional fertilizer pond and the crops are coming out nearly identical in terms of production time and plant weight.

One difference between the organic- and conventional-grown crops is the time in propagation.

“The crops are finishing at the same time from transplant to harvest time, but we are keeping the plants an extra week in the seedling stage for the organic fertilizer,” Baras said. “We are running the seedlings for two weeks with the conventional fertilizer and about three weeks with the organic fertilizers.

“The organic plugs are started a week earlier, but they are transplanted on the same day as the conventional plugs. We want the roots coming out of the side of the plugs before we transplant them into the ponds. The seedlings are fairly similar in size when they are transplanted into the ponds.”

Plugs grown in organic substrates and fed with an organic fertilizer remain on the propagation bench one week longer than plugs receiving conventional fertilizer to ensure good root growth.

Once the organic and conventional plugs are placed into the ponds, they both spend the same amount of time there until the crops finish.

“The plants are coming out of the ponds with nearly identical weights,” Baras said. “Overall the seed to harvest time is faster with the conventional fertilizer, but that it is because we are able to transplant the plugs into the pond faster because the roots are coming out of the plugs sooner.”

Baras said the plants grown with the organic fertilizers have also shown they can be grown with lower levels of other nutrients. For example, with the conventional fertilizer the nutrient solution may contain 200 ppm potassium and the level is only 12 ppm with the organic fertilizers.

“Aquaponic growers have seen similar situations,” he said. “Some aquaponic growers may be running an EC of 0.7 with a relatively low nutrient level, but they are still seeing good growth.

We are seeing that as well with the organic fertilizers. There are low nutrient levels in the solution, but the crops are coming out the same and the leaf tissue analysis is nearly the same as well.

“For our trials the macronutrient uptake for the plants, even when they are grown in a low fertilizer concentration like 0.5 EC, they are still able to pull what they need out of the solution. Leaf sample analyses of butterhead lettuce and Italian basil grown in 0.5 EC organic fertilizer vs. 2.5 EC conventional fertilizer, most of the macronutrient levels in the leaves are very similar. It appears the plants are doing a good job of regulating the nutrient uptake to get what they need.”


Aging fertilizer solutions

Baras said letting the organic fertilizer solutions age in the ponds may have an impact on the availability of nutrients for some crops. The aging of the fertilizer solutions also has an impact on increasing the microbial population.

“We have definitely seen some differences in plant growth,” he said. “Our first crops of butterhead lettuce and basil did very well with Pre-Empt organic fertilizer. However, one of the other organic fertilizers we trialed grew a quality first crop of lettuce, but not the best looking basil. As we continued the trial with our second and third crops, the basil grown with the other organic fertilizer started doing much better. It appears the organic solutions in the ponds may need to age until the nutrients reach adequate levels.

“This is what we were seeing in a 9-month old Pre-Empt pond vs. a 2-month old Pre-Empt pond. A lot of nutrients have accumulated in the 9-month pond and are approaching the recommended nutrient levels that would be found in a conventional fertilizer system. Organic fertilizers like Pre-Empt don’t have a lot of magnesium in them. However, when the fertilizer is run in a pond system for 9 months the magnesium level rises and approaches what would be considered a conventional fertilizer target level for magnesium.”

Aging of the fertilizer solution also has had an impact on the root growth of the crops.

“When we compare how the roots look visually in the 9-month solution vs. the 2-month solution, the roots in the 9-month solution look much healthier,”Baras said. “The roots are very white, are longer and look really healthy and well-developed. There are also more roots on plants in the 9-month system.

“The root color is also significantly different. In the 2-month solution the roots look healthy, but there is some browning. They don’t have that crisp white look.”


Aging of the fertilizer solution can impact root growth. Plants (left) in a 9-month old organic fertilizer solution had more roots that looked healthy and well-developed compared to the root system of plants in a 2-month old organic fertilizer solution.

Rethinking optimum pH levels

Baras said he has been able to produce healthy crops in a pH range from as low as 4 up to 6.5.

“For hydroponic leafy greens the recommended pH ranges from 5.5 to 6.5,” he said. “We have basil and butterhead lettuce growing very well in organic systems at a pH of 4. On the other side of the pH range, I’ve heard of aquaponic growers growing these crops at a pH up to 7 without any problems. Based on our trial results some of the conventional recommendations for hydroponics for both pH and nutrient levels might need to be revisited.

“One of the biggest issues I see with hydroponic growers is overcompensating. For instance, they feel that they need to be constantly watching the pH. They may set up monitoring and dosing systems to ensure the pH doesn’t go below 6 or 5.5. They are investing in extra equipment because they think they need to keep the pH precisely in this range. It may be a case that the plants will do well outside this range.”


Impact on crop timing

Baras said one factor that could affect the optimum pH and nutrient range is the light level.

“If a grower is providing supplemental light, then the optimum pH and nutrient range may be different,” he said. “With the trials we are conducting we aren’t that far off from what most hydroponic growers are targeting for growth rates. Thirty-five days is a target number for a lot of lettuce growers. We have done 35-day crops. We want to be able to grow an organic crop in the same amount of time as a crop grown with conventional fertilizers.”


For more: Hort Americas, (469) 532-2383;;


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

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Breeding crops for controlled environment production

Controlled environment agriculture growers have been trying to fit a square peg into a round hole by growing field crops in indoor environments. This is changing as research tries to match plant genetics with the production environment.

During this year’s International Congress on Controlled Environment Agriculture (ICCEA) in Panama City, Panama, University of Florida horticulture professor and keynote speaker Kevin Folta discussed the overlooked reality that food crop varieties have not been bred for indoor controlled environment production.

“One of the limitations of controlled environment agriculture (CEA) is that the conditions do not match the genetics,” Folta said. “Plants being grown in CEA environments were actually developed for field production. There are a lot of opportunities that go unrealized by growing plants in a controlled environment. It’s like asking Chihuahuas to pull a dog sled. Plants that were bred for one application are expected to perform under very different applications. The genetics don’t match.”

Research has begun to develop the next generation of plants with the potential to develop different products using the same set of genetics by changing the environment.

Creating the next generation of plants

Folta said research has begun to develop the next generation of plants with the potential to develop different products using the same set of genetics by changing the environment.

“By flipping a switch and varying the light spectrum we could change green leaves to purple or have the plants accumulate specific flavors or textures or nutraceutical compounds,” he said. “That is all very realistic. This is like being able to shine a different light spectrum on a Chihuahua and turning it into an Alaskan malamute or a dachshund. A plant’s body, its composition, its chemicals, its secondary metabolites could be altered by changing the light environment. We need plants that are ready to do that. We need to identify or create those genetics.

“We are exposing plants to different light spectra and evaluating how the plants behave and perform. Then we will work with plant breeders to develop the next varieties.”

Varying the light spectrum has the potential to change leaf colors and textures and to have plants accumulate specific flavors or nutraceutical compounds.
Photos courtesy of Kevin Folta, University of Florida

Need for more industry involvement

Folta said the companies that are developing and manufacturing the lights for CEA production should become more involved with the development of plants grown in these environments.

“The lighting companies should be working with the university researchers and plant breeders,” he said. “The lighting companies should be financing the development of proprietary varieties. Unfortunately that hasn’t been an area of interest for the lighting companies. They want to make and sell lights. They forget the seed. The seed is a much more complicated machine.

“The lighting companies should be able to say to the growers here are the grow lights we are offering and here are the seeds that grow best under them. That opens up recurring revenue for the lighting companies. It behooves the lighting companies to focus on identifying plants that perform best with their products. It’s like saying that a Ford engine does best with a Motorcraft oil filter. It’s manufacturer’s optimized matching parts.”

Folta said plants are the most complicated part of matching the genetics with the environment and the part that people worry least about.

“It doesn’t matter whether the breeding company or the lighting company takes the initiative to develop the genetics,” he said. “This is going to happen whether it’s private plant breeders, universities or technology companies. This is another niche to create new genetics. You’ll see people filling this void.”

Researchers are learning that green, far red and UV light have important roles to play in controlled environment agriculture plant production.

Limiting, changing the production environment

Even technology companies like Panasonic, Toshiba and Fujitsu are finding opportunities in controlled environment agriculture.

“These types of companies will develop the genetics or will find the genetics that work well in CEA environments,” Folta said. “For now the field genetics will continue to be put in artificial conditions and the indoor environment will be reshaped to accommodate the plants. What should be done is finding or developing plants for these energy-efficient, artificial conditions that are sufficient to support growth. Research needs to be done to determine how to maximize output or yields with fewer photons of light or colors of light. Research is going to focus on economic viability. I expect the pharmaceutical companies will get involved in this research.

“My interests are much more about food and how we create the next generation of profitable growers and higher nutrient crops that are more readily available for consumers. That’s what gets me fired up.”

While matching the genetics to fit the environment is important, Folta said researchers also need to be looking at limiting the environment.

“At the same time that we are looking at the breeding and genetics, we are also looking at how we can deliver shorter pulses of light that still maintain the same output,” he said. “We have cut energy application by 50-80 percent and grown comparable products. The viability of these systems has come from people who have focused on the diminishing return of light efficiency. What they need to work on is the plant efficiency. That is something that is extremely viable.”

Folta said all of the research he has been focused on is with small format, high value crops, including lettuces, sprouts and microgreens.

“Our university does not have the facilities to conduct the necessary experiments,” he said. “But we are partnering with others to do that. We will have good access to larger spaces in the upcoming months. It’s less likely that this type of production would be done with crops that take more space like melons. We are looking at plants where the vegetative portions of the plants are eaten. If you consider a head of lettuce, every photon that is invested results in the plant structure. With a crop like tomatoes, 80-90 percent of the biomass is being thrown away or composted.

Kevin Folta at the University of Florida is interested in how to create the next generation of profitable growers and higher nutrient crops that are more readily available to consumers.

“Growing the plants in shorter production times, shorter supply chains, better postharvest quality because of shorter supply chains, possibly lower costs, a lower carbon footprint and access to local markets, these are the issues I want to address. I see this being done with lettuces, microgreens and herbs such as cilantro and basil. Not so much with corn or melons where a huge amount of energy is invested in a relative small return in terms of calories. These types of crops do better using the sun.”

Folta said 15 years ago people thought the idea of light recipes and changing the spectrum was a crazy and senseless idea.

“Researchers and light manufacturers thought mixtures of red and blue light were all that was needed to grow plants in controlled environments, so there wasn’t any concern about doing anything different,” he said. “Now people understand that green, far red and UV light have important roles and that light quality should change throughout the day. With that in mind, it gives us some flexibility when it comes to changing the production environment, which is a really good thing.”


For more: Kevin Folta, University of Florida, Horticultural Sciences Department, Gainesville, FL 32611;;

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

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AmericanHort technology tour to visit Hort Americas hydroponic research greenhouse

Tour of Hort Americas research and demonstration greenhouse in Dallas will show growers different hydroponic production systems for various vegetable crops.

Growers of hydroponic vegetables or those considering starting growing vegetables hydroponically should plan on attending the AmericanHort Production Technology Conference. Scheduled for Oct. 9-11 in Dallas, the conference begins with a Technology in Action Tour on Oct. 9 which will visit three local production operations: Hort Americas research and demonstration greenhouse, Seville Farms and Southwest Nursery.


All things hydroponic

Hort Americas, a horticulture and agriculture wholesale supply company, has retrofitted a 12,000-square-foot floriculture greenhouse for the hydroponic production of vegetable crops. Tyler Baras, who is the special projects manager at Hort Americas, is overseeing the trialing of five different production systems along with the testing of potential products for the company’s online catalog. The production systems include: nutrient film technique (NFT), deep water culture floating raft, a vertical hydroponic tower system, a flood-and-drain vertical rack system and a new capillary mat manufactured in Europe. The greenhouse is being used to grow a wide variety of lettuces, leafy greens, herbs and microgreens.

During the AmericanHort Technology in Action Tour on Oct. 9, Tyler Baras, special projects manager at Hort Americas, will be talking about the five different hydroponic production systems he is trialing.
Photos courtesy of Tyler Baras

The NFT system uses a new channel design. Baras said the narrower channels allow for the aging of crops without having to physically move plants from nursery channels to finishing channels.

Hort America’s main floating raft deep water system is an in-house custom design that measures 32-feet by 28-feet.

“We have tried using a Venturi system to incorporate oxygen, but for the last two months we have been doing trials with compressed liquid oxygen,” Baras said. “We have been doing trials to see how plants respond to increased levels of dissolved oxygen. This deep water system hasn’t been flushed in over a year.

“We have been managing the nutrient solution with water tests and individual salts. Instead of using a standard N-P-K fertilizer like we have been using in the other production systems, we have really focused on water tests and making nutrient adjustments based on those tests. We have been trying to keep the nutrients within a target range and trying to run the system for as long as possible without having to flush any of the nutrient system. We are testing for all of the essential nutrients. We are also looking at sodium chloride levels and seeing how those accumulate. Also, we are tracking what essential nutrients accumulate over time and how we can adjust the fertilizer being added to accommodate the natural accumulation in the system.”

In addition to trialing crops in different hydroponic production systems, Tyler Baras is also studying a variety of crops grown with conventional and organic substrates and fertilizers.


Baras is also studying how the water source can contribute to the nutrient level.

“We are considering how source water may be a limitation to applying this no-flush technique,” he said. “Our source water is municipal water, but it has a high sulfur content of about 44 parts per million. So we are looking at cutting out all sulfur inputs. We are learning the challenges of trying to manage a no flush system.”

In addition to the main deep water system, Baras said tour attendees will also see several smaller deep water culture systems.

“In these smaller deep water culture systems we will be showing the use of three different organic fertilizers where we are comparing the growth between them,” he said. “We will also be showing a smaller scale deep water culture system receiving aeration compared to one with no aeration.”


Vertical production systems

Another hydroponic system that Baras is working with is a vertical tower commonly used by smaller growers.

“We have a lot of customers who use this system so we decided to install one in the greenhouse so we could look at some of the issues that they are dealing with,” he said. “We also were looking to answer some of the questions that our customers had about using the system. An example is can this system be used to grow organically? We’ve done both organic and conventional trials with this system.

“We’ve also been looking at what crops perform best in this vertical system. We’ve done a lot of variety trials as well as with the other systems we’ve installed.”

Hort Americas is also trialing a vertical Growrack from Growtainer.

“This is a flood-and-drain vertical rack system,” Baras said. “The rack has three levels, but it could be expanded. The rack has a 2-foot by 5-foot footprint. We have equipped it with GE LED lights. This would be the type of system used in a vertical farm setup.”

Although the Growrack hydroponic system can be used to grow full size crops, Tyler Baras is using it primarily for seedling propagation.

Baras said the Growrack system, which is set up in the greenhouse, has done well in warm conditions because its water reservoir is below the rack.

“The reservoir is usually stored underneath the racks so it is in shade,” he said. “The water isn’t always in the trays so it doesn’t collect the heat from the trays. It works well in warm climates.”

Although Baras has grown full size crops in the Growrack, it is being used now primarily for seedling propagation.

“The focus of the system is how it has enabled us to cut back on the amount of space that is needed for propagation,” he said. “We can easily grow enough seedlings in this system for a 10,000-square foot greenhouse.

“The system is also being used by a Central Market store in Dallas to finish crops for its Growtainer farm. We helped consult on the management of the system and showed store officials how it could grow crops from start to finish in the same Growracks. The store is growing fully mature butterhead lettuce and basil in the system. This system can definitely work in indoor vertical farms.”

Baras said he has grown both organically and conventionally with the Growrack system.

“We have done organic seedling propagation in it,” he said. “We have used a variety of conventional and organics substrates and fertilizers with it.”


LED studies

In addition to trialing LED lights vs. natural light for greenhouse seedling propagation and crop staging, Baras said he is also looking at using LEDs supplemental light throughout the production of butterhead lettuce in the floating raft system.

“We are looking at how LED light affects leaf texture and plant morphology of butterhead lettuce,” he said. We are trying supplemental lighting during the summer. We are pulling shade so the light isn’t very intense. It appears that intense light can lead to tip burn that damages the plants leading to a poor quality crop. So we pull shade cloth and then run a prototype high-output LED grow light provided by GE for almost 20 hours. We deliver a low intensity of light over a longer period so we can provide the plants the light they need without stressing them. We are trying to improve the quality by adding LED light in order to produce more compact growth that is associated with LEDs.

“Under greenhouse shade cloth the lettuce leaves look fragile. We are trying to grow the lettuce to hit a certain weight. If the plants are grown under shade they look fairly large and floppy and the head doesn’t have the right density at its core. By using the LEDs we can produce the more traditional morphology where the plants have a dense core. The leaves aren’t floppy and the plants look more like traditional butterhead should look.”


Matching plants and production systems

Baras said he is trialing a wide range of crops in all of the production systems he is using.

“Primarily we are focused on lettuce and basil, but we are trialing a lot of varieties,” he said. “We definitely see some systems are capable of growing some varieties that other systems are not. We want to be able to recommend what varieties grow best in what systems. We are preparing a book based on our research that will include an entire section on strategies for how to use these production systems. We will provide example situations in the book discussing location, climate, market, what crops are being requested by that market and how to use that information to determine what production system is most appropriate.

“We are looking at primarily butterhead, romaine and oakleaf lettuce and 20 different basil varieties. We are also doing trials with arugula, spinach, cilantro, kale, chard, Asian greens and microgreens. We are doing an extensive study of herb varieties. There are also some unusual crops like stevia, wasabi arugula, celeriac and sorrel. We are determining all of these plants growth habits in the different production systems. This information will be in the book along with the details and nuances of growing each crop.”

A vertical hydroponic tower commonly used by smaller growers has been installed to answer some of the questions that Hort Americas customers have about using the system.

Based on the trial results, Baras said the book will provide details on each plant variety and its performance in each system.

“The book will provide information on the growth a grower should expect in different environments based on the amount of light and temperature,” he said. “The book will offer projected production numbers a grower should be able to reach. These will be realistic targets for each of the production systems we have studied.”


For more: Hort Americas, (469) 532-2383;


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

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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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The impact of transplanting times, light exposure on hydroponic crop production

How quickly hydroponically-grown lettuce and leafy greens seedlings are transplanted and their exposure to LED light during propagation can impact crop production times.

Most growers using traditional hydroponic substrates transplant lettuce and leafy greens seedlings as soon as the roots reach the bottom of the plugs. This usually takes from seven to 10 days.

“We are trying to see if we can go far longer in Stage 1, which is this seedling stage,” said Tyler Baras, special projects manager at Hort Americas in Bedford, Texas. “Stage 1 occurs in a propagation area.

“Some growers incorporate an intermediate phase (Stage 2) which is a growing out stage. Stage 2 might consist of nutrient film technique (NFT) channels closely spaced next to each other or a deep water raft system with high density spacing. Generally a 2-foot-by-4-foot raft holds 72 plants or more. Both Stage 2 and 3 occur in the final growing out system. During Stage 3 those same NFT channels are spaced further apart or in a deep water system the plants in a 72-count raft are transplanted to a lower density 28- or 18-count raft.”

Some hydroponic growers incorporate an intermediate Stage 2 during which nutrient film technique channels are spaced close together.
Photos courtesy of Tyler Baras

Baras said holding the seedlings in Stage 1 for a longer period would reduce the amount of time that is required in the final Stage 3.

“This would actually be a two-stage system with an increase in time the seedlings are in the propagation stage or Stage 1,” he said. “Our reason for doing these studies is to see if we can eliminate the labor required to transplant the plants from Stage 2 to Stage 3, but still achieve yields similar to three-stage systems. Three-stage systems generally achieve more crop turns per year than two-stage systems. For many small growers trying to find enough labor and high labor costs can be major issues. If we can reduce the amount of labor required by extending Stage 1 this could help growers.”

Baras said the reason most growers don’t try to grow the seedlings longer during Stage 1 is the chance for root damage that can occur when the plugs are transplanted into the final production system.


Most growers are concerned root damage may occur when plugs are transplanted into the final production system if they hold seedlings too long in Stage 1.

“If seedlings are held too long, especially in a sheet substrate where there isn’t any divider between the plants, the roots can easily grow into the neighboring plugs,” he said. “When a grower goes to transplant the plugs and tries to pull them apart damage can be done to the roots. When the plugs are transplanted into the final system this root damage can lead to stunting and leaf dieback. The damaged leaves are more susceptible to disease pathogens and can attract fungus gnats. The plants will also require additional cleaning at harvesting to remove damaged leaves.”

Baras has observed the problems caused by holding the plugs longer in Stage 1 occur more often with transplanting into NFT systems than with deep water raft culture.


Promising results

Baras said that he has conducted several trials with different substrates holding the seedlings in Stage 1 up to six weeks.

“We have gone the longest with self-contained plugs,” he said. “This is usually with organic production where there is slower growth. We have pushed the seedlings for a longer period of time. So far the best results with conventional hydroponic production are at about three weeks. With organic production it’s around four weeks because the plugs are self-contained and the roots don’t grow into neighboring plugs.

“We are pushing some of the seedlings to nearly a month and not seeing significant leaf dieback or stunting from root damage. We are shaving off several weeks within the final production system. It’s still possible to damage the seedlings if they are held in Stage 1. We are seeing the upper limit is higher for deep water culture than it is for NFT.”


Impact of LED lighting

Baras said another factor that can impact seedling development is exposure to supplemental light.

“We have been trialing different photoperiods and light intensities,” he said. “We have found that the light treatments that we give the seedlings can actually affect whether the plants produce more roots or more leaves. We are looking at the differences between exposing the seedlings to sunlight and LED light from GE Arize Lynk fixtures and different photoperiods.

“Depending on the lighting treatment we can create a smaller plant on top but increase root mass. This allows us to grow the seedlings longer without the plant canopies growing into each other. When the seedlings are removed for transplanting there is no damage to the leaves. There are more leaves left intact by growing more compact plants. We are still able to get a lot of root development.”

One of the most exciting findings that Baras is seeing is the increase in final weight of lettuce given LED supplemental light.

“When we started our research we were using traditional production methods,” he said. “We would sow the butterhead lettuce seed and place the trays under sunlight and then transplant the seedlings between seven to 14 days. With this traditional growing method we would produce a 6-ounce head. With the adjustments that we are making to staging and using LED lighting we are producing 8-ounce heads in the same amount of time. We are very excited about that. We think it is one of the most significant things coming out of our research greenhouse right now.

“The plants grown with LED light are finishing with 2 ounces more of plant weight. This seems to be related more to light quality and the influence that it has on the seedlings’ morphology than on total light received. It is not like the plants are receiving a lot more light when they are exposed to LEDs instead of sunlight. The morphology of the plants is completely different because of the light quality spectrum they are receiving. We now want to look further at light quality treatments during the seedling stage. This includes different ratios of blue/red LEDs, the inclusion of different colors and checking for variety specific results. There are still a lot of trials to do.”


Butterhead lettuce seedlings lit with LED lights during propagation are producing larger heads in the same amount of time as seedlings exposed to sunlight during propagation.

One of the trials that Baras wants to study further is varying the length of time the lights are on.

“We are also looking at how long the lights are on,” he said. “Whether there is a big difference depending on the length of the photoperiod. We have not found an optimum length of time. We have found that more light is not always better.

“We are looking at exposing the seedlings to 20 hours or 24 hours of light. Right now 20 hours of light is outperforming 24 hours of light. But 24 hours of light is outperforming natural sunlight. This is across all crops, including a couple varieties of lettuce and Italian basil.”


For more: Hort Americas, (469) 532-2383;


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

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Be aware of the challenges of using loose substrates in hydroponic production systems

If you’re going to use a loose substrate in a hydroponic production system, you may have to change how you handle starter plants and the treatment of recycled water.

Many growers of ornamental plants including annuals and perennials traditionally use a peat-based substrate such as 70 percent peat, 30 percent perlite. The growers, who produce these crops in containers, will often use the same substrates if they expand their crop offerings to include hydroponically-grown edible crops, including lettuces and leafy greens.

“There are some growers who use these peat-based substrates in hydroponic production systems, but it is more difficult to manage because hydroponic systems need to run clean,” said Tyler Baras, special projects manager at Hort Americas in Bedford, Texas. “Debris from these loose substrates can lead to clogging of irrigation lines in hydroponic systems like nutrient film technique (NFT). In the case of a deep water culture floating raft system the goal is to flush the system as infrequently as possible because there is so much water involved. Growers want to keep both of these hydroponic production systems fairly clean.

“The loose substrates used by traditional bedding plant growers can break apart so that there is some peat and perlite floating in the system or sinking to the bottom of the pond or water reservoir.

Debris from loose substrates like peat and perlite can lead to clogging of irrigation lines in hydroponic systems.
Photos courtesy of Tyler Baras

Baras who recently completed trials with loose substrates in a 12,000-square-foot research and demonstration greenhouse in Dallas said the more commonly used substrates for hydroponic systems are inert materials. These include preformed plugs, such as stone wool plugs or cubes, polyurethane foam blocks, stabilized medium like synthetic polymer peat plugs and wrapped plugs which can have an outside coating like Riococo Closed Bottom Organic Plugs.

Focused on root growth

In the greenhouse trials that Baras is doing with lettuces and basil in NFT and deep water raft systems, he is studying the differences between peat and coir.
“Coir has more water retention from what we have seen,” he said. “It really depends on the production system, the growers’ staging strategy and how the seedlings are watered. There are a lot of factors that are similar and they both have the possibility of being used for hydroponic production.

“Coir is often used as a substitute for peat. Often when coir is used, growers have to change their irrigation strategies. Fine coir holds more water than peat. Once the seed has germinated and is at the seedling stage the goal is to establish a strong root system regardless of the substrate used. The plug should be dominated by roots. As long as the plug has a large enough root mass once it is transplanted into a hydroponic system, there is a good chance for success.”

Seedling plugs transplanted into a hydroponic system should be dominated by roots regardless of the substrate used.

Growers should consider young plant development strategies specific to the substrates they are using.

“An example would be plugs with some type of wrapping around the outside,” he said. “The bottom is open, but the plants should be grown until there are enough roots to cover the bottom of the plug so it doesn’t fall apart once it is placed in the hydroponic system.”

Limited choice of organic substrates

Baras said growers doing organic hydroponic production have a more limited selection of substrates.

“Growers who want to grow organically can’t use stone wool, foam blocks or any polymer peat plug,” he said. “Organic production is generally limited to loose substrates. This would include loose peat- or coco-based substrates and coco plugs. There aren’t a lot of options.

“If a loose substrate is used and some of it is falling apart and into the production system it can quickly clog the irrigation system. It’s important to have a solid root structure before transplanting the plugs into an organic hydroponic system.”

Although organic production is generally limited to loose substrates, the Riococo Closed Bottom Organic Plug offers an alternative stabilized medium.

Whether growing organically or not, when using loose substrates in hydroponic systems, Baras said growers need to have a good filtration system.

“Anything coming off the tail end of the NFT channels is going to have to be run though some kind of filtering stage to collect any debris before the water goes back into the reservoir,” he said. “The irrigation lines are usually ¼-inch or smaller and those can clog quickly when loose substrates like peat or coco are used.”


For more: Hort Americas, (469) 532-2383;

For more information on choosing a substrate for hydroponic production systems,

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

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Are you maintaining the proper oxygen levels in your hydroponic production system?

Growers have affordable options for ensuring plants receive sufficient oxygen in hydroponic production systems to maximize growth and to reduce the chances of disease.


Oxygen is critical in the development and growth of edible crops grown in hydroponic systems such as nutrient film technique (NFT) and deep water raft culture. Tyler Baras, special projects manager at Hort Americas, is studying methods of adding oxygen to both conventional and organic hydroponic production systems in the company’s 12,000-square-foot research and demonstration greenhouse in Dallas, Texas.

“One of the big differences is how growers add oxygen,” Baras said. “A lot of times in conventional hydroponics, growers use air pumps and air stones to add oxygen. In organic systems these tend to be hot spots for biofilm development. We have removed all air pumps and air stones from the organic systems we are trialing.

Tyler Baras, special projects manager at Hort Americas, is studying methods of adding oxygen to both conventional and organic hydroponic production systems.
Photos courtesy of Tyler Baras


In the conventional production systems Baras is studying he has installed water pumps with a Venturi attachment to add oxygen to the nutrient solution reservoir.

“The pumps aren’t injecting air into the irrigation lines, but simply into the reservoir to circulate the water and to create a circular flow within the fertilizer reservoir,” he said. “As the pumps operate they draw in air through a ¼-inch emitter. There is the benefit of moving around the solution and the air being drawn in increases the level of dissolved oxygen.”

A method that organic growers use to increase oxygen levels is cascading the water when it returns to the reservoir. As water returns it is allowed to fall and break the surface of the reservoir so that the water can pull in oxygen.

“This can also be done in vertical farms where the water will fall down large return pipes to the reservoir,” Baras said. “This can happen in multiple stages where the water will drop several times. This is an effective method for increasing dissolved oxygen.

“For NFT, it appears more oxygen can be delivered to plant roots when the flow rate is increased per channel. As the flow rate increases, more oxygen is delivered to the roots so water isn’t sitting in the channel as long. This allows freshly oxygenated water to be delivered quickly to the roots. In conventional hydroponic NFT systems the flow rate is about ½ liter per minute. In our hydroponic NFT system I have been aiming for about 1-2 liters per minute.”


Adequate oxygen levels

Baras said oxygen is necessary for plant roots to perform metabolic processes.

“Most of the water uptake in plants is passive,” he said. “But there is a stage where the plants use energy to actively pull up water through the roots. This requires oxygen. If there isn’t any oxygen in the root zone no water will make it up through the roots to the top of the plant. Low oxygen in the root zone can appear as wilting at the top of the plants. This can seem counterintuitive in a hydroponic system because the roots are sitting in water, but the tops of the plants look like their wilting if there isn’t any oxygen in that water.”

As the flow rate increases in a NFT system, more oxygen is delivered to the roots so water isn’t sitting in the channel as long.


Baras said the need for oxygen in an organic hydroponic system is even more important because of the presence of living microbes in the fertilizer solution reservoir.

“These microbes also require oxygen,” he said. “The oxygen demand is often higher in organic systems than conventional systems because not only do the plant roots need oxygen, but the microbes need oxygen as well. In an organic hydroponic system one of the best ways of keeping biofilm in check is to keep the beneficial microbes happy.”

Baras said most of the oxygen measurements he has been taking in his research have been showing very similar oxygen levels for both conventional and organic production systems when the crops are performing well.

“I have been aiming for a level of 7-12 parts per million (ppm) dissolved oxygen, but generally the readings fall between 7-9 ppm,” he said. “I’m using a ProODO meter from YSI that is a very sensitive piece of equipment that accurately measures dissolved oxygen.”

Although most hydroponic growers are concerned with maintaining adequate oxygen levels, Baras said if too much oxygen is added to the solution it can cause root stunting.

“I haven’t reached that threshold yet in my trials,” he said. “It’s crop dependent on what that level is. When there is too much oxygen the roots have less motivation to grow larger because they are getting everything they need with a smaller surface area. That can then translate to the plants producing less biomass resulting in less leaf tissue. So at some point too much oxygen can actually cause less growth. For crops like tomatoes, peppers and cucumbers the whole plant would be stunted.

“The only way growers could reach excessive oxygen levels that damage the plants are when liquid oxygen or possibly ozone is used. Using air pumps or air stones to add oxygen, the levels won’t be high enough to stunt plant growth. To reach higher oxygen levels of 15-16 ppm, a grower would have to use other methods like liquid oxygen and ozone. It’s very difficult to reach high oxygen levels above 10 ppm unless an alternative method is used beyond air pumps, Venturis and cascades. I haven’t seen any growers go much higher than 8-9 ppm using the conventional methods.”

Baras said growers using a deep water raft system could try increasing turbulence in the pond to increase oxygen level. However, too much turbulence can sometimes cause damage to the roots.

Increasing turbulence in a deep water raft system can increase the oxygen level. But too much turbulence can damage roots.


“The roots in the turbulent areas are the ones that often times grow poorly,” he said. “The plants that are near the irrigation outlets where the currents are stronger, they have the poorest root growth. Sometimes growers will use air pumps in their ponds and those plants directly above where the air stones are located grow poorly.”

For more: Hort Americas, (469) 532-2383;


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

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Industry survey seeks information on hydroponic food production

Researchers at Michigan State and Iowa State Universities are looking for feedback from hydroponic food growers to help them determine where research is needed to benefit the industry.

If you are doing hydroponic food production or thinking about doing this type of production, your input is needed. Controlled-environment agriculture (CEA) production researchers Roberto Lopez and Kellie Walters at Michigan State University and Chris Currey at Iowa State University have developed a survey to gain a better understanding of current hydroponic food production practices. The researchers will also use the results of the survey to help determine future research projects as well as their extension efforts.

Kellie Walters, a PhD graduate research assistant at Michigan State University, is conducting a hydroponics industry survey to see where she can make the biggest impact with her research.
Photo courtesy of Mich. St. Univ.



“One thing we like to do as researchers is to see where we can make the biggest impact,” said Kellie Walters, who is a PhD graduate research assistant at Michigan State. “We want to know what matters to growers. What would they like to see done? Some of the information collected from the survey might impact the research I will be doing for my PhD. I have already set up some experiments working with some of the environmental parameters that we ask growers about in the survey.

“One of the things that I am interested in is the environment, including temperature, carbon dioxide, light intensity and quality, how these interactions affect the growth and flavor of different herbs and leafy greens. In the survey we asked about the value of crop flavors. I want to know if growers really care if their crops are more flavorful.”


Determining production protocols

Walters is working with Michigan State horticulture professor Roberto Lopez, who is her major advisor for her PhD degree.

“Kellie did her master’s degree with Chris Currey at Iowa State where she focused on hydroponic herb production,” Lopez said. “Now she is doing her PhD with me and she is going to focus on hydroponic leafy greens production in greenhouses and indoor controlled environments.

“We wanted to survey the industry and determine production protocols for growers. So we are asking questions related to where they grow hydroponically—in a greenhouse, hoop house, indoors or outdoors? What types of systems are they using? What crops are they growing? Even though we are focusing much of our research on leafy greens, we wanted to find out what food crops are being grown currently. We wanted to determine growers’ inputs as well as their cultural and environmental parameters. This includes their water source, temperature set points, and if they provide supplemental or photoperiodic lighting. Also, do they grow young plants for hydroponics or are they basically just finishing the crops?”

Michigan State horticulture professor Roberto Lopez said the hydroponics industry survey will provide researchers with information about growers’ production protocols.
Photo courtesy of Mich. St. Univ.


Lopez said the survey results will help determine the direction of his, Walter’s and Currey’s research.

“The survey will impact the way Kellie does her research and the direction of her research as well as for Chris,” Lopez said. “The survey will help to determine the major needs of hydroponic growers.”


Determining production challenges, research needs

Currey said the survey offers the opportunity to find out what challenges are occurring with hydroponic growers.

“There are so many more growers out there than I will ever have the chance to personally interact with whether that is with a phone call, through email, or visiting their facilities,” he said. “When I talk to growers and get to know them and learn what they are doing, I learn about their problems. It’s helpful to have all of those perspectives. It’s good to get a view of the landscape and the challenges that exist.

“Even before we did the survey we knew that growers were having certain issues with lighting and temperature, so we have been working on those. Productivity under low light or productivity under cool temperatures and coming up with predicative models for growth. There are certain things we know growers could use. Hopefully we are already focusing our research programs on some of those. The survey will hopefully validate the need for some of the research we have already been doing. The survey will also help us to plan research in the future to make sure that it is relevant and needed.”

Iowa State University horticulture professor Chris Currey is working primarily with leafy greens and herbs, which are generally a more accessible crop for growers beginning to do food production.
Photo courtesy of Iowa St. Univ.

Currey said most of the research conducted as a result of the survey results will likely be done using nutrient film technique or deep water raft systems.

“I work primarily with leafy crops, mainly herbs and greens,” he said. “Our facilities are well-suited for leafy crops. It takes a little more of a specialized facility for vine crops like tomatoes and cucumbers because of their dimensions. I also work on the leafy crops because I think they are generally an accessible crop for growers to begin food production. The barrier to entry with leafy greens can be a little lower than with tomatoes with respect to some of the learning curves. Leafy greens also have shorter crop times for ornamental growers who are looking for fast crops. Leafy greens could be a short “gap” crop rather than something like tomatoes which can be a six- to nine-month crop.”

Currey said he is also hoping the survey helps to identify growers’ needs that also compliment his skill set as a researcher.

“I expect there will be comments and questions about powdery mildew management on lettuce or some other pest issues,” he said. “There are other people aside from myself who are better equipped to conduct powdery mildew research. Hopefully the survey results will give ideas to other researchers as well. We want to make the results publically available. The survey might give other researchers ideas about what needs can be addressed with their skill sets.”

Walters said they will be publishing the results of the survey to give the industry access to the information.

“There is no way that we can create the optimal guidelines for growing all of the hydroponic crops growers are producing,” she said. “The survey will help other researchers know what areas growers would like to focus on and to help inform growers of issues other growers are currently facing.”

The Hydroponics Industry Survey consists of 24 questions and should take less than 10 minutes to complete. The deadline for participating in the hydroponics survey is Friday, May 12.

For more: Kellie Walters, Michigan State University, Department of Horticulture, East Lansing, MI 48824; Roberto Lopez, Michigan State University, Department of Horticulture, East Lansing, MI 48824;; Chris Currey, Iowa State University, Department of Horticulture, Ames, IA 50011;;

Editor’s note: This month Kellie Walters  was selected as a 2017-2018 Future Academic Scholars in Teaching (FAST) Fellow.


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


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Organic vs. traditional hydroponic production: the top 3 differences

When it comes to changing from conventional to organic hydroponic production methods, there are three main areas that growers find most challenging.

Tyler Baras, special projects manager at Hort Americas in Bedford, Texas, said growers are increasingly inquiring about organic hydroponic production. Baras is running hydroponic production trials comparing organic and conventional production methods in a 12,000-square-foot research and demonstration greenhouse in Dallas.

“We’re doing the research because of market demand,” he said. “A lot of growers are getting feedback from their customers that they would prefer to have produce that is certified organic. Produce suppliers and brokers hear from the grocery stores and then they bring those requests to the growers.


Tyler Baras, special projects manager at Hort Americas, is comparing organic and conventional hydroponic production methods using a variety of edible crops.
Photos courtesy of Tyler Baras


“We don’t necessarily believe that produce grown with organic production methods is superior. We believe in conventional production methods as well. What we are trying to do is provide as many options to our customers as possible.”

Baras said that organic production is a whole system that includes substrates, fertilizers and pest management. But most of the questions coming from growers about organic production are related to fertilizers.


  1. Inoculants and tank culturing

Baras said an advantage of traditional fertilizers is all of the research that has been conducted on them has enabled growers to target exact nutrient profiles for specific crops.

“Research has enabled traditional fertilizers to come down to fairly exact levels,” he said. “Growers are able to figure out exactly how many parts per million of each nutrient they want to put into nutrient solutions. The chemistry allows them to be that exact.

“Organic fertilizers are a little trickier because there isn’t the precision targeting each nutrient. Generally there are inputs that are going to have several nutrients in them. Growers don’t have the ability to adjust individual nutrients as easily.”

Another issue with many commercial organic fertilizers is they are animal-derived. These organic fertilizers include manures, bone meal, blood meal and feather meal.

“These animal-based organic fertilizers don’t mix well with water,” Baras said. “If growers are using recirculating hydroponic systems, these animal-based fertilizers tend to start going rancid and smell in a few days. These fertilizers can also form a sludge that can clog irrigation lines and emitters.”

Baras has focused his research trials on Pre-Empt, a plant-derived organic fertilizer which has blackstrap molasses as its major component. He has been comparing organic vs. traditional fertilizers in several hydroponic production systems, including flood-and-drain grow racks, two different nutrient film technique (NFT) systems, deep water culture floating rafts and a ZipGrow Tower system.

“We have successfully grown butterhead lettuce and basil in all of these systems using organic inputs,” he said. “We have several other crops that we are running through these systems in smaller trials, including spinach, cilantro, arugula, strawberries and other lettuce and herb varieties. Most of research is still focused on butterhead lettuce and basil.

“We currently don’t have any trials going with microgreens, but some of our first trials were with microgreens under LED lights using organic substrates and organic fertilizers. We definitely proved that is a viable production system.”

Baras said he knows of growers using Pre-Empt organic fertilizer who haven’t flushed their nutrient solution tanks for five months.

“The key is the slow development of the fertilizer tank,” he said. “Some growers have immediately added the organic fertilizer to their reservoir at full strength and they quickly notice that their tank starts to foam at the top and starts to smell similar to what happens with animal-based organic fertilizers. We’ve found if an initial charge, about half the target rate, is added first, along with a microbial inoculant at the same time, these issues can be avoided. We are using Terra Bella as the microbial inoculant because it has an extensive profile of different microbes.”

Baras said the half rate of fertilizer and microbial inoculant are run through the system for about two weeks.

“Once the microbial population becomes established, the nutrient solution in the tank can be brought up to full strength without any foaming or odors,” he said.


  1. Nutrient solution pH management

Baras said one of the major issues with the organic nutrient solution during the first two weeks is pH swings.

“The pH of the nutrient solution on the first day the organic fertilizer is added to the tank is in a good range around 6-6.5,” he said. “Within a couple days of adding the fertilizer, the nutrient solution pH shoots up to around 8.0. There are a lot of plants that do not like a high pH. Iron-inefficient crops like basil have a hard time taking up iron at a high pH. There will be a lot of chlorosis at the top of the plants. This happens within a couple days of the pH going above 7.

“During the second week the pH drops to between 4 to 5. The plants continue to grow, there are a lot of nutrients in the solution, but the quality is very different. During the third week the pH stabilizes. As the microbial population stabilizes, the pH stabilizes around 5.5-6.5, which is ideal for leafy greens.”

Baras said growers have taken two routes to stabilize the nutrient solution pH.

“There are growers who will let the solution go for this two-week swing and let the solution stabilize similar to what we have been doing,” he said. “Other growers are trying to control the pH with inputs. When the pH goes up they will add citric acid. When the pH starts to drop they will add sodium bicarbonate.

“The inputs to adjust the pH are very limited. The main downfall with citric acid is that it is anti-microbial. So although a grower is able to lower the pH, it’s not good for the microbial population. Another option is vinegar, but most commercial growers are using citric acid for controlling pH for organic production.”

Baras said the options for raising the pH are also limited.

“Growers would like to use potassium bicarbonate, but potassium bicarbonate is not allowed for pH management under the organic rules,” he said. “Potassium bicarbonate can be used to control powdery mildew, but it can’t be used to control pH in the nutrient solution tank. What growers are left with is sodium bicarbonate or baking soda. The pH can be raised, but over time sodium accumulates. Once a certain threshold of sodium is reached then problems start to occur including nutrient disorders.”

Baras said another issue with using citric acid and sodium bicarbonate for pH management is the longevity of the nutrient tank solution is shortened.

“It could be a couple months, but at some point the sodium levels are so high that either the whole solution or part of the solution is going to have to be dumped,” he said. “The tank is going to have to be flushed. The amount of citric acid and sodium bicarbonate added can be done in small increments, but it is the accumulation that causes problems.”

Baras said once the nutrient solution stabilizes, the swings in pH won’t be as drastic when additional water and fertilizer are added to the tank.

Another option for controlling pH includes adding more water or fertilizer.

“Depending on the water source, adding water to the tank can sometimes raise the pH,” Baras said. “Also, the Pre-Empt fertilizer is somewhat acidic and that could be used to lower the pH simply by adding more fertilizer.”


  1. EC targets and nutrient analysis

Baras said growers who switch to organic production systems should continue to measure the electrical conductivity (EC) of the nutrient solution to determine soluble salts levels.

“A lot of the nutrients in organic fertilizers won’t register on EC readings because of the forms they are in,” he said. “They aren’t yet broken down into simple salts. If growers are basing their feedings solely on EC readings, the EC of the nutrient solution will probably read much lower even when sufficient nutrients are being provided to the crop.

“The specific makeup of the nutrient profile, how many parts per million of each nutrient, for organic and conventional fertilizers are not the same. I don’t target the same nutrient profile for an organic nutrient solution that I do with conventional nutrient solutions.”


Butterhead lettuce and basil have been grown successfully in Hort Americas’ research greenhouse using several hydroponic production systems and organic inputs.



Baras said plants are fairly flexible on many of the nutrients, which can be maintained within a fairly wide range.

“With organics, sometimes the calcium level may only be 100 parts per million where with conventional fertilizers the target calcium level for most leafy greens is around 200 ppm,” he said. “But even at 100 ppm calcium with an organic fertilizer, we are not seeing the issues that we would expect from having a low calcium level.”

Baras said for fruiting crops like tomatoes, calcium can be an issue with organic production.

“Calcium sulfate is an amendment that can be used to correct calcium deficiency,” he said. “Another nutrient that can be low with plant-based organic fertilizers is magnesium. What we have found is nutrients like calcium and magnesium that are usually lacking in the organic fertilizer we are using, they are generally found in the source water of most growers.

“In our research greenhouse the source water contains 30 ppm magnesium and 30 ppm calcium. Those can make a fairly significant contribution to the nutrient solution, especially with calcium that isn’t taken up as quickly as other nutrients. Over time the calcium level accumulates in the fertilizer tank. As the organic nutrient solution is used over several months, the calcium level rises and nearly reaches the conventional target of 200 ppm calcium. Like calcium, magnesium generally rises over time with source water contributions.”


Measuring changing EC levels

Baras said that he uses an EC meter to get an estimate of the soluble salts level in the organic nutrient solution.

“For lettuce the EC of the nutrient solution in the greenhouse for conventional production is usually run at 2-2.3,” he said. “For organic lettuce production I typically run an EC between 1.2-1.6. I make sure that the crop has the nutrients close to the target range by sending water samples to a testing lab to get an exact analysis. But even that has some issues with organic production.

“I’ve found that the amount of time a nutrient solution sample sits after it is sent out can affect the nutrient analysis from the lab. Since nutrient solution microbes are constantly active, changes can occur within the sample. Initially a sample sent to a lab may have 100 ppm nitrogen. But a few days later the same sample may indicate there is 150 ppm nitrogen.”

Baras has sent the same samples to multiple labs and he has received analyses with significant variations, especially with nitrogen. He suggests growers stick with one lab.

“If there is a lab that is relatively close to a grower’s operation, this can help ensure that results are returned relatively quickly,” he said. “The best practice is for growers to create their own archive of the nutrient analyses so that they can compare test results to previous notes. Lab test results are likely mimicking what is happening in the nutrient solution tank. The microbes’ activities are also affected by temperature the solution is stored at as well. The readings could come out higher or lower.

“There are different factors that can affect the EC including the temperature and the crop stage when a water sample is taken. Crop age, whether plants are young or mature, whether there is a well-developed root system along with the crop itself, impact the interaction with the nutrient solution. These can affect the form the nutrients are in and how that would read out on a nutrient analysis.”

Baras said how often an EC analysis should be done depends on how large the reservoir is and how often water is added to the reservoir.

“A small reservoir that is frequently amended with water should be tested fairly often,” he said. “Nutrients can quickly accumulate in a small reservoir. Growers with a small reservoir might be testing every week. With a large reservoir used for deep water culture that may contain 8,000 gallons of water, it is not as urgent to test as frequently.”

For more: Hort Americas, (469) 532-2383;


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

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Looking for a better, easier way to do greenhouse IPM?

Greenhouse Scout is an integrated pest management app that makes it easier to collect, store and analyze scouting data along with identifying insect pests and which beneficials can be used to control them.

Most greenhouse growers know the benefits of scouting their crops for pest insects and mites. Scouting can help to identify and minimize pest outbreaks, reduce plant damage and crop losses and save on pesticide and biological control costs.

Greenhouse Scout mobile app developed by the New York State Integrated Pest Management Program at Cornell University initially began as a how-to notebook for greenhouse ornamental plant growers.

“Incorporating beneficial organisms for insect and mite management in greenhouses is not something that growers can just jump into,” said Elizabeth Lamb, ornamental IPM coordinator at NYS IPM Program. “A lot of information is required for someone trying to successfully do biocontrol. Once it becomes part of the production system it can work, but getting started is the hard part. We didn’t see one good way of putting all of the information together in a relatively easily accessible format.

Elizabeth Lamb, ornamental IPM coordinator at NYS IPM Program, worked with GORGES Inc. to develop the Greenhouse Scout app.
Photos courtesy of NYS IPM Program

“We initially started putting the information together in a notebook. We said this is great, but we knew people weren’t going to carry the notebook into the greenhouse. When we started asking growers if they would like this as an app, something they could carry on their smart phones, we received a lot of positive responses. That’s how we decided to develop the app.”

Developing an interactive app

NYS IPM Program staff began working with GORGES Inc. in Ithaca, N.Y., to develop the app program. The funding to create the app came from a USDA National Institute of Food and Agriculture grant.

“The company asked me during the initial discussion if we wanted to make the app interactive so that is when we decided to add the scouting and record keeping functions. The app really has two applications. In addition to the scouting function, it’s a source of information for pests and pest identification and for beneficials identification and usage. Even if a grower is not using the app to collect scouting data, it can be used to identify common greenhouse pests like green peach aphid. The app will also determine what beneficials can be used, how to apply them and the environmental factors that need to be considered. All of that information is available on the app.”

Although the Greenhouse Scout app was developed for greenhouse ornamentals, it has application to other protected environment crops.

Lamb said that even though the app was initially developed for greenhouse ornamentals, it could be used with greenhouse vegetables and other protected environment crops.

“The app is specialized by insect pest,” she said. “Anyone who has these insect pests potentially could use the app. For the most part, many of the insect pests we see in ornamental greenhouses are also found in vegetable greenhouses. For vegetable greenhouses a grower could certainly use the app because many of the insect pests and biologicals are the same. We can also add new insect pests and beneficials as they become important.”

More effective scouting

Lamb said even though growers are good about identifying pest problems on their plants, they can have a difficult time tracking the data, especially from year to year.

“We are trying to help growers make scouting easier so that they will do a better job of scouting,” she said. “If a grower is walking through the greenhouse and sees something, he can easily take out his smartphone, go to the app and put that information in. If a grower is doing more organized scouting, the app can be set up to do scouting in specific locations. If there are multiple scouts collecting information all of that data can be inputted simultaneously.”

One of the biggest scouting gaps the app can help eliminate is determining the effectiveness of pesticide and/or beneficials applications.

“At the same time the app is used to note numbers of pest insects and beneficials, it can also be used to record applications of beneficials or pesticides,” Lamb said. “While the app does not include recommendations on what pesticides to use to manage a particular pest, those active ingredients labeled for New York State are listed.”

Although scouting information is being written down on paper or in a notebook, Lamb said having all of this data doesn’t indicate whether beneficials and pesticide applications are working.

“Growers might have a general idea if they are seeing fewer or more of a particular pest from the previous week,” she said. “The app offers growers the ability to look at the scouting data on graphs so they can see whether the pest numbers are going up or down. This gives growers more information to use in terms of deciding what to do.

“We are hoping to reduce pesticide applications by encouraging the use of biological controls. However, if growers are using the app to scout and are only applying pesticides, we would hope that they would also be able to reduce their pesticide use. Growers can use the app’s graphs to determine a pesticide’s effectiveness so that they don’t over apply. If a pesticide is not particularly effective, growers can come back and apply something else.”

Greenhouse Scout offers growers the ability to look at scouting data on graphs so they can see whether pest numbers are going up or down and whether a control application is effective.

Lamb said being able to print the graphs enables growers to keep a running record of what has happened with their crops in previous years.

“Growers can see if there is a pattern for a pest,” she said. “Whether a pest keeps coming in at the same time on the same crop. Growers usually remember those kinds of things, but it’s nice having a resource they can refer to to see what controls actually worked.”

Ease of use

Lamb said the app was designed to be used in all size greenhouses.

“If growers have an internet connection the recording of the scouting data to their computer is automatic,” she said. “If growers don’t have an internet connection in the greenhouse, the app holds the information until the connection is made. It doesn’t have to be plugged into something else. The data is synced directly into the computer. If there are four workers scouting simultaneously in different greenhouses, they can input data on the same account. Growers could sit in their offices looking at what is going on with pest management in all of those greenhouses at the same time.

“The only thing growers need to add is their locations. A location could be designated as Greenhouse 1, Section 1, Bench 1. In some cases growers move their crops around and five different crops may move through that area during the production season. In that case, it might make more sense to call a crop by its name such as pansies. Pansies may move from Greenhouse 1 to Greenhouse 2 and then they move onto sales. The intention was to make the app as flexible as possible. Growers can use the data from year to year if it’s something that makes sense for their operation.”

Lamb said she has received requests to translate the Greenhouse Scout app. She is currently working with GORGES to find out the costs involved with translating the app into Spanish and French. She is also working on apps for conifers and greenhouse hops that will include both insect and disease pests.


For more: Elizabeth Lamb, NYS Integrated Pest Management Program, Cornell University, Ithaca NY 14853; (607) 254-8800;;
NYS IPM’s Greenhouse Scout is available for $9.99 at the Android and iPhone app stores.

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

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P.L. Light Systems’ HortiLED series of grow lights meets the requirements of controlled environment agriculture

Whether greenhouse, vertical farm or warehouse growers are propagating or producing ornamental, vegetable or cannabis crops, P.L. Light Systems offers the LED fixtures to meet their lighting needs.

P.L. Light Systems develops and manufactures supplemental lighting systems for the horticultural industry. The nearly 40-year-old company manufactures traditional light sources, including high pressure sodium (HPS) and metal halide, as well as its own light emitting diode (LED) fixtures.

“There are a lot of lighting products hitting the market right now, especially when it comes to LEDs,” said Eric Moody, P.L. Light Systems western USA Lighting Solutions Specialist. “The future of the horticultural lighting market is moving toward LEDs as the technology continues to advance. Every week it seems like there is another company entering the horticultural lighting market. Growers need to carefully look at the lighting companies they are considering working with. How long has a company been around and is it focused on horticulture or is it just buying circuit boards and selling them as LED horticulture lights?”

Even though P.L. Light Systems has been marketing horticulture grow lights for nearly 40 years, it was not one of the first companies to offer LED lights. “One of the reasons that we weren’t one of the first companies is because of the intensities and efficiencies of LEDs,” Moody said. “In 2014-2015 the market started to see LED diodes that could deliver 2.1 micromoles per joule (μmol∙J–1). When this occurred everyone that was selling LEDs to the horticulture industry got excited.

“Double-ended HPS lamps that are used in horticulture put out 2,100 micromoles per 1,000 watts, which is 2.1 μmol∙J–1. So what happened is LEDs finally equaled HPS. LEDs didn’t surpass HPS. When this happened P.L. started looking into the LED market and to surpass what was available.”

P.L. Light Systems’ HortiLED TOP and HortiLED INTER fixtures are finalists in the Horticultural Lighting Category for LEDs Magazine’s 2017 Sapphire Awards. The awards will be presented March 1, 2017, in Anaheim, Calif.


P.L. Light Systems HortiLED TOP

P.L. Light Systems HortiLED TOP light is a fully enclosed fixture with an integrated driver that delivers 2.7 μmol∙J–1. The TOP fixture measures 38 inches long by 4.7 inches wide by 3.7 inches tall and weighs 18 pounds. The fixture is available in two distribution angles, 80º and 150º, and light spectrum of red/blue, red/white, full spectrum and customized.

“P.L. started in the greenhouse market so we are catering to that segment of the market even though there are a lot of indoor growers using our fixtures,” Moody said. “We want to be sure everything we manufacture is able to be used in a greenhouse.

PL Light Systems HortiLED toplighting

“The TOP fixture drivers are driving the diodes to 2.7 μmol∙J–1. But the diodes we are using are capable of going above 3 μmol∙J–1. We are driving our diodes to a lower percentage because we don’t want to overheat them and we want them to last for 28,000 hours. We are better able to control the heat by not overdriving the diodes. Our goal is to have totally passive cooling so the fixture can be hung right up under a truss and it is fully enclosed.” Moody said having a totally enclosed fixture offers an advantage over other toplight LEDs on the market.

“Other manufacturers are either installing fans in their fixtures or they are mounting the drivers separately,” he said. “The LEDs with fans built into the fixtures can suck in dust and insects. These fixtures can short out because they get a build-up of debris inside the fixture. The fans push air across an electrical circuit board. There are also water-cooled fixtures. There is a water line running from one fixture to the next.

“Other manufacturers’ fixtures are large units in order to get the light output. These fixtures might work for some indoor growers, but they’re not going to work in a greenhouse. These larger fixtures reduce the amount of sunlight reaching the plants by casting shadows over them.”

Moody said with LEDs the light is very directional so it doesn’t cover as big of a footprint as HPS.

“We offer two TOP light LEDs that have different distribution patterns,” he said. “It’s not a reflector, it’s the diode itself. We have an 80º diode which is very common. This fixture puts out an 80º wide distribution pattern. We also have a 150º diode that puts out a much wider distribution pattern. This enables us to cater light plans to the growers’ crops. It offers a lot of room to move up and down depending on how far the fixtures need to be from a crop.”


P.L. Light Systems HortiLED INTER

The HortiLED INTER fixture is made for tall vine vegetables, ornamentals and some cannabis production. “The fixtures are mounted down the center of the crop,” Moody said. “It is supplementing the light that is being received from above the crop. For a 14-foot tall greenhouse tomato crop a grower may have HPS or LED toplights above and then the interlights below. Sometimes growers will use two rows of interlight fixtures in order to get more light deeper into their crops.

“The INTER fixture has the same high output diode as our TOP fixture, but because of the cover on the INTER fixture, the output reaches 2.5-2.6 micromoles per joule depending on the light spectrum.”

The INTER LED is a fully enclosed fixture equipped with a polycarbonate cover that keeps it totally waterproof. Moody said this ensures that the fixtures are not affected by high humidity environments, mist systems and spray applications.

The INTER fixture measures 48 inches long by 2.2 inches wide by 4.8 inches tall and weighs about 4 pounds. The fixture operates with an external driver and is available with a red/blue spectrum.

“With an interlighting fixture hanging in the crop, the light distribution pattern should go out to the sides hitting all of the leaves that are around the fixture,” Moody said. “Our INTER fixtures put out what looks like a butterfly wing pattern. The light pattern goes out sideways, but at the same time it also goes down. We use reflector technology to direct the light.

“The INTER fixture has one bank of LEDs. Some other interlight fixtures are larger and heavier units because they have two LED circuit boards back-to-back putting light out on each side of the fixtures.”

Eight of the 4-foot INTER fixtures can be run together using one driver. Moody stated interlight fixtures need to be lightweight because growers hang them on crop wire or whatever is being used inside the crop.

The INTER fixture is not yet available for the U.S. market. “We are still finalizing our UL listing in the U.S. for the INTER fixture,” Moody said. “This fixture is available in the red/medium blue spectrum. The INTER fixture is expected to be available for the U.S. market by the end of the first quarter.”


P.L. Light Systems HortiLED MULTI

The P.L. Systems HortiLED MULTI fixtures are being used primarily for propagation, young plant production and vertical farming.

“Just like with the TOP fixtures, our MULTIs are available in 80º and 150º distribution outputs,” Moody said. “We also have two different lengths, basically a 4-foot (122 cm) and 5-foot (152 cm) fixture. These fixtures have an integrated driver and are available in low and high output versions. There are some applications where a low output is needed, better uniformity, closer to the crop like with tissue culture and early plant propagation applications. The high output fixture is for later in propagation or for propagation of bigger plants. For the MULTIs we can do numerous light spectrum combinations.”

Moody said the MULTI fixtures are ideal for vertical farming applications. “We can do vertical growing with lettuces, mixed greens, microgreens, all of those under these lights as well. Our MULTI lights have a higher output than most other LEDs used for this application.


“For propagation most growers use multiple layers. Typically they are built with two to four layers on racks. The MULTIs were designed to be installed on the underside of a rack pointing down toward the crop below it, from 9 inches to as far away as 2 feet from the crop.”

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Grodan rockwool substrates offer growers more control

Grodan stone wool products offer the benefits of high irrigation efficiency, plant steerability and uniform crop development.

Grodan stone wool substrates are made from basalt rock that is processed at a very high temperature (over 2,900ºF). This hygienic, inert substrate offers vegetable and ornamental plant growers the opportunity to control growth from propagation to harvest.

“Grodan stone wool products are inert,” said Rens Muusers, Grodan Technical Sales Manager for the USA. “This means the grower has full control over what is happening in the substrate. Being inert, Grodan stone wool doesn’t bind nutrients and chemicals like other substrate types may do. Any fertilizers, pesticides or other chemicals, including growth regulators, that are applied to the stone wool are available to plants.

Linked to stone wool’s inert nature, Muusers stated growers have more opportunities to steer their crops.

“Other substrates that aren’t inert may bind elements, pesticides or other chemicals that are applied to enhance plant growth or health,” he said. “This may result in having to apply more of a chemical in order to have the same efficacy. The amount of chemical that will need to be applied to stone wool will be lower and it will be more effective than in non-inert substrates. This also helps growers to minimize their input costs.

“Using methods to control water content and EC (electrical conductivity) levels within the substrate allows growers to influence plant growth.”

Muusers stated by controlling the water content and EC in the stone wool, growers can influence the plant balance between vegetative and generative development.

“The steerability offered by Grodan products can result in earlier production, improved plant, fruit and flower quality and improved plant health,” he said. “All of these benefits result in better resilience to insect pests and disease pathogens.

“Also, stone wool can have a buffering impact on the pH in the nutrient solution, slightly increasing pH in the substrate. This increase is minimal compared to the impact of plant and microbial activity in the root zone on pH.”

Muusers indicated another benefit of using stone wool is crop uniformity.

“Because Grodan stone wool products are manufactured in state-of-the-art facilities with strict standards and quality controls, it is a very uniform substrate,” he said. “Depending on the Grodan product being used, this allows growers to produce very uniform crops. The uniformity of seedlings produced in stone wool plugs results in faster germination and quick crop establishment.


Grodan AO plugs and Grodan AX plugs

Grodan AO and AX stone wool plugs are ideal for starting many crops. The plugs are available in sheets that fit into 1020 trays. AO plugs are connected to each other at the top of the plugs. AX plugs are attached to each other at the bottom of the plugs. Muusers said there are also some options in regards to the seeding hole size as well as with the dimensions of the plugs.

“The properties of the AO plugs are exactly the same as the properties of the AX,” he said. “The only difference is where the plugs are attached to each other.

Grodan AX 25/40 cube with lettuce roots and stem post-harvest.

“AO plugs are ideal for NFT systems with smooth gutter surfaces and also for deep flow systems. Some NFT systems use gutters with grooves on the surface for which growers may prefer the wider base and greater bottom surface area of the AX plugs which may be more stable in these systems.”

Muusers said both plugs are used mainly for leafy greens and culinary herb production. There are also growers who are using them for aquatic plants.

Grodan Cress Plate

The Cress Plate is a fairly new product used primarily for the production of microgreens. It is the thinnest product of Grodan. It is only 1 cm thick, less than ½ inch.

Cress Plates come in two sizes. One size fits into 1020 trays. A larger size is used by some growers who need customized sizes. Growers are able to cut the Cress Plate sheet to the exact size they need.

“The Cress Plate has the same beneficial characteristics as other Grodan products,” Muusers said. “It’s inert, clean and hygienic. It’s a uniform product. It holds water evenly. The Cress Plate also provides quick, easy germination and even development of a microgreen crop.”

Muusers indicated growers use Cress Plates in a couple of ways.

“Some growers sell the microgreens with the Cress Plate, essentially selling a living product,” he said. “This allows the end consumer to use the freshest product longer, something that is valued by customers like restaurants. “Growers who produce baby greens and baby lettuce tend to harvest off of the Cress Plates. By harvesting higher up the plants, the plants continue to grow and produce for several harvests. This multiple harvest method is preferred to the uncommon practice of reusing substrates.”

Muusers stated reusing the Cress Plates is risky, just like reusing any substrate.

“There is the possibility of sterilizing the used substrate with steam or some other technique,” he said. “When a sterilizing technique like steam is used, it can have a negative impact on the properties of the substrate. I wouldn’t recommend harvesting and then resowing on top of a previously used Cress Plate because of the risk with potential disease issues and the potential negative impact on germination and growth.”

Grodan Delta Blocks

Grodan blocks come in different sizes and are ideal for both ornamental and vegetable crops.

“Depending on the crop, once a seedling is germinated in a plug it can be transferred into a block and then transplanted into a finish substrate to be grown on,” Muusers said. “Tomatoes and peppers are usually propagated in plugs and then transplanted into blocks. The final grower purchases the young plants in blocks and transplants them into the final substrate such as Grodan slabs. For cucumbers, which are a relatively quick crop, those are sometimes sown directly into blocks, instead of plugs.”

There are different size blocks for different size crops. A standard block size is 10 cm-by-10 cm-by-6.5 cm, which is referred to as a 4-inch block.

Muusers indicated that some growers put multiple plants into one block depending on the crop.

“For tomatoes, growers are looking for a certain head density per square meter,” he said. “The head density per square meter is sometimes achieved by growing multiple plants or by pinching the plants. Tomatoes are the primary crop that growers plant more than one seedling in a block.”

Muusers stated this method of planting multiple plants is also done with cucumbers and peppers. Another reason a grower sows multiple plants into blocks is to try to save on the cost of the blocks.“Some growers use 6-inch blocks instead of 4-inch blocks and put two plants in them,” he said. “In my opinion, it is always better to put one plant in one block. There is less competition resulting in better seedling uniformity as well as a more uniform crop.”

The blocks, like the plugs, are inert and are steerable. Muusers stated the blocks are also important in regards to irrigation efficiency—how the water content and more particularly, the EC, are refreshed within the substrate.

“Grodan focuses on good root growth and uniform root growth throughout the blocks,” he said. “Also, the blocks need to be able to withstand the rigors of handling during propagation. Their structure must remain stable throughout the growing process to be able to support the plants especially when the blocks are moved around. The blocks won’t break or fall apart.”


Grodan Gro-Slabs

Muusers indicated that Grodan slabs come in different product types developed to meet the challenges and needs of different crops.

“We have different slab types for different applications,” he said. “The slabs differ in fiber orientation and fiber thickness to deliver the kind of functionality a grower is looking for. The Grodan plugs and blocks have the same fiber orientation. They are designed for quick root establishment.”

There are Grodan slabs designed for vegetable crops. These crops are usually short term, less than one year. There are slabs designed for longer horticultural ornamental crops that are grown for longer than a year. The slabs for long term crops, including cut roses and gerbera, have a stronger fiber structure to withstand the longer production period.

“Grodan slabs are very uniform,” Muusers said. “Since the substrate is inert, they offer a high degree of crop steerability. This offers a lot of options for irrigation strategies combined with the substrate to influence plant development in a vegetative or generative way.”


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


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Substrate trials look to assist hydroponic growers avoid propagation-related issues

Substrate trials in Hort Americas’ research greenhouse are looking at conventional and organic propagation substrates along with different irrigation strategies for producing healthy starter plugs for hydroponic production systems.

Hort Americas has retrofitted a 12,000-square-foot greenhouse in Dallas, Texas, for the purpose of studying edible crop production in a variety of hydroponic production systems. The greenhouse is also being used to demonstrate products offered in the company’s online catalog.

Tyler Baras, who is the company’s special projects manager, is overseeing the trialing of conventional and organic substrates in different production systems.

Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs propagated in conventional and organic substrates. The seedlings are transplanted into a deep water culture, NFT or vertical tower production system.
Photos courtesy of Tyler Baras, Hort Americas

“The trials I am focusing on are organic substrates vs. conventional substrates,” Baras said. “I’m primarily using stonewool or rockwool as the conventional propagation substrate. I am also starting to trial some loose substrates, including peat and perlite.

“The seedlings are never moved into another substrate. The seed is sown into plugs and then the rooted seedlings are moved into a deep water culture, NFT (nutrient film technique), or vertical tower production system. The plugs are really only useful for the first two weeks in propagation. Then it is really about getting the roots to grow outside the plugs so the roots grow directly in the water.”

For the organic production systems, Baras is working primarily with expandable coco plugs. He has also started working with some organic loose substrates including coco peat and perlite.

For the substrate studies Baras is working with two standard hydroponic crops, basil and lettuce, primarily butterhead lettuce.

“When I’m testing the lettuce I use either raw or pelleted seed,” he said. “With basil it’s all raw seed. Basil tends to germinate relatively easily, whether the seed is planted into a dibbled hole or sown on top of the substrate.”

Focused on irrigation strategies

A primary objective of the substrate trials is to determine the best irrigation strategies for both organic and conventional substrates.

“This is probably more important with some of the organic substrates than the conventional substrates because the organic substrates tend to hold more water,” Baras said. “One of the big challenges that organic hydroponic growers run into is overwatering their plugs because coco holds more water than conventional substrate plugs that growers are used to. Coco plugs hold more water than stonewool, phenolic foam and polymer-based peat plugs. These other plugs dry out faster than coco plugs.”

For the substrate trials, rooted seedling plugs are finished in a deep water culture, NFT (nutrient film technique) or vertical tower production system.

Baras said growers who are moving from conventional to organic production tend to use the same irrigation techniques they employed with their conventional propagation program.
“The growers will continue to irrigate the plugs a couple times per day,” he said. “With a lot of the organic plugs, when the seed is sown, they only need to be irrigated once every three days. If the plugs are overirrigated the roots don’t have an incentive to search out the water when they are planted into the production system. The search for water is what drives the seedling roots down to the bottom and out of the plugs.

“The goal of planting into plugs is to have the seedling roots grow outside of the plugs into the water of the deep water culture or NFT system. If the plugs are overwatered as young seedlings, the roots don’t make it down to the bottom of the plugs so it takes longer to start the seedlings and sometimes they just end up rotting because the plugs remain too wet.”

Type of irrigation system

In addition to looking at the irrigation frequency of plugs during propagation, Baras is studying the impact of different methods of irrigation during propagation, including overhead and subirrigation.

“When deciding whether to use overhead or subirrigation, it depends on whether raw or pelleted seed is being sown,” he said. “If pelleted seed is going to be used, a lot of times it’s advantageous to use overhead irrigation because it helps to dissolve the coating surrounding the seed. This helps to ensure the seed has better contact with the substrate. Sometimes it’s almost a little easier to get good germination with subirrigation if raw seed is used because of the direct contact with the substrate.

Growers need to avoid overwatering young seedling plugs or their roots may not make it down to the bottom of the plugs, which could delay transplanting into the production system.

“Smaller indoor growers often use subirrigation for germination. A lot of the large growers, especially those coming from the ornamental plant side such as bedding plants, usually have overhead irrigation systems installed. These growers have propagation areas set up with overhead irrigation, which can be used to start their hydroponic vegetable crops.”

Baras said most indoor warehouse growers are not going to be using watering wands or overhead irrigation in their operations.

“Most of the warehouse growers will be using subirrigation, such as flood tables,” he said. “For them it is going to be important that they select the right kind of seed to get good germination. They may have to try other techniques like using a deeper dibble or covering the seed with some kind of loose organic substrate such as perlite or vermiculite. Growers using overhead irrigation can usually sow pelleted seed without having to dibble the substrate.

“Many growers tend to have issues when they are using pelleted bibb lettuce seed with subirrigation. We are looking at ways of increasing the germination rate using dibbling with the pelleted seed or increasing the dibble size or covering the seed.”

Baras said growers who are using automation, including mechanized seeders and dibblers, prefer to use pelleted seed.

“With pelleted seed it’s easier to be more precise so that there is only one seed planted per plug cell,” he said. “I have seen automation used with raw basil seed. I have also seen organic production done where automation was used just to dibble the plug trays. Dibbling seems to be one of the biggest factors when it comes to getting good even germination.


Need for good seed-substrate contact

Baras said occasionally with tightly packed coco plugs, if the seed is not pushed down into the plug the emerging radicle may have issues penetrating the substrate.

“This helps push the radicle down so it contacts the substrate and establishes more easily,” he said. “When subirrigation is used it can be advantageous to cover the seed with vermiculite or just brush the top of the coco plug after the seed is planted to get some coverage of the seed.

“What usually affects the way that coco plugs work is the size of the coco particles. There is really fine coco. There is coco fiber, which can be mixed into the plug to help with aeration and increase drainage. We are looking at various plugs with some increased fiber content trying to aerate the plugs in order to speed up the drainage.”

Stonewool or rockwool is the primary conventional propagation substrate in the trials. Other loose substrates, including peat and perlite, are also starting to be trialed.

Baras is also looking at using loose substrates in different ratios in plugs and then transplanting them into deep water culture, NFT, and vertical tower systems.

“One of the issues with hydroponic systems and loose substrates is these substrates can enter the production system and clog up the irrigation lines,” he said. “The trick is trying to avoid having any loose substrate enter the system. We are looking at using loose substrates and allowing the seedlings to establish longer in the plug cell during propagation before transplanting them into the production system. This enables the seedlings to develop a larger root system, which can prevent loose substrate from falling into the system.”


For more: Hort Americas, (469) 532-2383;

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


Products being used in greenhouse trials

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Fertilizer trials look at leafy greens, herb growth in hydroponic production systems

Early results from fertilizer trials in Hort Americas’ research greenhouse show knowing the levels of nutrients in fertilizer solutions can go a long way in avoiding problems with deficiencies and toxicities.

Hort Americas has retrofitted a 12,000-square-foot greenhouse in Dallas, Texas, for the purpose of studying edible crop production in a variety of hydroponic production systems. The greenhouse is also being used to demonstrate products offered in the company’s online catalog.

Tyler Baras, who is the company’s special projects manager, is overseeing the trialing of leafy greens and herbs in five different production systems.

“We’ve got a deep water culture or raft system using Hort Americas’ fertilizer blend with calcium nitrate and magnesium sulfate,” Baras said. “We are using that same nutrient mix in a nutrient film technique (NFT) system and a capillary mat system.

“I’m using Terra Genesis organic fertilizer in a vertical grow tower. I’m also using the same organic fertilizer for all of the seedling propagation in a flood-and-drain vertical rack.”

Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs in different production systems, including deep water culture and nutrient film technique. Photos courtesy of Tyler Baras, Hort Americas
Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs in different production systems, including deep water culture and nutrient film technique.
Photos courtesy of Tyler Baras, Hort Americas

Baras said the fertilizer recipe he is using in the deep water culture and NFT systems is based on general recommendations from Cornell University and the University of Arizona for leafy greens crop production.

Differences in nutrient levels

The deep water culture system has been running for three months. The water reservoir for the system is 8,000 gallons.

“Even if water evaporates, since it is such a large body of water, the electrical conductivity (EC) doesn’t really move much,” Baras said. “The EC has been very stable during the three months it has been operating. The reading has barely moved.”

The first trial with the NFT system, which has a reservoir of about 140 gallons, lasted for three months.

“Every week I added an additional 40 gallons of water on average to the NFT reservoir,” Baras said. “The water is evaporating and the salts are accumulating a lot faster in the NFT reservoir than in the deep water culture system. Because the NFT system has a smaller water reservoir, the quicker evaporation rate and the water replacement in the reservoir, has caused the EC to shift a lot more.”

One of the goals of the fertilizer trials is to see what salts are accumulating in the NFT system and to see how long the system can run before it has to be flushed.
One of the goals of the fertilizer trials is to see what salts are accumulating in the NFT system and to see how long the system can run before it has to be flushed.

Baras said even with the changes in nutrient levels all of the plants have been performing well.

“I haven’t seen any nutrient deficiencies or toxicities even as the fertilizer recipe has shifted over time. We have been trialing a wide range of crops, including butterhead and romaine lettuces, kale, spring mixes and basil. I’m trialing a lot of crops to figure out when these crops start to be impacted by possibly too much salt accumulation. I haven’t seen anything yet that is alarming.

“One of the things that I have seen over the years working with fertilizers is how wide the acceptable range is for plants to grow well. Between the NFT and deep water culture, the NFT is using half the nitrogen and the plants are performing very similarly. There are recommendations for EC, but none of these fertilizer levels are set. I have some systems that have 20 parts per million phosphorus and some that have 50 ppm and the plants look the same. Most general recommendations say 40-50 ppm. I’ll have some solutions that have 3 ppm iron and others that have 6 ppm iron. It is interesting to see how wide the range is for a lot of these nutrients and the crops are performing the same.”

During the three months that the deep water culture system has been running the electrical conductivity (EC) has been very stable with plants showing no signs of nutrient deficiencies or toxicities.
During the three months that the deep water culture system has been running the electrical conductivity (EC) has been very stable with plants showing no signs of nutrient deficiencies or toxicities.

Baras said he has seen a slowing of plant growth in the NFT system.

“I’m not seeing any deficiencies or toxicities, but the crops have slowed down about a week over the deep water culture,” he said. “Depending on the crop, it’s taking a week longer to reach either the plants’ salable weight or height.

“The slowing in growth could be related to the nutrients. This could be useful information for growers. If they are checking the EC, which may have been 2.3 when a crop was started, if there is a slowing of growth, growers may want to have a water test done. The test could show that the amount of nutrients might be changing.”

Identifying what makes up the EC

During the three months that Baras had been running the NFT system he never flushed the system.

“All that I’ve done with the NFT system is add water and additional fertilizer to maintain a targeted EC,” he said. “One of the goals of the trials is to see what ions are accumulating in the system and to see how long I can run the system before it has to be flushed. When I started the target EC was 2.2-2.3. I still achieved the target EC at three months, but the composition of what was actually in the water changed.

“Originally the NFT fertilizer solution contained about 185 parts per million nitrogen. At the end of the trial the EC was the same but there was only 108 ppm nitrogen in the solution. The calcium concentration was originally 250 ppm and ended at 338 ppm. Sulphur was originally at 80 ppm and rose to 250 ppm. Nutrients have accumulated as the water evaporated. Solely going by the EC meter reading doesn’t tell the full story of what is in that water. The EC of the fertilizer solution that I started with is the same as the EC for the fertilizer solution three months later. The difference is the ions that are making up that ending EC.”

Herb production with organic fertilizer

Baras is growing a variety of cut herbs in vertical grow towers. The plants are fertilized with Terra Genesis, a molasses-based organic fertilizer. He said Hort Americas has been hearing from tower growers who are interested in trying to grow organically.

“What we are seeing is the organic fertilizer solution can change a lot over time,” he said. “The fertilizer tank solution matures as time goes on. With the organic fertilizer, the nutrients tend to balance out as the solution is run longer.

“Our city water contains calcium and some magnesium. These elements are actually the nutrients that the organic fertilizer is slightly low in. So as I run the system longer, through the addition of city water, I actually start to see an accumulation of both calcium and magnesium, which actually helps balance out the total fertilizer recipe. The balance of the nutrients has improved over time.

A variety of cut herbs are being grown in vertical grow towers and fertilized with Terra Genesis, a molasses-based organic fertilizer.
A variety of cut herbs are being grown in vertical grow towers and fertilized with Terra Genesis, a molasses-based organic fertilizer.

The pH was fairly unstable as it seemed to be going through several biological waves. It was moving rapidly between high and low. As I run the tank solution longer the total alkalinity has increased, which has stabilized it. The biological activity has also started to stabilize. The pH has stabilized in the upper 5 range. For the plants grown organically I have seen deficiencies pop up. The deficiencies were reduced as the fertilizer tank solution ran longer. The deficiencies appear to have balanced out.”

Baras said one noticeable difference between the NFT, deep water and vertical grow towers is how much slower the plants grow in the towers.

“I don’t know what to contribute the slower growth to yet,” he said. “It could be trying to determine the best fertilizer rate for the fertilizer. It could be the crop selection, because most of the crops in the towers are different from what I’m growing in the NFT and deep water culture.

“I’m going to start a deep water culture and NFT trial using organic fertilizer. I’ll have three different organic production systems running simultaneously so I will be able to compare the plant growth in each system. I’ll also be able to compare the growth of the same crops grown with organic or conventional fertilizers.”

Controlling biofilm, disease pathogens

Baras said one of the issues that can arise with using organic fertilizer is the development of biofilm in the irrigation lines that can cause emitters to clog.

“I am incorporating a product called TerraBella, which contains beneficial microbes,” he said. “These microbes help mobilize certain nutrients, like phosphorus, which can promote the formation of biofilms. This biofilm buildup is usually more of a problem with high water temperatures.

“About every six weeks I add a booster application of the beneficial microbes depending on the production system. The deep water culture system has a larger reservoir so I am not replacing evaporated water as often. For the other productions systems, like the NFT and grow towers, where I am replacing the water, I am incorporating the beneficials more often. For these systems, the fresh city water that is added dilutes the fertilizer solution. Also, there is chlorine in the city water that possibly could negatively impact some of the beneficial microbes.

For more: Hort Americas, (469) 532-2383;

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


Products being used in greenhouse trials



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Hort Americas retrofits greenhouse for trialing hydroponic growing systems, products

Hort Americas’ special projects manager Tyler Baras is using a 12,000-square-foot hydroponic greenhouse to teach company staff and customers what it takes to economically grow leafy greens and herbs.

Tyler Baras is a well-traveled grower. He has worked in Florida and Colorado growing hydroponic greenhouse vegetables, including organic crops. He is now taking the knowledge and experience he has gained from those growing operations and putting it to use in a 12,000-square-foot demonstration and research greenhouse in Dallas, Texas.

Baras, who is the special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs in five different production systems along with the testing of potential products for the company’s online catalog.

“Chris Higgins, the general manager at Hort Americas, brought me to the greenhouse and asked if I would be interested in running a demonstration and research facility,” Baras said. “He was also interested in collecting data and writing a book about leafy greens production.

“After I agreed to accept the position, I drew up blueprints of the greenhouse, preparing a design of the production systems, writing a budget and proposals on how it was going to look, and how much it was going to cost to operate, including projected sales from the produce that was grown.”

Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs in five different production systems. Photos courtesy of Tyler Baras, Hort Americas
Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs in five different hydroponic production systems.
Photos courtesy of Tyler Baras, Hort Americas

The retrofitted greenhouse is located behind a grocery store and prominent Dallas garden center. The grocery store and garden center will allow Baras to test his projected budgets and produce sales.

“The greenhouse was originally built for growing bedding and flowering plants,” Baras said. “It was built with passive ventilation and was not designed for leafy greens production. We had to make some major modifications. Renovations included leveling the floor, adding a vestibule air lock, upgrading the electrical system, installing evaporative cooling pads, insect screening and landscape fabric, and upgrading the motors for the shade system along with installing new shade cloth. We have been growing in the greenhouse since September.”

Hort Americas, which is a horticulture and agriculture wholesale supply company, provided the materials for the retrofit along with the hydroponic production systems that Baras will be using. The production systems include a capillary mat system, a deep water culture floating raft system, a nutrient film technique (NFT) system, a hydroponic tower system and grow racks. Hort Americas has also provided a variety of equipment and products, including substrates, fertilizers, LED lights and other products it offers to its wholesale customers.

Collecting, disseminating production data

Dallas was chosen for the research location because it is one of the hardest places to grow hydroponic leafy greens. Baras will be trialing primarily leafy greens, including a variety of lettuces (bibb and Romaine), kale, bok choy, basil and other herbs.

“We believe that if leafy greens can be grown here then they can be grown nearly anywhere by everyone,” he said. “Year-round production here is difficult. We know that we will be able to grow during the fall, winter and spring. The tricky part is going to come during the summer when there are high temperatures and high humidity. The project will take a minimum of a year to collect the data.”

Baras said he will be collecting a lot of data including: cost per plant size, how much does it cost over the production cycle to operate each system and the labor costs involved with operating each system.

The 12,000-square-foot demonstration and research greenhouse contains five different production systems including a deep water culture floating raft system.
The 12,000-square-foot demonstration and research greenhouse contains five different production systems including a deep water culture floating raft system.

“The goal is to collect data that can be used by everyone,” he said. “We are going to collect data that includes the total light delivered. If growers in more northern latitudes are dealing with lower light, they can look at the light levels we maintained in the greenhouse and reach those same levels using supplemental light so that they can mimic the exact same conditions.

“The data collected will be available to whoever has an interest in reading about it. This will enable growers to be knowledgeable about making decisions about these production systems and operating them. They will also have access to some real world baseline data from trials so they will know if they are achieving the proper metrics. For example, we will share the data of how long it took to grow a certain size head of lettuce or a certain weight of basil using specific inputs. Growers will be able to look at real world environmental conditions under which a crop was grown.”

Preliminary results

Baras said based on initial production results what makes most financial sense at this time is growing basil and lettuce.

“Our initial metrics from the data that we have collected have been good,” he said. “We are producing 8- to10-ounce heads of bibb lettuce in 38 days and we are harvesting commercial size sleeved basil in 26 days from seed.

“Most commercial standards for lettuce in the U.S. are between 6 and 10 ounces. For basil there is a wide range in regards to the standard size for weight. Generally it is done by size or by what fills up a 10-inch tall sleeve. We have been able to fill a 10-inch sleeve and make it look really good.”

Preliminary production results include harvesting commercial size sleeved basil in 26 days from seed.
Preliminary production results include harvesting commercial size sleeved basil in 26 days from seed.

Having experienced a warmer than normal October, Baras said the water temperature in most of the production systems has been 85ºF or warmer.

“Generally the water temperature for most hydroponic crops is between 65ºF-70ºF,” he said. “The water temperature here is definitely warm, but we are still having really great growth. So far it is looking like we can grow a crop during the summer. But we haven’t gone through a full summer yet and that is going to be the real test.
Baras said they want to try to avoid chilling the water and will only use this production technique as the last resort.”

“We are trying to find ways around having to chill the water, including increasing the level of dissolved oxygen in the water using a variety of methods. This includes using Venturi aerators, and if needed, injecting liquid oxygen. These methods are less costly than running chillers. Chillers can be expensive and they use a lot of energy.
“We really want to find a model that is going to be acceptable to small scale growers. We are trying to keep the inputs to a minimum and still achieve our production goals.”

Teaching and trialing

Baras said the greenhouse has already been used for onsite training.

“That is one of our main goals with the site,” he said. “We want to be able to bring in people and provide them with hands-on training, both our customers and the Hort Americas staff. For example, we want to be able to show them how to blend fertilizer, what the process looks like for moving seedlings through a hydroponic system, how to measure light levels in a greenhouse and best pest control methods.

“We want to be able to assist customers who are starting to build a greenhouse and are looking to install hydroponic equipment. The greenhouse will enable them to see what is involved before they make any purchases.”

Dallas Grown
The greenhouse will be used to provide training to Hort Americas’ customers and staff, as well as the trialing of new products.

The greenhouse will also be used for trialing new products.

“Companies often approach Hort Americas about carrying their products, the greenhouse will enable us to put them through real world trials before they’re put in our online catalog,” Baras said. “Some of the products we plan to trial include dosing systems, monitoring systems for greenhouse environmental control and meters for measuring pH and EC. We are open to looking at other equipment and other automation technology.”

For more: Hort Americas, (469) 532-2383;

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


Products being used in greenhouse trials

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LEDs offer option for photoperiodic control

Research at Michigan State University shows growers have a choice when it comes to lights for photoperiodic control.

As light bulb manufacturers phase out the production of incandescent bulbs, growers are looking for replacements to control flowering of ornamental plants. Researchers at Michigan State University have compared the efficiency and efficacy of LEDs for flowering applications with traditional light sources including incandescent, fluorescent and high-pressure sodium lamps.

“After we determined that LEDs were as effective at controlling flowering as other traditional light sources, we began to look more closely at how different wavebands emitted by LEDs actually regulate different aspects of flowering and photomorphogenesis,” said Michigan State Ph.D. graduate research assistant Qingwu (William) Meng. “In our experiments we used experimental LEDs manufactured by a company in Japan called CCS and commercial LEDs from Philips Lighting. For this particular study we used four different LEDs that are commercially available to growers to control flowering.”


Qingwu (William) Meng is studying how different wavebands emitted by LEDs actually regulate different aspects of flowering and photomorphogenesis.
Photos courtesy of William Meng, Mich. St. Univ.


Meng used an Apogee spectroradiometer to collect data from the four different LEDs.

“We measured the spectral output from 350 nanometers to 850 nanometers,” Meng said. “We were able to measure the total light intensity from each of the four lamps to quantify the exact spectral distribution.”


Lamp placement impacts light intensity

Meng said he did not compare the light output data he collected with data reported by the light manufacturers.

“It is relatively difficult to find light intensity data from some of the light manufacturers,” he said. “What some companies report in regards to light output is the total photon flux from the light source captured by an integrating sphere device that we don’t have here at Michigan State. Others show a graph of the emission spectrum, but the spectral data are not available.

“For greenhouse flowering applications the lamps can be installed at different heights. Depending on the distance between the bottom of the light source and the plant canopy, there can be different levels of light intensity. Even though a light may be advertised to have a very high light output, if the lamps are hung high above the plant surface then growers are going to get a lower light intensity at the plant level. It is very situational and depends on how far apart the lights are spaced out in the greenhouse and how high the lights are installed above the plant canopy.”


Ensuring proper light spacing

Meng said growers typically space out LED lights for flowering regulation about 10 feet apart horizontally.

“Light uniformity and light intensity are the two most important characteristics,” Meng said. “To ensure that there is an accurate layout of the lights, it is ideal to conduct a trial to see exactly what is happening below the lights. Growers can go into a greenhouse at night and measure the light intensity under the lights to see if the light intensity is sufficient and the light distribution is uniform. Light uniformity is very crucial. A grower doesn’t want to cause non-uniform flowering of the same crop.

“Growers can take one light and then measure the light output at different points under the light. By measuring the light distribution, growers can determine where the highest output and lowest output occur under the lamp. If growers don’t have the expertise to develop a light map, they can consult lighting experts.”

Some lighting companies have developed software to design light maps.


Differences in wavelength effects

Meng said for effective photoperiodic control only 1-2 micromoles per square meter per second (µmoles/m2/s) at plant height is needed either to promote flowering of long-day plants or inhibit flowering of short-day plants.


If red or far red are the predominant wavebands provided by LED lamps, 1-2 micromoles per square meter per second should be effective for speeding up the flowering of long-day crops.
If red or far red are the predominant wavebands provided by LED lamps, 1-2 micromoles per square meter per second should be effective for speeding up the flowering of long-day crops.


“For specific wavebands, red light is the most prominent in terms of regulating the flowering pathways of plants,” he said. “The four LEDs lamps we tested that are all marketed for flowering applications, all have some level of red or red/far-red light. If red or far red are the predominant wavebands, then 1-2 µmoles/m2/s should be effective for most flowering crops.

“In contrast, if only blue light, which is from 400-500 nanometers, is used to regulate flowering, there won’t be any effect if a low intensity of 1-2 µmoles/m2/s is provided. Blue light at 1-2 µmoles/m2/s doesn’t create long days for a variety of photoperiodic crops. However, when the intensity of blue light is elevated to 15 or 30 µmoles/m2/s, blue light is able to regulate flowering as effectively as red or as a red/far red combination. Overall, the efficacy of a lamp depends on its light spectrum.”


Differences in plant species sensitivity

Meng said for different ornamental species or cultivars there are different sensitivity levels in terms of the light spectrum that should be used to control photoperiod. He trialed about 20 different photoperiodic ornamental crops popular with commercial growers.

“For long-day plants, including petunia and pansy, there should be red light or a combination of red and far-red light to speed up flowering,” he said. “Some crops, like snapdragons, are really sensitive to far-red light. In this case, growers should use lamps that emit both red and far-red light to accelerate flowering, otherwise flowering won’t be promoted at all.”

He said for petunias, plants flower earlier under red light, but with both red and far-red light, flowering can be promoted even more.

“In order to achieve the benefits of photoperiodic lighting to promote flowering of long-day plants, growers should look at the crops they’re producing, and then decide what kind of spectrum the LEDs should have to provide the maximum capability of flowering promotion,” Meng said.

For more: Qingwu (William) Meng, Department of Horticulture, Michigan State University, East Lansing, MI 48824;
Meng is working with professor Erik Runkle;;


Funding for this research was provided by USDA National Institute of Food and Agriculture’s Specialty Crop Research Initiative, Michigan State University’s Project GREEEN, and horticulture companies supporting Michigan State University floriculture research. Nate DuRussel, Michigan State University greenhouse research technician, provided greenhouse technical assistance, and C. Raker & Sons and Syngenta Flowers donated plant material.


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





New horticultural lighting blog

LightHort is a science blog created by Qingwu (William) Meng to communicate the latest scientific findings on light in horticulture to the public. Meng is working with graduate students from various institutions, including Michigan State University and Purdue University, specializing in photobiology and horticultural lighting to employ various forms of multimedia to effectively deliver scientific ideas worth sharing. A variety of topics are covered ranging from sole-source lighting for plant factories to photoperiodic and supplemental lighting for greenhouse operations. Follow LightHort on its website, Facebook and Twitter.