How you grow and process fresh cut basil will impact the flavor and shelf life of the harvested product.
Basil is one of the most popular culinary herbs. Whether grown as a potted crop or for fresh cut sales, basil is an herb that’s in demand year-round. Growers looking to add edibles to their product mix should consider basil to be a must-have herb in their product offerings.
Monitoring and collecting environmental conditions during controlled environment agriculture production can assist growers in making the best use of integrated pest management strategies.
While maintaining the proper temperature and humidity is important to ensure the optimum growing conditions for controlled environment agriculture, these environmental factors become even more important when using biological controls.
The Lighting Approaches to Maximize Profits (LAMP) project aims to determine how growers can maximize their return on investment when considering installing grow lights.
As light emitting diodes (LEDs) become more efficient and more affordable, an increasing number of greenhouse and plant factory growers will consider installing LED luminaires to light their crops. In the case of greenhouse growers, these luminaires would provide light to supplement natural sunlight. For plant factory growers, production depends entirely on the light provided by an artificial light source including LEDs, high pressure sodium or metal halide luminaires.
The use of supplemental light to control downy mildew on food and ornamental crops could be integrated into current disease management practices.
Downy mildew is a major disease on both ornamental and food crops. Whether these crops are grown outdoors or in a controlled environment, environmental conditions, generally cool to moderate temperatures and high humidity, are favorable to downy mildew development. Warm temperatures and high humidity are conducive to powdery mildew development.
Growers of ornamental and edible crops can use the 30MHz platform to capture and manage real-time data on crops and environments.
From cultivation to harvest, packing, processing and shipping, agri- and horticulture faces challenges that can be avoided with environmental and crop-level data. Real-time monitoring with wireless sensor technology empowers agribusinesses to look back on their crops’ history and current status, quickly respond to prevent a range of risks including disease, rot and sunscald and take proactive measures to ensure the highest quality, best flavor and most efficient use of resources. Developed with input from leading growers, the smart sensing solution offered by Dutch-founded agritechnology provider 30MHz makes it easy for growers to deploy wireless sensors and start capture the metrics most crucial to their operations in minutes, without technical expertise.
The LED light recipes that NASA scientists are developing on Earth could eventually be used by astronauts in space and growers on the ground to optimize the production of food crops.
National Aeronautics and Space Administration (NASA) has been growing plants in space for research since the early 1980s. Within the last five years, NASA has been focusing on growing plants in space primarily for food production and as an astronaut life support system.
Incorporating air or oxygen into irrigation water using nanobubbles can improve crop yields and reduce susceptibility to disease pathogens.
What started out as a way of making wastewater treatment systems more efficient with oxygen enrichment has expanded to how nanobubble aeration technology can improve production of agricultural crops. Moleaer Inc. in Torrance, Calif., filed a patent on nanobubble aeration technology in 2016 with the intention of using it as a way to deliver gas in a number of different applications.
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.
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.”
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 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.”
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 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; email@example.com.
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.”
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.
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.”
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; firstname.lastname@example.org; https://hortamericas.com.
David Kuack is a freelance writer in Fort Worth, Texas; email@example.com.
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.
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.”
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.”
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; firstname.lastname@example.org; https://hortamericas.com.
David Kuack is a freelance writer in Fort Worth, Texas; email@example.com.
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.
“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.”
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.”
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.”
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.
“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; firstname.lastname@example.org; http://www.hos.ufl.edu/faculty/kmfolta.
David Kuack is a freelance technical writer in Fort Worth, Texas; email@example.com.
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 greenhousefor 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 greenhouseis being used to grow a wide variety of lettuces, leafy greens, herbs and microgreens.
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.”
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.”
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.
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.”
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.”
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.”
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.”
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.”
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.”
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.”
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.”
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.
“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.
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.”
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; https://hortamericas.com.
David Kuack is a freelance technical writer in Fort Worth, Texas; firstname.lastname@example.org.
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.
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.”
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.”
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; https://hortamericas.com.
For more information on choosing a substrate for hydroponic production systems, https://hortamericas.com/grower-resources/growing-media-and-substrates/
David Kuack is a freelance technical writer in Fort Worth, Texas; email@example.com.
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.
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.”
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.
“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; https://hortamericas.com.
David Kuack is a freelance technical writer in Fort Worth, Texas; firstname.lastname@example.org.
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.
“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?”
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.”
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 Surveyconsists 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; email@example.com. Roberto Lopez, Michigan State University, Department of Horticulture, East Lansing, MI 48824; firstname.lastname@example.org; http://www.hrt.msu.edu/people/dr_roberto_lopez. Chris Currey, Iowa State University, Department of Horticulture, Ames, IA 50011; email@example.com; https://www.hort.iastate.edu/directory/christopher-j-currey.