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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; info@hortamericas.com; http://hortamericas.com.

 

David Kuack is a freelance writer in Fort Worth, Texas; dkuack@gmail.com.

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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; http://hortamericas.com.

 

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

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Colorado State University’s new horticulture center will focus on research with LEDs

An agreement between Colorado State University and Philips Lighting to equip its new 27,000-square-foot horticulture center with LEDs will put the focus on using the lights for improving ornamental and vegetable plant production.

When officials at Colorado State University went looking for property to build a new football stadium they didn’t have to look far. They decided that the land on which the 65-year-old W.D. Holley Plant Environment Research Center resided was the perfect location for the new stadium.

“The old horticulture facility, which had been built in 1949, was considered a hot property by school officials,” said Steve Newman, who is greenhouse crops extension specialist and professor of floriculture. “To replace the old site, the university provided the department with a new $7.5 million 27,000-square-foot research and teaching facility. There is also a 3-acre outdoor area for plant trials.

“The horticulture center was built in eight months. The university facilities team that I worked with to design and build the center was awesome.”

Greenhouse specs

The horticulture center’s new greenhouse is a Nexus Vail model frame which is covered with Thermaglas polycarbonate. It is equipped with Ludvig Svensson retractable heat curtains and Wadsworth Control vents, Modine Effinity 93 natural gas unit heaters and American Coolair fan boxes. The control technology is all Wadsworth Control Systems.

 

Colorado State University’s 65-year-old W.D. Holley Plant Environment Research Center has been replaced with a new $7.5 million 27,000- square-foot research and teaching facility.
Colorado State University’s 65-year-old W.D. Holley Plant Environment Research Center has been replaced with a new $7.5 million 27,000-square-foot research and teaching facility.

 

The 21,000-square-foot greenhouse is divided into six bays. All of the bays are connected by a ventilation corridor that has a 20-foot high gutter line. One bay will contain a Crop King NFT trough system consisting of six modules. The other half of the bay will be equipped with a traditional raft culture set up that has six 5-foot by 10-foot rafts.

“I’m a hard core supporter of Colorado companies,” Newman said. “We are also trying to make the greenhouse as energy efficient as we can.”

Perfect timing

In December 2014, Ron DeKok, North America director of business development, Philips Horticulture LED Solutions, visited Newman to discuss supporting LED research at Colorado State.

“Ron visited me on the same day I was given permission to talk about the budget for the center,” Newman said. “The timing was perfect. He asked me what kind of LED research CSU wanted to do and I asked him how committed Philips was to supporting LED research at the university. He said let’s equip the facility with Philips lighting and we’ll do research projects together.

“The greenhouse is being equipped with the latest Philips horticulture LED fixtures, including top lighting, interlighting and flowering lamps. One house will have suspended interlighting modules for high wire vegetables. We are looking at being able to do all kinds of ornamental and vegetable plant research using different combinations of the fixtures.”

Crops to be studied

Newman said it hasn’t been determined yet how much of the greenhouse space will be dedicated to ornamental and vegetables crops.

 

Steve Newman, who is Colorado State’s greenhouse crops extension specialist and professor of floriculture, said the new horticulture center will be used for research, teaching and training.
Steve Newman, who is Colorado State’s greenhouse crops extension specialist and professor of floriculture, said the new horticulture center will be used for research, teaching and training.

 

“I expect the research is going to be about 60 percent ornamentals and 40 percent vegetables, but that could change,” he said. “Initially the greenhouse vegetable production will be used primarily for teaching and demonstration. We will get into the vegetable research later.

“Our primary focus initially is going to be on ornamental plug production and reducing plant bench time after transplanting. This includes whether we can grow better quality plugs using LEDs with less plant growth regulators. We will be looking at root development under LED lights, trying to increase rooting and production efficiency. This includes trying to improve rooting of stage 4 tissue culture propagules coming out of overseas production.”

Newman said fellow researcher and horticulture professor Bill Bauerle is planning to use the greenhouse’s corridor to study hops production using LEDs.

“Northern Colorado is becoming a central location for craft breweries,” Newman said. “There is a lot of interest in locally grown hops for the craft breweries.

“The 20-foot high ventilation corridor is ideal for growing hops. We are redesigning and reconfiguring to install the LED interlighting in order to get good vegetative growth. The hops plants will receive natural light from above and the LED interlighting between the rows. The local craft brewers are very interested in the hops research that we are planning to do.”

Collaborative research

Newman said that Philips has some of its own research agenda items that it would like to study in the horticulture center.

“The research that the company wants to do is not that different than the research that we want to do,” he said. “What Philips is planning to look at fits in with everything else that we are doing in many ways. The company will be making some specific requests. The company will be funding those project directly just like any other research program.

“The Philips research team I’m working with is very grower-oriented. The company is interested in finding out how many LED lights does it take to produce a bedding plant crop more

efficiently. How LEDs can be used to produce better quality plants. Meanwhile we will be doing our own research taking advantage of the lights. The hops research was not an agenda item for the company four months ago. Bauerle went to company officials and said let’s do this hops research and they agreed that it was worth doing.”

 

Philips Lighting has some of its own research agenda items that it would like to study in Colorado State’s horticulture center, but the research is not much different than what university scientists want to do.
Philips Lighting has some of its own research items that it would like to study in Colorado State’s horticulture center, but the research is not much different than what university scientists want to do.

 

Newman said that Philips is interested in looking at vegetable production for the warehouse farming market, which it refers to as its city farming program.

“Unfortunately we don’t have the type of facility set up to do the warehouse style growing on site,” Newman said. “I would like to see us go into that type of production eventually. Initially with our vegetable crops we will look at biomass production. We will be putting in NFT lettuce trials.

“We also want to study nutraceutical compounds, including vitamins, and if LEDs can increase the production of nutraceuticals in vegetables. I am working with my colleagues in the horticulture and food science departments looking at the mouth feel in regards to high quality lettuce production. We will also probably look at tomatoes to increase production efficiency, plant yield, and lycopene development in the fruit. We will probably start looking to do that research in the fall.”

Future plans

Newman said he is in negotiations with the university’s dining services department to produce vegetables for its dining centers.

“I am in negotiations with dining services, which is looking to start vegan salad bars in the dining halls,” he said. “Dining services wants to put in salad bars with as much produce as possible grown in Colorado. They would like to have a certain percentage of that produce be CSU student grown. We are going to redo our student farm to try to accomplish that during the growing season. We will also be trying to grow as much of the leafy greens in this new facility to provide to the dining services’ salad bars.

“I am also working very closely with a university environmental hygiene staff person. We have to be sure that we are in compliance so that whatever produce we sell to the dining halls is as safe as it needs to be. We have to set up a good agricultural practices (GAP) plan and to review the guidelines of the Food Safety Modernization Act that just went into effect. The students who are growing the produce have to be trained in the exact practices they need to follow to deliver quality, safe food. The students have to be taught the proper ways of growing and handling food from the greenhouse to the table. All of the practices that we have to incorporate are the same as if we were going to sell the produce to a retail grocery store.”

 

For more: Steve Newman, Colorado State University, Department of Horticulture and Landscape Architecture; (970) 491-7118; Steven.Newman@ColoState.edu.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

Photos courtesy of Steve Newman, Colo. St. Univ.