Do you want to sell the freshest, most flavorful and fragrant cut basil?

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.

Continue reading Do you want to sell the freshest, most flavorful and fragrant cut basil?

Dissolved oxygen improves plant growth, reduces crop time

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

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

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

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

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

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

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

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

 

Trialing different levels of dissolved oxygen

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

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

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

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

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

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

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

 

Some dramatic results

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

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

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

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

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

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

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

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

 

Differences in root growth

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

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

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

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

 

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

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


For more: Hort Americas, (469) 532-2383; info@hortamericas.com; https://hortamericas.com.

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

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; https://hortamericas.com.

 

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

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; https://hortamericas.com.

 

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

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

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

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

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

Organic vs. traditional hydroponic production: the top 3 differences

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

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

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

 

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

 

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

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

 

  1. Inoculants and tank culturing

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

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

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

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

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

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

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

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

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

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

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

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

 

  1. Nutrient solution pH management

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

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

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

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

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

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

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

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

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

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

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

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

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

 

  1. EC targets and nutrient analysis

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

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

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

 

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

 

 

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

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

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

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

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

 

Measuring changing EC levels

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

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

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

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

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

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

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

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

For more: Hort Americas, (469) 532-2383; https://hortamericas.com.

 

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

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

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

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

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

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

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

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

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

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

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

Focused on irrigation strategies

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

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

closed-bottom-organic-plug-hydroponic-substrates-growing-system
For the substrate trials, rooted seedling plugs are finished in a deep water culture, NFT (nutrient film technique) or vertical tower production system.

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

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

Type of irrigation system

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

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

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

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

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

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

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

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

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

 

Need for good seed-substrate contact

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

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

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

hydroponic-cilantro-grodan-rockwool-deep-water-culture-grodan-ao-hydroponic-production-system-herbs
Stonewool or rockwool is the primary conventional propagation substrate in the trials. Other loose substrates, including peat and perlite, are also starting to be trialed.

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

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

 

For more: Hort Americas, (469) 532-2383; https://hortamericas.com.

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

 

Products being used in greenhouse trials

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

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

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

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

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

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

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

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

Differences in nutrient levels

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

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

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

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

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

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

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

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

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

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

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

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

Identifying what makes up the EC

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

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

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

Herb production with organic fertilizer

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

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

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

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

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

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

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

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

Controlling biofilm, disease pathogens

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

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

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

For more: Hort Americas, (469) 532-2383; https://hortamericas.com.

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

 

Products being used in greenhouse trials

 

 

Monitoring is crucial for growing lettuce and leafy greens year round

Since lettuce and leafy greens have short production cycles, greenhouse growers need to stay focused if they want to be successful growing these crops year round.

The increasing demand for locally-grown vegetables is causing more field vegetable growers, ornamental plant growers and new growers to look at trying to satisfy this market. Cornell University horticulture professor Neil Mattson said he works with all three types of growers.

“I see both vegetable field growers and ornamental greenhouse growers trying to produce lettuce and leafy greens year round,” he said. “Both are quite common. Field vegetable growers are looking for a crop that can generate year-round cash flow. Ornamental growers are looking to fill their greenhouses in the off-season. A lot of ornamental growers no longer produce poinsettias in the fall or spring bulb crops and spring plant propagation that they would normally do in the winter. Growers could have as much as a six-month window when their facilities are not being used.”

Mattson said ornamental growers tend to better understand what it takes to grow a year-round crop.

“Ornamental growers tend to be aware of differences in crops and the problems that can arise,” he said. “They also understand the concept that there is much less light in the winter so they may have to consider using supplemental light. Ornamental growers are usually aware of the high cost of heating a greenhouse year round, especially during the winter.

“In general, field vegetable growers who have greenhouses, may only be using those structures in the spring to produce their transplants. That means they may be used to heating a couple months each year.”

 

Controlling environmental parameters

During this year’s Cultivate’16 conference and trade show in Columbus, Ohio, Mattson did a presentation on the year-round production of leafy greens using controlled environment agriculture (CEA). The main environmental conditions growers need to monitor and control include light, temperature and relative humidity.

 

Light

Mattson said in the northern half of the United States light availability during the winter months is the most difficult environmental issue to deal with when growing plants year round.

“The target light level for lettuce production is 17 moles of light per square meter per day (daily light integral, mol/m2/d) for optimal growth,” he said. “In most parts of the country achieving that target usually isn’t an issue during the summer. In the winter, in the northern part of the country, light levels can be 5 mol/m2/d on average and even 1-3 mol/m2/d is common. That is three to five times less light than what is needed for optimum lettuce growth during the winter.”

 

Photo 1, Lettuce overview 1, Neil Mattson, Cornell Univ.
The target light level for lettuce production is 17 moles of light per square meter per day (daily light integral) for optimal growth.
Photos courtesy of Neil Mattson, Cornell Univ.

 

Mattson said supplemental light, using LEDs or high pressure sodium lamps (See the Lamps Needed Calculator, can be provided to deliver higher light levels to increase lettuce biomass. But going above 17 mol/m2/d can cause growers to have issues with tip burn.

“In the case of head lettuce, a grower can go from seed to harvested head (5-6 ounces) in 35 days if there is 17 mol/m2/d. If there is only 8.5 mol/m2/d, it takes the plants twice as long to produce that same biomass.

“For baby leaf greens, if they are seeded and transplanted and grown on for two weeks before harvesting and only receive 8.5 moles of light, the plants will only produce half the yield. If a grower normally harvests 10 ounces per square foot and there is only half the light, the plants will produce only 5 ounces per square foot.”

Mattson said a rule of thumb for New York is a grower can light a 1-acre greenhouse and produce the same yields as not lighting a 3-acre greenhouse to produce the same yields during the winter months.

 

Temperature

Lettuce and many other leafy greens are cold tolerant. Mattson said a lot of growers want to grow them cold.

“The Cornell CEA research group proposes that these crops be grown at fairly warm temperatures so that they have the faster 35-day crop cycle,” he said. “This is based on having 17 mol/m2/d and a daily average temperature of 70ºF-75ºF during the day and 65ºF at night.

“During the winter the issue with temperature is paying to heat the greenhouse. It’s easy to control the temperature, growers just have to be willing to crank up the thermostat.”

Mattson said temperature can be really hard to control in southern climates in the U.S.

“Under hot conditions, temperatures in the 80s and 90s, head lettuce is going to bolt prematurely,” he said. “It can be difficult to drop the day temperature low enough to avoid early bolting.”

Beyond trying to reduce the air temperature, research done by the Cornell CEA group has shown that lowering the root zone temperature to 74ºF or less using chilled water can help prevent premature bolting.

“Chilling the root zone temperature allows growers to grow using warmer air temperatures by having the cooler water temperature,” Mattson said. “This is an effective way to chill the plants even when the air temperatures reach the 80s and 90s.”

Mattson said the biggest issue with warmer air temperatures occurs with lettuce and spinach. Warmer temperature and long day conditions can both cause spinach to experience premature bolting. Mattson said warmer temperatures can also promote Pythium root rot on spinach. Spinach is much more susceptible to this water mold than lettuce or other leafy greens.

“Chilling the root zone temperature can help to prevent the disease organism from developing as quickly as at warmer temperatures,” Mattson said. “If the root zone temperature can be kept cool, it won’t completely avoid the Pythium issue, but it will help control it.”

 

Pythium baby leaf spinach, Neil Mattson, Cornell Univ.
Cooling the root zone temperature won’t completely avoid Pythium disease, but it will help control it.

 

Pythium spinach closeup, Neil Mattson, Cornell Univ.
Close-up view showing Pythium root rot on spinach.

 

The Cornell CEA group found that the optimum root zone temperature for spinach was 64ºF-65ºF. At this temperature Pythium was deterred, but there was no crop delay. If the root zone temperature is lowered to 62ºF, plant growth is slowed.

 

Relative humidity

Mattson said the relative humidity for lettuce and leafy greens should be between 50-70 percent. He said the lower humidity helps to limit pathogen issues.

“High humidity favors powdery mildew and Botrytis,” he said. “High humidity also favors the physiological disorder tip burn. Tip burn is caused by a calcium deficiency. The higher the relative humidity the less transpiration occurs in the plant resulting in the plant not taking up an adequate amount of calcium.”

 

Lettuce tipburn, Neil Mattson, Cornell Univ.
High humidity favors the physiological disorder tip burn, which is caused by a calcium deficiency.

 

Mattson said a relative humidity lower than 50 percent can cause an outer leaf edge burn, which is a physiological disorder.

“This is a different disorder than tip burn caused by calcium deficiency,” Mattson said. “The outer leaves develop lesions where the veins end on the edge of the leaves. The lesions occur where the sap exudes out of the veins and then is reabsorbed by the plant and there is a kind of salt buildup.”

 

Fertilization, water quality

Although fertilization and water quality are not environmental parameters, growers can have issues with both if they don’t monitor them. Lettuce and leafy greens are not particularly heavy feeders compared to other greenhouse vegetables like tomatoes and other vine crops. Mattson said lettuce and leafy greens are relatively forgiving crops when it comes to fertilization.

“Growers need to monitor the nutrient solution every day in regards to pH and electrical conductivity (EC),” he said. “The reason for testing the nutrient solution at least daily is because in hydroponics the nutrient solution pH can change by one or two units in a day.”

Mattson said for container crops like petunia and geranium, pH does not usually change by more than one unit in a week. He said container growers may check the pH every week, and some may only do it every two weeks. But for hydroponics a grower needs to stay on top of changes in pH.

In addition to daily pH and EC monitoring, Mattson said a detailed elemental analysis of the nutrient solution is important.

“Periodically, about every four weeks, growers should send a sample of their nutrient solution to a testing lab to determine if the plants are absorbing nutrients in the proportions the growers expect,” he said. “Certain elements in the solution may decline over time and a grower may have to add more of these elements and less of others.”

Mattson said some systems, like CropKing’s Fertroller, have automated sensors which measure pH and EC in line so it’s a real time measurement. The controller makes the necessary adjustments.

“Typically if a grower is putting high alkalinity water into the system, the pH tends to creep up over time, so the controller automatically adds acid to reach a target pH,” he said. “Likewise, the machine does that with EC too. If the EC is going down because the plants are taking up nutrients, the controller adds fertilizer stock solution to reach a target EC.”

Mattson said iron deficiency due to high pH is the most common nutrient disorder he sees on lettuce and leafy greens. Occasionally magnesium deficiency occurs because the water source contains enough calcium, but not enough magnesium.

 

ca
Iron deficiency due to high pH is usually the most common nutrient disorder on lettuce and leafy greens.

 

“Many fertilizers don’t include calcium and magnesium, so growers can run into issues with magnesium deficiency,” he said. “Basil tends to have a high need for magnesium. We usually recommend basil be provided twice as much magnesium as lettuce.”

 

Photo 6, Basil magnesium deficiency, Neil Mattson, Cornell Univ.
Basil tends to have a high need for magnesium and usually should receive twice as much magnesium as lettuce.

 

Mattson said growers should test their water more frequently to determine if there have been any changes in the alkalinity of the water, including calcium, magnesium and sodium concentrations.

“In the Northeast this summer, we are experiencing a drought,” he said. “I’ve heard from growers who say the EC of their water is going up, which implies that some salt levels are going up. But we don’t know specifically which salts and that would be useful to know what specifically is changing.

“It really depends on their water quality. In particular, EC, alkalinity and whether there are any nutrients in high concentrations, like sodium, can be an issue. It really comes down to how long they are trying to capture and reuse the water. In our Cornell system we have traditionally grown in floating ponds. We use that same water cycle after cycle for several years. We can continually use the same water because we start with deionized water. However, even if the water has fairly low salt levels, using the same water will result in the accumulation of sodium to harmful levels over time.”

 

For more:
Neil Mattson, Cornell University
School of Integrative Plant Science, Horticulture Section
49D Plant Science
Ithaca, NY 14853
(607) 255-0621
nsm47@cornell.edu
https://hort.cals.cornell.edu/people/neil-mattson
http://www.cornellcea.com
http://www.greenhouse.cornell.edu

Cornell Controlled Environment Agriculture “Hydroponic Lettuce Handbook”

 

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

 

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

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

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

Part 1: Common production systems, pH and EC management

Presented by Dr. Chris Currey, Iowa State University


 

Part 2: Nutrient solution recipes, common nutrient disorders

Present by Dr. Neil Mattson, Cornell University

Evaluating field-bred lettuce varieties for hydroponic greenhouse production

University of Arkansas researchers trialed 65 lettuce varieties to determine their potential for production in greenhouse hydroponic systems.

 

By David Kuack

 

An increasing number of greenhouse ornamental plant growers are looking to expand into edible crops. There are also field vegetable growers who would like to expand their production to include greenhouse crops.
Some of the easier and faster crops for growers to try to produce in a greenhouse are lettuce and other fresh greens.
One of the issues these growers are facing is what varieties of lettuce can be grown in a greenhouse environment. Much of the commercial lettuce breeding is focused on outdoor field production. Growers looking to expand their lettuce offerings beyond commonly produced greenhouse varieties usually have to do their own trials looking for field varieties that can be adapted to a greenhouse environment.

 

Need to expand greenhouse varieties
University of Arkansas horticulture professor Mike Evans said he is constantly receiving inquiries from growers about what lettuce varieties can be grown in greenhouses.
“At Cultivate’14 we surveyed growers who participated in one of the greenhouse vegetable seminars about their educational and research needs,” Evans said. “One of the growers’ responses was the need for variety information.
“If you look at seed catalogs, most of the information describing lettuce varieties is based on field production, not greenhouse. So if a grower wanted to grow lettuce hydroponically in a greenhouse during the winter there is little information available. If a grower wanted to use nutrient film technique or deep flow floating systems in a greenhouse, there’s basically very little information on how lettuce varieties would do in these production systems. Most of the production information is field-based.”
Evans said there is also a need for evaluating lettuce varieties for fall, winter and spring greenhouse production. He said these variety evaluations need to be done in different regions of the country to see how they perform under different climates.

 

Lettuce variety evaluations
University of Arkansas researchers selected 65 lettuce varieties for evaluation in greenhouse production systems. A nutrient film technique and deep flow floating system were used for the trials.
“Our goal with the variety trials was to generate better and more variety information and to determine which varieties would work best in climates similar to ours,” Evans said. “We especially wanted to be able to make variety recommendations across a production year. That is, varieties which work well in the fall, winter and spring.

“There are certain varieties that do well during winter. But as soon as the days start getting longer, the variety begins to bolt. Or a variety may do well in the fall and spring, but during the lowest light levels of winter, it has some type of production issue.”

Photo 1, IMG_1619, Mike Evans, Univ. of Ark.
University of Arkansas researchers selected 65
lettuce varieties for evaluation in greenhouse
production systems.
Photos courtesy of Mike Evans, Univ. of Ark.

 

Evans said the information that has been collected is for lettuce varieties that perform well in a glass greenhouse in Arkansas.
“These varieties may not respond the same way in Michigan, Arizona, Florida and Texas,” he said. “They also won’t respond the same way in locations where the light and humidity levels are different. These trials are probably good recommendations for growers in climates similar to ours.”
Lettuce varieties were planted from September through May. No crops were grown in June, July and August. Four crops were produced during the fall to spring cycle.
“Some growers try to grow during the summer months by chilling the nutrient solution,” Evans said. “We weren’t set up for summer production. Having trialed 65 varieties we will probably select 15 of the best performing varieties to evaluate for summer performance. For the summer evaluations we will have to use a different greenhouse set up in order to chill the nutrient solution.”

 

Measuring growth rate
Evans said one of major growth parameters measured was biomass production or growth rate.
“The quicker the plants grow, the shorter the production cycle,” Evans said. “Every day on the bench is cost to the grower. We looked at fresh weight and dry weight, two measures of growth.
“Some growers let lettuce grow for a specific amount of time. Other growers try to achieve a specific weight.”
Evans said the lettuce crops were grown on a 42-day production cycle in both the NFT and deep flow systems. At the end of the 42-day cycle the lettuce was harvested and measurements were taken.
“Sometimes if a variety is a fast grower, the lettuce might exceed the weight that a grower would want,” Evans said. “That tells us this variety could have been grown in a much shorter period of time. Or a variety that didn’t reach a minimum weight at the end of the 42-day cycle was considered a slow grower. Fresh and dry weights were used as a measure of how fast a variety can grow. How fast can a variety put on biomass? That is what growers are selling—biomass.”

 

Photo 2, IMG_1600, Mike Evans, Univ. of Ark. (1)
Lettuce varieties that did well in a nutrient film
technique system tended to do well in a deep
flow float system.

 

Evans said there were similarities in how varieties performed in the two production systems.
“If the varieties did poorly in NFT, they tended to perform similarly in deep flow too,” he said. “If a variety did well in NFT, odds were high that it did really well in deep flow.”

 

Identifying disorders
Evans said the two most common problems he hears about lettuce from growers are powdery mildew and tipburn.
“Ninety percent of the calls I receive are about these two problems,” he said. “We rated the lettuce varieties we trialed for tipburn and powdery mildew. Powdery mildew, in our region of the country, is the disease that can often give growers fits. It can really wallop a lettuce crop.  We also measured the incidence of tipburn, which can be a problem on a number of greens.”
Evans said semi-heading and heading (butterhead) types seem to be more prone to tipburn.

“What happens is that as these varieties start to form heads there is an area of high humidity,” he said. “There is this little microclimate of high humidity. If a grower is growing under real high humidity, has structures with poor air circulation or the nutrition levels aren’t right, a calcium deficiency can occur. These can create a tipburn problem. We saw much less tipburn on varieties that tend to be loose leaf types.

 

For more: Mike
Evans, University of Arkansas, Department of Horticulture, Fayetteville, AR
72701; (479) 575-3179 (voice); mrevans@uark.edu; http://hort.uark.edu/5459.php.

 

Top performing lettuce varieties
The following lettuce varieties did well in the four greenhouse production trials conducted at the University of Arkansas.

 

Butterhead types
Adriana
Deer Tongue
Nancy

Rex

Rex
Rex

 

 

Skyphos
Fancy leaf types
Black Hawk
Cavernet

Dark Red Lollo Rossa

Dark Red Lollo Rossa
Dark Red Lollo Rossa
New Red Fire
Outredgeous
Red Sails
Ruby Sky
Oak leaf types
Oscarde
Panissee
Rouxa

 

Panissee
Panissee

 

Romaine types
Green Forest
Red Rosie
Red Rosie
Red Rosie

 

Ridgeline
Salvius
Truchas

 

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

Meeting the fertilization needs of greenhouse lettuce

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

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

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

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

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

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

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

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

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

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

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

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

Mattson said monitoring pH is important as it impacts
nutrient availability. He said lettuce isn’t commonly susceptible to iron
deficiency, but it will start to show up when the pH starts to increase above
6.5-7.
“Monitoring EC and pH is especially important in
hydroponics,” he said. “A good grower who is producing his crop in a growing
medium in containers will monitor the pH every week or two. The pH may change
over the course of a week by maybe one unit.
“Growing hydroponically, a grower should be monitoring
the pH every day and make adjustments. Depending on the type of fertilizer and
the quality of the water, the pH in a hydroponic set up could change two units
in a day.”
Optimizing lettuce
production

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

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

For more: Neil
Mattson, Cornell University, School of Integrative Plant Science; (607)
255-0621; nsm47@cornell.edu.

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

Visit our corporate website at https://hortamericas.com

Plant factories continue to evolve

As technology improves, plant factories have the
potential to operate in the U.S. and Canada to produce crops that are difficult
to grow using current conventional methods.

By David Kuack
When you hear the term “plant factory” what picture comes
to mind? University of Florida professor and mechanical engineer John Schueller
said the traditional definition of a plant factory is a place in which there is
no natural light and artificial light is used to produce plants.
“I’m more of a traditionalist in that I feel a plant
factory is a place that has mainly or only artificial lights in order to grow
plants,” Schueller said. “But a greenhouse with multiple levels of plants in
which natural light is the dominant source and is supplemented with artificial
light, I would also consider that to be a plant factory.
“People involved in protected plant agriculture,
including greenhouses and indoor plant factories, are displaying a lot of
creativity. There are a lot of different systems being tried out. It’s
difficult to make a hard and fast definition of a plant factory. A traditional
greenhouse with plants on raised benches or growing on the floor is not usually
recognized as a plant factory.”
Plant factory
automation

Schueller, who spoke at the Plant Factory Conference in
Kyoto, Japan, in Nov. 2014, said the most important automation that occurs in a
plant factory is during the growth stage.

“The application of light and fertilizer is when the main
automation occurs,” he said. “There is automation during planting when a grower
is trying to establish the plants. And there is also automation during
harvesting.”

University of Florida mechanical engineer John
Schueller
said the technology of plant factories
is improving with the main improvement
occurring with LED lighting.

Photos
courtesy of John Schueller, Univ. of Fla.

Schueller said during the Plant Factory Conference there
was a lot of discussion about which lights are the best for using in plant
factories.
“There are questions that still need to be answered about
what are the best wavelengths and what are the best cycles for different
crops,” he said “Even though there are a considerable number of plant
factories, we still don’t know what the optimal conditions are for growing
plants. There is a lot of variation and experimentation occurring.”
Schueller said automation in the plant factories will
probably occur with the planting practices before it happens with harvesting.
“In Japanese plant factories the finished plants are
brought to the harvesters,” he said. “There is automation to transfer the
plants. People are doing the harvesting of leafy greens, but they are brought
to the workers at an appropriate height and position so that they can be very
efficient and very productive. Obviously, if there are 14 layers of plants
under lights the plants are moved to the harvesters. But there is still some
human involvement in harvesting the plants.”
Schueller said an advantage to a plant factory is the
ability to precisely control the environment. “The technology is improving,” he
said. “The main improvement is with LED lighting. As LEDs become less expensive
and better that will help in the development of plant factories. Also, less
expensive sensors for measuring nutrient solutions are becoming available. As
growers gain more experience with this technology they get better at
controlling the production environment.”
Plant factory
economics

Schueller said economics play a big role in what will be
feasible in how these factories operate.

“The Japanese market for fresh fruits and vegetables is
much different than in the U.S. and Canada,” he said. “In the U.S. and Canada,
vegetables are cheaper. The market will not bear some of the costs that will be
accepted in Japan. In Japan consumers are willing to pay $40 for a watermelon.
“From an agricultural economic standpoint, it seems to me
the big advantage of a plant factory is that a grower can control the
production situation very well. The disadvantages are the energy costs for
running the artificial lights and the capital equipment costs. The best
opportunity is to produce a product that has certain characteristics, that has
no pesticides applied, that has no bacterial contamination, so that a grower
can demand a premium price for it.”

John
Schueller said one area of plant factory production
that shows great potential
is being able to develop
techniques that allow high end vegetables to have
nutritional characteristics that can be easily manipulated.

Schueller said one area of plant factory production that
shows great potential is being able to develop techniques that allow high end
vegetables to have nutritional characteristics that can be easily manipulated
more so than in other production environments.
“One of the Japanese plant factories that was built by
Fujitsu is growing lettuce which has a low potassium content,”
he said. “This lettuce is being produced for kidney dialysis patients and
people with chronic kidney disease. This type of crop has a lot of potential
for U.S. and Canadian markets. Developing vegetables that have nutritional
characteristics so that the markets will be able to tolerate higher production
costs that are associated with plant factories.”
Schueller said the plant factories in Japan can produce
leafy green vegetables in about 15 days.
“The production cycle needs to be as short as possible,”
he said. “If a plant factory is controlled properly and maintains sanitary
conditions, it is possible to produce leafy green vegetables with specific
nutrient characteristics without pesticides. For those types of crops a grower
can demand a premium price to pay for the equipment and energy to produce
them.”
Fast, precise
production

Schueller said the plant factories in Asia are producing
primarily leafy green vegetables.

“I expect these crops would have the greatest potential
in the U.S. as well,” he said. “As more consumers move away from iceberg
lettuce and romaine lettuce, they tend to look for other types of lettuce and
leafy greens and microgreens. There might be real potential with these crops
because they can usually be turned much more quickly.”

Japan
has over 200 plant factories. One of the reasons that
the country has experienced
a proliferation of these facilities
 is food security. Sixty percent of the country’s
food is imported.

Schueller said some of the issues pushing plant factories
in Asia are related to domestic food production and land availability.
“Japan imports almost 60 percent of its food,” he said.
“For the Japanese it’s an issue of food security. Singapore has increased its
vegetable consumption from 7 percent to 8 percent. In Singapore there is a
limited amount of land. They are looking for ways to maximize food production
and plant factories offer them a solution. With plant factories that have
vertical farming they can push the production to maximize the space. In the
U.S. that isn’t a big concern. The plant factories in the U.S. that will be
successful are the ones that grow products that are difficult to produce using
conventional methods.”

For more: John
Schueller, University of Florida, Departments of Mechanical and Aerospace and Agricultural
and Biological Engineering; (352) 392-0822; schuejk@ufl.edu.

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

Visit our corporate website at https://hortamericas.com

Using Grodan for Lettuce and Herbs

Using Grodan for Lettuce and Herbs 

In recent years there has been
a worldwide increase
in the consumption
of lettuce and fresh herbs. Naturally this has led to an increase in production.  More and more growers are now opting to use GRODAN
as their substrate.
The benefits of
using GRODAN in the production process are:
  • It is an
    inert and hygienic substrate
  • The speed and
    uniformity of germination and growth.
  • There is
    sufficient substrate volume to propagate to the
    desired plant size.
  • Once it is
    placed in the gutter or raft system the
    propagation blocks provide further stability.
Inert and clean
GRODAN stone wool
is an inert and hygienic
substrate, so it provides your crop with a clean,
disease free start. Furthermore, stone wool retains its structure throughout the cultivation
cycle. Filters remain clean and free from blockages, cleaning between crops is
easier and more importantly, faster, allowing less downtime between crops. The
fact that it is also inert means that all applied nutrients and
water are directly available for the growing crop. The combination of faster turnaround
and faster growth adds to the possibility of extra cultivation cycles during
the year.
Uniformity and speed of germination and growth
One of the most critical
stages of cultivation is germination. Seed holes cut into the stone wool plugs provide
the perfect air/water ratio around the seed which facilitates a high
germination percentage. More importantly, as the stone wool substrate is
uniformly saturated, each seed has the same germination environment, which provides uniformity in
emergence and initial growth. The speed and uniformity of growth which
follows results in a higher quality end product. It also provides a crucial opportunity
for additional cultivation cycles during the year.
Substrate volume to propagate the desired plant size
There are two distinguishable
stages in the production process; propagation and final production.
With the propagation of lettuce, a favorable microclimate is required. This is partly achieved
by retaining a high plant density. 
In GRODAN trials, we have seen that when the propagation period
is extended (21-24 days), the microclimate created results in more speed in
final production. Also, as larger plants are used, the production cycle is shortened,
once again providing an opportunity for additional cultivation cycles during
the year.
In order to extend the propagation
period you also require a larger substrate volume (i.e. AO
36/40 or MM40/40). This larger volume allows more root growth and
more stability.  Crucially, it also
allows irrigation to be managed. Often in propagation, too much water is given.
This results in weaker plants with greater susceptibility to disease.
Having the right irrigation strategy with the right substrate volume will give
you the possibility to be critical to the moment of irrigation. Having a precise irrigation
strategy will also retain the roots within the plug and therefore result in less
damage during transplanting.
To improve the irrigation strategy, we would suggest that you weigh
the blocks or AO sheets to decide if irrigation is needed (table 1).
Table 1. Indicative weights to irrigate the
blocks or AO sheets.
Grodan product
Approximate substrate volume
Indicative weight to base irrigation on (±60% WC)
MM 40/40
64 ml per block
40 gram per block
AO 36/40
40 ml per plug
3926ml per sheet
24 gram per plug
2.4 kg per sheet

Stability during use in gutter or raft system

Depending on the production system
which is used, the
GRODAN propagation component provides a certain degree of stability. For plants in
gutter systems, suitable products are MM blocks or the AX
plugs (figure 1). For plants in a raft system an AO plug is recommended, as its tapered
base makes planting
into the raft faster.
Figure 1. Left picture showing Grodan AX  plugs with basil seedlings, middle Grodan MM
blocks with lettuce during propagation stage, right picture showing Grodan AO
plug.
Conclusion
GRODAN stone wool
will give you an inert, clean substrate which provides fast, uniform
germination and growth. Whether you have a raft or gutter system, we have a plug or block that
will fit your needs.

For more information
contact Hort Americas at 469-532-2383 or customerservice@hortamericas.com 

Visit our corporate website at https://hortamericas.com

Update on trialing supplemental lights in Hawaii

By David Kuack

On Dec. 14, 2014, a Hort Americas blog update was posted about University of Hawaii graduate student Robert Saito, who is
comparing the growth of pak choi (Chinese cabbage) under T5 fluorescent lamps
and Philips GreenPower LED Production Module Deep Red/Blue 120 fixtures. Saito
has conducted seven trials. The first four trials were preliminary to determine
the best growing medium and which plants should be used to measure light effect
differences. Initially Saito was planning to grow mizuna, but he ran into
issues with micronutrient deficiencies and switched to pak choi instead. Both
of these leafy greens are in the Brassica family.

University of Hawaii graduate student Robert Saito is studying
the differences in growth of pak choi under fluorescent (top)
and LED lights (bottom).
Photos courtesy of Robert Saito


Preliminary results
Saito has measured fresh weight, height and chlorophyll
content of the plants grown under the two light sources.
“I also took SPAD readings to measure the relative chlorophyll
and there were differences among the treatments,” Saito said. “I am now going
to run the data statistically to see if there was a significant difference.”
Plant samples are also being analyzed for nutrient
content to see what kind of nutritional value they can offer to consumers.
“I am doing a tissue analysis to measure some of the
secondary metabolites,” he said. “I am looking at total phenolics, carotenoids
and glucosinolates. A mineral nutrient analyses will measure such things as
total nitrogen, phosphorus and potassium. Once the mineral and tissue analyses
are done then I hope to publish the results.”
For more:
Robert Saito, University of Hawaii, College of Tropical Agriculture and Human
Resources, Manoa, Hawaii; rjnsaiot@hawaii.edu.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com
Visit our corporate website at https://hortamericas.com

LED Grow Lights used in Leafy Green Trials

Philips GreenPower Production Module LED Experiment with
Specialty Greens in Lafayette, CA

Lights: Philips GreenPower Production Modules Deep
Red/Blue 120cm

Objectives: 1.) Can a variety of greens (gourmet
lettuces, high nutrient greens and herbs) be grown under production LED lights
well enough and quickly enough to be commercially viable. The target is a 30
day cycle from seed to harvest.

2.) Would two lights per hydroponic unit (ez clone
cloner) achieve this goal or are three necessary?

Seeded: 9/15/13

Experiment under lights began: 9/26/13
Initial recommendation to hang lights 16-18” above plants produced
leggy and weak seedlings.  Lights
remounted above plants 7-8” Philips GreenPower Production Modules are being run
14 hours/day.  Ambient room temperature
ranges from 70 degrees during the night to 85 degrees during the day. The
nutrient used is DynaGrow at a dilution of 1/2 teaspoon per gallon so about 5-6
teaspoons per cloner. ProTect, an auxiliary nutrient, was used at the same
dilution. An ArtDne recycling timer is being used 24 hours per day at a rate of
1 minute on for every 5 minutes off. There will be one nutrient change during
the experiment after approximately two weeks to refresh the set up and new
nutrient will be applied at the dilution described above.
Specialty Greens is providing growers interested in hydroponics all the they need to grow hydroponically in a 2 ft sq. space!
To
find out more about Specialty Greens Check them out here or like them on Facebook
Here are some photos taken of the Experiment on 9/26/13

Experiment information provided by Patty Phaneuf from Specialty Greens, and Posted by Maria Luitjohan from Hort Americas.
Visit our corporate website at https://hortamericas.com

Using organic fertilizers for hydroponic lettuce production


Research at Kansas State University shows comparable size
and quality lettuce plants can be grown hydroponically with organic or
inorganic fertilizers.
 
By David Kuack

According to the Organic Trade Association’s “2013 U.S. Families’ Organic Attitudes and Beliefs Study,”
81 percent of U.S. families report they purchase organic products at least sometimes.
The study found that the majority of those buying organic foods are purchasing
more items than a year earlier. Those households that are new to buying organic
products represent 41 percent of all families.

The study showed that produce continues to be the leading
category of organic purchases. Ninety-seven percent of organic consumers
indicated they had purchased organic fruits or vegetables in the past six
months. Breads and grains, dairy and packaged foods all scored above 85 percent
among those who buy organic products.
 
A 2013 study done by the Organic Trade Association showed
that 97% of consumers indicated they had purchased
organic fruits or vegetables in the past six months. 
Retailers should be particularly interested in the
results of the study. Organic buyers reported spending more per shopping trip
and shopping more frequently than those who never purchase organic food.

This month national retailer Target
announced its plans to begin offering a new line of organic products called
Simply Balanced. The line is an outgrowth of similar products within its existing
Archer Farms store brand. The Minneapolis-based company plans to boost its
organic food selection by 25 percent by 2017.

Comparing organic,
inorganic fertilizers

With the increased interest in organic produce by growers,
retailers and consumers, researchers at Kansas State University looked at the
production of hydroponically-grown lettuce using organic fertilizers. Jason
Nelson, who received his Master’s degree this year, said the purpose of the
research was to study overall plant performance with organic and inorganic
fertilizers. Another aspect of the research was to study the effects of
commercial microbial inoculants that are marketed to promote plant growth.

Lettuce plants were grown hydroponically comparing organic
and inorganic fertilizer solutions to which were incorporated
microbial inoculants.

‘Rex’ butterhead lettuce was grown in nutrient film
technique troughs. The nitrogen sources of the complete inorganic fertilizer were
ammonium nitrate and ammonium phosphate. The organic fertilizers consisted of four
Kimitec products for hydroponic production,
including Bombardier (8-0-0), Caos (10.5 percent calcium), Espartan
(2.7-3.0-2.6) and Tundamix NOP (micronutrients), plus KMS (potassium magnesium
sulfate) from a different supplier. The microbial inoculants included
SubCulture-B bacterial root inoculant and SubCulture-M mycorrhizal root
inoculant.

“Nitrogen in organic fertilizers is primarily found in proteins
and other complex molecules that break down to ammonium,” Nelson said. “The
ammonium levels could be considered comparable between the two types of
fertilizer systems, although the level was slightly higher with the inorganic
fertilizer. The biggest difference was in the nitrate nitrogen. Starting out,
the inorganic fertilizer contained 75 parts per million nitrate. With the
organic fertilizer there was no nitrate at all. For the other nutrients,
including phosphorus, potassium, calcium and sulfur, using all of Kimitec
products except Katon, which is a potassium source, those were all comparable
with the inorganic fertilizer.”

Nelson said the purpose of incorporating the microbial
inoculants was to learn if they had any impact on the plants grown with either
of the fertilizers.

“Growers have had some trouble getting the same amount of
growth using organic fertilizers compared to inorganic fertilizers,” he said.
“These microbial inoculants are advertised as being able to boost plant growth.
One purpose of the study was to determine if the inoculants would boost growth
in an organic hydroponic system so that it would be comparable to plant growth
with inorganic fertilizers.”

Differences in
growth

One of the things that Nelson noticed in his trials was
that the inorganic-fertilized lettuce plants were harvestable earlier than the
organic-fertilized plants. He said this was particularly evident during the
summer trial when the inorganic lettuce actually bolted.

“Comparing the amount of nutrients in the inorganic fertilizer
to the organic, it makes sense that this growth difference occurred,” he said. “There
was more nitrate in the inorganic fertilizer, so there was a better nitrogen
balance from the start and the plants grew and matured a little faster and were
probably about five days earlier to harvest in the summer and fall trials.

“The limiting factor with the organic fertilizer is the
nitrate. If a grower added some calcium nitrate to the organic nutrient
solution the plants would catch up to the inorganic plants. I expect it would
only take a small amount of nitrate, 30-50 ppm, for the organic plants to match
the growth rate of the inorganic plants.”

Lettuce grown with the four Kimitec products and
potassium magnesium sulfate were comparable to the inorganic plants in size and
fresh weight. However, the inorganic plants consistently had a higher dry
weight than the organic plants.

“The heads of lettuce looked comparable in size,” Nelson
said. “If a consumer was buying a fresh head of lettuce they wouldn’t be able
to tell the difference between the organic- and inorganic-fertilized plants.”

Heads of lettuce grown with inorganic or organic fertilizer
looked comparable in size. The growth rate of the inorganic
lettuce was slightly faster, finishing about five days earlier
than the organic lettuce. Microbial inoculants didn’t seem to
have an effect on this short-term crop.
One area where there was a noticeable difference was in
the taste of the lettuce. Nelson said that the inorganic-fertilized lettuce is
going take up nitrate nitrogen, which is going to be deposited in the leaves.

“There was definitely a flavor difference between the
inorganic and organic plants,” he said. “I attribute the flavor difference more
to the nitrate level than anything else since the other nutrient levels were very
similar between the inorganic and organic plants. The petiole nitrate level was
much higher in the inorganic plants. The flavor was much heavier. We did an
informal classroom taste-test with students and that was a common response. Many
of them preferred the taste of the organic lettuce over the inorganic lettuce.”

Nelson said the use of microbial inoculants with both the
inorganic and organic fertilizers didn’t appear to have any effect on the
growth of the lettuce plants.

“The plants that we were growing were under a relatively
stress-free, temperature-controlled environment,” he said. “I really didn’t see
any difference in the studies with the inoculants except in one circumstance.
That was when the solution nutrient levels were incredibly low. The inoculants
actually had some nitrogen bound up in kelp meal as part of their constituents.
I saw some growth differences in that instance.

“Mycorrhizal fungi take about eight to 10 weeks to become
established and colonize the plant roots. For crops like lettuce which finish
as quickly as four weeks, a mycorrhizal inoculant isn’t going to become active
within such a short production cycle.”

Managing fertilizer
solution pH

Nelson said one of the biggest challenges facing growers
who are trying to grow in an organic hydroponic system is pH management.

“The Kimitec line of products was able to provide an
adequate amount of nutrients for the plants to grow. But the nutrient solution
required more pH management,” Nelson said. “Managing the pH is the biggest
challenge with organic fertilizers because a grower can follow the recommended
rates so the proper amounts of nutrients are available, but the pH fluctuation
is so much more pronounced than it is with inorganic fertilizer treatments.

“It depended a little on plant size, but the nutrient
solution pH for the inorganic plants was adjusted on average maybe once a week.
For the organic plants, at minimum I was checking the solution pH and electrical
conductivity at least once a day whether I was making any changes or not. Some
days I would check the pH twice. If I checked the pH, adjusted it to what I
wanted, by the next day I would have to add acid to bring the pH back down
because it would increase overnight. Somebody might be able to stretch that to two
to three days. When the plants were young, I was checking every day and
adjusting the organic solution pH every day. That’s what the organic solution seemed
to require.”

For more:
Jason Nelson, jsn0331@k-state.edu. Kim Williams, Kansas State University, Department of Horticulture, Forestry and
Recreation Resources; kwilliam@ksu.edu. http://krex.k-state.edu/dspace/bitstream/handle/2097/15574/JasonNelson2013.pdf?sequence=5

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

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