The importance of knowing basics of plant nutrition

By Karla Garcia, Hort Americas Technical Services

Plant nutrition is a key factor in growth and yield. But how can we know which nutrient is missing? Or which is the best fertilizer for our crop?

In learning about plant nutrition, we first need to know there are nutrients required in greater quantities than others. The nutrients that are essential for plant growth are called “macronutrients”. The rest of the nutrients also essential for plant growth but in lower quantities are called “micronutrients”.

Continue reading The importance of knowing basics of plant nutrition

2017 retail sales of organic fresh produce reach nearly $5 billion

The Organic Produce Network and Nielsen report sales of organic fresh produce items approached $5 billion in 2017, an 8 percent increase from the previous year. Nearly 2 billion pounds of organic produce were sold in grocery stores last year, which is a 10 percent volume increase from 2016.

At U.S. retail stores, sales of organic fresh vegetables were $2.4 billion. Organic fresh fruit sales exceeded $1.6 billion. Sales of nearly $1 billion in organic value-added produce items brought total sales to $4.8 billion in 2017.

In 2017 organic packaged salad was again the leading organic fresh produce item, approaching $1 billion in sales. Packaged salad still accounts for one in five organic dollars.

Topping the sales in organic fruit were berry crops, which saw a 22 percent increase in volume sales. Organic berry sales, which include strawberries, blueberries and blackberries, topped $586 million in 2017.

http://www.organicproducenetwork.com/article/384/nielsen-and-opn-announce-organic-fresh-produce-retail-sales-reach-nearly-5-billion-in-2017

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

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.

 

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

Grower goes vertical to increase production, revenue

Fresh cut flower grower Flowers By Bauers & Greenhouses has installed
a vertical production system to increase the production of ornamental and
edible crops.

By David Kuack
Flowers By Bauers & Greenhouses in Jarrettsville, Md., has been
growing fresh cut snapdragons since 1996. The company produces the snaps
year-round in perlite using a recycled nutrient solution. The flowers are sold
through the company’s own retail outlet and to retail florists in the surrounding
Baltimore, Washington, D.C., and Wilmington, Del., areas.
Matt Bauer, who is a partner in the company, said the
snaps go from a 20-week crop during the winter to a 10-week crop during the
summer.
“With the quicker crop time during the summer, half the
greenhouse goes out of production so we add sunflowers during that time,” Bauer
said. “The sunflowers are sold to the same customer base as the snaps. As the
days start to get shorter in the fall, the sunflowers come out and are replaced
with snaps for winter production.
Expanding
production space

Bauer said selling directly to retail florists has
allowed the company to achieve a higher price point, but has limited its
revenue.

“We are limited on how much we can raise the price on the
snaps,” Bauer said. “We wanted to get more money out of the production space we
currently have, so that is why we decided to go to a vertical production
system.”

Charles Bauer (left) and his son Matt installed
a vertical production system in their existing
greenhouse rather than expanding
their
operation with additional greenhouse space.
Photo by Edwin
Remsberg, Univ. of Md.

Bauer said additional production space could be built on
to the existing structure, but it would not make a major impact on the
company’s income.

“Where we are operating the greenhouse now we are limited
as to how much we could expand,” he said. “Another reason we chose to go
vertical was the little investment we had to make compared to the income we
could generate from that space. We are only adding troughs and the
infrastructure to install them. Everything else we needed to grow the
additional crops is already there.”
Since the greenhouse has a gutter height of 12 feet,
Bauer has been able to install a three-tier vertical system.
“We have five bays with 6-foot wide by 100-foot long
rolling benches that have support hoops,” he said. “There are hoops that go
over the benches every 10 feet. We ran a metal suspension tube on each side of
the benches. We installed troughs on top of the suspension bars. I can also
suspend cables from the greenhouse trusses so that another layer of troughs can
be added.
Bauer said when he first proposed the three-tier vertical
production system to the University of Maryland researchers he is working with,
they were concerned with the impact the additional overhead crops would have on
the snapdragons.
“Adding the other crops above the snaps lowers the light
levels, but only adds about a week to the snaps’ production schedule,” he said.
“We aren’t using any supplemental lights. The double layer poly the greenhouse
is covered with provides diffused light. The quality of the snaps hasn’t
suffered with the additional crops. And the income we are generating with the
added production offsets the additional crop time.”
Lettuce added to product
mix

The crops that Bauer has grown in the vertical production
system include a summer crop of celosia, Dianthus
barbatus
(Sweet William) and European gourmet bibb lettuce. This summer he
is trialing a crop of Matthiola incana
(stock).

“We grow everything in perlite, which is not reused,”
Bauer said. “We compost the perlite and plant debris that is left over. We used
to grow in perlite grow bags that we reused for five to seven years. We found
that as the bags are reused there are more roots which can change the whole
dynamics of how the plants need to be watered and can impact the quality of the
snapdragons. Another reason for using perlite with the lettuce is it keeps the
roots cooler during the summer and can help prevent bolting. The temperature
can reach 100ºF
during the summer and we have not had any issues with bolting. We also use high
pressure mist to help lower the temperature.”
Bauer said he trialed the bibb lettuce for two years
before he started growing it as a regular crop. Initially he fertilized the
lettuce with the same nutrient solution that he was using for the snapdragons.

Flowers By Bauers & Greenhouses is growing a
European gourmet bibb lettuce in
a vertical
 production system along with other cut flower crops.
Photo courtesy of
Flowers by Bauer’s.

“When we began trialing the lettuce we applied the snap
nutrient solution. It worked, but the flavor of lettuce was off,” he said. “When
we started growing the lettuce we used a commercially blended fertilizer. My
father has since developed our own custom fertilizer mix for the lettuce.”

Bauer said well water is used for all the crops. It is
run through a series of sand filters before being applied with a closed-loop
irrigation system.
“Our well water is almost like distilled water,” he said.
“We don’t do any type of water treatment for disease control. We have a small
storage tank for the nutrient solution so we are constantly drawing it down and
filling it back up. The water doesn’t sit very long, it is always moving. We
constantly monitor the electrical conductivity and pH.”
Bauer said that he is planning to grow the lettuce
year-round.
“We expect that we will be able to grow five to six crops
of lettuce per year,” he said. “We run the temperatures cooler at night, around
50ºF, because the
snapdragons do better under those conditions. If we raised the night
temperature to 65ºF
we could probably produce nine to 10 crops of lettuce a year. We want to keep
the temperatures cooler for the flowers.”
Bauer said he has overhead production space to grow 600
heads of lettuce per week. He said one of the biggest adjustments was how much
faster the lettuce grows compared to the cut flowers he is growing.
“A lettuce crop during the summer is harvested in six
weeks,” he said. “During the winter and growing under cooler temperatures, the
lettuce finishes in eight to nine weeks.”
Creating a local market

One of the advantages that Bauer had with trying to sell
the lettuce was having an established customer base. The lettuce is marketed in
plastic clam shells with a label that reads: “Flowers By Bauers, Eat Healthy,
Feel Better.”

“I contacted the University of Maryland extension service
prior to growing the lettuce to see what kind of regulations and requirements
were in place for edible crops,” he said. “If we sold the lettuce from our
flower shop and from our delivery trucks within the state, there weren’t any
major issues. If we were to sell the lettuce to supermarkets like Wegmans or
Giant, we would have to become GAP certified.”
Bauer visited with his customers telling them about the
lettuce and how it was produced. He said he offered them samples and once they
tried it that was enough to convince them to start buying it.
Bauer said some of the most enthusiastic customers for
the lettuce are women between the ages of 25 and 35 who have children.
“When I first started marketing the lettuce, I would also
take some of the flowers in five-stem bunches,” he said. “I visited hair salons
and other businesses in Jarrettsville that are women-driven. Whatever I sell in
lettuce, I always double the sale with flowers. The mothers would buy the
lettuce for their families because it was healthy. But they would buy the
flowers for themselves because they made them happy. With the lettuce, they
will only buy so much. But with the flowers, there doesn’t seem to be a limit.”

Matt Bauer is excited by the response he has
received from retail
florists and consumers to
the locally-grown cut flower and
lettuce crops
he is producing in the same
greenhouse.

Photo by Edwin Remsberg,
Univ. of Md.

Bauer visits local businesses every Thursday with lettuce
and bunches of flowers.

“Initially everyone in the community thought the lettuce
was for decorative purposes because we hadn’t sold an edible crop before,” he
said. “They didn’t know they could eat it. I determined that I had to get out
and let people know this was edible lettuce.
“Another thing is listening to what your customers are
saying. The retail florists that I sell to ask what else do we grow. I listen
to them to find out what they’d like to be able to buy from me. I’ll try
growing it to see if I can produce it and whether it is feasible on a
commercial scale.”

For more: Flowers
By Bauers & Greenhouses; mb.harcream@mindspring.com;
http://www.flowersbybauers.com.

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

Updated: LED Grow Lights used in Leafy Green Trials

Specialty Greens
experiment is going well. In the first eight-ten days, Specialty Greens saw
little difference between the LED lights and the T-5 lights, but as we
approached the two week mark Specialty Greens began to see significant differences,
as seen in the photos. There does not seem to be an appreciable difference
between the two LED light set up and the three light set up. The main
difference I am noticing is that there is a bit less color in the leaves of
lettuce produced under the LED lights. There is however, amazing growth and in
looking at the photos of the Mizuna leaves, it’s clear that as a commercial
grower, Specialty Greens could get two, possibly three harvests out in 30 days.
Overall, everything is growing well and if were it not for this experiment, Specialty Greens
would have pulled some of the crops a week ago (e.g., kale, mizuna, some
lettuces).
Chard under Two LEDs
Chard under Three LEDs
 
 
Specialty Greens also decided to compare Hort
Americas LEDs to T-5 lights. In these photos Specialty Greens tried to show the
visible difference between the plants grown under the LED lights (in each photo
they are the larger plants) vs growing under T-5 lights and the incredible
difference between the small (background) and large (foreground) Mizuna leaves
 
Mizuna grown under LEDs on Left, T-5’s on right
 
Mizuna grown under LEDs on Left, T-5’s on right

Also showing the difference in Chard growing under LED
lights (left) vs T-5 lights. (right)

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

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.

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