DALLAS—June 4, 2024—In a move to enhance the sustainability and efficiency of horticultural practices, Hort Americas announced today an exclusive partnership with Meteor Systems to distribute their HDPE floating rafts in North America.
Continue reading Hort Americas Partners with Meteor Systems to Exclusively Distribute HDPE Floating Rafts in North AmericaTag: leafy greens
How to avoid calcium deficiency in controlled environment food crops
Leaf Area Index: Definition and importance in crop production
Leaf area index (LAI) is a key variable used in horticultural studies involving the relation between crop growth and yield. This variable can be a very useful tool when looking to evaluate the performance of your crop.
Continue reading Leaf Area Index: Definition and importance in crop productionFresh Weight vs. Dry Weight
When evaluating crop performance and yield we usually look to evaluate different traits such as Size, Shape, Brix levels, Leaf area, Titratable acids, Flavor, Texture, Fresh weight, Dry weight, and more.
Continue reading Fresh Weight vs. Dry WeightThe 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 nutritionHow to improve controlled environment crop production with LED lighting
By Karla Garcia, Technical Service
The development of new lighting technologies such as light-emitting diodes (LEDs) can increase the capability to provide ideal light conditions to crops. This makes it possible to improve crop performance and product quality.
Continue reading How to improve controlled environment crop production with LED lightingHort Americas releases new CEA publication, “Roadmap to Growing Leafy Greens and Herbs”
The new online publication “Roadmap to Growing Leafy Greens and Herbs” focuses on sound planning for controlled environment hydroponic production.
Not All LEDs Are Equal: How Greener Roots Farm Is Growing Faster With Horticulture Lighting From Current
This article was originally posted on currentbyge.com
Meet the light bars behind “the best damn lettuce you’ve ever tried.”
e-Gro Blog shares new greenhouse disease management recommendations
New Greenhouse Disease Management Recommendations for Vegetables and Herbs
Originally written by e-Gro (Heidi Wollaeger) on Jan 24, 2019
Continue reading e-Gro Blog shares new greenhouse disease management recommendations
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?
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
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.
Continue reading Dissolved oxygen improves plant growth, reduces crop time
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.
Continue reading What are the optimum nutrient levels for hydroponic edible crops?
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.
Continue reading Organic vs. traditional hydroponic production: the top 3 differences
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.
“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.”
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.
“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.”
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
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Grodan AO Plugs, Rockwool Cubes
$240.00 – $260.00 Select options This product has multiple variants. The options may be chosen on the product page -
Washed 4.5kg Coco Coir Peat Block
$16.75 Add to cart
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.”
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.”
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.”
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.
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
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Hort Americas Hydroponic Fertilizer (9-7-37)
$25.00 – $90.00 Select options This product has multiple variants. The options may be chosen on the product page -
Terra Bella Organic Fertilizer – 1 Liter jug
$225.00 Read more -
Grodan AO Plugs, Rockwool Cubes
$240.00 – $260.00 Select options This product has multiple variants. The options may be chosen on the product page -
Pre-Empt, OMRI-listed Organic Hydroponic Nutrients 2.5 gal jug
$52.00 Add to cart -
EpsoTop Magnesium Sulfate K+S, 25kg Bag
$45.00 Add to cart -
Yara Tera Calcium Nitrate
$53.88 Add to cart
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.”
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.”
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.”
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.
“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.”
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.
Some of the easier and faster crops for growers to try to produce in a greenhouse are lettuce and other fresh greens.
“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.”
University of Arkansas researchers selected 65 lettuce varieties for evaluation in greenhouse production systems. Photos courtesy of Mike Evans, Univ. of Ark. |
Lettuce varieties that did well in a nutrient film technique system tended to do well in a deep flow float system. |
“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.
Evans, University of Arkansas, Department of Horticulture, Fayetteville, AR
72701; (479) 575-3179 (voice); mrevans@uark.edu; http://hort.uark.edu/5459.php.
Rex
Dark Red Lollo Rossa
Worth, Texas: dkuack@gmail.com.
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