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 WeightTag: Lettuce
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 nutritionHow to determine if LED grow lights are a good investment
Based on the benefits controlled environment growers are experiencing with LED grow lights, a return on investment (ROI) analysis could help you decide how quickly the payback would be for your operation.
Continue reading How to determine if LED grow lights are a good investmentHort 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.”
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
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 -
Terra Bella Organic Fertilizer – 1 Liter jug
$225.00 Add to cart -
Grodan AO Plugs, Rockwool Cubes
$230.00 – $260.00 Select options -
Pre-Empt, OMRI-listed Organic Hydroponic Nutrients 2.5 gal jug
$52.00 Read more -
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.
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.
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.
greenhouse crop may want to try lettuce. Neil Mattson, associate horticulture
professor at Cornell University, said lettuce is a plant with moderate
fertility needs.
fertility needs than a greenhouse tomato crop,”
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.”
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.
is directly sown into the growing medium and grown for three to four weeks
until plants reach suitable size.
tipburn
Leaf tipburn is a physiological disorder that can occur
when growing greenhouse lettuce. It can greatly impact the salability of a
crop.
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. |
lack of calcium supplied to the plants, but an inability of the plants to
transport enough calcium to the young leaves.
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.”
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.
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.
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.”
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.
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.”
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.
electrical conductivity and pH
One strategy that Mattson recommends growers do periodically
is to monitor the electrical conductivity (EC) and pH levels.
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. |
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.
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.
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.”
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.
lettuce head. If plants are grown in small containers and spaced pot-to-pot,
the lettuce heads may not reach full size.
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.
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.
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.
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.
snaps go from a 20-week crop during the winter to a 10-week crop during the
summer.
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.
production space
Bauer said selling directly to retail florists has
allowed the company to achieve a higher price point, but has limited its
revenue.
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.”
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.
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.”
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.
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.
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.”
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).
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.”
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.”
run through a series of sand filters before being applied with a closed-loop
irrigation system.
“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.”
year-round.
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.”
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.
weeks,” he said. “During the winter and growing under cooler temperatures, the
lettuce finishes in eight to nine weeks.”
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.”
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.”
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.
the lettuce are women between the ages of 25 and 35 who have children.
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.”
Bauer visits local businesses every Thursday with lettuce
and bunches of flowers.
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.
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.
Worth, Texas; dkuack@gmail.com.
Visit our corporate website at https://hortamericas.com
Using Grodan for Lettuce and Herbs
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.
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.
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.
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.
stages in the production process; propagation and final production.
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.
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.
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
|
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.
blocks with lettuce during propagation stage, right picture showing Grodan AO
plug.
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
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).
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
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
Specialty Greens in Lafayette, CA
Red/Blue 120cm
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?
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
and quality lettuce plants can be grown hydroponically with organic or
inorganic fertilizers.
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.
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. |
results of the study. Organic buyers reported spending more per shopping trip
and shopping more frequently than those who never purchase organic food.
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.
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.
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.”
inoculants was to learn if they had any impact on the plants grown with either
of the fertilizers.
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.”
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.
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.
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.”
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.
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.”
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.
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.”
inorganic and organic fertilizers didn’t appear to have any effect on the
growth of the lettuce plants.
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.
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.”
solution pH
Nelson said one of the biggest challenges facing growers
who are trying to grow in an organic hydroponic system is pH management.
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.
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.”
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
Worth, Texas; dkuack@gmail.com.
Visit our corporate website at https://hortamericas.com
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