Nutrient Management Level 1 Starts July 10!

One of the biggest factors affecting the success of your crop is correctly managing nutrients in the root zone. Nutrient Management Level 1 is part of the award-winning Greenhouse Online Training program offered by the University of Florida IFAS Extension. This course is intermediate level and designed for people with some experience or entry university level, who are in production, technical, or sales role for greenhouse and nursery crops. Topics covered include common nutrient problems, essential nutrients, fertilizer types, growing media, and testing (soil, nutrient solution and tissue). The course is offered in English and Spanish. Rated 4.4 out of 5 by grower participants, with over 90% graduation rate last year! Over 900 growers have successfully taken this course.

The course runs from July 10 to August 4, 2023. The cost is $US265 per participant, with a 20% discount if you register 5 or more. All course material is completely online and available at any time of the day, and includes pre-recorded videos, an interactive discussion board with PhD professors, and quizzes. Two new modules are activated each week during the course, for a total of 8 learning modules. Instruction is at your own pace and time within the 4 weeks of the course, with a typical time commitment of about 6 hours per week. Click here to register.

Nutrient Management 1 is one of six courses that counts towards the Plant Health Professional certificate offered by University of Florida UF IFAS Extension (UF Greenhouse Training Online) and the Michigan State University Floriculture Program Extension (MSU Online College of Knowledge) to help greenhouse clientele grow their career in plant health management.

For more information, go to http://hort.ifas.ufl.edu/training/, or contact Greenhouse Training, Environmental Horticulture, University of Florida, USA, Email: greenhousetraining@ifas.ufl.edu.

Nutrient Management Level 2 (Advanced) Starts August 22!

Train your staff to make better crop management decisions by learning in depth aspects of plant nutrition management. Nutrient Management Level 2 (Advanced) is the third course of the award-winning Greenhouse Online Training program offered by the University of Florida IFAS Extension. This course is advanced level and designed for an experienced, well-trained greenhouse or nursery grower of transplants, ornamental or vegetable crops. Topics covered include fertilizer calculations, pH management, how to formulate your own fertilizer from individual salts, and diagnose nutritional problems and take corrective actions. The course is offered in English and Spanish. Rated 4.5 out of 5 by grower participants.

The course runs from August 22 to September 16. The cost is $US249 per participant, with a 20% discount if you register 5 or more. All course material is completely online and available at any time of the day, and includes pre-recorded videos, an interactive discussion board with PhD professors, fertilizer assignment and quizzes. Two new modules are activated each week during the course, for a total of 8 learning modules. Instruction is at your own pace and time within the 4 weeks of the course, with a typical time commitment of about 6 hours per week. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, go to http://hort.ifas.ufl.edu/training/, or contact Greenhouse Training, Environmental Horticulture, University of Florida, USA, Email: greenhousetraining@ifas.ufl.edu.

Nutrient Management 2 (Advanced) Starts August 31!

Train yourself and your staff to make better crop management decisions by learning in depth aspects of plant nutrition management. Nutrient Management 2 (Advanced) is the third course of the award-winning Greenhouse Online Training courses offered by the University of Florida IFAS Extension. This course is advanced level and designed for an experienced, well-trained greenhouse or nursery grower of transplants, ornamental or vegetable crops. Topics covered include fertilizer calculations, pH management, how to formulate your own fertilizer from individual salts, and diagnose nutritional problems and take corrective actions. The course is offered in English and Spanish.

The course runs from August 31 to September 25, 2020 and includes a personalized certificate of completion. The cost is $US199 per participant, with discounts if you register 5 or more. The last day to register is September 7, 2020. Over 4 weeks, there are streaming video lessons, discussions, readings and assignments (about 4 hours total commitment per week), which can be accessed at any time of day and paced at your convenience. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, including discounts for registering multiple staff, email us at greenhousetraining@ifas.ufl.edu, or visit http://hort.ifas.ufl.edu/training/.

Registration is free. For more information, go to https://greenhouse.uconn.edu/webinars/

Advanced Nutrient Management

Train yourself, or your staff, to make better crop management decisions by learning in depth aspects of plant nutrition management. Advanced Nutrient Management is the third course of the 2019 Greenhouse Online Training program offered by the University of Florida IFAS Extension. This course is advanced level and designed for an experienced, well-trained grower, or upper university level. Topics covered include multiple aspect of pH management, how to formulate your own fertilizer from individual salts, and diagnose nutritional problems and take corrective actions. The course is offered in English and Spanish. 

The course runs from August 5 to August 30, 2019 and includes a personalized certificate of completion. The cost is $US199 per participant, with discounts if you register 5 or more. The last day to register is August 12, 2019. Over 4 weeks, there are streaming video lessons, readings and assignments (about 3-4 hours total commitment per week), which can be accessed at any time of day. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, including discounts for registering multiple staff, email us at greenhousetraining@ifas.ufl.edu, or visit http://hort.ifas.ufl.edu/training/.

Nutrient Management 1 (Introduction)

Train yourself, or your staff, to make better crop management decisions by learning the basics of plant nutrition management. Nutrient Management 1 is the second course of the 2019 Greenhouse Online Training program offered by the University of Florida IFAS Extension. This course is intermediate level and designed for people with some experience or entry university level, and are in production, technical, or sales role. Topics covered include common nutrient problems, essential nutrients, fertilizer types, onsite pH and EC testing, and growing media. The course is offered in English and Spanish.

The course runs from July 1 to July 26, 2019 and includes a personalized certificate of completion. The cost is $US199 per participant, with discounts if you register 5 or more. Over 4 weeks, there are streaming video lessons, readings and assignments (about 3 hours total commitment per week), which can be accessed at any time of day. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, including discounts for registering multiple staff, email us at greenhousetraining@ifas.ufl.edu, or visit http://hort.ifas.ufl.edu/training/.

Advanced Nutrient Management /Manejo Avanzado de Nutrientes

Train yourself, or your staff, to make better crop management decisions by learning in depth aspects of plant nutrition management. This course covers multiple aspects of pH management, how to formulate your own fertilizer from individual salts, and diagnose nutritional problems and take corrective actions. Advanced Nutrient Management is the fifth course of the Greenhouse Training Online program offered by the University of Florida IFAS Extension, winner of the 2018 ASHS Extension Division Education Materials Award. This course is advanced level, designed for an experienced, well-trained grower, or upper university level. The course is offered in English and in Spanish.

The course runs from September 3 to 28, 2018. It costs $US 199 per participant, and includes a personalized certificate of completion. Over 4 weeks, there are streaming video lessons, readings and assignments (about 3-4 hours total commitment per week), which can be accessed at any time of day. Click here to register (http://hort.ifas.ufl.edu/training/)/.

PDF: Advanced Nutrient Mgt 2018

For more information, go to http://hort.ifas.ufl.edu/training/, or contact Greenhouse Training, Environmental Horticulture, University of Florida, USA, Email: greenhousetraining@ifas.ufl.edu.

Voluntary USDA grade standards designate different levels of quality in agricultural products. The USDA has official standards used to grade a lot of different crops including leafy greens like Greenhouse Leaf Lettuce, Field Grown Leaf Lettuce, Kale, Beet Greens, Collard Greens, Dandelion Greens and Mustard Greens. The standards for butterhead lettuce currently fall under the same standards used for Iceberg lettuce. Although the U.S. Standards for Grades of Lettuce do acknowledge the significant differences between the two types of lettuce, they are still grouped under the same standards. And there is no mention of living lettuce in the U.S. Standards for Grades of Lettuce, while living lettuce is one of the primary crops grown by hydroponic leafy greens growers. If the hydroponic lettuce industry is to grow beyond the premium product niche and enter the ‘real world’ of lettuce production, it would be helpful if hydroponic growers decided upon grading standards appropriate for hydroponically grown lettuce.

When hydroponic lettuce growers try to compete against field growers they almost never win in the battle for price per pound. Field growers can sell heads of lettuce wholesale under $0.75. Large hydroponic lettuce growers (3+ acres) can get their price per head close to $0.90. Field lettuce is generally packed in a 24 count box that will weigh 50+ pounds. The heads are easily 1 to 2 pounds. Hydroponic lettuce is often packed in a 6 or 12 count box and the heads rarely weigh over 10 ounces (0.625 pounds).

While hydroponic crops have a lot of external benefits like water savings and food safety, those benefits are not shown when a hydroponic butterhead is graded with the U.S. Standards for Grades of Lettuce. To preserve the narrative around hydroponic lettuce, it may be necessary to have USDA grading standards specifically for hydroponic lettuce so the crop does not lose some of its value when it enters the larger lettuce market that puts it ‘head-to-head’ with field grown crops.

USDA grade standards are helpful in international trade. The U.S. has one of the biggest lettuce importers on the northern border… Canada! (See Stats). Currently most hydroponic lettuce growers sell to local markets or if they are one of the larger hydroponic lettuce growers they might sell to a grocery store chain or produce broker that distributes their product in multiple states. I have seen living butterhead lettuce from Canada in the U.S. but I’m not aware of any U.S. hydroponic leafy greens growers shipping internationally. I would think that the increased shelf-life of living lettuce would be an advantage in international trade since lettuce is highly perishable.

The Standards for Butterhead Lettuce Quality

What should a USDA Grade A butterhead lettuce look like? How big should it be?

I’ve seen a wide range of targets from growers across the US and internationally. The majority of US hydroponic butterhead growers target a head that is between 5 oz. and 8 oz. (with roots attached). Many aquaponic and indoor vertical farms sell heads closer to 5 ounces. Many of the larger hydroponic lettuce growers (1+ acre greenhouses) target heads between 6-8 ounces. I’ve seen some greenhouse lettuce growers target 10 ounce heads. In Europe, it is common to see butterhead lettuce over 1 pound. In Japan, it is common to see living lettuce sold at less than 5 ounces. The market standards for hydroponic butterhead lettuce minimum weight vary but generally the bottom line is the head should not bobble around when packaged in a clamshell. Most living lettuce labels do not even state a minimum weight, instead the label might have “1 Count” or “1 Head”. Beyond weight there’s the more qualitative traits like leaf texture, leaf color and head formation. Check out these unofficial visual aids provided by the USDA to help grade romaine and lettuce. What would a visual aid for hydroponic butterhead lettuce look like?

Here are some of my favorite butterhead lettuces I’ve grown over the years, which do you think looks most like a ‘standard’ butterhead?

This article is property of Urban Ag News and was written in cooperation with Tyler Baras.

Know your goals before investing in a water treatment system.

A water treatment system is not going to add value to your product. It’s all about reducing the risk of crop losses.

One of the advantages that ornamental plant growers have over growers of hydroponic edible crops is that ornamental crops are usually produced with some kind of root substrate.

“Most ornamental plant growers are not purely hydroponic,” said Paul Fisher, who is University of Florida professor and floriculture extension specialist. “That means ornamental growers have more options they can use for water treatment compared with a hydroponic system where the roots are bathed in the recirculating solution. For instance, with hydroponics, a grower needs to be especially sensitive to the accumulation of chloride from chlorination or copper from copper ionization in the recirculating nutrient solution.”

Know your water concerns first

Fisher said one of the challenges that growers face with water treatment is the tendency to choose a solution without first finding out what the problem is.

“There are many different potential water quality problems that growers can have,” he said. “These can be broken down into microbial problems (plant pathogens or biofilm), chemical problems (salts, alkalinity and occasionally pesticide residues) and particle (filtration) problems. Growers should think in terms of these three different types of potential problems.

“They should test their water and only then decide on the appropriate solution. No single technology is a silver bullet. In some instances, water treatment companies are aggressively pushing one particular technology that they sell, which may be a good solution for one problem, but not others.”

Fisher said before growers make any decision about water treatment, they need to define what issues of water quality they want to address.

“When a grower sends a water sample to an analytical testing lab, the most common water test is to measure the concentration of dissolved ions,” he said. “These tests could include alkalinity, sodium and chloride, electrical conductivity (EC), hardness (calcium and magnesium) and other ions such as iron or boron in the water.

“A complete lab analysis will help growers select the best fertilizer recipe, because the nutrient solution is a combination of the water source and added fertilizers. For example, if growers have enough calcium and magnesium in their irrigation water, then they may not need to add these nutrients in the fertilizer. Chemical water analysis also helps decide if additional treatment is necessary, such as acidification if water alkalinity is high or reverse osmosis if the EC is high.”

Common, uncommon water issues

Fisher said if growers are using well water or a municipal water source, the most likely problems to treat for are alkalinity or high salts, depending on where a grower is located.

“High alkalinity is a very common water treatment issue in our industry,” he said. “Irrigating with highly alkaline water is like adding lime to a crop with each watering. The pH climbs over time leading to iron deficiency. Injecting an acid such as sulfuric, nitric, or phosphoric acid may be needed.”

Fisher said another common issue with water is high EC. Typically the most common cause for this is sodium chloride. He said reverse osmosis is one of the treatment options for high EC where ions are removed when water is passed at high pressure through a membrane.

“One of the biggest differences from one hydroponic location to another is the incoming water quality,” he said. “For example, in the Midwest if there is a limestone aquafer and growers are using well water, there may be enough calcium and magnesium that these nutrients don’t need to be in the fertilizer solution. In contrast, in parts of the Northeast and North Carolina where the water has a low EC, growers must choose a fertilizer that is going to contribute most of the nutrients.

Fisher said another challenge with EC management that is important for hydroponic growers is to know what is making up the EC in their recirculating solution.

“For example, nutrient levels drop over time because of uptake by plant roots, but the water source contains a significant amount of dissolved ions,” he said. “Then much of the EC may be coming from sodium and chloride rather than nutrients such as nitrogen, phosphorus and potassium. These growers will have to do a certain amount of replacement of their nutrient solution. For example, they may have to dump a certain amount of their nutrient solution every two weeks to prevent the sodium chloride from accumulating. This can be an environmental hazard (encouraging eutrophication of water supplies) and also increases fertilizer costs.”

Fisher said once growers deal with common water quality issues they may face issues that are unique to different parts of the country.

“I am working with a grower in Indiana and another grower in Florida who have high iron in their water,” he said. “The iron is clogging filters either directly because of rust particles or because of bacteria growing on the iron. There can be a mix of iron that is already a solid particle, which is rust, and there is also dissolved iron.

“The process of removing iron is to oxidize it and turn it into rust. This can be done using chlorine or potassium permanganate or some other oxidant. Ozone could also be used. Once the iron is turned into rust the water can be run through a sand filter. The filter will trap the iron particles. The filter will have to be washed out periodically to remove the particles. These are examples of why it is important to test the irrigation water first, identify the issues, and choose appropriate solutions.”

Biological issues

Fisher said if growers are using well water or municipal water it is very unlikely that the water is going to be the source of a plant pathogen. These water sources may be helping to distribute a pathogen if growers are recirculating the water, but the incoming water is likely to be very clean. He said when the water source is surface water, from a pond, or from a recirculation tank, it’s more likely that the water could be a significant source of pathogen inoculum.

Fisher said one of things that can happen with any of these water sources is that there are three types of biological problems:

1. Plant pathogens

2. Biofilm

3. Human safety bacteria (i.e. E. coli)

“The most common pathogens that would be favored in irrigation water are the oomycetes of Phytophthora and Pythium,” Fisher said. “If growers have root disease problems and suspect that their irrigation water may be a part of the disease distribution, they can send a water sample to a university extension lab for testing. However, it can be hit-or-miss as to whether or not a pathogen is going to be present in a particular water sample. Routine sampling of irrigation water for disease detection is not something that most growers normally do because of the time and cost.”

Fisher said many of the state extension plant diagnostic testing labs are able to run samples for plant pathogens.

“The labs typically plate organisms out to the genus level of the organism, identifying whether it is Pythium or Phytophthora,” he said. “It really matters a lot what the species is, which many labs are able to analyze, although this may take longer and cost more. Pythium can be quite ubiquitous. Phytophthora tends to be more aggressive than Pythium.

“The University of Guelph diagnostic lab will check the DNA fingerprint of what’s in the water. The lab can compare a sample with a data base of other plant pathogens.”

Dealing with biofilm

Fisher said when growers contact him with a biofilm problem, he asks them to send samples to a water testing lab to measure the aerobic bacteria count from different sampling points in their irrigation system. Usually, but not always, he said, well water has a low bacteria count.

“If growers are using pond water, it is very likely that there is going to be a high bacteria count,” he said. “These high bacteria counts occur because of the presence of microbes including cyanobacteria and other algae. When there are very high bacteria counts, growers usually have to treat for microbes if they use mist nozzles or drippers. The microbes may not be plant pathogens that cause disease, but they may clog irrigation emitters and filters.”

Fisher said if growers have a biofilm problem, they need to determine where the bacteria are coming from.

“Growers would collect water samples from the water source, after the water is chlorinated, after the fertilizer is added to the water, and out in the greenhouse,” he said. “By testing samples from these different locations will identify where the bacteria are growing in the irrigation water and where the water treatment needs to occur. It will also tell growers, whether the treatment systems they are using, for example, chlorine, chlorine dioxide or ozone, are effectively controlling the microbes.”

Particle issues

Fisher said particles in the water could include algae from pond water or sediment (clay, silt or sand). These particles can clog up filters and water emitters.

“Water testing labs should be able to provide a measurement of turbidity, which is the clarity of the water, and also the amount of total suspended solids (TSS),” he said. “A lab will take a specific water sample volume, filter it through a very fine filter and then dry it down and weigh it. This will determine the TSS in terms of milligrams (weight) of particles in a liter of water.

“From experiences with growers, if there is more than 5 milligrams of suspended solids per liter of water, it is quite likely that there are enough particles in the water to cause some issues in the irrigation lines.”

Fisher said growers who are using municipal water typically use screen filters.

“It is unlikely that a high concentration of suspended particles will come from a municipal water source,” he said. “For risk management purposes, however, growers usually install one or more screen filters with enough filtration to remove any suspended particles that are large enough to clog up the finest irrigation emitters in the system.”

In the case of well water, Fisher said growers occasionally may pull up some suspended particles like silt that may require they install some additional filtration.

He said there are two kinds of recirculated water. Pond water usually comes from the water that is drained off outdoor areas or as runoff from a greenhouse. The other source of recirculated water drains off from ebb-and-flow concrete floors or troughs/benches in a greenhouse and is stored in concrete tanks. Water from these sources has similar needs in regards to filtration.

“Pond water will contain algae and other bacteria,” Fisher said. “With ebb-and-flood systems there can be root substrate and plant debris. With pond water there are usually pumps that are pumping water through a filter and then the water, which is under pressure, goes all the way to the greenhouse. There is usually a series of filters for organic materials, including disc filters, sand filters and sometimes screen filters.

“The greenhouse that is being filled with water and then drained back is filtered and stored in another supply tank. This is typically where paper filters, vibrating screen filters and rotating drum filters are used. This is usually a gravity-fed system.”

Agrichemical residues

Fisher said if growers suspect they are having a problem with their crops that is not related to nutrition or disease, it may be an agrichemical issue.

“Growers may suspect there is something toxic in their water that might be herbicide runoff from a neighboring farm or it may be growth regulator residues from past applications,” he said. “There are special labs that are able to test for these chemicals. But growers need to know what chemicals to specifically ask a lab to test for.

“In my research program we are doing a lot of work on removing paclobutrazol residues from irrigation water using carbon filtration. Paclobutrazol has a half-life of about six months in irrigation water. It is normally applied in the parts per million range. But the chemical has activity in the parts per billion range, even as low as 5 parts per billion, on sensitive crops like begonia. There can be some leachate from the spraying or drenching of paclobutrazol that gets into recirculated irrigation water that can then impact untreated plants.”

Keep the system clean

Fisher said growers should try to keep their irrigation systems clean, but they don’t have to sterilize them.

“Cleaning out the recirculating tanks, greenhouse surfaces and irrigation lines several times a year is good idea,” he said. “Although most of the microbes in a recirculation system are likely to be beneficial or benign, the equipment can start to clog. There is going to be algae growth and there is the possibility of pathogen spores getting embedded in biofilm. The goal is to keep the system clean, but there is no need to continually kill all of the organisms in the system.

“Growers who are not using fine drippers or mist nozzles are less likely to have a problem with clogging from biofilm.”

Fisher said after power washing the water storage tanks growers can apply an agricultural cleaning product, such as Strip-It, which is widely used. This helps to remove biofilm.

“This treatment may keep the system clean enough that it is not necessary to continually inject some type of sanitizing agent,” he said.

Maintaining dissolved oxygen levels

Fisher said dissolved oxygen is mainly an issue for hydroponic growers because roots are bathed in the nutrient solution. In contrast, when growing in a root substrate with a high level of air porosity (from large particles in the substrate), the roots will receive adequate oxygen so long as the plants are not overwatered.

“If growers are using a nutrient film technique (NFT) system, then the movement of the water helps oxygenate the nutrient solution,” he said. “Aeration of the nutrient supply tank may still be required.

“With floating pond systems, low oxygen conditions are likely to occur. If the water temperature is warm, there is going to be a lot of biological activity occurring and respiration by the microbes. Warm water also holds less oxygen than cool water. It is a good idea to install some type of bubbler. A bubbler creates small bubbles that add oxygen to the water and raise the dissolved oxygen level. If the oxygen level becomes low in a hydroponic solution then it can favor pathogenic organisms such as Pythium. The water should contain at least 5 parts per million of dissolved oxygen.”

Investing in a treatment system

Fisher said growers should place their emphasis first on ensuring their plants are healthy and growing well. Their incoming water should be from a high quality well or municipal source and there should be a high level of overall sanitation. With this foundation in place, he said, an expensive water treatment system may not be needed.

Fisher said growers need to think in terms of profitability of their business when considering water treatments.

“Margins are tight for most growers so they need to think about how they are going to generate a positive return on their investment,” he said. “If there is an existing chemical, biological or physical water quality problem that has been clearly identified (including lab testing), then investing in a targeted water treatment solution to that problem will rapidly be paid back.

“However, if growers are spending money on a water treatment system that they don’t need, then they don’t have that capital available to spend on an alternative investment such as supplemental lighting that could increase their yields.”

Fisher said a water treatment system is not going to add value to growers’ products.

“No one is going to pay growers more for their product just because they have installed a water treatment system,” he said. “It’s really about crop losses and reducing the risk. When growers have a root rot problem caused by a water-borne pathogen, then they can very quickly pay back the benefits of a water treatment system.”

For more: Paul Fisher, University of Florida, Institute of Food and Agricultural Sciences Extension.

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

Growers who incorporate water-driven injectors into their production systems are usually looking for simplicity and flexibility.

Whether fertilizing greenhouse ornamental or vegetable crops, many growers use an injector to take up fertilizer concentrate and mix it with water and apply it to the plants.

“From an application standpoint the same type of information related to water flow, pressure and dilution rate is going to be used whether a grower is producing ornamentals or vegetables,” said Chris Lundgren, national sales manager for horticulture at Dosatron International Inc. “The difference with greenhouse vegetable production compared to traditional bedding plant production is sometimes vegetable growers want more flexibility in their control over the rates of nitrogen, phosphorus and potassium. In vegetable operations, growers sometimes operate multiple injector units in line or in series. There is a tank A, a tank B and a tank for a diluted acid or some other supplement like a calcium-magnesium product that provides them with more control.

“The traditional bedding plant grower may be using a bag of 20-10-20 or 17-5-17, mixing the fertilizer and using one injector to deliver it to the whole production facility in a constant liquid feed program. In the vegetable greenhouse, the grower is looking for more variable control.”

Lundgren said as vegetable crops like tomato and cucumber go from the vegetative stage to the flowering and fruiting stages that most growers are going to want to have more control over how much nitrogen, phosphorus and potassium and any other supplements are going to be provided to the plants. He said this is the major difference between fertigation of traditional greenhouse/nursery crops and greenhouse vegetable production.

Adding edibles to the product mix

Lundgren said ornamental plant growers who want to try their hand at producing edibles usually start with crops like lettuce, leafy greens and microgreens.

“The crop turnaround time is quick,” he said. “It’s a onetime harvest and the crop doesn’t have to be held for very long. The grower is trying to harvest as much off of one plant as possible. This is the quickest, easiest way to go from flowers to food.”

Lundgren said for crops like leafy greens only one fertilizer solution is usually needed because growers are trying to keep the plants vegetative.

“Because of the way these crops are produced, growers can get away with the same single bag fertilizer program that they are using to grow bedding plants,” he said. One change that Lundgren has seen bedding plant growers make when adding edible crops is to install some type of water treatment system.

“Bedding plants growers who are adding short-term crops like leafy greens have to be sure they are successful with those crops from the start,” he said. “Bedding plant growers are installing hydroponic production systems like nutrient film technique because that is going to be the quickest way to turn around these crops. The growers are being advised that water treatment is an important part of an edible crop program because the water is now being used as part of or as the substrate. This means the water’s contaminants are much more highly concentrated in the root zone compared to a soilless medium that is used for bedding plants.” Lundgren said growing poinsettias, tomatoes, cucumbers and peppers, are similar in that they are long-term crops.

“Typically for poinsettia, it’s a six month crop from stick date to out the door,” he said. “Six months of pest control monitoring and the IPM program has to be pretty much spot on as well as the plants having to ship on time. Tomatoes are more like a poinsettia crop.

“With long term crops, growers have more flexibility to make changes to rectify issues that occur. With a quick crop like leafy greens, a grower doesn’t have as much flexibility to fix mistakes.”

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An intimate, hands-on relationship

Lundgren said growers who incorporate water-driven injectors like Dosatrons into their production systems are usually looking for simplicity and flexibility.“Growers who are using Dosatrons tend to be more of hands-on growers,” he said. “The injectors become an integral part of how growers are doing things. Because these injectors are mechanical, growers have to physically make adjustments to change the ratios. There is an intimate relationship that happens between something mechanical, even though it is automating the process, and the users. That, in and of itself, becomes a reason why people are so attached to their injectors.”

Lundgren said proper maintenance can go a long way in extending the lifespan of the injectors. Some growers are operating injectors that are 15-20 years old.

“Water-driven injectors are mechanical devices and need maintenance just like a car,” he said.

“The harder an injector is run the quicker it has to be serviced. Those that are used to apply the same product all the time and aren’t used frequently don’t need maintenance as often. The longer injectors are operated, the harsher the chemicals that are run through them, and the more chemical diversity injectors are exposed to, the more frequently maintenance will be needed.

Injectors are used to apply everything from fertilizers, PGRs, sanitizers, insecticides and fungicides.”

Level of control

Lundgren said fully-automated environmental control systems that incorporate chemical injection usually require someone with technical expertise to do maintenance or repairs because of the complexity of these systems.

“Some growers desire more control and prefer using injectors,” he said. “Typically the growers who use injectors are out in the greenhouse manually testing the EC (electrical conductivity) and pH. Other growers need something that is not as mechanical that is tied in more to an automated environmental control system. These automated systems give them the capacity to make changes on the fly, using a phone or a computer. These systems are going to typically be provided by the environmental control companies.”

Lundgren said many of the large greenhouse vegetable operations have so much diversity that they need to rely on an automated system that is going to do a large capacity and be centralized.

“These growers are not going to want a lot of Dosatron stations throughout their facilities,” he said. “They don’t want to have to make mechanical adjustments in every pump house. It is much more sensible to use a fully integrated system in these operations. They might use some mechanical injectors for certain applications.”

Lundgren said fully integrated, automated environmental control systems have the ability to monitor the system and the plants, as long as the system is maintained. These systems can provide a lot of data including pH, EC, temperature and relative humidity.

“One of the greatest pros with fully integrated systems is growers can sit at home and monitor the greenhouses from their smart phones knowing that the fertigation program is spot on,” he said. “That definitely is an advantage.

“The discussion for growers using any type of fertigation technology comes down to: what makes sense for their operation and what makes sense for their business plan? Secondly, what level of technology are they ready for? If growers are more mechanical in nature and go out and monitor their crops daily, injectors probably better fit their production system. If they are a grower who wants an automated streamlined production facility and prefers working on a computer, then a fully integrated control system is likely a better choice.”

For more: Dosatron International Inc.; (800) 523-8499; Chris.Lundgren@DosatronUSA.com;

http://www.dosatronusa.com.

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

Growers who are doing hydroponic production in nutrient film technique (NFT) or deep water raft systems should be monitoring pH and soluble salts content (electrical conductivity) more often than growers using container substrates.

“With hydroponics, especially with NFT production systems, the root zone conditions can change very quickly,” said Neil Mattson, associate horticulture professor at Cornell University. “The pH can change very rapidly because the water doesn’t have a lot of buffering capacity.

“With deep water culture (DWC) where there is typically a larger volume of water used, things like water temperature, pH, fertilizer strength and the overall concentration of the nutrients, are relatively stable over time as compared to NFT systems. In DWC, these parameters don’t change that much hour to hour. There may be slight changes from day to day and more changes from week to week. Deep water raft systems don’t generally take quite the degree of management that NFT systems do in terms of constant or continuous monitoring.”

Mattson said it would be good for growers using deep water raft systems to monitor soluble salts and pH every day.

“In terms of taking action with deep water raft systems such as adjusting the fertilizer strength that can be done on a weekly basis,” he said. “Adjusting the pH can be done daily or every two to three days. But that is better than with NFT systems that need continuous monitoring. Sometimes for nutrient management in NFT systems there is a need to do pH management every day if not several times a day. Some people have automated inline pH and EC sensors with peristaltic pumps that turn on automatically to add acid to the water reservoir or add fertilizer solution. Typically with NFT systems there is a much smaller water reservoir in relationship to the plant surface area that is growing.”

Mattson said monitoring whether growing in a deep water or NFT system is especially important in the early stages of growth.

“The young plants are the most valuable because they are initially at a high density,” he said. “The young plants need to get off to a good start because growers will never be able to recover that growth,” he said. “If growers start with poor plants, they are never going to achieve the optimum plants they are trying to harvest. Growers should focus on their crops more closely when they are younger.”

Mattson said lettuces, leafy greens and herbs are the most common crops grown in deep water systems.

“I have also seen growers grow microgreens with raft systems,” he said. “The microgreens are seeded onto substrate mats on top of the rafts. The growers add some weight to the rafts so the microgreens sit lower and are in constant contact with the water. This method has worked well for microgreen growers using pond systems.”

Maintaining water quality

Mattson said deep water raft systems typically don’t require as elaborate a water treatment system as NFT systems.

“There could be a benefit for water disinfestation for the raft systems, but growers in practice aren’t really using that for a couple of reasons,” he said. “A grower can’t easily sanitize a whole pond at one time. All the grower can do is pump out water and run it through a disinfestation system and then pump it back in. A grower is never completely getting rid of all of the disease organisms.

“Some of the water is being taken out, treating it and putting the water back in and then taking up more of the pond water. A grower never fully gets rid of the disease organisms. More commonly with DWC, growers will periodically pump water out and sanitize a whole pond before refilling with a nutrient solution and transplanting.”

Mattson said growers using hydroponic systems often have algae problems because algae will also access the water and nutrients.

“Algae make their own food,” he said. “They photosynthesize and use light to make their own energy. Algae will grow and become established naturally wherever there is light, moisture and a source of nutrients. If light can be excluded from a surface this can help to deter algae formation. When sunlight hits uncovered pond water there is a food source for algae. This can occur whether a grower is using conventional or organic fertilizers. This can also occur with NFT systems if the channels aren’t covered. If the channels are exposed to light where water and the fertilizer solution trickle down, algae starts growing very quickly.

“If light can be excluded from a surface this can help to deter algae formation. If a grower is using a pond system he doesn’t want to leave the pond water exposed to light. The water is covered with dummy rafts until that space is used again.”

Mattson said growers who keep reusing the same pond water have found they don’t normally run into problems with root diseases if temperature and dissolved oxygen are at optimal levels.

“There are communities of beneficial microorganisms that become established in the pond water that naturally suppress root diseases,” he said. “Even with the establishment of the beneficial microbes, growers need to maintain the dissolved oxygen level to near saturation (about 8 parts per million O₂ at room temperature) in the pond water to keep the plant roots and beneficial microbes actively growing.

“Growers can bubble in air or can inject pure oxygen into the water. It is also important to circulate the pond water so there is a uniform gradient related to temperature, pH, fertilizer and oxygen.”

Mattson said the Cornell University Controlled Environment Agriculture group found good plant performance in a 1,500-square-foot pond where water was recirculated and distributed through manifolds in the pond. Pumping capacity achieved a complete water recirculation exchange every 12 hours.

Monitoring water temperature

Water temperature can also be an issue with lettuces and leafy greens grown in warmer climates.

“The best water temperature is around 68ºF so even if the air temperature increases it helps to delay bolting of lettuce and helps to reduce disease organisms,” Mattson said. “Water heats up much more quickly in a NFT system than in a deep pond system. The NFT channels are not insulated. The NFT water is in contact with a large surface area so it starts heating up quickly if the air temperature in the greenhouse is warm.

“A pond is usually well insulated. Often the outer edge and the floor of the pond will be insulated. There are also the polystyrene rafts that float on top of the pond so the pond does not heat up very quickly.”

Despite having a beneficial microbial community in the water, Mattson said every once in while root disease can develop in the pond. Pythium is the major root disease.

“Usually it’s because of warm water temperatures that occur under summer conditions,” he said. “This can be a major issue for the grower who has to drain the pond, scrub and remove any debris, use a disinfesting agent and then refill the pond. The whole time the pond is being cleaned it can’t be used for growing a crop.”

Mattson said with NFT systems it is imperative to have a backup electrical source and pump backup because if there is an electrical outage or a water pump breaks then the plants can dry out within hours.

“In a pond if the power goes out, there is a concern about controlling the greenhouse temperature, but the plants are sitting in water and have access to plenty of nutrients,” he said. “The supply of dissolved oxygen could become depleted or run out, but that would take days if not weeks for that to happen. It is a much more robust system in that way.”

Fertilizer considerations

Mattson said growers who are considering using organic fertilizers with either NFT or deep water raft systems need to be aware of issues inherent with the source of the nutrients.

“I have tried organic fertilizers in a pond system and found that biofilm grows very quickly,” he said. “Organic fertilizers are byproducts of plants and animals. The biofilm microbes use the carbon in the organic fertilizers as a food source and use up a lot of the oxygen in the pond water. The microbes are respiring so it is difficult to maintain a good dissolved oxygen level in the water.

“The biofilm also quickly coats the plant roots making it more difficult for the plant roots to access oxygen and nutrients. They are not disease organisms, but the root system becomes coated with biofilm and the plants can’t grow. The biofilm is starving the plants for oxygen and nutrients. In a pond, the biofilm, which is floating in the water, will also coat all of the surfaces in the pond including the walls and the rafts.”

Mattson said another benefit of a NFT system in reducing biofilm buildup is the continual flow of water.

“There could still be biofilm and some coating, but the water in a NFT system is saturated with dissolved oxygen that is continually moving though the root zone,” he said. “That helps to deliver oxygen to the roots. There still may be some biofilm formation in the channels, but not nearly as much as in a pond.

“Growers who are using a NFT system and organic fertilizer are more used to starting a new crop over and over again. It’s up to the growers whether they want to start fresh with each crop cycle. Draining the reservoir after each crop cycle, cleaning the channels and the reservoir and sanitizing fits better with NFT systems. Growers using pond systems are not going to want to drain and clean the pond every crop cycle. That is very wasteful in terms of water and fertilizer and is labor intensive.”

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.

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

Regardless of the crop being grown or the irrigation system being used, growers face the same issues related to water quality, nutrient delivery and nutrient uptake.

One size doesn’t fit all when it comes to fertilizing plants. Regardless of the crop being grown, whether ornamental or vegetable, different species have a nuance in what they require when it comes to fertilization, said George Murray, tree crop and horticulture specialist at Brandt Consolidated, Inc.

“Fertilization requirements can depend on the cultivar, on the growing conditions, on the substrate and the pH,” Murray said. “Once you start looking at specific crops and the different stages of the life cycle of a crop, you’re going to have to look at making changes to the nutrient solution.

“For leafy greens you can use the same fertilization solution through the whole production cycle from day one. There is no reproductive cycle that the crop is going through. The crop may start out at a lighter concentration when the plants are seedlings and then increase the rate when the plants are put out into the production system. For crops like tomatoes and cucumbers, a grower will switch to different nutrient solutions as plants move through the different stages of a crop’s life.”

Simple vs. sophisticated

Murray said the way growers fertilize their crops can vary from simple delivery equipment to sophisticated automated systems.

“Some growers use very simple fertilizer delivery systems and others have very high tech systems that are computerized and automated,” he said. “Bottom line, as long as you are able to control your parameters such as the parts per million and the nutritional output, basically the plant isn’t going to know the difference. What will make a difference is the labor you are putting into it, the input costs, and the costs it takes to maintain the equipment or system. The input costs and the costs it takes to maintain the equipment or system. The plant doesn’t know how the fertilizer is delivered and what kind of technology is used.”

Murray said those growers who are using automated systems know the parameters that they need to be at and depend on the technology they’ve installed to replicate those set points.

“A grower has to be at a certain size in order to cover the overhead expenses, those fixed costs, for that technology,” he said. “For the grower who prefers to grow by “feel,” there are probably going to be times during the production cycle where there is over fertilization as well as under fertilization. These growers are also not going to know what their true costs are, both in materials and labor. Consequently, these growers may not make as much money as they could.”

Murray said that technology can also have its limits.

“When trying to determine what is a causing a problem with a crop, in some cases, the grower who is growing by “feel” might have a better understanding of the science behind what problems to look for,” he said. “The grower who is producing on a large scale with computer inputs may be too far removed from a crop to understand what is going on from a nutritional or disease standpoint. It’s really a case by case situation.”

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Impact of water quality

Murray said the biggest problem growers have regardless of their irrigation system or level of greenhouse technology is water quality.

“The water pH dictates so much of what ends up in the plant and in what quantity,” he said. “With a lot of the fertilizer mixes when there is a high water pH, the micronutrients are not going to be available to the crop. It is really important since growers are using a lot of nitrogen-based fertilizers which tend to raise the pH of the rhizosphere, which is the area around the plant roots. What are the nutritional sources as well and how do they react separately and to the environment? Sulfate-based micronutrients are not protected as well as EDTA-based micronutrients and will be less available to plants when the pH starts to climb.

“Growers looking at installing a closed loop irrigation system need to first look at the quality of their water source. Water quality is going to affect what nutrients the plants are going to take up and how much they are going to take up. Sometimes nutrients are not in a format that is readily available to the plants.”

George Murray said growers need to know:

• What nutrient levels are in the water. • How much of the nutrients will have to be added.
• What nutrients are available to the plants that are in the water.
• How much of a nutrient is going to have to be added in.

“Growers who are using more of a traditional watering system like drip irrigation with a soilless growing medium, there is some buffering of the pH in that medium,” he said. “Changes to the pH are going to occur a lot more quickly in hydroponic situations and symptoms of those changes also will appear more quickly. A closed loop system is kind of a double-edged sword. There aren’t concerns with a poor substrate structure and those types of issues. But at the same time there aren’t any buffers or safeguards either.”

Maintaining a nutrient balance

Murray said once a grower has resolved any issues with water quality, then the nutrition-related factors the grower would be dealing are similar regardless of the crop grown or the type of irrigation system used.

“The amount of calcium in water tends to be relatively high,” he said. “Phosphorus interacts with calcium, magnesium and iron in the soil. A concern is what happens to that interaction in a closed loop system without a substrate. Up until now most of the research that has been done with the phosphorus cycle has been done with phosphorus in the soil. What needs to be determined is how does phosphorus move in a closed loop system.

Murray said growers need to be sure that they maintain a balance of micronutrients and macronutrients.

“There are certain sites on the roots where certain micronutrients and macronutrients are taken up,” he said. “Zinc, copper and nickel have the same uptake sites in the roots. If you have a higher percentage of one micronutrient and a lower percentage of another, say copper and zinc, if they are out of balance then deficiencies of one or the other occurs relatively quickly. From a closed system perspective, even though the soil may have been eliminated, the mechanics of the plant haven’t been eliminated. The plants are still taking up nutrients through the roots in the same way. Although a closed loop system may be more efficient and sustainable, growers need to understand that they have not eliminated the hurdles of the plant genetics, and more specifically how certain micronutrients move through a plant’s vascular system.”

Even with a closed loop system, Murray said there are still opportunities for foliar applications of nutrients when crops are flowering and fruiting.

“Boron is important in cell wall formation,” he said. “Boron can be in the water solution, but it can be immobile in the plants. Once boron is taken up by a plant, is it going to be where it needs to be when it needs to be there? Calcium deposition is also important in the formation of cell walls, especially in tomatoes. Just because there is calcium in the water doesn’t mean that it is going to get into tomato plants at the right time and be in the right place.”

For more: George Murray, Brandt Consolidated, Inc.; (812) 701-4076; George.Murray@brandt.co; brandt.co.

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