The speakers and topics are:

Dr. Jim Owen, USDA-ARS, Water in Ohio – nursery use and return including reservoirs

Dr. Sarah White, Clemson, Reservoir water quality and management

Dr. Jeb Fields, LSU, Substrates and water management

Dr. Jake Shreckhise, USDA-ARS, Irrigation frequency and container color affect substrate temperature and controlled-release fertilizer longevity

Dr. Garrett Owen, OSU, Basics of substrate pH and soluble salts sampling and monitoring

Dr. Raul Cabrera, Texas A&M, Managing soluble salts in nursery and greenhouse production

Dr. Amy Fulcher, UT-Knoxville, TBD

Click here to enroll: https://cfaesosu.catalog.instructure.com/courses/water-management-and-quality-for-greenhouse-and-nursery-crop-production

Carson, CA — NovaCropControl, an industry-leading research and testing centre based in the Netherlands, has completed its independent study evaluating the impact of chemical-free nanobubble enriched irrigation water on tomato fruit growth, pathogen control, and nutrient uptake.

In a side-by-side study, NovaCropControl irrigated plants with technology provided by Moleaer, the global leader in nanobubble technology. Plants irrigated with Moleaer’s nanobubbles had:

• More efficient nutrient uptake and water usage
• Improved capillary root development
• Increased resilience to high heat
• Reduced Pythium levels of up to 80%

The study also showed plants irrigated with Moleaer nanobubble enriched water produced a 9% increase in fruit weight without sacrificing nutrient content or BRIX value (grams of sucrose). 

Tomatoes provide a rich source of vitamins A, C, K, and minerals, including iron and phosphorus, making them one of the most popular and valuable crops grown in greenhouses. 

Moleaer’s patented nanobubble technology is installed at over 200 horticulture facilities, enabling growers to enhance existing irrigation water, promote beneficial bacteria, suppress pathogens and diseases, and increase nutrient uptake.

Moleaer delivers these results by providing a consistent flow of nanobubbles to the plant’s roots to maintain high oxygen levels in irrigation water and deep water culture (DWC) systems. Increased root zone oxygenation through nanobubbles increases plant nutrient uptake. The outcome is healthier, more resilient plants, increased crop yields, and decreased time to cultivation.

“We know that improving water quality through increasing sufficient oxygen levels are important for plant health and crop resilience. Our trial confirmed that Moleaer’s oxygen-filled nanobubbles are a very efficient method of delivery,” said Koen van Kempen, Consultant, NovaCropControl Research Center.

“Nanobubbles are a complex science, but this latest third-party research demonstrates in the simplest of terms the value nanobubbles provide to our food supply by enhancing water quality, without using chemicals, to improve plant health and resilience to environmental stress, which ultimately leads to increased crop yields,” said Nicholas Dyner, CEO of Moleaer.

For more information, please visit moleaer.com.

About NovaCropControl

NovaCropControl is a research and test centre specializing in plant sap analysis. NovaCropControl aims to provide insight into the plant‘s nutrient uptake with a fast and accurate service based on low cost. To reach that goal, NovaCropControl uses plant sap analyses and, if necessary, in combination with (ISO-17025) accredited drip, drain or substrate water analyses. To learn more, visit: www.novacropcontrol.nl/en/method

About Moleaer

Moleaer^TM is an American-based nanobubble technology company with a mission to unlock nanobubbles’ full potential to enhance and protect water, food, and natural resources. Moleaer has established the nanobubble industry in the U.S. by developing the first nanobubble generator that can perform cost-effectively at municipal and industrial scale. Moleaer’s patented nanobubble technology provides the highest proven oxygen transfer rate in the aeration and gas infusion industry, with an efficiency of over 85 percent per foot of water (Michael Stenstrom, UCLA, 2017). Through partnerships with universities, Moleaer has proven that nanobubbles are a chemical-free and cost-effective solution to increasing sustainable food production, restoring aquatic ecosystems, and improving natural resource recovery. Moleaer has deployed more than 700 nanobubble generators worldwide since 2016. To learn more, visit: www.Moleaer.com 

About nanobubbles

Nanobubbles are tiny bubbles, invisible to the naked eye and 2500 times smaller than a single grain of table salt. Bubbles at this scale remain suspended in water for long periods, enabling highly efficient oxygen transfer and supersaturation of dissolved gas in liquids. Nanobubbles also treat and eliminate pathogens and contaminants of emerging concern as well as scour surfaces to break apart biofilm matrices, creating a powerful, sustainable, and chemical-free disinfectant (Shiroodi, S., Schwarz, M.H., Nitin, N. et al., Food Bioprocess Technol, 2021). 

By Jim Lauria, Mazzei Injector Company

In indoor crop production systems, water is vital for crop growth, handy for delivering nutrients and other inputs…and a major cost. As a result, managing every drop of water—and every ounce it carries, whether it’s a biodynamic compost tea or a conventional crop protection product—is critical to maintaining a healthy bottom line.

As closed-system farms become ever more precise, their owners are assessing their choices with an eye toward maximizing precision and efficiency. That has led many to struggle to choose between water-run pumps and venturi injectors for dosing and mixing inputs into their water.

Comparing Technologies

Both water-run pumps and venturi injectors operate on long-established technologies. Water-run pumps use pressure from irrigation flow to lift an injector piston, drawing in a known dose of fertilizer or chemical before it is forced back down by a spring and delivers the dose into a sealed chamber. Injection rates are calculated as a ratio to the flow of irrigation
water through the main line.

Venturi injectors use line pressure to constrict flowing water in a conical inlet chamber, then release it into a cone-shaped outlet port. As the flow expands in the outlet port, it creates a vacuum that draws in nutrients, chemicals or air and mixes it thoroughly. Injection in venturi systems is measured in percentages, parts per million, or gallons per acre.

While water-run pumps require regular replacement of seals and springs, venturi injectors contain no moving parts, so there is minimal wear and virtually no maintenance. The difference is apparent in both acquisition cost and maintenance cost, says John Petrosso, agriculture sales engineer for Mazzei Injector Company.

“A greenhouse can put in four pumps with a manifold, or they can put in venturis for the cost of the rebuild kits the pump manufacturers recommend buying every 12 months,” he explains. He adds that venturi injectors may be specified in sizes ranging from 0.5 inches to four inches, allowing growers to precisely size their venturi injection system to their needs.

Petrosso points out that venturi injectors blend injected materials more evenly than pumps do—a huge advantage in improving precision and reducing physical footprint.

“With a pump, every time that piston goes up, it’s sending out a pulse, where with a venturi you have a more homogeneous mixture that’s going out into that irrigation system,” he explains. “That’s why you’ll also see that water-run pumps usually require a mixing chamber or static mixer. It’s also why pumps can be incompatible with biological products like compost teas or microbial pesticides—the pistons can exert a lot of force and tear up microbes.”

Aeration Excitement

One of the most exciting applications of injection systems is aerating the crop root zone. Petrosso says a recent study at the Center for Irrigation Technology at California State University, Fresno and Memorial University of Newfoundland, Canada, suggested that AirJection® improved nitrogen use efficiency, lowered the potential for NOx production, and created an aerated environment that tipped the soil’s microbial population toward aerobic bacteria that correspond with crop vigor and growth.

“Most urban and indoor farms aim to set a higher standard for food quality and sustainability,” Petrosso says. “Venturi injectors take those benefits a step further as the ultimate complement to sustainable systems. They allow growers to fine-tune their input use, gently and efficiently mix even the most sensitive biological products, and they literally go with the flow, minimizing energy consumption.”

This comprehensive summary is an essential information for indoor farming! February Indoor Ag Sci Café focused on water quality and biofilm for indoor production.

Dr. Fisher discussed characteristics of different source water and their potential issues (alkalinity, chlorine, salinity, and pathogens) as well as mitigation measures. Key steps of biofilm management was introduced and efficacy of different commercial products was discussed.

Indoor Ag Science Café is an outreach program of our project OptimIA, funded by USDA SCRI grant program (http://www.scri-optimia.org). The café forums are designed to serve as precompetitive communication platform among scientists and indoor farming professionals.

The Café presentations are available from the YouTube channel. Contact Chieri Kubota at the Ohio State University (Kubota.10@osu.edu) to be a Café member to participate.

University of Florida Greenhouse Training Online courses 

Our last Greenhouse Training Online courses for 2019!

Weed Management

Earn CEUs

An intermediate level course that teaches all aspects of weed management in nurseries and greenhouses, including weed identification, developing herbicide programs, and the latest non-chemical methods of weed control that work.

Irrigation Water Quality & Treatment

An advanced level course that helps interpret water quality tests for irrigation of greenhouse and nursery crops, select appropriate water treatment technologies, and design a water treatment and monitoring system.

Both courses run from November 4 to December 6, 2019, are offered in English and Spanish, and include a personalized certificate of completion. Weed Management has been approved for CEUs in several States. Each course has a cost of $US199 per participant, with discounts if you register 5 or more. The last day to register is November 11, 2019. Over 4 weeks, there are streaming video lessons, readings and assignments, 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/.

If you are growing crops hydroponically in deep-flow or raft systems, one of the last things you want to see is an unusually low or empty tank. It is not uncommon for nutrient solution levels to be reduced by evaporation and transpiration, but when levels decrease rapidly, there may be a larger issue.

A common issue in nutrient film technique (NFT) or with drip systems is a leak from the tube delivering the nutrient solution. Another possibility is a crack in a tank or tube. However, what could be the cause if you do not see a leak? A less-intuitive issue that may occur is siphoning.

Watch out for siphoning if you are using air stones or tubes for oxygenation in deep-flow or raft systems or reservoir tanks. Siphoning may happen if the air pump is not supplying air flow due to a broken tube or the power going out. If the nutrient solution is siphoned into the pump, damage to the pump may occur. Siphoning may also be a result of air stone tubes breaking or coming loose from the air pump.

To prevent this issue, position air pumps higher than the nutrient solution reservoir. This will stop siphoning from a pump or power failure. However, if the tubing becomes loose, cracks, and falls outside of the tank beneath the water level siphoning may still occur. If feasible, consider installing in-line back flow prevention valves. Be aware this may be a problem and, if the nutrient solution is suspiciously low, check for siphoning.

About the Author:
Kellie Walters and Roberto Lopez Assistant Professor and Floriculture/Controlled Environment Extension Specialist(Michigan State University), and PhD candidate (Michigan State University), Roberto G. Lopez is an Assistant Professor and Floriculture/Controlled Environment Extension Specialist at Michigan State University. He has an appointment in research, teaching and extension. His area of expertise is; controlled environment specialty crop production; Lighting applications for greenhouses and indoor vertical production; light-emitting diodes; young plant propagation.

Nursery and greenhouse growers comprise an important sector of United States agriculture that is uniquely situated to conserve water while growing plants that provide many social and environmental benefits. In order for Extension professionals to effectively help growers use water conservation technologies, it is important to understand the knowledge level and adoption rates growers have surrounding different water conservation techniques. It is also important to understand how grower perceptions of water conservation strategies relate to their adoption. In this publication, we present results of a study designed to understand the knowledge level, adoption rate, and levels of continuance associated with eight water conservation technologies among nursery and greenhouse growers. We also examined whether five characteristics of these technologies (trialability, complexity, compatibility, relative advantage, and observability) predicted grower adoption.

Click here to read the publication: https://www.cleanwater3.org/research.asp

This is taught at an advanced level, designed for an experienced grower or technical manager. Lessons are offered in English and Spanish, and are taught by professors from six universities in the United States.

The course runs from November 5 to December 7, 2018. It costs $US 199 per participant, and includes a personalized certificate of completion. Over 4 weeks (no classes over Thanksgiving week), there are streaming video lessons, readings and assignments. The 3 to 4 hours of lessons and activities each week can be accessed at any time of day. Bilingual PhD instructors are available via discussion features. 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 Dept., University of Florida, USA, by emailing greenhousetraining@ifas.ufl.edu.

This course is supported by the Specialty Crop Research Initiative project ‘‘Clean WateR3 – Reduce, Remediate, Recycle’’, #2014-51181-22372, from the USDA National Institute of Food and Agriculture. Spanish translation is supported by a grant from the American Floral Endowment.

Irrigation Water Quality PDF Flyer

This tool interprets the quality of a water source to irrigate plants in greenhouses and nurseries, and is available in English and Spanish.

Link to the WaterQual Tool

Clean WateR3 is a federally funded Specialty Crops Research Initiative grant focused on research and outreach to help growers Reduce, Remediate and Recycle irrigation water. The grant team is managed by Dr. Sarah White at Clemson University and includes many research collaborators.

Clean WateR3 – Reduce, Remediate, Recycle

Our projects focus on developing sustainable remediation technologies to encourage use of alternative water resources, especially recycled irrigation runoff, to decrease dependence on potable water, and enhance long-term economic viability. This is possible thanks to an award from the National Institute of Food and Agriculture Specialty Crop Research Initiative, and the involvement of 22 researchers in 9 universities. The objectives of this project are to:

• Reduce contaminant loading into recycled water sources via treatment technologies and improved water management strategies.
• Evaluate treatment technologies (physical and biological) to Remediate pathogen, pesticide, and nutrient contaminants.
• Provide online and published information to help growers successfully Recycle water.

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 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.

With continuing concerns about water availability, safety and regulations, more growers are looking at water treatment to protect this vital resource.

The United Nations’ Intergovernmental Panel on Climate Change is scheduled to release a report on the impact of climate change in March 2014. A leaked copy of the final draft identifies key risks that could occur because of climate change. One of these key risks is related to the lack of availability of drinking and irrigation water to farmers and the impact it could have on their livelihood. The draft indicates that increasingly rising temperatures will reduce renewable water sources. Climate change is also expected to reduce raw water quality and to pose risks to drinking water quality. e panel advises that “adaptive water management techniques” could address the uncertainty caused by climate change.

Rising concerns over water availability and the potential for increased legislation related to water issues are causing more growers to look more closely at their water supplies. Proactive growers are determining how they can better use and protect their sources of water.

For many greenhouse vegetable growers collecting, recycling and reusing their water is critical to the success of their business. e increasing focus on food safety issues is also causing growers to examine the impact water treatment can have on the production, harvesting and handling of their crops.

The recycle movement

Charlie Hayes, founder and president of Advanced Treatment Technologies, said an in- creasing number of people in the greenhouse industry have accepted the fact that water will eventually have to be recycled.

“Some growers are already recycling their water and long term I think everyone will have to be moving in that direction,” he said. “Unfortunately, mistakes in how to accomplish this are going to occur. Growers stand the chance of damaging their whole crop with different forms of contaminants or with disease-causing organisms through recycling water that has not been effectively and appropriately treated.

“Understanding water treatment involves a lot of things, including types of filtration, types of oxidizers, dissolved oxygen levels, what is being le in the water and what is be- ing taken out of the water. A grower can take too much out of the water. For example, if a grower uses reverse osmosis, it puts a much bigger onus on him to make sure the proper nutrients for the plants are reintroduced into the water. is will require much more test- ing because there are some micronutrients in water that growers don’t consider when they are looking at fertilizers. Using RO water that is devoid of all ions will require a grower to make sure he puts back the nutrients that the plants are going to need.”

The goal of water treatment

Hayes said it doesn’t matter whether growers are producing edible or ornamental crops, they want the best quality water they can get for their plants.

“Looking at the incoming water for food crops, increasing regulatory mandates are requiring growers have potable quality water if it has the potential to ever contact the surface of the plants,” Hayes said. “ is could happen in any irrigation system that greenhouse vegetable growers are using, including troughs or channels and floating pond systems. e type of irrigation system won’t impact the quality of the incoming water, but if the water is in a closed loop system, the type of crop and production method will impact the water treatment system.”

Hayes said the goal of water treatment in most industries is twofold: 1.) to keep equipment, piping and delivery systems clean and 2.) to kill the potential pathogens in the water.

“My water treatment goal is very different,” he said. “My goal is to deliver water that is going to produce the healthiest plants possible. I have learned over the nearly 30 years of being a biochemist and studying water treatment that accomplishing that goal will take care of the other goals related to mechanical issues and the destruction of potential plant pathogens.”

While incorporating chemicals into their water supplies can keep the growers’ equipment clean and control pathogens, Hayes cautions that these same chemicals can have an adverse effect on the growers’ plants.

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“Plants can be sensitive to oxidizers,” he said. “Even though growers may not be seeing any negative effects on the plants, these chemicals may be affecting plant growth. The beneficial microbes around the plant roots may also be negatively impacted.”

Hayes said the most common oxidizers used for greenhouse vegetable crops include different forms of chlorine, chlorine dioxide, ozone and peroxide.

“Some oxidizers are more prone to phytotoxic effects than others,” he said. “With all oxidizers, it is a case of what is the target level, what level is being taken up by the plants and how well can that level be controlled? Many growers don’t understand and know what level of oxidizer residual is being delivered to their plants. is can occur with any of the oxidizers. e control system that is used to inject and monitor the oxidizer is critical. Some oxidizers are very pH sensitive and in order to work correctly the pH has to be within a narrow range. Other oxidizers create byproducts that can be phytotoxic or have negative effects on the plants depending on what inorganic or organic compounds are in the water.”

Avoid a pieces-parts system

Hayes said a common mistake made by growers trying to install a water treatment system is they look at it as a component purchase.

“A grower thinks he needs a filter so he buys one and installs that into his irrigation system,” he said. “ Then the grower may consider adding an oxidizer to treat the water and adds that to his system. What eventually happens is the grower has installed a conglomeration of components that are dispersed throughout his system that were never designed to work together. Some of those components can cause problems for each other and sometimes they can leave gaps in the system.”

Hayes advises growers considering treating their water to work with companies that design water treatment processes and are not simply trying to sell treatment components.

“Very often growers don’t have the upfront capital to install a water treatment system all at once,” he said. “What I do is work with growers to determine where they are currently, where they could potentially be and determine the steps necessary to get them there, allowing them to take the right steps in the right order.”

Hayes said the process usually begins with the water source.

“Many growers are pulling from ponds that are collecting rain water runoff from their greenhouses,” he said. “It could start with something as simple as aerating the pond. en the grower might add beneficial organisms to the pond in order to prevent the buildup of pathogens and to ensure the breakdown of nutrients that need to be removed from the pond. By having a well-designed and well-thought-through plan growers can gradually and continually improve their water quality as they invest in their water treatment system.”

Monitoring is critical

Hayes said water sources change and they can get better and worse.

“Water sources can swing back and forth in the types of contaminants and pathogens that they contain,” he said. “ ese things should be monitored. Growers need to know their source water quality during the summer and winter. In addition, when growers do something to manipulate the water quality, they need to test, verify and monitor the water. If growers are not monitoring their water, they will never know that changes have occurred. They will see problems in the crop that they can’t explain because they weren’t monitoring their water quality both during and a er the treatment process.

Hayes recommends that growers monitor their in- coming source water twice a year. “Growers should monitor during the driest time and the wettest time of year because the water table goes up and down,” he said. “I recommend growers monitor the treated water in the greenhouse on a continuous basis. If not on a continuous basis, the water quality should be checked daily.”

Don’t forget maintenance

Jerry van Kampen, inside sales support at Priva North America Inc., said one of the biggest adjustments some growers have to make a er installing a water treatment system is maintaining the system.

“For those growers who installed a water treatment system, they went from not having to do anything to now having to maintain it to ensure it operates optimally. Maintenance of the system needs to be ongoing. Growers should also step up their water quality analysis once they have a treatment system in place.”

van Kampen said even if a grower’s water treatment system consists of only installing a filter, the filter will require regular maintenance to perform at its optimal level.

“Installing a filter is the easiest way to go,” he said. “Maintaining the filter will result in less maintenance in the greenhouse or the eld. The water will be cleaner so valves won’t stick as o en and the irrigation drippers won’t clog as much. But the filter is going to have to be maintained in order for it to be effective.”

For more: Advanced Treatment Technologies, (855) 696-6348; http://advancedtreatmenttechnologies.com.

Priva North America Inc., (903) 562-7351; http://www.priva.ca.

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

The United Nations’ Intergovernmental Panel on Climate Change is scheduled to release a report on the impact of climate change in March 2014. A leaked copy of the final draft identifies key risks that could occur because of climate change. One of these key risks is related to the lack of availability of drinking and irrigation water to farmers and the impact it could have on their livelihood. The draft indicates that increasingly rising temperatures will reduce renewable water sources. Climate change is also expected to reduce raw water quality and to pose risks to drinking water quality. The panel advises that “adaptive water management techniques” could address the uncertainty caused by climate change.

Rising concerns over water availability and the potential for increased legislation related to water issues are causing more growers to look more closely at their water supplies. Proactive growers are determining how they can better use and protect their sources of water.

For many greenhouse vegetable growers collecting, recycling and reusing their water is critical to the success of their business. The increasing focus on food safety issues is also causing growers to examine the impact water treatment can have on the production, harvesting and handling of their crops.

>>> Read the whole article from Issue 4 here