Fortunately and unfortunately there are so many ways to manage pathogens in a hydroponic nutrient solution. Having options is great but these options can be difficult to navigate for new growers. Hopefully this overview comparing three popular management styles makes it easier to understand the tradeoffs between each.

Pictured above: Rhizoctonia and other root rot pathogens can spread through a recirculating hydroponic nutrient solution infecting all susceptible crops. Sterilization methods can help reduce the spread of spores in the nutrient solution while microbial inoculants can help reduce the chance of infection in individual plants.

Nutrient Solution Disease Management

There are many more decisions to make after selecting a general management style. For biological or hybrid technique, what inoculant and where should it be applied? For sterilization or hybrid, what is the best sterilization method for the specific farm design and what constraints can inform that decision? 

For more information on the many options for managing pathogens in a recirculating nutrient solution I recommend reading “Disinfestation of recirculating nutrient solutions in greenhouse horticulture” by David Ehret, Beatrix Alsanius, Walter Wohanka, James Menzies and Raj Utkhede. For more information on the many other considerations when designing a hydroponic farm for leafy greens production I recommend reading “Roadmap to Growing Leafy Greens and Herbs” by Tyler Baras (that’s me!).

To continue the conversation, email us and schedule some time with either Chris Higgins or our newest grower consultant Tyler Baras (aka The Farmer Tyler.)

In the faceof climate change, rising populations, rapid urbanization – and a global pandemic – cities face increasing pressure to forge new partnerships and attract innovative solutions to guarantee thefood security of their residents.

• Unique virtual experience: an emphasis will be placed on driving engagement amongst viewers through our interactive platform and solving for the “virtual fatigue” through crisp, pre-edited content and a concise daily agenda.
• Peer-to-peer connections: interact through virtual networking groups, private 1-1 chat, and live Q&A forums.
• Global audience: consisting of AgTech startups, investors, new & expanding farmers, technology providers, urban planners, corporates, city officials, and more.
• New insights: You’ll hear honest takes from leaders in the industry and gain first access to newly released reports, including Agritecture’s Global CEA Census.

Check out the great line-up of speakers!

For anyone that has called me to discuss the design of their new vertical farm or greenhouse, they have probably grown quickly tired of me using the term buffer capacity.  But, of everything I have learned over the past 25 years, the understanding of “buffer capacity” might possibly be the most important.  It makes your production system easier to manage, more predictable and more stable.  All traits that can be found in all successful farming and commercial horticulture production facilities.  (You might remember my recent article on simplicity, well this goes right back to that.)

Let’s start by agreeing that I am not properly using the term buffer capacity which is normally defined as the moles of an acid or base necessary to change the pH of a solution by 1, divided by the pH change and the volume of buffer in liters; it is a unitless number.  A buffer resists changes in pH due to the addition of an acid or base though consumption of the buffer.

Now let us focus on how we can manipulate that definition to fit the needs of designing a greenhouse or an indoor farm.  When referring to buffer capacity in our production environment we are referring to our system’s ability to keep key elements (temperature, humidity, wind, nutrients, light, CO2, oxygen, water) from fluctuating unless we as the grower determine that we want it to and have the ability to manipulate these key variables while keeping the others in balance.

The ability to keep key elements from fluctuating unless the grower determines that the variables should be adjusted to produce a crop response.  Adjustments should be met with the abilities to keep all other elements in balance.

For this article I am going to use (3) examples of how designing “buffer capacity” into your farm  will lead to better production and more consistency.

Greenhouse Structure.

For those starting to investigate different greenhouse types and designs or for those that have already gone through the process, I think we can all agree that the choices are limitless,  and for the most part the look of the greenhouse has not changed much of the years with one major exception.  They have gotten much taller.  Taller greenhouses provide a more uniform, stable and ultimately superior growing environment for the crop. During hot weather (as an example), the additional  space creates a buffer that avoids trapping heat and humid air around the plants.

Water holding tanks and nutrient solutions reservoirs

For beginning growers this is the area where the right decisions might provide the biggest advantages.  Experienced growers may choose to size their systems differently depending on their budget, crop and space but one thing is for sure, they will make sure that they have ample water availability as well as on demand storage to respond to changing crop needs.

Larger tanks and reservoirs (as compared to the amount of plants in the system) have a considerable buffer before they will run out or need to be dumped.  The most obvious benefit is that of ensuring the tanks don’t run dry and cause extensive damage to the pump(s) or loss of crops and production.  The most important benefit might be a properly sized system’s ability to keep the nutrient solution from having big erratic swings in EC and pH.

Substrates.

Hydroponic substrates provide an (additional) reservoir for water, a place for plants to take up nutrients, an area for the plant to develop a sufficient root system as well as location for gaseous exchanges.  A good grower will consider all the other decisions that he or she has made in building the greenhouse and designing the irrigation system then decide how much buffer capacity their substrate needs to provide.  If the buffer capacity of the irrigation system is limited, the grower may choose to use more substrate with a higher water holding capacity so the total system is more durable on hot summer days.  If the grower has a tremendous amount of confidence in their access to water, the responsiveness of their irrigation system and their ability to fix the system if they have problems then the grower might choose a substrate that they can steer thereby providing them more control in the greenhouse.

Growers should always choose a properly sized and engineered system.  The reality is that the budget will drive many of the growers’ decisions.  Understanding buffer capacity in the system will allow growers to get the most out of their investment while still focusing on consistent and uniformed crop production.

To continue the conversation, email us and schedule some time with either Chris Higgins or our newest grower consultant Tyler Baras (aka The Farmer Tyler.)

Next article.  Can indoor farming be profitable?.  Simple answer: of course.  Complexed answer it all depends.

Our last Greenhouse Training Online course for 2020!

The most requested course by participants of the award-winning Greenhouse Online Training program from University of Florida IFAS Extension is here! Learn to manage different hydroponics systems, as well as the fundamentals of climate, water, nutrition, and plant health in these systems. This intermediate course is designed for growers with some experience and training. Topics covered include hydroponics growing systems and structures, specific vegetable crop examples, business management, and food safety. The course is offered in English and Spanish.

The course is taught by a team of instructors from the University of Florida and Cornell University, which include Bob Hochmuth, Assistant Center Director for the UF/IFAS North Florida Research & Education Center at Live Oak and Regional Specialized Extension Agent for commercial vegetable crops, and Tatiana Sanchez Commercial Horticulture Agent for UF/IFAS in Alachua County. Bob and Tatiana along with other extension staff, collaborate to teach hands-on courses on hydroponics at the UF Small Farms Academy, a popular Extension program hosted at Live Oak since 2009. These popular hands-on trainings have been enjoyed by over 1,000 attendees from 20 states in the United States as well as 8 other countries.

The course runs from November 9 to December 11, 2020 (with a week break for the Thanksgiving holiday in the United States) 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 November 16, 2020. Over the 4 weeks of the course, 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/.

Jonathan Webb, founder and CEO of AppHarvest in Morehead, Ky., is a big believer in controlled environment agriculture. How big? His company is constructing a 60-acre state-of-the-art greenhouse facility in Eastern Kentucky to grow hydroponic tomatoes. Even though his background is in the energy sector, Webb said controlled environment agriculture is becoming a critical factor in solving many of the issues facing traditional field agriculture.

“During the last 15 years there was a transformation in the energy industry involving the rebuilding of energy systems across the United States,” Webb said. “Our team at AppHarvest believes there is an inflection point in agriculture right now where a lot of private sector capital will come into agriculture to utilize technology and infrastructure to rebuild farming in this country.

“What is happening in agriculture today reminds me of the energy conversations that people were having in the early 2000s. There were discussions about a world where we would have cars that wouldn’t run on oil and power plants that wouldn’t run on fossil fuels. I expect within my
lifetime we are going to see these things happen. The same thing is happening in the agriculture industry.”

With estimates of a 25-75 percent increase in food production needed by 2050 to meet the demands of the world’s growing population, Webb sees controlled environment agriculture playing a critical role.

“How are we going to grow more food with increased climate disruptions,” he asked. “More food is going to have to be grown in controlled environments. CEA is ever-evolving and there is going to be a continuous escalation of private sector dollars coming into farming in the U.S.
AppHarvest wants to be a player to move the industry forward.”

A greenhouse is not a greenhouse

Webb is quick to point out that not all controlled environment production is the same.

“Technology-infused and technology-focused controlled environment agriculture is not the same,” he said. “A greenhouse is not a greenhouse. A grower can operate a plastic hoop house with no lights and no environmental control and that can be called a greenhouse. At AppHarvest we are building a state-of-the-art facility that uses controlled environment technology. That is where agriculture is going and we want to be a part of it.”

“Part of our production focus is on sustainability and utilizing technology to build the most resilient systems possible,” he said. “Our focus on people and planet is core to the founding principles of AppHarvest. As the industry moves forward it is going to be a constant evolution.

The facilities that we will be building three to six years from now hopefully will be evolving even more beyond where we are at today.”

AppHarvest’s facility will be equipped with one the largest LED installations in the world. It will also be one of the largest greenhouse operations to run completely on recycled rainwater.

“There are other greenhouses around the world that maintain retention ponds, but this facility has been designed to run completely on recycled rainwater with no need for city water,” he said. “We will have no agricultural runoff as a result and we will be putting no wastewater back into the city sewer system.

“We are trying to move the needle forward and design the most efficient, resilient and sustainable systems possible. This facility will be a good benchmark for the CEA industry to go off of.”

Webb said AppHarvest is working with its utility partner to purchase energy from renewable resources.

“There is a lot of hydro-generated electricity in the area,” he said. “We are working with our utility partner to develop energy assets that would allow us to receive all of our energy from renewable resources. Jackie Roberts, who recently became our first chief sustainability officer, is going to be focused on making sure we are using the most efficient designs possible while making sure we receive energy from renewable resources.”

Having previously been involved in the energy sector, Webb expects his company will be involved with the development of additional renewable energy sources as future facilities are added.

“We are working with our utility partner and I’m confident there will be more solar-generated energy systems going into the state to support our energy demands,” he said. “These won’t be built on AppHarvest farms, but we are using our purchasing power to help move our utility partner forward with us.”

Why Appalachia?

Having grown up in Kentucky, Webb has a fondness for his home state. But that’s not the only reason he’s building the AppHarvest operation there.

“I worked in New York City and Washington, D.C., for about 10 years before moving back to Kentucky,” he said. “Picking Kentucky is far more involved than just having a passion for the place that I’m from. There are a lot of strategic reasons. One of which is we can reach about 70 percent of the U.S. population in a one-day drive. Our products will be on the store shelves of the top 25 grocers with deliveries to the Northeast, Midwest and Southeast.
“In this facility we will be hydroponically growing two different types of tomatoes, 30 acres of tomatoes on-the-vine and 30 acres of beefsteak tomatoes. We are trying to compete with large tomato production that is done either in open fields or indoor facilities and then are trucked for
six to eight days to Eastern markets.”

AppHarvest is planning to build additional production facilities in Eastern Kentucky.

“Our company is planning to focus on the central Appalachian area because of the number of markets we can reach within a one day drive,” he said. “Right now there is no reason for us to go anywhere else.

“The increased interest in and discussions about AppHarvest from investors and public officials are about the benefits of fruit and vegetable production in controlled environments. We’re able to use 90 percent less water and produce 30 times more yields per acre and not have to worry about
the climate disruption occurring with open field farming. We see controlled environment agriculture as a big part of the solution to the problems that are plaguing agriculture right now.”

For more: AppHarvest, info@appharvest.com; https://www.appharvest.com.

This article is property of Urban Ag News and was written by David Kuack, a freelance technical writer in Fort Worth, Texas.

HYDROPONICS 101 – Growing systems

Learn all the important aspects of growing crops hydroponically, from hydroponic growing system selection, best substrate options for your plants and how to create the proper environment to promote growth and development successfully.

Instructor: M.S. Karla Garcia

• Hort Americas Technical Service
• Master in Plant Sciences from The University of Arizona
• Recognition by ISHS in strawberry hydroponic research
• Editor: Book Roadmap to Growing Leafy Greens and Herbs
• CEO at Microgreens FLN

Date: Saturday, May 2, 2020

Schedule: 12 PM to 6 PM (Central Time)

Platform: ZOOM US

Price: $50 US

Once you have registered, we will make contact to provide access to our LIVE session.

Course Content

-Introduction to hydroponics

-Hydroponic systems

-Substrates

-Basics of plant nutrition and system monitoring

-Hydroponics system in leafy greens

a) Lettuce, culinary herbs and microgreens

-Hydroponic system in vine crops

a) Tomatoes, Pepper, cucumbers

BREAK

-Hydroponics system in strawberry

-Hydroponic system in cannabis/hemp

-Hydroponic system in ornamentals

-Introduction to plant response to environmental factors

-Introduction to artificial lighting

Each fully equipped, plug and play 20’ fully insulated container-based Clone Facility has a separate utility area and provides climate controlled vertical production space for cloning and mother plant storage. Each unit is specially designed for maximum efficiency and workflow. Besides our dedicated technology for the ebb and flow irrigation system installed, a state-of- the-art water monitoring and dosing system and high-pressure fog system, each production area is equipped with energy efficient LED production modules, offering wavelength and intensity specifically designed for cloning and vegetative growth. The LED environment for cloning provides light levels from 50 to 100 micromoles with an incremental increase as the plant becomes established and the Mother plant storage area provides up to 700 micromoles for faster vegetative growth. In addition, each clone factory provides a warm, humid LED lit micro climate for germinating seeds. Based on the current configuration, each unit is capable of producing 1080 4” pots per cycle or substantially more in standard 1020 trays.

We’re in the process of finalizing agreements with some of the world’s top Cannabis consultants to provide marketing, sales and technical support for our clients. We have already bought on board a Container modification expert with over 20 years of hands on experience to manage our agreement with the world’s largest container manufacturer to provide large quantities of ISO certified 20’, 40’ and 45’ Container Farms for quick deployment for all stages of growth in the food production, research and international cannabis market.

For more information contact us by email at GB@cea-advisors.com

BY THE COALITION FOR SUSTAINABLE ORGANICS

The Center for Produce Safety delivered a petition to the U.S. Department of Agriculture calling for the USDA to

1. Issue new regulations prohibiting organic certification of hydroponic agricultural production based on the National Organic Standards Board’s April 29, 2010 recommendation on Production Standards for Terrestrial Plants in Containers and Enclosures.
2. Specifically, amend 7 C.F.R. 205.105, Allowed and prohibited substances, methods, and ingredients in organic production and handling, to prohibit hydroponic systems.
3. Ensure that ecologically integrated organic production practices are maintained as a requirement for organic certification as defined by the existing OFPA regulations.
4. Revoke any existing organic certifications previously issued to hydroponic operations.

The petition defines “hydroponics” as “a diverse array of systems which incorporate, to some degree, containers that house plant roots in either a liquid solution or various solid substrates, including coconut coir, soil, compost, vermicompost, peat moss, bark, sawdust, rice hulls, potting soil and a number of other growing media.” In short, any production system that uses a container or tray or soil lining that isolates the roots of a plant from the outer crust of the Earth is targeted for decertification by the petition.

The petition states that the following groups support the decertification effort – The Cornucopia Institute, Food & Water Watch, Cultivate Oregon, Maine Organic Farmers and Gardeners Association (MOFGA), Maine Organic Farmers and Gardeners Association Certification Service, Northwest Organic Dairy Producers Alliance (NODPA), Organic Farmers Association (OFA), Northeast Organic Farming Association of Connecticut (CT NOFA), Northeast Organic Farming Association Interstate Council, Northeast Organic Farming Association of New Jersey (NOFA-NJ), Northwest (sic) Organic Farming Association – New York (NOFA-NY), Northeast Organic Farming Association of Vermont (NOFA-VT), and PCC Community Markets.

Here is a copy of the press release issued by CFS. The CFS did successfully bring legal action to overturn USDA National Organic Program guidance that allowed the use of compost made from materials collected under municipal yard clipping collection programs.

We have not heard any reaction from USDA at this time.

BY THE COALITION FOR SUSTAINABLE ORGANICS

Michiel de Jong has worked the past years as Sales Manager for Oreon, a leading horticulture LED manufacturer. In his role he has built an extensive network around the world in horticulture and has propelled Oreon’s current commercial success.

“We are thrilled to have someone with Michiel’s experience join our organization,” said Nick
Dyner, Chief Executive Officer of Moleaer. “Michiel will help us develop the European horticulture market, which is critical to Moleaer’s growth and success.”

“Like lighting, oxygen is a crucial element to every grower’s success,” said Michiel De Jong, Director of Business Development for Moleaer. “Moleaer nanobubble generators are robust and highly efficient and the company has already proven their leading role in research, product development and marketing. I look forward to introducing the benefits of Moleaer’s nanobubble technology to growers to help them increase production yields and reduce costs.”

About Moleaer

Moleaer develops industrial scale nanobubble generators to enhance a wide range of processes, enabling a radical change in the economics of indoor farming, metal separation, wastewater treatment and oil recovery. The Company’s nanobubble technology enables customers to increase productivity more responsibly by fundamentally changing how gases are utilized to enhance industrial systems, eliminate chemicals, save energy and treat water. Moleaer’s plug-and-play nanobubble generator has proven to help farms grow more crops, oil and mining companies recover more valuable resources, and industries efficiently treat water and wastewater.

By Eri Hayashi, Japan Plant Factory Association, Industry Expert

For anyone who believes plant factories (PFALs)/vertical farms are only for leafy greens or for anyone who has given up growing strawberries in plant factories, they may have to reconsider their way of thinking. There is a great future ahead for strawberries, especially after the Japan Plant Factory Association (JPFA) held its 96th monthly workshop on “Next-Generation Strawberry Growing System.”

The workshop gave participants the opportunity to learn what is happening in Japan’s commercial strawberry PFALs. Also during the workshop, academic researchers and research institutes provided updates on what they have been working on with state-of-the-art strawberry cultivation methods which further raised the excitement about the positive growth potential of strawberry PFALs.

Workshop topics

JPFA has been organizing workshops every month together with companies and academics/research institutes since 2009. Every session deals with different subjects and allows for the exchange of views from various backgrounds. During each workshop more than 100 PFAL-conscious farmers, companies, researchers and individuals invigorate the discussions.

The most recent workshop sessions included:

• LED grow lights. Product features were presented by seven of Japan’s major LED grow light companies to learn about each product’s characteristics based on real data that had been released by the companies.

• The real issues related to workability, operational management, sales and distribution confronting commercial farm operators. The details of actual experiences were talked about by large scale commercial PFAL farms. One of the topics covered was how these farms have overcome operational issues and improved their profitability after having received support from Chiba University and JPFA, etc. Unique vegetable suppliers and distributors shared their expertise with the attendees.

• Current situations on leading Japanese greenhouse farms (CEA).

Much more than education

On July 13, 2016, JPFA will be celebrating its 100th event in Kashiwa-no-ha campus. Japan Plant Factory Association (JPFA) is a non-profit association devoted to academic and business advancements in the plant factory/vertical farm/CEA industry. More than 10 consortium R&D projects are conducted in PFALs and greenhouse facilities onsite. Along with the monthly workshops, JPFA also offers training courses and intensive business session courses every month for professional growers and potential industry entrants. Business matching, consulting service, research activities and any collaborations are always welcome.

For more: http://npoplantfactory.org/english.html

]]> https://urbanagnews.com/blog/exclusives/japan-plant-factory-association-workshops-focus-on-plant-factory-production-business-issues/feed/ 0 3720 https://urbanagnews.com/blog/exclusives/using-water-driven-injectors-and-fertigation-for-greenhouse-production/ https://urbanagnews.com/blog/exclusives/using-water-driven-injectors-and-fertigation-for-greenhouse-production/#respond Fri, 01 Sep 2017 14:11:56 +0000 https://urbanagnews.com/?p=3533 Originally published in Issue 11

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.

Which are the best strawberry varieties for greenhouse production? Combining June-bearing and everbearing varieties can help ensure fruit is available during periods of premium pricing.

Trying to decide which strawberry varieties to produce in a controlled environment production system can be a challenge for growers using field-bred varieties. Mark Kroggel, research specialist at the University of Arizona’s Controlled Environment Agriculture Center in Tucson, said it is possible for growers to produce strawberries nearly year-round by combining greenhouse and field production. 

June bearing short day strawberry varieties 

Kroggel said the traditional strawberries grown for field production are often referred to as June-bearing varieties and are actually short day plants.

“These plants require certain photoperiods to begin flower initiation just like poinsettias,” he said. “The strawberry plants are transplanted into the field and become established during late summer. Depending on the critical photoperiod, which varies between varieties, many of the short day varieties start to initiate flowers when there are 12-13 hours of day light. Flower initiation occurs on the crowns the plants have or produce in the fall.”

During the winter the plants go dormant. In spring, the flowers, which have already been initiated, open and bear fruit. During the early spring as additional growth occurs, the plants continue to initiate and produce flowers until that critical photoperiod is exceeded. Once the critical photoperiod is reached, the plants won’t initiate any more flowers.

Short day strawberry varieties in the greenhouse

Kroggel said when short day strawberry varieties are grown in a greenhouse, the winter dormancy period is eliminated.

“In the fall instead of letting the plants go dormant, they are being kept actively growing in the greenhouse through temperature and nutrition,” he said. “A June-bearing, short day variety that’s planted in August in the greenhouse is going to grow vegetatively until some point in the fall when the days are short enough to initiate flowers. Then it is usually 30 days from flower initiation until flowers appear. It takes another 30 days from the time of flowering until fruit is produced. So, from the point of flower initiation it takes 60 days before fruit is ready to harvest.”

Kroggel said a grower could plant strawberries in the greenhouse during late summer and early fall to produce a crop by Christmas using the natural photoperiod.

“Starting in late September the plants are going to receive 12 hours of natural day light,” he said. “It takes several weeks for the plants to initiate flowers. Then in October there is about four weeks of flower development. In November, from flower to fruit takes another four weeks. Then in December the fruit develops.”

Kroggel said short day varieties produce fruit fairly consistently in the greenhouse.

“What we have seen with our own trials with the June-bearing or short day varieties, once the days start to exceed 12 hours of day light in April, the plants stop initiating flowers. We’ve found that six months is our production limit for any strawberry variety in the greenhouse. The substrate starts to break down and the plants start to lose their vigor. This applies to both short day and everbearing varieties. We also run into problems when we can’t cool the greenhouse causing the fruit quality to suffer. I expect the typical crop life for winter production of greenhouse strawberries for most growers is going to be about six months.”

Inducing strawberries to flower and fruit

Because of the lack of commercially available actively growing starter plants during the summer, Kroggel said he is producing his own tip runners in 38-cell plug trays or 2-inch tree bands (with permission to propagate from patent holders when varieties are protected).

“Since we want to start growing the strawberries during the summer, this is a time of year that there usually are no starter plant material available from most commercial propagators, and so we need to produce our own,” he said. “Usually the very latest dormant runners are available is in June.”

These strawberry plantlets are stuck in a substrate and placed on a mist bench until they are rooted in. Rooting and acclimation takes two to three weeks and the plants need several more weeks of greenhouse growth to be established enough to transplant into a growing system. The plants are ready to be transplanted when they can be removed from the plug cells or pots with roots and substrate intact.

“To initiate flowers in short day plants in this high density propagation when the natural day length is still longer than the flower-inducing day length, we provide the rooted and acclimated plants a short day treatment,” Kroggel said. “This treatment consists of eight hours of daylight in the greenhouse and then the plants are moved into a dark cooler for 16 hours at 59ºF (15ºC). This is the most ideal temperature for flower induction.

“The plants are moved back and forth on carts between the cooler and the greenhouse. It is labor intensive, but they can be moved relatively easily because they are in a dense planting situation. They come out of the cooler at 8 a.m., receive eight hours of light in the greenhouse, and then at 4 p.m. they are moved back into the cooler. A grower who has rolling benches could move the plants back and forth between a cooler and the greenhouse. For the short day varieties that we have grown in the greenhouse it takes three to four weeks before flower initiation occurs. Once the initiation of flower buds is confirmed under a microscope, the short day treatment is no longer needed.”

Kroggel said the 24-hour average temperature for strawberries should not exceed 77ºF (25ºC).

“If growers lived in regions where the temperatures were cool enough to stay below the 77ºF daily average, they could probably pull black cloth to provide the required short day conditions for flower initiation as an alternative to moving the plants into a dark cooler,” he said. “As long as the plants are kept in that temperature range of 59ºF-77ºF pulling black cloth won’t be a problem. Growers need to monitor the temperature under the cloth to be sure not to overheat the plants.”

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Everbearing strawberry varieties in the greenhouse

Kroggel said one of the issues with everbearing strawberry varieties is the terminology used to describe them.

“Everbearing varieties are often referred to as being day neutral. We don’t know of any day neutral everbearing strawberry plants,” he said. “These varieties tend to be facultative long day plants. They will flower all the time, but if they’re provided with a longer photoperiod, they will produce more flowers.”

Kroggel said one of the ways to keep everbearing varieties flowering during the short days of winter is to provide them with photoperiodic lighting.

“During short days the everbearing varieties benefit from an extended photoperiod,” he said. “The plants need 2-3 micromoles, which is about 20 footcandles. We provide the plants with 12-14 hours of light using fluorescent or incandescent lights.”

Timing fruit production

For growers using dormant runners or propagating their own tip runners of everbearing varieties, flowers must be removed in order to allow the plants to become established before producing fruit.

“These varieties naturally produce flowers as soon as they can,” Kroggel said. “For a period of four to six weeks after planting into the production system, the flowers should be removed to allow the runners to develop roots and leaves. The plants need to have a good initial vegetative establishment period so they have well-established roots and leaves in order to support the fruit. By removing these flowers some of the fruit is lost, but this establishment period is necessary.”

Strawberry plants produce their first flush of fruit about one month after the flowers appear (short day varieties) or the flowers are left on the plants (everbearing varieties).

“At some point after the first flush, the everbearing variety plants tend to temporarily stop producing flowers,” Kroggel said. “There will be anywhere from a six-week to a two-month period when no fruit is produced. That is a real issue with producing everbearing varieties. Then there is a massive second flush of flowers and fruit.”

Kroggel said this cyclical production of flowers and fruit can be accommodated by staggering planting dates and using different varieties that have varying production schedules.

“Really high yielding everbearing varieties have less cyclical production because they produce more crowns more often. Unfortunately we haven’t found a really high yielding everbearing variety yet with really good flavor. The June-bearing or short day varieties have a more linear production cycle.”

Kroggel said that he recommends that growers producing greenhouse strawberries plant both June-bearing and everbearing varieties.

“With the short day varieties, they begin flowering at some point either naturally or by being induced,” he said “Their weekly yields are fairly consistent and their cumulative yields are linear. The flower and fruit production of the everbearing varieties tend to be cyclical over the season. I recommend growers produce both June-bearing and everbearing varieties to ensure they are always producing fruit. But growers need to know how to manage both types. Being able to produce fruit during November, December and January is critical. This is the period when premium pricing occurs.”

For more: Mark Kroggel, Ohio State University, Department of Horticulture and Crop Science, Columbus, OH 43210; (614) 292-3767; kroggel.4@osu.edu; https://hcs.osu.edu/our-people/mark-kroggel.

For more information on greenhouse strawberry production, check out: Hydroponic Strawberry Information Website, http://cals.arizona.edu/strawberry; Sustainable Hydroponic and Soilless Strawberry Production Systems, https://www.youtube.com/user/sustainablehydro.

Mark Kroggel provided information on greenhouse strawberry production in Urban Ag News Issue 9, “Strawberries can be adapted to greenhouse production systems” (https://urbanagnews.com/emag/issue-9-2).

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

Greenhouse growers looking to diversify into edible crops may want to consider strawberries, which can be adapted to production systems they are currently using for other crops.

Greenhouse growers looking to diversify their product mix with a fall to spring edible crop might want to consider strawberries.

“There is still a pretty big hole in the strawberry supply chain for November, December and January,” said University of Arizona research specialist Mark Kroggel. “In Arizona, we can produce good quality strawberries in greenhouses from October through April. The best greenhouse strawberry yields occur during March and April.

“Off-season greenhouse strawberry production is trying to accomplish two things: Fill a void in the local supply. And more importantly, produce a premium product. Greenhouse strawberries are going to be better tasting than the field-grown strawberries consumers find in grocery stores at this time of year. Consumers should be willing to pay a premium price for these highly flavored greenhouse berries.”

Use existing production systems

Kroggel said one of the advantages of growing greenhouse strawberries is they can be adapted to existing production systems.

“Growers should use their existing production systems and try to make them work,” he said. “They are familiar with how their systems work. This also helps to minimize investment costs.

“In most cases, strawberries are going to be different than anything else that growers have produced before. But strawberries are adaptable to all types of growing systems. Growers need to start with what they have so that they can learn as much as they can about the plants. They need to become familiar with how strawberries grow. That’s going to take a couple of years. Then if growers want to switch to a different, more expensive production system designed for strawberries, they can.”

Temperature control is critical

Strawberries grown in greenhouses prefer day temperatures below 77ºF (25ºC), which Kroggel said is a temperature that works for many food crops. The ideal temperature range for strawberries is 65ºF-77ºF (18ºC -24ºC).

“The temperature shouldn’t go much above 77ºF because higher temperatures can negatively affect growth,” he said. “Night temperature is much more important for strawberries. We try to maintain night temperatures between 50ºF-54ºF (10ºC-12ºC). Being able to maintain the temperature below 59ºF (15ºC) at night is critical for strawberries because higher night temperatures result in lower quality due to respiration in the fruit.

“If greenhouses cannot be cooled to 59ºF or lower at night, fruit quality is going to be drastically affected. Primarily the acidity will be too high, the Brix (sugar content) will be too low and the surface of the fruit will be off. The strawberry starts to get mealy or soft. The texture, sweetness and acidity are all affected by the temperature.”

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Kroggel said greenhouse strawberries are typically grown in the United States from the fall through the spring. He said most growers wouldn’t be producing strawberries in a greenhouse during the summer because of the competition from field-grown crops.

“There are greenhouse growers in Europe who produce strawberries year-round, but they have a climate that is more amenable to that type of production,” he said. “Day temperatures are less important than night temperatures in regards to fruit quality.

“We can grow a crop later in the spring when the outside day temperature can reach 95ºF-100ºF, but because of the low humidity in Arizona, we can still cool the greenhouse temperature to 75ºF during the day and 59ºF or cooler at night. We can maintain the fruit quality. In most U.S. locations, growers should be able to maintain the required cooler night temperature during the fall to spring period.”

Ensuring adequate light levels

Kroggel said growers interested in producing greenhouse strawberries should be able to provide a minimum daily light integral (DLI) of 12 moles per square meter per day inside the greenhouse.

“Light levels below 12 moles are most likely too low for strawberries,” he said. “The big difference between a fruiting crop and an ornamental flowering crop is that fruit is expensive for the plant to produce. It takes a lot of energy to produce a strawberry or tomato. Ornamental plants can produce leaves and flowers under lower light conditions. Growers in areas that don’t receive 12 moles of light from November through February are going to produce a minimal yield of fruit. With reduced light and photosynthetic activity, the plants cannot support as many fruit.”

Growers in high light areas like Arizona also need to be concerned about too much light. Kroggel said growers should try to keep light levels below 25 moles per square meter per day.

“We have seen some plant stress when the light level starts to reach 30 moles per day in March,” he said. “That’s when we start to shade the greenhouses.”

Humidity control to prevent disease, tipburn

Kroggel said if the greenhouse humidity level is 85 percent or higher during the day and night, foliar diseases including powdery mildew and Botrytis on the fruit, can occur.

“In those parts of the country where the greenhouses are closed at night there can be a problem of high humidity,” he said. “If it’s too cold, heating can lower the humidity. Venting during the day to allow outside air to enter the greenhouse helps to lower the humidity. That’s standard practice and normal day time humidity is usually manageable.”

If the greenhouse humidity is high, the plant canopy can remain wet if there is not adequate air flow. Kroggel said the horizontal airflow fans in the university’s strawberry greenhouses run continuously and help keep the canopy dry. Because of Arizona’s low humidity levels, he said fog has to be used in the greenhouses at night during certain times of the year to raise the humidity in order to prevent tipburn on strawberries.

“We prevent leaf and calyx tipburn by humidifying at night,” he said. “We try to maintain 95 percent humidity inside the plant canopy for three hours at night. Typically that creates a high enough night humidity to prevent tipburn, but is not a long enough time to promote disease.”

Tipburn in strawberry is caused by calcium deficiency just like in poinsettias and lettuce. Kroggel said strawberry tipburn occurs very early in the leaf and calyx development stage.

“When a leaf is developing, if there isn’t sufficient calcium then leaf tipburn has already occurred before the leaf emerges,” he said. “During the day when transpiration in the plant is high, calcium is moving into the mature leaves and not into the growing tip.”

For plants with a mild case of tipburn, Kroggel said there is probably not going to be much effect on photosynthesis. In severe cases, tipburn could impact the fruit.

“If the tipburn is mild and is not on all the leaves, it is probably not affecting photosynthesis that much,” he said. “If the tipburn is severe, then the area of photosynthetic activity is being impaired. Over half the leaves may not be working properly.

“If tipburn occurs on the calyx of the fruit, then most consumers are not going to want to purchase the fruit. The fruit itself might be beautiful, but most consumers won’t buy it because of the calyx burn. Similar to ornamental plants, a grower is impairing his ability to market the fruit if there is calyx burn.”

Photoperiod control

Kroggel said like poinsettias and chrysanthemums, strawberries respond to short day conditions. These plants, called June-bearing types, require short days in order to initiate flowering.

“We are growing both June-bearing and ever-bearing strawberry varieties,” he said. “Ever-bearing varieties prefer longer days and lighting helps to promote flowering.”

Kroggel said 12-13 hours of day light are likely short enough to initiate flowering in most U.S. June-bearing varieties.

“For winter production, if a grower is planting June-bearing varieties in August, by the time the plants start growing and developing there will be 12 hours of light and the plants will begin to initiate flowers,” he said. “Then the plants start to fruit naturally because the days are getting shorter. From the time flower initiation occurs until flowers appear takes about a month. From flowers to fruit is about a month. If plants initiate flowers in late September, the fruit should be ready to harvest in December.”

Kroggel said in some parts of the world greenhouse strawberry growers provide short day treatments to ensure the plants initiate flowering and produce fruit. Some strawberry growers can pull black cloth just like ornamental plant growers do with poinsettias and mums as long as the temperature under the cloth doesn’t get too high. Other growers use temperature-controlled growth chambers to provide short days.

“We do use photoperiodic lighting on ever-bearing varieties to promote flowering because winter days are too short,” he said. “Ever-bearing varieties prefer longer days and the lighting helps promote flowering. We use T5 fluorescent lights to do photoperiodic lighting, but we don’t do any supplemental lighting. About 3 micromoles per square meter per second at the canopy level is a sufficient amount of light.”

For more: Mark Kroggel, University of Arizona, College of Agriculture and Life Sciences, The School of Plant Sciences, Tucson, Ariz.; (520) 626-3928; kroggel@email.arizona.edu. For more information on greenhouse strawberry production: Hydroponic Strawberry Information Website, http://www.cals.arizona.edu/strawberry; Sustainable Hydroponic and Soilless Strawberry Production Systems, https://www.youtube.com/user/sustainablehydro.

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