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BEDFORD, Texas, Sept. 22, 2015 -- Hort Americas is a proud sponsor (and rider participant) of the Tour de Fresh. This one-of-a-kind collaborative event unites the most significant brands and influencers in the fresh produce industry for a four-day cycling event that raises funds to benefit the Let's Move Salad Bars to Schools campaign. The inaugural 2014 event raised over $142,000 and placed over 40 salads bars in communities in 11 states, including California, Colorado, Florida, Illinois, Michigan, Minnesota, Missouri, New York, Ohio, Texas, Wisconsin and the District of Columbia.
The goal of Tour de Fresh 2015 and its participants is to privately finance 100+ new salad bars in school districts across the country. At a cost of less than $3,000 per salad bar per school, sponsors and participants strongly believe that providing healthy eating opportunities for school children should be a requirement and is the foundation of creating positive change for our future.This year Hort Americas efforts are also being supported by Village Farms, Riococo, Houweling's Tomatoes, Grodan, Age Old Organics, UrbanAgNews.com as well countless other friends and family. All of our efforts will directly benefit the Earl Nance Sr. Elementary in the St. Louis Public School system.For those interested, there is still time to contribute. Please visit Hort Americas Donation Page for more details.
Contact: Maria Luitjohan, 1-469-532-2383, mluitjohan@hortamericas.com
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Greenhouse ornamental plant growers adding edible crops to their product mix should consider incorporating biological controls into their integrated pest management program.
By David Kuack
An increasing number of ornamental plant growers are looking to take advantage of the growing demand for locally produced edible crops. Whether it’s for sales in their own garden centers, roadside stands, farmers markets, grocery stores and restaurants, the demand for locally-grown produce continues to increase.
Before starting to produce edibles, ornamental growers should thoroughly investigate how they’re going to produce and market their crops, including pest and disease management.
“There are less active ingredients registered for insect and disease control on vegetable crops than for ornamentals,” said Ron Valentin, technical lead at Syngenta Bioline. “It would be difficult for greenhouse growers to do vegetable production without the use of biological controls. Most greenhouse vegetable growers opening new facilities today are making biological controls a fundamental part of their control programs.
“The use of biological controls on vegetable crops began in the late 1960s and early 1970s. Greenhouse vegetable growers began running into issues of efficacy with conventional chemical control products that were available at the time.”
Develop a knowledge base
Valentin said the most important things a grower can do when starting to use biological controls on edible crops is to develop a knowledge base and to be prepared.
“Don’t wait until you have a problem, especially with aphids,” Valentin said. “It is important that growers understand the life cycle of insects and how that relates to the plants. Before ornamental growers plant any edible crops they should become familiar with those crops and the pest problems they can have and the control options that are available.”
He said using biologicals is much different than traditional pesticide control programs where growers treat a problem rather than trying to prevent it.
Syngenta Bioline sachets containing
Amblyseius cucumeris predatory mites
placed on cucumber plants for thrips control.
Photos courtesy of Syngenta Bioline
“Ornamental growers are used to spraying instead of releasing predators,” he said. “In the case of greenhouse vegetable growers, they are trying to prevent problems from occurring rather than trying to fix problems. Biological controls are used to prevent pests from becoming established rather than trying to fix a problem after it occurs.”
Using biological controls
Valentin said ornamental growers may initially want to try biological controls on some of their ornamental plants before trying to produce edible crops.
“Growers who are producing ornamental crops for the spring and summer months and are looking to add leafy greens for the fall and winter could have some issues with using biological controls,” he said. “One of the problems that could occur is the type of insecticides being applied to the ornamental plants. Some of these chemistries have long residuals that can affect beneficials.”
If possible, ornamental growers should try to isolate their edible crops especially if they are continuing to use a traditional pesticide program on their ornamental crops. Valentin said ornamental growers who are using biological controls on seasonal edible crops have an opportunity to extend their use onto their ornamental crops.
Valentin said growers who are using “softer” chemical controls like insecticidal soap and horticultural oil need to be aware of the impact these products can have on biological controls.
“Insecticidal soaps and horticultural oils are not selective,” he said. “These products can also kill some of the predatory insects that a grower may be releasing. With spray applications of insecticidal soaps there is very little or no residual.
“Horticultural oils are comparable in use to insecticidal soaps. They are often presented as being IPM-friendly. To some degree, if more of the biological controls are killed than the actual pest that is trying to be controlled, that could actually work opposite to what a grower is trying to accomplish. Growers have to be careful when they start spraying because they may have to delay application of biological controls. It is important that growers understand the life cycles of the pests and how that relates to the plants.”
Identifying potential pest problems
Thrips pupate in the soil. Valentin said if there is a lot of exposed soil under greenhouse benches along with weeds that can harbor thrips pupae, this could make it more difficult to get started with biological controls.
Valentin said a technique that some vegetable growers use to eliminate a thrips problem is to solarize the greenhouse.
“A grower can close the greenhouse and allow the temperature to rise to 111ºF-113ºF (44ºC-45ºC),” he said. “I tell growers not to close up the greenhouse altogether because the temperature could go higher and damage equipment. Solarizing the greenhouse can reduce possible carryover of pests.
“A lot of large cucumber growers use this solarization technique. This may be harder to do during the winter, but in May and June there are more sunny days. Growers close up their greenhouses and solarize before they plant the next crop.”
Valentin said Amblyseius cucumeris predatory mites for thrips control need to be placed on susceptible crops like cucumber and basil before there is a problem with thrips.
Amblyseius cucumeris predatory mites need to be placed
on susceptible crops like cucumber and basil before there
is a thrips problem. The mites only feed on thrips larvae,
not on thrips adults.
“Growers should be releasing predators from the beginning of the crop not after the thrips become established. If the thrips are already established, it’s too late. The predatory mites only feed on the thrips larvae, not on the thrips adults.”
Valentin said whitefly is the primary pest of tomatoes. Whiteflies predominantly lay their eggs at the top of the plants.
“Encarsia formosa and Eremocerus eremicus, which are predatory wasps, are used for whitefly control,” Valentin said. “Growers react to seeing adult whiteflies, but if they look more closely at the plants, they would see the wasps feeding on the larvae. One Eremocerus adult wasp feeds on 20-30 whitefly larvae a day. It’s important that growers not only act on what they see when it comes to adult whiteflies.”
One Eremocerus eremicus predatory
wasp, which is used on greenhouse
tomatoes, feeds on 20-30 whitefly
larvae a day.
Growers who are producing leafy greens and other quick-turn crops are limited to some extent in what biological controls that they can use. For crops like lettuce and basil the turnover can be really quick.
Valentin said the parasitic wasp Aphidius colemani can be an effective control for aphids even on quick-turn crops.
“For these types of crops growers may want to consider setting up a banker plant system to provide the wasps with a constant food source,” he said. “The system is based on introducing cereal aphids into the greenhouse on cereal plants such as rye, barley or wheat. The cereal aphids only reproduce on monocotyledonous plants and will not infest the edible crops.
“Cereal aphids serve as a food source for the parasitic wasps. For the banker plant system to be most effective, the cereal plants need to be introduced as early in the edible crop as possible before aphids appear.”For more: Syngenta Bioline, (805) 986-8265; Ronald.Valentin@syngenta.com; http://www3.syngenta.com/global/bioline/en/Pages/home.aspx.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.
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As pressure on fresh water supplies increases, more growers will look at recycling their water. Recycling water can add a whole range of challenges that growers may not have had to deal with before. Speakers at this year’s Cultivate’15 discussed some of the issues growers may face when recirculating and treating irrigation water.
By David Kuack
As drought conditions worsen along the West Coast and wildfires scorch many parts of the country, water continues to be on the minds of the public, government officials and water regulating agencies. Environmental disasters like the recent wastewater spill from an abandoned Colorado gold mine into the Animas River also add to the concerns about water availability and water safety.
Organisation for Economic Co-operation and Development (OECD) reports in its “OECD Environmental Outlook to 2050: the Consequences of Inaction” the demand for water will increase globally by some 55 percent. This increase in demand will come primarily from manufacturing, thermal electricity generation and domestic use. The report said “groundwater depletion may become the greatest threat to agriculture and urban water supplies in several regions.”
Challenges of recirculating water
As more growers look to save water by collecting irrigation runoff and recirculating their water, the chance for issues with soluble salts, pH and disease pathogens can be expected to increase. Plant pathologist Ann Chase at Chase Agricultural Consulting told Cultivate’15 attendees during her presentation "Meeting the Challenges of Recirculating Water" that use of automatic watering systems has increased watering efficiency, but in some cases, these systems have also led to less monitoring of crops on a daily basis.
She said algae tend to be the biggest problem with recirculating water. She said the optimum conditions for growing greenhouse crops, including warm temperatures, high humidity and applying fertilizer in irrigation water, are the same conditions that allow algae to thrive in many areas of a greenhouse. Many algae also move with water. It’s common in greenhouses to see algae growing on concrete floors and aisles, benches, evaporative cooling pads and even on the surface of growing media.
Plant pathologist Ann Chase at Chase Agricultural Consulting
said algae tend to be the biggest problem with recirculating
water. The optimum conditions for growing greenhouse crops
are the same conditions that allow algae to thrive.
Photos courtesy of Peter Konjoian, Konjoian’s Horticulture
Education ServicesChase said a major reason many disease fungal pathogens can thrive in greenhouse conditions is they are “good” saprophytes that don’t require plants to survive. These water-loving and water-tolerant fungi have a wide host range. They produce many spores quickly and the spores are motile making it easy for them to move through water. These spores are also long-lasting which allows them to wait until conditions are optimum for them to germinate on host plants.
Chase said growers have a lot of choices when it comes to how to recirculate and treat their water. She said before deciding on what water treatment should be used, growers should first lower the rate of fertilizer they are applying and incorporate a filtering system.
“Filtering has to be done before any type of water treatment,” she said. “Depending on how fast the water is needed and the volume of water required will help to determine the type of filtration and treatment system that should be installed.”
For more: Chase Agricultural Consulting, http://www.chaseagriculturalconsultingllc.com; archase@chaseresearch.net.
Algae-biofilm relations
During his presentation on “Water enhancement and hydroponics,” Peter Konjoian, president of Konjoian’s Horticulture Education Services, discussed the relationship between algae and other microorganisms living in water. He said if algae are present, one should assume fungi, bacteria, and viruses may be as well.
“Algae and bacteria produce biofilm,” Konjoian said. “There is symbiotic relationship between algae and biofilm. These organisms are highly evolved and highly adaptive.”
He said biofilm can provide algae with enough nutrients that algae do not need the light necessary to produce these nutrients. Because of this relationship, algae can grow in water pipes, even in pipe buried underground.
Biofilm can come into a greenhouse in a municipal water source
even though the water has been treated. Schedule-40 polyvinyl
chloride irrigation line: new pipe (top), “clear” water line with
biofilm (middle), and fertilizer line that carries 200 parts per
million nitrogen with layer of algae (bottom).He said biofilm can come into a greenhouse in a municipal water source even though that water has been treated. While algae can establish themselves on a wide range of surfaces inside a greenhouse, it is the irrigation system that can help promote their growth. If a line is dedicated solely for fertilizer, even if that pipe is buried underground, algae can become established.
Konjoian said one of the common irrigation system design flaws made by growers is they do not provide enough filtration. He said the mesh size of the filter system needs to be able to filter out particles of at least 50 microns.
For more: Konjoian’s Horticulture Education Services, peterkfes@comcast.net.
Water treatment options
Don Merhaut, associate extension specialist for ornamental and floriculture crops at the University of California-Riverside, and Sal Mangiafico, environmental and resource management agent at Rutgers Cooperative Extension, discussed “Water treatment options for irrigation and tailwater recycling.” The researchers said there are five basic steps to recycling and treating water:
1. Collection of water runoff.
2. Removal of floating debris.
3. Removal of suspended particulate matter, including organic matter, clay, sand and silt.
4. Sanitation treatment for pathogens.
5. Control of fertilizer levels.
If irrigation runoff is going to be collected into a collection basin, the size of the greenhouse or nursery and its water demands have to be considered.
Merhaut said plant pathogens, including Phytophthora and Pythium, are usually present in runoff water and irrigation water that comes from surface water sources. The method of water treatment chosen by a grower will depend on how clean the water is, the level of sanitation a grower wants to achieve, the type of recycling system and local regulations.
Mangiafico said the method of fertilizer injection is usually one of the last things determined because of the impact water sanitation treatments can have on some nutrients. Some treatment methods may denature fertilizer chelates suspended in water or remove nutrients from the water. He said the smaller the container size that is being used to produce a crop, the more a grower needs to be concerned about micronutrients that are sensitive to poor quality water.
Merhaut and Mangiafico said the most common water treatment methods include:
1. Chlorination
2. Slow sand filtration
3. Rapid sand filtration
4. Membrane-mediated filtration
5. Heat
7. Ozonation
8. Copper ionization
The two researchers advised growers, depending on which treatment method they were interested in, to first try out a small pilot system before investing in and installing a full scale treatment system for an entire greenhouse or nursery operation. Once a treatment system has been installed, it should be inspected and tested on a regular basis to ensure it is operating properly and is providing the sanitation results expected of it. Records should be kept of any type of maintenance, parts replacement, etc. that are done on the system in the event that any problems occur.
For more: Don Merhaut, University of California, Department of Botany & Plant Sciences, Riverside, Calif.; donald.merhaut@ucr.edu; http://plantbiology.ucr.edu/people/faculty/merhaut.html. Sal Mangiafico, Rutgers Cooperative Extension, Woodstown, N.J.; mangiafico@njaes.rutgers.edu.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.
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Houston, Texas, June 25, 2015 — Indoor Harvest Corp (OTCQB:INQD), through its brand name Indoor Harvest™, is a design build contractor, developer, marketer and direct-seller of commercial grade aeroponic and hydroponic fixtures and supporting systems for use in urban Controlled Environment Agriculture and Building Integrated Agriculture. The Company is pleased to provide an update on the Pasadena, Texas Community Located Agricultural Research Area ("CLARA") project.On March 31, 2015 the Company announced the signing of a LOI with the City of Pasadena, Texas to fund the establishment and provisioning of an indoor agricultural facility (vertical farm) to be located in Pasadena, Texas. Under the LOI, the City was to provide Indoor Harvest, or a partner of their designation with City approval, with two facilities owned by the City for the sum of ten dollars ($10.00) per annum for a period not to exceed twenty (20) years as well as provide tax abatements on these properties for use in a CLARA project. In addition, the Pasadena Second Century Corp. (economic development entity for the City of Pasadena) has been asked by City officials to consider a budgetary proposal of $500,000 as seed money for the project’s economic development portion in north Pasadena.Mr. Chad Sykes, Chief Executive Officer of Indoor Harvest, stated, "We've received a timeline for the project through the City. We're currently in the final stages of drafting the MOU and expect to be in a position to begin work on the project as soon as August, based on the timeline provided by the City. All of the parties involved are working together to create an agriculture campus in Pasadena that we hope will become a model for the rest of the nation. By combining agricultural research, education and commercial operations in one campus, we're working to build a foundation to turn North Pasadena into a leader in new, innovative agricultural trends. We've also begun discussions with several potential commercial partners and investors interested in locating operations at the CLARA campus. Although we don’t have any binding agreements, interest seems to be significant given the background and history of groups with whom we are discussing the project."The CLARA project, based on current negotiations, is expected to be divided into two phases. Phase One will focus on developing the non-profit aspects of the project and is envisioned to include the construction of a 6,000 sq. ft. vertical farm R&D facility and 6,000 sq. ft. of classroom and office space. Phase Two is envisioned to support a commercial retail operation with greenhouses built on approximately two acres of land adjacent to the vertical farm and education centers.The Phase One vertical farm facility is intended to serve dual roles, with Indoor Harvest using the facility as a demonstration farm and R&D facility and Harris County BUILD Partnership, a non-profit group, using the facility for educational and charitable purposes. It is anticipated that the crops grown will be donated, or sold at cost, to provide fresh produce to low income families in the North Pasadena area. The entire proposed campus area, almost two city blocks, will be designed and built to allow the flow of tourists without impacting operations. The City has been asked to develop a project overview to be presented in August to department heads at the Pasadena Independent School District's Kirk Lewis Career & Technical High School and the Continuing and Professional Development Department of San Jacinto College regarding academic curriculum development to be located at the CLARA campus.The Harris County BUILD Partnership was established in January 2015 to eliminate the conditions that cause food insecurity in north Pasadena by launching a new healthy, accessible, and community-supported local food system. The conveners of the BUILD Partnership are the Houston Food Bank, the Harris County Public Health & Environmental Services ("HCPHES") and The University of Texas MD Anderson Cancer Center. Additional members of the BUILD Partnership include CHI St. Luke’s Health, Memorial Hermann Health System, Brighter Bites, CAN DO Houston, City of Pasadena, Neighborhood Centers Inc., Pasadena Health Center and the U.T. School of Public Health.The BUILD Partnership is an extension of Healthy Living Matters (HLM), a county-wide collaborative of over 80 organizations chartered in 2011 to address childhood obesity in Harris County. There is also a Pasadena-specific version of HLM called the HLM-Pasadena Community Task Force that has 23 members local to the Pasadena community.On June 9, 2015, the Harris County BUILD Health Partnership was selected as one of seven projects out of over 300 applicants nationwide, to receive a $250,000 grant from the inaugural BUILD Health Challenge class. The announcement was made live from the National Press Club in Washington, D.C., featuring Karen DeSalvo, Acting Assistant Secretary for the U.S. Department of Health and Human Services and was followed by a congratulatory letter from LaMar Hasbrouck, MD, MPH and executive director of the National Association of County and City Health Officials who remarked, “I look forward to tracking your progress and learning more about your projects’ best practices and challenges.” A portion of this grant funding will be used towards setting up the academic and non-profit portion of the CLARA project.The Phase One initial project meeting has already been held. Caleb Harper, the Principal Investigator and Director of MITCityFarm, attended the meeting. As part of the non-profit academic portion of the CLARA project, all research would be made open source. The MIT Media Lab's Open Agriculture (OpenAG) Initiative seeks to make agricultural research and data more available to researchers through an innovative cloud based system. Indoor Harvest is excited to continue its relationship with MITCityFarm by looking at ways to deploy the Open Ag platform at the CLARA research facility.Chris Higgins from HortAmericas, a company involved in horticulture product distribution, consulting and services, also attended the meeting. Indoor Harvest has selected HortAmericas as a project consultant to the CLARA project. HortAmericas will assist the project by evaluating methods and process and providing feedback through the design phase as well as assisting in preparation of standard operating procedures.It is expected that the project MOU will be finalized and property lease executed by August 2015 based on an existing timeline provided by the City. Construction on Phase One is planned for completion June 2016.Phase Two of the project is anticipated to be developed on two acres of land currently available adjacent to the existing properties being provided by the City. Indoor Harvest, as the primary developer of the campus, expects to be able to provide commercial operators who build on the CLARA campus a unique group of incentives and key advantages in regards to distribution, manufacturing intelligence and access to resourcing and key agricultural production talent. Phase Two timeline will be dependent upon securing commercial partners who have adequate funding and approval by the City. The Company is currently in talks with several commercial parties interested in building on the CLARA campus.In addition, the City of Pasadena is currently considering creating a tax increment reinvestment zone (TIRZ) in the immediate area surrounding the CLARA campus. A TIRZ is a public financing structure that Texas law allows to target tax revenue helping to support redevelopment in underserved areas. Such a zone, if created, could provide an additional economic incentive for tangential services to locate on the project site. As of now, the City is not obligated to create a TIRZ zone and no such zone may ever come to fruition.Consistent with the SEC’s April 2013 guidance on using social media outlets like Facebook and Twitter to make corporate disclosures and announce key information in compliance with Regulation FD, Indoor Harvest is alerting investors and other members of the general public that Indoor Harvest will provide weekly updates on operations and progress through its social media on Facebook, Twitter and Youtube. Investors, potential investors and individuals interested in our company are encouraged to keep informed by following us on Twitter, Youtube or Facebook.Twitter: http://www.twitter.com/indoorharvestABOUT INDOOR HARVEST CORPIndoor Harvest Corp, through its brand name Indoor Harvest™, is an emerging design build contractor and OEM manufacturer of commercial aeroponic and hydroponic system fixtures and framing systems for use in Controlled Environment Agriculture and Building Integrated Agriculture. Our patent pending aeroponic fixtures are based upon a modular concept in which primary components are interchangeable. We are developing our aeroponic and hydroponic systems for use by both horticulture enthusiasts and commercial operators who seek to utilize aeroponic and hydroponic vertical farming methods within a controlled indoor environment. Please visit our website at http://www.indoorharvest.com for more information about our Company.FORWARD LOOKING STATEMENTSThis release contains certain “forward-looking statements” relating to the business of Indoor Harvest and its subsidiary companies, which can be identified by the use of forward-looking terminology such as “estimates,” “believes,” “anticipates,” “intends,” expects” and similar expressions. Such forward-looking statements involve known and unknown risks and uncertainties that may cause actual results to be materially different from those described herein as anticipated, believed, estimated or expected. Certain of these risks and uncertainties are or will be described in greater detail in our filings with the Securities and Exchange Commission. These forward-looking statements are based on Indoor Harvest’s current expectations and beliefs concerning future developments and their potential effects on Indoor Harvest. There can be no assurance that future developments affecting Indoor Harvest will be those anticipated by Indoor Harvest. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond the control of the Company) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by such forward-looking statements. Indoor Harvest undertakes no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws.Contacts:Indoor Harvest CorpCEO, Mr. Chad Sykes713-410-7903
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Proper processing of coir to lower its natural high salts level should eliminate the need to buffer it with calcium nitrate.
By David Kuack
Coir has become a major component of both greenhouse vegetable and container crop production. It can be used by itself, for instance in grow bags, slabs and propagation cubes, or it can be used in growing mixes with other components like sphagnum peat, perlite and bark.
Coconuts, which are produced by coconut palms (Cocos nucifera), consist of husks that surround the nuts. The nuts are consumed as food and the husks are used to produce various types of coir growing substrates, including chips, chunks and peat. Coir peat is a by-product of the husk fibers that are used to fill cushions and car seats.
Naturally high in salts
Dr. Hugh Poole, international agricultural consultant, said coconut coir is initially high in sodium, potassium and chloride salts.
“Where the coconut coir originates from can have an impact on the salt levels,” Poole said. “Coconut palms produced inland away from the ocean may not accumulate as much sodium, potassium and chloride, but growers should assume that all coconuts will have high salt levels.
“These salts are relatively soluble and are not totally bound by the coir so they are easily leached. Most coir producers use rain water for most of the year to remove the salts. If the EC (electrical conductivity) level is below 1.0 milliSiemens per centimeter (mS/cm), growers should not have to leach the coir. In most cases, the coir producers have already leached the coir for the growers. It should be ready to use. If the salts level is high, then the coir producer has not done its job. A producer should be able to provide growers with the coir’s EC value, its pH value and other information, including percent moisture, as well.”
Coir producers should be able to provide growers
with the coir’s EC value, its pH value and other
information, including percent moisture.
Photos courtesy of Riococo
Poole advises growers using coir to test for soluble salts before it is combined with other mix components and before any plants are placed in the coir.
“If the level of salts is low, then a grower doesn’t need to worry about sodium, potassium and chloride,” he said. “Many growers say the soluble salts level should be less than 1.0 mS/cm. Others say the salts level should be less than 0.5 mS/cm. It really comes down to how the coir is going to be used. If Ellepots are going to be filled with coco peat for young seedling production, then the soluble salts level should be around 0.5 mS/cm. If the coco peat is being blended with sphagnum peat, perlite or some other growing mix components and plants are being transplanted into containers, the coir soluble salts level can be higher. I have seen EC values as high 3-6 mS/cm. In these instances, unless the coir is being diluted with a lot of other mix components, growers would certainly want to leach the coir before it is used.”
Poole said growers who ask their suppliers for a low EC coir is similar to asking for a low EC peat moss or compost.
“If growers have to deal with a growing mix component with an EC level that is always bouncing around, it is going to be very challenging for those growers from crop to crop and from year to year,” he said.
To buffer or not to buffer
Poole said some growers are asking suppliers to buffer their coir with calcium nitrate.
“These growers are thinking that the cation exchange sites are loaded with potassium and sodium ions and if the coir isn’t buffered with calcium nitrate then their crops may suffer a calcium or magnesium deficiency,” he said. “These types of deficiency problems are more commonly encountered with hydroponic systems. If a substrate is being used, then this usually isn’t a concern.
“Most of the coir’s exchange sites are tied up with sodium and potassium. These ions are readily replaced by calcium. If calcium is applied, much of that calcium is going to be tied up in the exchange capacity taking out sodium and potassium. Therefore calcium is not in the substrate solution for utilization by the plants. There is a lag before the cation exchange capacity can be fully charged with calcium, potassium and magnesium. If a grower isn’t cognizant of this lag and doesn’t address it, it can cause deficiency problems. When 50 ppm calcium is incorporated in the fertilizer solution, the leachate may only contain 10 ppm calcium. Not that the plants utilized the other 40 ppm. Much of that 40 ppm was tied up at the exchange sites and will be available later.”
Avoiding deficiency problemsPoole said if the coir’s EC level is initially low and growers apply a Cal-Mag fertilizer at the beginning of a crop, there shouldn’t be deficiency problems. He said growers using reverse osmosis water, in which there is no calcium or magnesium, should make adjustments in fertility especially if they are producing a fast growing crop. Although no deficiency problems might occur, Poole said growers should be diligent in monitoring fertility levels.
“Once the cation exchange sites are charged with calcium and magnesium, then there is free exchange and there shouldn’t be any problems,” he said. “In the first two to four weeks, growers should probably start out with higher calcium and magnesium levels if they’re growing with coir. They should try to favor calcium and magnesium absorption at the exchange sites. This is a precautionary step.”
If the coir’s EC level is initially low and growers
apply a Cal-Mag fertilizer at the beginning of a
crop, there shouldn’t be deficiency problems.
Poole said growers, who are using coir and are planning to use a 20-10-20 fertilizer, need to be aware that this fertilizer does not contain any calcium, magnesium or sulfur.
“The growers are going to have to add these nutrients,” he said. “If growers are using coir they have to recognize that the exchange sites need to be filled or charged with calcium and magnesium before there starts to be a free exchange of nutrients back and forth.
“With coir where the exchange sites are filled with sodium and potassium, the only way of removing these ions is by reducing them with leaching with water or by overcompensating with calcium and magnesium.”
Poole said initially, the natural salts found in coir must be leached with water. The remaining salts will be exchanged with calcium and magnesium by a buffering treatment or with elevated levels in the fertility program. He said buffering is not an option for organic growers.
“If coir is washed well and its EC is below 0.5 mS/cm or lower, then the coir shouldn’t have to be buffered for most crops. If calcium nitrate is used to buffer the coir, magnesium has to be provided as well.”
Poole recommends growers should review both their water analysis and their fertilizer analysis to know what nutrients they are applying and to confirm nutrient levels.
“Young plants and bare-root plants are more sensitive to high salts than to short-term nutrient imbalances,” he said. Long-term crops should be monitored using tissue analyses to optimize plant nutrition and crop productivity.For more: Hugh Poole, FloraSynergy; (864) 359-7090; hapoole@Interact2Day.com.
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University of Arkansas researchers trialed 65 lettuce varieties to determine their potential for production in greenhouse hydroponic systems.
By David Kuack
An increasing number of greenhouse ornamental plant growers are looking to expand into edible crops. There are also field vegetable growers who would like to expand their production to include greenhouse crops. Some of the easier and faster crops for growers to try to produce in a greenhouse are lettuce and other fresh greens.
One of the issues these growers are facing is what varieties of lettuce can be grown in a greenhouse environment. Much of the commercial lettuce breeding is focused on outdoor field production. Growers looking to expand their lettuce offerings beyond commonly produced greenhouse varieties usually have to do their own trials looking for field varieties that can be adapted to a greenhouse environment.
Need to expand greenhouse varieties
University of Arkansas horticulture professor Mike Evans said he is constantly receiving inquiries from growers about what lettuce varieties can be grown in greenhouses.
“At Cultivate’14 we surveyed growers who participated in one of the greenhouse vegetable seminars about their educational and research needs,” Evans said. “One of the growers’ responses was the need for variety information.
“If you look at seed catalogs, most of the information describing lettuce varieties is based on field production, not greenhouse. So if a grower wanted to grow lettuce hydroponically in a greenhouse during the winter there is little information available. If a grower wanted to use nutrient film technique or deep flow floating systems in a greenhouse, there’s basically very little information on how lettuce varieties would do in these production systems. Most of the production information is field-based.”
Evans said there is also a need for evaluating lettuce varieties for fall, winter and spring greenhouse production. He said these variety evaluations need to be done in different regions of the country to see how they perform under different climates.
Lettuce variety evaluations
University of Arkansas researchers selected 65 lettuce varieties for evaluation in greenhouse production systems. A nutrient film technique and deep flow floating system were used for the trials.
“Our goal with the variety trials was to generate better and more variety information and to determine which varieties would work best in climates similar to ours,” Evans said. “We especially wanted to be able to make variety recommendations across a production year. That is, varieties which work well in the fall, winter and spring.
“There are certain varieties that do well during winter. But as soon as the days start getting longer, the variety begins to bolt. Or a variety may do well in the fall and spring, but during the lowest light levels of winter, it has some type of production issue.”
University of Arkansas researchers selected 65
lettuce varieties for evaluation in greenhouse
production systems.
Photos courtesy of Mike Evans, Univ. of Ark.
Evans said the information that has been collected is for lettuce varieties that perform well in a glass greenhouse in Arkansas.
“These varieties may not respond the same way in Michigan, Arizona, Florida and Texas,” he said. “They also won’t respond the same way in locations where the light and humidity levels are different. These trials are probably good recommendations for growers in climates similar to ours.”
Lettuce varieties were planted from September through May. No crops were grown in June, July and August. Four crops were produced during the fall to spring cycle.
“Some growers try to grow during the summer months by chilling the nutrient solution,” Evans said. “We weren’t set up for summer production. Having trialed 65 varieties we will probably select 15 of the best performing varieties to evaluate for summer performance. For the summer evaluations we will have to use a different greenhouse set up in order to chill the nutrient solution.”
Measuring growth rate
Evans said one of major growth parameters measured was biomass production or growth rate.
“The quicker the plants grow, the shorter the production cycle,” Evans said. “Every day on the bench is cost to the grower. We looked at fresh weight and dry weight, two measures of growth.
“Some growers let lettuce grow for a specific amount of time. Other growers try to achieve a specific weight.”
Evans said the lettuce crops were grown on a 42-day production cycle in both the NFT and deep flow systems. At the end of the 42-day cycle the lettuce was harvested and measurements were taken.
“Sometimes if a variety is a fast grower, the lettuce might exceed the weight that a grower would want,” Evans said. “That tells us this variety could have been grown in a much shorter period of time. Or a variety that didn’t reach a minimum weight at the end of the 42-day cycle was considered a slow grower. Fresh and dry weights were used as a measure of how fast a variety can grow. How fast can a variety put on biomass? That is what growers are selling—biomass.”
Lettuce varieties that did well in a nutrient film
technique system tended to do well in a deep
flow float system.
Evans said there were similarities in how varieties performed in the two production systems.
“If the varieties did poorly in NFT, they tended to perform similarly in deep flow too,” he said. “If a variety did well in NFT, odds were high that it did really well in deep flow.”
Identifying disorders
Evans said the two most common problems he hears about lettuce from growers are powdery mildew and tipburn.
“Ninety percent of the calls I receive are about these two problems,” he said. “We rated the lettuce varieties we trialed for tipburn and powdery mildew. Powdery mildew, in our region of the country, is the disease that can often give growers fits. It can really wallop a lettuce crop. We also measured the incidence of tipburn, which can be a problem on a number of greens.”
Evans said semi-heading and heading (butterhead) types seem to be more prone to tipburn.
“What happens is that as these varieties start to form heads there is an area of high humidity,” he said. “There is this little microclimate of high humidity. If a grower is growing under real high humidity, has structures with poor air circulation or the nutrition levels aren’t right, a calcium deficiency can occur. These can create a tipburn problem. We saw much less tipburn on varieties that tend to be loose leaf types.
For more: Mike Evans, University of Arkansas, Department of Horticulture, Fayetteville, AR 72701; (479) 575-3179 (voice); mrevans@uark.edu; http://hort.uark.edu/5459.php.
Top performing lettuce varieties
The following lettuce varieties did well in the four greenhouse production trials conducted at the University of Arkansas.
Butterhead types
Adriana
Deer Tongue
Nancy
Rex
Rex
Skyphos
Fancy leaf types
Black Hawk
Cavernet
Dark Red Lollo Rossa
Dark Red Lollo Rossa
New Red Fire
Outredgeous
Red Sails
Ruby Sky
Oak leaf types
Oscarde
Panissee
Panissee
Rouxai
Romaine types
Green Forest
Red Rosie
Red Rosie Ridgeline
Salvius
Truchas
David Kuack is a freelance technical writer in Fort Worth, Texas: dkuack@gmail.com.
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Researchers at Michigan State University used LED lights to produce compact flower and tomato seedling plugs.
By David Kuack
Growers and researchers are studying the effects that specific light wavelengths can have on ornamental and edible crops. Research studies are focusing on the effect light wavelengths can have on a variety of plant processes including growth, flowering, fruiting and postharvest quality.
Michigan State University horticulture professor Erik Runkle and former graduate student, now floriculture/nursery production extension educator Heidi Wollaeger studied the impact the ratio of red to blue light can have on the production of annual bedding plant seedlings. They looked at the effects of red and blue light on impatiens, petunia, salvia and tomato plugs.
Michigan State University floriculture/nursery production
extension educator Heidi Wollaeger and horticulture
professor Erik Runkle studied the impact that red and
blue light can have on bedding plant seedlings.
Photos courtesy of Heidi Wollaeger, Mich. St. Univ. Ext.
“These four species are very common bedding plants for U.S. growers,” said Wollaeger. “They are key crops for their sales. The tomato plugs were being grown as vegetable transplants and not for production as greenhouse tomatoes for fruiting.
“We have also used these four species in other lighting trials that we have done recently. We wanted to be able to extrapolate from one study to another. In previous studies we looked at green light and the ratios of blue, green and red light.”
Seed was sown into 128-cell plug trays at a commercial propagator and moved into a large growth chamber at the university within two days where LED and fluorescent light treatments began immediately. The plants were Stage 2 plugs when the light treatments began. The seedlings had cotyledons and no true leaves. They were under the light treatments throughout the entire duration of the study.
Light treatmentsThe bedding plant plugs were grown in a growth chamber equipped with six individual LED chambers. The plugs grown under fluorescent lamps were grown in a separate growth chamber.
For all light treatments, plants were exposed to 160 micromoles per square meter per second (µmol·m−2·s–1) for 18 hours a day.
Plug trays of impatiens, petunia, salvia
and tomato were grown in a large growth
chamber at Michigan State where they
received LED or fluorescent light treatments.
“We chose 10 moles per day because that is a suggested light integral for most plants to be of at least moderate quality,” Wollaeger said. “We didn’t want to deliver a light intensity much greater because as the intensity increases so does the light installation cost as well as the energy costs to run the lamps. We were implementing a practical light level for growers.”
Wollaeger said the study was terminated after four to five weeks because at that time the plants were ready for a commercial grower to transplant.
“This study simulated what growers would actually do in their facilities if they were to install a sole light source LED chamber,” she said. “They would use this high value propagation space to produce the propagules and then transplant them and put them into the greenhouse. These could be used by growers who are finishing the plants themselves or by a propagator who is selling the plugs to other growers.”
Light effects on bedding plantsWollaeger said all of the species grown under the red light dominant background with at least 10 µmol·m−2·s–1 of blue light displayed desirable plant growth responses.
“These plants showed compact growth, thicker leaves and thicker stems,” she said. “As a general rule of thumb, growers should provide at least 10 µmol·m−2·s–1 of blue light if they are providing a red dominant environment to increase plant quality, which results in compact, well-branched growth.
“This treatment might reduce the need for plant growth retardants. If the light environment is being altered to include more blue light in a sole-source environment, stem elongation is reduced. This will depend on the crop. Every crop has a different vigor depending on the species and cultivar. This study only looked at four commercially important species.”
Four bedding plant species, including tomato, grown
under a red light dominant background and under at
least 10 µmol·m−2·s–1 of blue light displayed desirable
plant growth responses, including compact growth,
thicker leaves and thicker stems.
Plants grown under the fluorescent lamps usually produced the most chlorophyll, but also had the thinnest leaves. Impatiens and salvia had greater fresh shoot weight when exposed to treatments without blue light than with at least 80 µmol·m−2·s–1 of blue light.
Impatiens grown under a high proportion of blue light developed more flower buds. Wollaeger said whether this early flowering is a negative or positive effect depends on the plug cell size.Impatiens grown under a high proportion of blue light
developed more flower buds than plants provided with
mostly red light.
“If the plants are being grown in a small plug size like a 288 cell and will be transplanted into large finished containers, it might not be desirable for early bud development,” she said. “The formation of flower buds could impact the rooting of the plants, but that depends on the cell pack size. If a grower is transplanting the plugs directly into smaller containers, he might want earlier flowering.”
Reduction of tomato intumescencesA benefit of growing tomato plugs under high blue light levels and fluorescent lamps was the reduced incidence of leaf intumescences (sometimes called edema), which are small protrusions that form on leaves, stems and petioles. Wollaeger said this physiological disorder has been associated with a lack of ultraviolet light or blue light.
“This physiological disorder is cultivar specific,” she said. “Some cultivars are more prone to developing this disorder compared to others. ‘Early Girl’ is the cultivar that we used and it did develop intumescences under treatments with small amounts of blue light.”
More greenhouse researchThis particular research study did not look at the effects of the light treatments after plants are moved into the greenhouse. Wollaeger said Dr. Runkle’s lab is currently conducting another study to determine the lasting effect of light treatments on transplanted plugs.
“Whether or not a light treatment has any lasting effect once the propagules are transplanted and placed in the greenhouse is going to depend on the light environment in the finishing location,” she said. “If the daily light integral is at least 10 mol·m−2·d–1 during the plug stage, there is probably going to be some height suppression when the plants are finished in the greenhouse. I wouldn’t expect there would be a major lasting effect of stem elongation suppression once in the greenhouse.”For more: Heidi Wollaeger, Michigan State University Extension, Nazareth, MI; (269) 384-8010; wollaege@anr.msu.edu; http://msue.anr.msu.edu/experts/heidi_wollaeger.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.
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High tunnels can be a part of a production system that allows growers to produce berries year-round while improving fruit yields and quality.
By David Kuack
High tunnels have different uses in different places, said Marvin Pritts, professor and chair of the Horticulture Section of Cornell University’s School of Integrative Plant Science in Ithaca, N.Y.
“In California, many growers use the tunnels for rain exclusion,” Pritts said. “In other places, tunnels are used to help cut down on the wind and to regulate temperatures. In the Northeast U.S. the tunnels work in multiple levels. They offer protection from rain. They also offer some temperature and wind control. Their only limitation in the Northeast is the length of the seasons.”
Pritts said growers in the Northeast have been using high tunnels for about 15 years.
“We have plenty of water, good soils and the population,” he said. “It has been exciting for growers to see the response of the plants grown in the high tunnels. Growers have been able to extend production by about a month on either side of the growing season so that it is earlier or later.”
Pritts said growers of tomatoes, cucumbers and greens have taken the most advantage of using the tunnels.
“Growers who produce tomatoes were the first ones who really got into using the high tunnels in a major way,” he said. “That was followed by cucumbers. These tunnels were used for summer vegetable production. During the cooler season there are a lot of greens produced, including spinach, arugula and some other greens that can almost be grown year-round in tunnels.
“Vegetable growers have been able to extend their production season for a longer period than ever before. Also, growers have been able to produce some crops, like blackberries and figs, that typically don’t grow here in the Northeast. Tunnels allow growers to overwinter these crops.”
Supplying local markets
Pritts said in the Northeast most of the crops are being grown for local sales.
“The growers supply local grocery stores like Wegmans and farmers markets,” he said. “Wegmans has its own farm where it is using high tunnels to grow various crops for its own stores.”
Wegmans Organic Farm in Canadaigua, N.Y., uses high tunnels to grow year-round at the 50-acre operation.
Pritts said he expects water restrictions in places like California will cause more growers to look at incorporating high tunnels into their production.
“At some point more of the production is going to have to shift eastward,” he said. “Growers in the Northeast don’t have a long season, but high tunnels offer some control. It makes sense to grow some of these crops locally where the markets are, where there is enough water and it’s relatively inexpensive to ship crops locally rather than shipping them across the country.”
Growing raspberries year-round
Pritts said growers in the Northeast are using high tunnels to harvest red raspberries earlier in the summer and to extend the production into the fall. Because the use of tunnels for berry production is a recent development, Pritts doesn’t really know which season the growers are using the tunnels for more. He expects it’s both.
Most of the high tunnel research that Pritts has done has been with primocane fall-bearing raspberries. These plants can be mowed down to the ground in the spring and they grow up and flower and fruit in the fall. Pritts said the canes can be pinched so that the plants flower and fruit later into the fall.
Marvin Pritts at Cornell University said growers could use
a combination of fall- and summer-fruiting raspberry
varieties along with outdoor field and high tunnel
production to produce a crop year-round.
Photos courtesy of Marvin Pritts, Cornell Univ.
“In October, raspberries aren’t available from field-grown plants in the Northeast because the temperature is too cold,” he said. “High tunnels allow raspberries to be picked in October when other locally-grown berries aren’t available. Growers in southern states are already done with their fall production. There also aren’t a lot of berries coming in from other parts of the world at this time. For those countries in the southern hemisphere, it would be too early to be harvesting berries. There is an opportunity for local growers in the Northeast to take advantage of limited market supplies. It’s a niche market.”
Pritts said growers also have the option of growing summer raspberries producing fruit in late June and early July.
“Summer production requires more trellising because the canes have to be maintained through the winter,” he said. “If a grower produces summer raspberries, the high tunnels have to be kept up year-round. With fall production, since the canes are cut back, the plastic covering on the tunnels can be removed for the winter. Since the covering is going to be removed, the tunnel structure doesn’t have to be as strong because snow loads aren’t an issue.
Pritts said being able to take the plastic off of the tunnels is a real advantage during the winter for the fall raspberries.
“Some of the salts in the soil can be leached out with the normal snow and rain during the winter,” he said. “Then the plastic can be put back on. If the raspberries are being grown in containers, then the growing medium can be flushed to leach out excess salts.”
Pritts said if a grower is producing summer raspberries or blackberries, the plants have to be brought through the winter in a tunnel.
“During a typical year, raspberries and blackberries make it through the winter in a tunnel just fine, although these past two winters were exceptions,” he said. “But the high tunnel has to be able to support the snow loads in order to protect the plants. During heavy snow storms, especially if the snow is wet, the snow needs to be removed from the high tunnel to prevent it from collapsing. These structures don’t usually handle more than a foot of snow.”
Pritts said it should be easier for growers to produce fall-fruiting raspberries.
“Fall raspberry varieties can produce a summer crop, but typically these varieties are grown solely as a fall crop,” he said. “If these plants are grown as a fall crop and allowed to go through the winter, they will produce a small summer crop. Most growers prefer to choose varieties specifically for summer production.”
Pritts said a grower could use a combination of fall- and summer-fruiting varieties along with outdoor field and high tunnel production to produce a raspberry crop year-round.
Differences in yield, quality
Pritts said one of the major reasons growers are producing raspberries in high tunnels is because of the difference in fruit quality.
One of the major reasons growers are producing raspberries
and blackberries (shown) in high tunnels is because of the
difference in fruit quality, including having a longer shelf life.
“Tunnels keep rain off of the fruit so that it doesn’t get moldy as fast as field-grown berries,” he said. “The quality is like day and night between raspberries grown in high tunnels and those grown in the field. Tunnel raspberries definitely have a much longer shelf life.
“In regards to flavor, the raspberries grown in tunnels are so high yielding that they are not as sweet as field-grown berries. Because the yields are so high in tunnels, it is hard for the plants to provide sugar to all that fruit. Even though the tunnel berries may be less sweet, the yields are so much higher. If someone ate the tunnel raspberries and didn’t have the field raspberries to compare them too, they would say the tunnel raspberries were very good tasting.”
Improving plant performance
Pritts said field-produced raspberries generally have a 10-year life span for the field they are being grown in.
“After a couple years for field-grown plants, there tends to be a decline in fruit production,” he said. “In high tunnels we never fertilize, but we amend the soil with compost before we plant. We don’t have to fertilize because the vigor of the plants is already good. There hasn’t been any decline in the yields of the high tunnel plants even after 10-12 years.”
Pritts said high tunnel plants aren’t exposed to the same environmental stress plants encounter in the field.
“Soil pathogens survive when the soil is wet for long periods of time,” he said. “In outdoor fields the soil is going to stay wet for long periods. Many of the disease pathogens also like cooler temperatures. I expect these pathogens gradually take the plants down in the field. In tunnels there usually aren’t long periods of standing water as would occur in outdoor fields.”
Another benefit of the high tunnels is wind exclusion.
“The stems on the raspberry canes are very thin and there is a lot fruit at the top of the plants,” Pritts said. “When the wind starts to blow, it whips the field-grown canes back and forth. This doesn’t happen in the tunnels. Previous research has shown the wind can be very detrimental to raspberry yields.”
Since the plants grown in tunnels aren’t exposed to the rain, drip irrigation is used to water the plants.
“Irrigation in the tunnels is between the plant rows,” Pritts said. “Outside when it rains the weed seeds germinate. In the tunnels there’s not much weed pressure at all.
“Another advantage of the high tunnels is the fruit can be harvested even when it’s raining, when it’s cold or when the wind is blowing. People don’t want to harvest in inclement weather. The tunnels enable a grower to schedule berry harvesting.”
Pritts said raspberry growers who use tunnels have to closely monitor plants for two-spotted spider mite.
“The difference in the populations of two-spotted mite is the biggest issue,” he said. “Outside, often times, growers don’t have to be concerned with mites. The mites are in the field, but they are at very low levels. They don’t like being wet so when it rains it depresses the populations. In the high tunnel where it doesn’t rain, there is a dry environment, which the mites thrive in.”
For more: Marvin Pritts, Cornell University, School of Integrative Plant Science, Horticulture Section, Ithaca, NY 14853; (607) 255-1778; mpp3@cornell.edu.
Other sources of information on the production of high tunnel berries:
High Tunnel Raspberries and Blackberries, http://fruit.cornell.edu/berry/production/pdfs/hightunnelsrasp2012.pdf. Raspberry Variety Review, http://www.fruit.cornell.edu/berry/production/pdfs/raspcultreview2012.pdf.
Low tunnel strawberries
Marvin Pritts, professor and chair of the Horticulture Section of Cornell University’s School of Integrative Plant Science is also doing a study on the production of strawberries in low tunnels. He is growing day neutral strawberries, which flower and fruit nearly all summer into the fall, in low tunnels.
“The strawberries are planted on a double row on a 16-inch raised bed with white plastic,” he said. “Hoops, which are covered with plastic film, go about 18 inches above the plants. The plastic is held down on the hoops with bungee cords.”
Marvin Pritts said it is about four times cheaper on a
per area basis to grow strawberries in a low tunnel
than in a high tunnel.
Pritts said the plastic film helps to keep the temperatures lower during the summer. The covered tunnels also retain some heat during the fall.
“The sides of the tunnels remain up almost all the time,” he said. “When it rains or it’s going to be cold or windy, the tunnel sides are lowered. The strawberries produce high quality fruit which can be grown nearly year-round.”
Pritts said it is about four times cheaper on a per area basis to use a low tunnel than it is to use a high tunnel because a tall hoop structure isn’t required.
“The plants only grow low to the ground so there’s no need to construct a 15-foot tall structure,” he said. “Like in the high tunnels, the plants in the low tunnels are watered and fertilized with drip irrigation. The drip line runs down the middle of the bed between the two rows of plants.”
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.
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The use of LEDs to provide specific light wavelengths could allow growers to increase nutritional values of edible crops, enhance the intensity of foliage and flower color and improve the postharvest longevity of ornamental and edible crops.
By David Kuack
Improvement in the light intensity delivered by light emitting diodes (LEDs) is helping to expand their use for the production of both edible and ornamental crops. Research with LEDs has been going on for about 30 years. Only within the last 10 years have increases in the light intensities of LEDs allowed researchers to study the direct effects of narrow wave bands of light on plant physiology.“LEDs are now available to deliver all blue, all red, all green, all yellow light or mixtures,” said University of Tennessee plant sciences professor Dean Kopsell. “White LEDs are almost a broad spectrum light source. White LEDs are actually mostly blue light with a little bit of red, yellow and green light with a white phosphor over them.”
Kopsell and his colleagues at the University of Tennessee are studying the impact individual types of light can have on the nutritional qualities of edible crops. Their work is focusing on crops that can be produced relatively quickly in 25-35 days, including microgreens and baby greens. They have also begun looking at some herbal crops including basil, tarragon and chives.
Researchers at the University of Tennessee are finding
that exposing plants like brassicas to blue light is
having a significant effect on their nutritional values.
Photos courtesy of Dean Kopsell, Univ. of Tenn.
“Some of the unique things we are finding are when we change the light quality environment, going away from broad band light sources like fluorescent, incandescent and HIDs, and exposing plants to narrow band wavelengths of red and blue light, many things are changing in the plants. These narrow bands of light are having an effect on several plant quality parameters from a metabolic standpoint.”
Potential of specific light wavelengthsUniversity of Tennessee researchers have found that exposing plants to narrow wavelengths of the light spectrum has resulted in the increased production of antioxidants and anti-carcinogenic compounds within the plants.
“What is even more interesting is some of the primary metabolites like the mineral nutrients are also increasing,” Kopsell said. “We are shifting the light ratios and putting more blue light into the mix. Blue light is close to the ultraviolet (UV) range and has higher energy values than red light. Because of the higher energy level associated with blue light, the more blue light we are exposing the plants to, it seems the more significant the results are on nutritional values.
“We haven’t got hard data yet, but everything that we can see, smell and taste, these blue lights not only affect nutrient uptake, and anti-oxidant metabolism, but they also affect aromatic compounds and flavor compounds. They make them more intense.”
Although researchers have only recently begun to study the impact of narrow light wavelengths on plant physiology, Kopsell said this will be the major use of LEDs in future applications.
“Not only is a grower going to be able to select the type of light and intensity from the LED manufacturer, but eventually the grower will know when is the critical time to apply a specific amount of light to a crop. One of the things that we have seen with these short term crops is using the light as a finishing-off treatment. The crops are grown under regular light conditions like any grower would have the ability to do and then just before harvest the plants would receive a specific type of light for a certain period of time. This light treatment would stimulate the plant physiology uptake and metabolism right before the plants go to the retail market.”
Kopsell said research exposing leafy brassicas to blue light prior to harvest has intensified pigments and green leaf color.
“We increased the green pigments in the leaves so that they looked more vibrant,” he said. “Other research has shown that UV light increases the anthocyanin compounds in leaf lettuce. Providing a little UV light, which is blocked out in most greenhouse environments, at the right time, a grower can get a crop to color up quickly before the plants are shipped out. What we have done with leafy greens to intensify the color of the leaves can also be done with petal tissue. By changing the light quality a grower could get more vibrant flower colors.”
Need for fine tune managementKopsell said whether plants are grown outdoors, in a greenhouse or in a closed controlled environment with artificial light, the plants are using specific wavelengths from the available light source.
“Horticulture, floriculture and agronomic researchers know how much light is needed in order to produce crops with broad spectrum light,” he said. “The million dollar question that hasn’t been answered is how much light is needed from LEDs to achieve that same level of production? It is going to be less than the daily light integral (DLI) from a broad spectrum light source. But, right now we can’t tell you how much less it’s going to be.
“Applying specific light wavelengths when the plants need them, whether it’s for juvenile growth, flowering or fruiting, we don’t have a good grasp on the amount of light that the plants actually need. If a grower is only going to supply his plants with red and blue light, how much less light can a grower use in that production system?”
One of the reasons that plants will not require as much light from LEDs is because of the reduction in light stresses.
University of Tennessee studies have shown LEDs
provide a less stressful light environment for plants.
“Providing specific types of red and blue light, the amount of stress on plants is reduced because the plants don’t have to tolerate the light not being used for metabolism and physiology,” he said. “We have data that shows LEDs provide a less stressful light environment for plants. So we have to determine how much less light is needed. It is going to require an extra level of management to know what kind of light, how much light and when to apply it. Growers are going to be able to use LEDs to fine tune the light environment. It’s going to depend on the crop, how it’s being grown, where it’s being grown and how the crop will be used. Is it an ornamental, edible or medicinal crop? It’s not going to be as easy as sticking a seed or cutting into a substrate and letting Mother Nature take control. It’s really going to take some fine tune management. But the future looks bright so far.”
For more: Dean Kopsell, University of Tennessee, Plant Sciences Department, Institute of Agriculture, Knoxville, TN 37996-4561; (865) 974-1145; dkopsell@utk.edu.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.
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