OptimIA project members are sharing their indoor farm research findings with the controlled environment agriculture industry and the public through a variety of educational and informational outlets.

The indoor farm industry is very fluid right now with changes occurring on a weekly basis. New companies are starting, some are leaving the industry, while others continue to receive millions of investor dollars to expand their operations. While financial stability is a key factor in the sustainability of some of these businesses, the need for production- and economic-related information is crucial to profitably producing quality leafy greens crops. Those with the financial backing have been able to develop and implement their own technology to produce indoor crops. New indoor farm growers, existing operations with limited financial resources, and even large-scale farms already in operation continue to look for sound production- and economic-related information that they can apply to their businesses.

Improving the indoor farm industry

In 2015 when members of the OptimIA project team initially submitted a USDA Specialty Crop Research Initiative grant proposal for funding, the primary focus of their research was on the production of leafy greens in indoor farms, but the focal points were moderately diverse.

“We went through the proposal submission process for several years before USDA approved the grant for the OptimIA project,” said Erik Runkle, who is project director and a horticulture professor at Michigan State University. “The proposal that was finally approved was to study the aerial environment as well as economics for leafy greens grown indoors. The aerial environment refers to air circulation, humidity, carbon dioxide concentration, light and temperature.”

One of the major objectives of the OptimIA project was to focus on industry outreach.

“The outreach program objective was to engage with stakeholders in the indoor vertical farming community,” Runkle said. “Prior to submitting the proposal to USDA, the project team members worked with an industry advisory committee and stakeholders from the indoor farm community.”

OptimIA team member Chieri Kubota, who is a professor and director of Ohio Controlled Environment Agriculture Center (OHCEAC) at Ohio State University, said proposals submitted for USDA Specialty Crop Research Initiative (SCRI) grants usually require both a strong research and outreach focus.

“USDA SCRI-funded projects focus on problem solving to move a specific industry forward,” Kubota said. “Not only is the research important, but also implementation of research findings in the industry sector. This is basically outreach extension. The proposals cannot just focus on research alone. It is important to have strong outreach activities.”

Multiple outreach activities, educational materials

Even before the grant proposal was submitted to USDA, OptimIA team members had already begun interacting with members of the indoor farm industry.

“We had been engaging stakeholders as a sort of proposal activities,” Kubota said. “We started doing the Indoor Ag Science Café almost a year in advance of submitting the grant funding proposal. That way we were engaging our stakeholders trying to develop a community educational platform that was a main activity. Indoor farm growers and equipment manufacturers are the general target audience of the project’s research. Team members are also constantly answering questions from growers and venture capital companies regarding indoor vertical farms.”

The OptimIA website includes a variety of educational materials including Research Highlights articles , scientific research journal publications and trade magazine articles, including Urban Ag News.

The OptimIA team members have also shared information from their research at various scientific- and grower-focused industry conferences. In July several members shared their research findings at Cultivate’23 during an educational workshop on the Essentials of Hydroponics Production: A tHRIve Symposium.

Team members have also been developing online educational materials under OptimIA University, which include YouTube videos.

“We have posted several lectures with topics based on discussions among the project members,” Kubota said. “The concept of OptimIA University is free access to whoever wants to use the online materials. The grower sector is the targeted audience.

“Rather than offering courses for a fee, we decided to make the information available to everyone, including growers and other companies that want to use it to train their employees. It consists of YouTube video lectures with pdf slides and additional reading materials. The OptimIA University website is about half completed and there are other course lectures still pending.”

The OptimIA researchers also hold an annual invitation-only stakeholder meeting.

“The annual meetings are specifically for our advisory committee which gives team members an opportunity to share information about the research in progress and that has been recently completed,” Runkle said. “It’s also an opportunity for the committee members to provide feedback and guide future project activity.

“We also invite growers and company representatives who we have worked with in some capacity on research projects. This includes growers with whom we may have conducted research trials or representatives from companies that have provided us with equipment or supplies used in our research.”

Educating the public

Even though the primary focus of the OptimIA project outreach program is members of the indoor farm industry, the team members also extend their educational activities to the general public.

“OptimIA researchers at Ohio State participated in the COSI Science Festival organized by the Columbus Museum of Science and Industry,” Kubota said. “This is a community STEM educational event in which companies and scientists participate and showcase their technologies and science. It is held in May over multiple days. We participated as an OptimIA group. We showed how leafy greens can be produced using different hydroponic systems with LED lights. OptimIA team members at Michigan State University and at University of Arizona have also done similar STEM programs related to hydroponic crop production for the public.”

For more: Erik Runkle, Michigan State University, Department of Horticulture; runkleer@msu.edu; https://www.canr.msu.edu/people/dr_erik_runkle; https://www.canr.msu.edu/profiles/dr_erik_runkle/cell. Chieri Kubota, Ohio State University, Department of Horticulture and Crop Science; kubota.10@osu.edu; https://hcs.osu.edu/our-people/dr-chieri-kubota; https://ohceac.osu.edu/. OptimIA, https://www.scri-optimia.org/.

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

OptimIA researchers are using crop modeling to identify the most favorable environmental parameters for growth and yield of indoor farm lettuce crops and how to prevent tipburn.

One of the research objectives of the OptimIA project, which is being funded by USDA to the tune of $2.4 million, is to study the aerial environment for producing indoor leafy greens. The aerial environment refers to air circulation, humidity, carbon dioxide concentration, light intensity, and temperature. Prior to preparing the project proposal, members of the OptimIA team surveyed stakeholders of the indoor farm industry to identify the challenges and needs of the industry.

“There was a lot of feedback related to environmental parameters, especially airflow,” said Murat Kacira, an OptimIA team member who is director of Controlled Environment Agriculture Center and professor in the Biosystems Engineering Department at the University of Arizona. “The indoor farm industry had a real need for optimizing the environmental variables related to light, temperature, humidity management and control. Leafy greens growers wanted to be able to understand plant growth, quantify the plant response, yield, as well as the quality attributes under various environmental conditions.”

Crop modeling predictions, potential

Kacira explains crop modeling is simply crop growth and yield prediction.

“Given setpoints for air temperature, photosynthetic active radiation, humidity, carbon dioxide enrichment, we were able to model crop growth and predict the kilograms or grams of lettuce yield on an hourly or daily basis and also at the end of the production cycle,” he said.

Kacira’s lab used modeling to focus on plant growth and yield predictions for lettuce in indoor vertical farms considering environmental variables, including temperature, humidity, carbon dioxide level and light intensity.

“Considering the co-optimization of different environmental variables, there are many combinations of those setpoints that are possible,” he said. “It takes a lot of time and effort to study all those combinations. A model we did was focused on plant growth and yield prediction for growing lettuce in indoor vertical farms considering environmental variables. Using modeling can help to narrow down the combinations or the possibilities that can occur.

Another modeling study enabled Kacira to identify the possibility of dynamic carbon dioxide enrichment.

“We looked at whether carbon dioxide enrichment should be done for the full production cycle from transplanting to little leaf harvest or whether it should be done during different phases of production leading to savings either for electrical energy or carbon dioxide use,” he said. “Also, we considered how carbon dioxide enrichment and control would be incorporated with lighting controls. For example, can the light be dimmed while increasing the carbon dioxide level to achieve a similar yield outcome, but with a control strategy enabling electrical energy savings during production.”

Determining best airflow distribution

Kacira is also using modeling and computer simulations to study airflow and airflow uniformity to design alternative air distribution systems to improve aerial environment uniformity and to prevent tipburn in lettuce crops.

“Early on we used computational fluid dynamics (CFD) space simulation and modeling to study airflow,” he said. “We looked at some existing air distribution systems to understand what would be the environmental uniformity and aerodynamics in indoor vertical farms. Then we studied what-if scenarios. We developed design alternatives that can deliver optimal growing conditions with improved aerial environment uniformity and help prevent lettuce tipburn.

“Our CFD simulations and experimental studies confirmed that vertical airflow compared to horizontal airflow was more effective reducing aerodynamic resistance with improved airflow and transpiration, thus preventing tipburn in lettuce.”

Some of the outcomes determined by Kacira and his team have been presented to OptimIA stakeholders and CEA industry members through seminars, webinars and research and trade publications. Kacira will continue using computer simulations, modeling, and experimental studies to design and test more effective localized air-distribution methods, environmental monitoring, and control strategies for indoor vertical farms.

Production techniques for preventing tipburn

Chieri Kubota, who is a member of the OptimIA team and professor and director of the Ohio Controlled Environment Agriculture Center at Ohio State University, and graduate student John Ertle studied various techniques for reducing or preventing tipburn. These techniques have application to lettuce crops produced in indoor farms and greenhouses.

“Growers can reduce the light intensity at the end of the production cycle to mitigate the risk of tipburn,” Kubota said. “If growers want to reduce tipburn and they can tolerate reduced yields, they can lower the light intensity towards the end of the production cycle.

“For example, when the daily light integral (DLI) was reduced by 50 percent for the final 12 days of production (out of 28 days), the incidence of tipburn can be largely reduced for cultivars sensitive to tipburn-inducing conditions. However, this approach reduces the yield and likely the quality of lettuce, while reducing the loss by tipburn. Therefore, efficacy of this approach is dependent on the cultivars and their growing conditions. More research needs to be done to refine this approach.”

Another technique growers can use to prevent tipburn is to stop growing lettuce before it enters the final 1½ weeks of the six-week growing period. This is what many growers are doing because they can’t take the risk of tipburn occurring. Plants are being harvested at this young stage.

Among the techniques that Kubota and Ertle examined, they found that the most effective in preventing tipburn was using vertical airflow fans. This technique was originally discovered by a research group at University of Tokyo in the 1990s and implemented into greenhouse hydroponics at Cornell University.

“We confirmed that when vertical airflow is applied under conditions that highly favor tipburn induction, tipburn can be prevented very effectively,” Kubota said. “We created an environment based on our previous knowledge which always induces tipburn. We confirmed the use of vertical airflow fans reduces tipburn.”

For more: Murat Kacira, University of Arizona, Controlled Environment Agriculture Center; mkacira@arizona.edu; http://ceac.arizona.edu/.

Chieri Kubota, Ohio State University, Department of Horticulture and Crop Science; kubota.10@osu.edu; https://hcs.osu.edu/our-people/dr-chieri-kubota; https://ohceac.osu.edu/. OptimIA, https://www.scri-optimia.org/.

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

OptimIA at Cultivate’23

If you are attending this year’s Cultivate’23, July 15-18 in Columbus, Ohio, you have the opportunity to hear OptimiA researchers, including Murat Kacira and Chieri Kubota, discuss some of the findings of their research. They will be speaking during the Essentials of Hydroponics Production – a tHRIve Symposium on Saturday, July 15 from 8-11 a.m.

More importantly, will consumers pay a higher price for controlled-environment-grown produce?

Over the last five years, leafy greens have been the “it” crop for indoor farm production. Most indoor farms have started with leafy greens, primarily lettuce, and have looked to expand their product offerings to include herbs, microgreens, strawberries and tomatoes.

The OptimIA project, which is funded by USDA, is studying the aerial production environment and economics for growing indoor leafy greens in vertical farms. While much of the research of this four-year project has focused on managing the environment for vertical farm production, the economics related to this production is a major objective of OptimIA researchers. Based on feedback from commercial vertical farm growers, one of the primary areas of research is to develop economic information, including costs, potential profits, and to conduct an economic analysis to determine the strategies to improve profitability based on that information.

OptimIA researchers at Michigan State University who are focused on the economic aspects of vertical farm production include: Simone Valle de Souza, an ag economics professor; Chris Peterson, an emeritus professor in the Department of Agricultural, Food, and Resource Economics; and PhD student Joseph Seong, who is developing his thesis on the economics of indoor agriculture.

“I was invited by the other OptimIA researchers to use mathematical models that take into consideration the biology and technical parameters to determine the potential revenues and costs,” Valle de Souza said. “My team of economists is looking to identify the economic tradeoffs from the implementation of multiple environmental factors that the other OptimIA researchers were optimizing or planned to optimize as part of the project. Our job is to identify the optimal parameters for profitability in controlled environment production. As part of the OptimIA project, we tackled two aspects of economic analysis: production and resource-use efficiency and consumer preferences.”

Maximizing profits

As part of the economic analysis, Valle de Souza considered the variable costs of labor, electricity, seed, substrates and packaging materials. Based on the information collected from commercial indoor farm growers, labor was the largest cost at 41 percent of total variable operating costs, followed by electricity at 29 percent, seed and substrates at 22 percent and packaging materials at 7 percent.

“We did a sensitivity analysis to determine what would happen to profits if wages increased,” Valle de Souza said. “We conducted a series of simulations and determined on average a 1 percent increase in wages would reduce profit per square meter for a day of production by 6 cents. A 1 percent increase in the price of electricity would reduce profits by 5 cents per square meter per day. The contribution margin to profit is normalized on a per square meter per day of production so that we can make comparisons.”

While many growers might look to lower variable costs to increase profitability, Valle de Souza found that increasing the price of lettuce could be the better way to go.

“A 1 percent increase in the price of a head lettuce could increase profits by 60 cents per square meter per day,” she said. “Our analysis showed a revenue maximizing strategy is superior to a cost minimizing strategy. Reducing variable costs could result in savings of 5-6 cents in profit. However, during simulation scenarios that we tried, a revenue maximizing strategy could proportionately increase profits 10 times more by as much as 60 cents.”

OptimIA economists determined a 1 percent increase in the price of a head of lettuce could increase profits by 60 cents per square meter per day. A 1 percent increase in wages would reduce profit by 6 cents per square meter a day. A 1 percent increase in the price of electricity would reduce profits by 5 cents per square meter per day. Graph courtesy of Simone Valle de Souza, Mich. St. Univ.

Optimal length of production

Another part of the analysis done by the OptimIA economic researchers was to estimate the optimum length of the lettuce production cycle.

“In terms of production cycle length, we compared the trade-off between costs from one extra production day and revenues from yield that could be achieved from one extra day of growth,” Valle de Souza said. “We tried to estimate how long growers could allow lettuce plants to grow to take advantage of the fast growth rate the plants experience at the end of a production cycle. Using estimates of plant growth and plant density under an optimized space usage defined by our OptimIA colleagues at the University of Arizona, we found that under specific environmental conditions, day 19 after transplant, or 33 days from seeding, was the ideal harvesting day.”

Even though maximum revenue could be achieved earlier, at day 15 after transplant, costs per day of growth were higher for shorter production cycles. The contribution margin to profit, which was estimated as the difference between revenue and costs in this partial budget analysis, was larger at 19 days after transplant. After 33 days, profit starts to decline because the speed of plant growth rate is not as fast as the increase in costs associated with growing.

“We have determined the economic results from space optimization, estimated optimal production cycle length under given conditions, and the economic results from alternate scenarios of light intensity, carbon dioxide concentration and temperature,” Valle de Souza said. “In collaboration with our OptimIA colleagues, we are now working on a final optimization model that will associate optimal profitability with resource-use efficiency.”

Opportunity to educate consumers

Another aspect of the OptimIA economics research looked at consumer behavior and preferences in regards to indoor farms and the crops they produce. Using a national survey, the researchers determined whether consumers are willing to buy lettuce produced in indoor farms and how much they would be willing to pay for the enhanced attributes of produce grown in indoor farms.

“The survey showed no consumers rejected the innovative technology being used by indoor farms,” Valle de Souza said. “There was a group of consumers who were very supportive of the technology and completely understood what an indoor farm is. Another group of consumers were engaged, but not very convinced of the technology. Another group was skeptical of the claims of indoor-farm-produced leafy greens and were less willing to consume them. This same group said they had no knowledge about indoor farms and how they work.

“There were no consumers who had knowledge about indoor farms and rejected the leafy greens grown in these operations. Some consumers are still cautious given their little understanding about how the production systems work.”

Based on the survey results, Valle de Souza said the indoor farm industry has an opportunity to educate consumers about its production technology.

“The indoor farm industry could promote information materials that explain the benefits of a fully controlled growth environment,” she said. “Growers could explain how this technology eliminates the use of pesticides, how it can improve crop quality attributes, along with the environmental benefits of significantly lower water consumption, reduced land use, and the ability to deliver fresh produce to consumers in urban areas.”

Consumer willingness to pay more

Consumers surveyed by OptimIA researchers indicated they were willing to pay a premium for lettuce with enhanced attributes.

“We tested for taste, freshness, nutrient levels and food safety,” Valle de Souza said. “Consumers were willing to pay a premium for these attributes, especially in urban areas.

“Rural dwellers usually have their own backyards in which they can grow vegetables. They are used to seeing vegetables growing in the soil using sunlight. Rural residents were not as convinced about the need for indoor farms to produce leafy greens. Another interesting survey result was that consumers, in general, are not very decided if they prefer produce grown in indoor farms, greenhouses or outdoors.”

For more: Simone Valle de Souza, Michigan State University, Department of Agricultural, Food, and Resource Economics; valledes@msu.edu; http://www.canr.msu.edu/people/simone_valle_de_souza.

OptimIA Ag Science Café #40: Consumer Varieties for Indoor Farm Produced Leafy Greens, https://www.scri-optimia.org/showcafe.php?ID=111156.

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

Researchers with the OptimIA project are working to solve the environmental control issues facing indoor farm growers.

While some might think that the environmental challenges facing indoor farm growers should be relatively minor and easy to overcome in a closed environment, they’d be wrong.

“Some of the challenges and bottlenecks facing indoor farms include insufficient airflow leading to a non-uniform environment, lighting that is wasteful and how light is delivered into the canopy,” said Murat Kacira, director of the Controlled Environment Agriculture Center (CEAC) at the University of Arizona and a member of the OptimIA project research team. “In addition to these challenges, there are those related to the humidity and water management in the aerial environment as well as identifying the best light quality, light intensity and light recipes for indoor farm crops.”

Prior to the start of the OptimIA project in 2019, surveys were conducted of stakeholders in the indoor farm industry, including growers, to determine what are the areas of greatest need for research.

“An indoor farm is a closed box,” Kacira said. “You know what goes in and what comes out, but it demands the resources to control that environment, which include controlling the light, temperature, humidity, carbon dioxide and all other processes to grow the crop to meet production expectations.  

“An indoor farm offers tighter control than in a greenhouse environment. There is not the same effect from the outdoor dynamics, for example the light intensity, temperature and water recirculation from the air. Being able to harvest the water from the air is easier in an indoor farm system compared to a greenhouse system. There is more controllability when it comes to an indoor farm compared to a greenhouse, of course with an additional expense for resource use to achieve such control.”

Focused on environmental control

Kacira and his team of graduate students KC Shasteen and Christopher Kaufmann at the University of Arizona are significant contributors on the environmental control aspects of the OptimIA project.

“We are also considering light because light brings the energy to the plants and then the energy has to be released for cooling and for proper transpiration and nutrient deployment from the roots,” Kacira said.

Kacira’s team conducted computer simulations to help improve airflow and to identify co-optimization of environmental variables for energy savings. Building upon computer simulation research outcomes, Kaufmann is conducting experiments in CEAC’s vertical farm facility to evaluate vertical and horizontal airflow system designs to mitigate tipburn on lettuce crops. Shasteen and Kacira worked on modeling with the co-optimization of variables, including light, temperature, relative humidity and carbon dioxide level.

“We have been able to quantify yield outcomes and to determine what the energy use would be for any of those environmental control strategies,” Kacira said. “These models and the outcomes and information that we have generated from this research are used by our OptimIA colleagues on the economics team. They are developing economic models for a variety of scenarios of profitability and economics for indoor farm applications and indoor farm systems.

“We are focused primarily on airflow system design and optimization, humidity management and co-optimization of environmental variables mainly for energy savings. Our collaborations also included Nadia Sabeh at Dr. Greenhouse on the humidity management side of the environmental control aspect.”

Real-world applications

Some of the research outcomes from the University of Arizona team related to airflow systems designs, concepts and recommendations have been incorporated into actual growing settings in commercial operations.

“We are able to incorporate some of our research results into commercial site trials through our collaborations,” Kacira said. “We have over 20 industry collaborators as part of the OptimIA project. Some of the collaborators showed interest in implementing some of the airflow system designs, environment control, and co-optimization of these variables into their operations. We will also have an opportunity before the OptimIA project ends to implement them directly and evaluate some of the research outcomes in commercial settings.”

Saving on energy costs

Sole-source lighting is the largest energy cost of indoor farms. Indoor farm energy costs account for at least 30 percent of the total operational costs. Other energy costs are related to operating fans, dehumidification and ventilation.

“The focus of the OptimIA research at Purdue University is to identify and try to reduce the energy costs related to growing indoor crops,” said Cary Mitchell, horticulture professor at Purdue University. “If an indoor farm grower is using sole-source lighting that is going to be the biggest energy cost. These indoor farms spend hundreds of thousands of dollars per year on electricity and it’s mostly for lighting.”

Mitchell has long been interested in energy as one of the profit-determining and profit-limiting parameters in indoor farming.

“All of the OptimIA researchers are interested in saving resources for growing leafy greens and culinary herbs indoors,” he said. “That is the common thread among all of us. Purdue researchers are focused on energy savings. “

Avoid wasting light

Mitchell and PhD graduate student Fatemeh Sheibani are working on close-canopy LED lighting. This lighting is similar to intra-canopy lighting that is used on some greenhouse crops including high wire tomatoes and fresh cut roses.

“One of our findings is if the separation distance is reduced between the LED light fixtures and the crop below without dimming the LEDs, the productivity of the plants goes up,” he said.

LEDs are a point source of light with much of the light radiating like a star in all directions.

“When LED fixtures are mounted overhead in an indoor farm much of the light goes to the side obliquely,” Mitchell said. “Not all of the light is going down towards the plants. There is a significant amount of photons wasted falling outside of the cropping area. There’s not much that can be done about it other than to move the lights closer to the plants.” 

Because LEDs are cool, unlike high intensity discharge (HID) lamps, the separation distance between LED fixtures and the plants can be decreased without burning the plants.

“The separation distance can be reduced so that most of the obliquely emitted photons actually are captured by the crop surface instead of going off the edge of the bench,” Mitchell said. “Regardless of whether growers run LED fixtures along the bench or across the bench, they don’t want gradients of crop growth. Growers want just as much growth on the edges as in the middle of the bench. This can cause growers to mount lights not only in the middle of the bench, but also out towards the edges. The further toward the edges the fixtures are mounted, the more photons are lost.”

Putting more light on the plants

Sheibani is studying two scenarios of close-canopy lighting. One scenario is as the LED lights are placed closer to the plants, the light is dimmed. Even though the light is dimmed, there is the same intensity of light at the plant surface because more laterally emitted photons are captured, but less electricity is used. In a second scenario, Sheibani placed the LED lights closer to the plants, but did not dim them.

“In this second scenario, placing the fixtures closer to the plants once again reduced the amount of photon loss,” Mitchell said. “In this case, for the same power and energy usage the plant yields increased because the effective light intensity increased. The plants grew faster and bigger. Each increment of closer spacing results in a higher energy utilization efficiency.”

In indoor vertical farms the traditional separation distance between the bottom of the LED fixtures and the top of the crop is 40-50 centimeters.

“We have tested separation distances between the fixtures and plants of 45, 35, 25 and 15 centimeters,” Mitchell said. “We found that energy utilization efficiency increases linearly as the lights are placed closer to the plants. This should be relatively easy to implement in most indoor farms, but may require some design modifications from equipment suppliers.”

Mitchell explained the reason the two scenarios were studied is because some indoor farms are equipped with non-dimmable LED lights.

“In the case of non-dimmable LED fixtures, when the lights are brought closer to the plants, the energy draw by the lights is the same, but the yield goes up, which means the plants grow faster,” he said. “This means the plants can reach the same biomass and be harvested earlier or the harvest date can remain the same and more biomass can be produced. This gives growers the option to use close-canopy lighting for what works best for their production needs.”

Mitchell points out that not every LED fixture commercially available works well in close-canopy lighting applications.

“There are some LED lights where the distribution of colors is not uniform, where there are clusters of blue light,” he said. “This is not a big deal with a 45-centimeter separation distance between the lights and the plants because with the amount of beam spread there is enough distance for the other colors to overlap the blue light. But when the lights are placed within 25 to 15 centimeters of the plant surface, there are clusters of blue light. Blue light inhibits leaf expansion and promotes leaf coloration. The result can be very strange looking crop stands if close-canopy lighting is done with LEDs with uneven light distribution. Fortunately for growers, most of the commercial LED arrays available today for horticultural lighting are quite uniform.”

For more: Murat Kacira, University of Arizona, Controlled Environment Agriculture Center; mkacira@arizona.edu; http://ceac.arizona.edu/. Cary Mitchell, Purdue University, Horticulture & Landscape Architecture; cmitchel@purdue.edu; https://ag.purdue.edu/department/hla/directory.html#/cmitchel.

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

OptimIA researchers are studying the impact light and its interaction with other environmental parameters can have on indoor leafy greens production.

When members of the OptimIA project contacted controlled environment agriculture industry members about their concerns about the growing environment, light was at the top of the list. The OptimIA’s project objectives were based on feedback from indoor farm representatives, growers and lighting manufacturers related to the production of food crops.

“Lighting is one of the biggest costs not only for purchasing the fixtures, but also for operating them,” said Erik Runkle, horticulture professor at Michigan State University and director of the OptimIA project. “Operating lighting fixtures is a big sink of electricity and therefore a major operating cost. Another large operational cost for indoor farms is air conditioning, but typically it is not as big as lighting.

“Looking at some of the other environmental control issues that indoor farms have had in the past, excessively high humidity was caused by inadequate HVAC systems. Humidity and temperature are tightly linked because temperature influences how much moisture the air can hold. We thought if we study humidity we should also study temperature. Temperature dictates the rate of development of plants.”

Runkle said carbon dioxide gets added to the environmental mix when looking at light intensity.

“The benefit of carbon dioxide increases as light delivered to plants increases,” he said. “Early on when we started this project we were delivering, what is considered by today’s standards, relatively low light intensities, so the value of adding supplemental carbon dioxide was minimal.

“Indoor farms are increasingly delivering higher light intensities, in which case carbon dioxide becomes more important. We knew that carbon dioxide is one of the factors to consider with indoor farms, but it was not considered one of the top factors like light, temperature and relative humidity.”

Divvying up the research projects

Prior to receiving $2.4 million in USDA funding in September 2019 for the OptimIA project, Runkle had started the Controlled-Environment Lighting Laboratory at Michigan State.

“The lab is a unique facility that has capabilities that few other researchers at the time had,” he said. “Having access to the lab, it made sense for me to focus on light quality or the different colors of light and how they affect growth. A lot of what each team member focused their project research on was imposed by their expertise in the topic and whether they had the facilities to conduct the research.

“Developing these research facilities is quite expensive, and usually with these types of research proposals, large equipment budgets are not favorably reviewed. OptimIA team members thought rather than requesting a large equipment budget, we would determine who had the equipment and facilities to do lighting studies. Also, we looked at who had past research expertise so it just made sense for them to perform the various environmental studies.”

Light was the single environmental factor that the OptimIA researchers keyed in on. Every member of the OptimIA team, other than its ag economists, has done some type of light manipulation research.

Studying different aspects of light

The three major areas of light study were: 1. light intensity or the brightness of the light; 2. the different colors of light, primarily blue light, far-red light and ultraviolet (UV) light, and 3. the uniformity of light, which is often an overlooked dimension of light.

“The brightness, the colors and how many hours light fixtures are operated per day are usually the focus of light research,” Runkle said. “Light distribution uniformity is often overlooked, but we have seen that uniformity can be an issue in indoor farms.

“For OptimIA researcher Cary Mitchell at Purdue University one of the focal points of his research is the positioning of light fixtures trying to reduce the amount of light that spills into areas where there are no plants. There is light that reaches the target within a crop, but there is also light that spreads out beyond where the plants are located. This is light that is wasted because it doesn’t reach the plants. Trying to deliver as much light from the fixtures to the plants can improve efficiency because the light is reaching the plants and is not wasted.”

The relationship between environmental parameters

OptimIA researcher Roberto Lopez, associate horticulture professor at Michigan State, is studying the interaction of light, temperature and carbon dioxide on leafy greens production.

“Previous research between these environmental parameters had been done in greenhouses,” Lopez said. “We are using walk-in growth chambers to provide more control over the light environment. Unlike in a greenhouse, there isn’t any sunlight in indoor farms that can impact the results.

“We wanted to see how carbon dioxide and temperature interact with light. Light and temperature studies can be done in a greenhouse, but carbon dioxide studies are going to be challenging. Being able to do the studies indoors makes it more feasible.”

Prior to the start of his OptimIA studies, Lopez was using dimmable white light LEDs in the growth chambers.

“Signify provided us with dimmable LED light fixtures which allow us to manipulate the spectrum,” he said. “With the new fixtures we not only can deliver white light, but we can change the spectrum whenever we need to during the growth cycle.

“In some of our later studies we have been looking at manipulating the color of the foliage with the spectrum. This allows us to start growing the plants under white light and towards the end of the production cycle we can change the light spectrum to potentially manipulate the color of the foliage or increase the amount of anthocyanin and other nutritional compounds.”

Impact of light intensity

Lopez said the impact of light intensity on lettuce production appears to be cultivar dependent.

“With some lettuce cultivars we found 150 micromoles of light is sufficient and with others we had to increase the light level to 300 micromoles to achieve an increase in yield,” he said. “With other cultivars we found by doubling the amount of light there isn’t an economic benefit to increase the light intensity. It wasn’t worth increasing the light intensity in terms of the yield that we were able to achieve, at least when based on our economic assumptions.”

Lopez said some indoor farm growers of leafy greens are increasing light intensity levels to 600 micromoles.

“Is that light level necessary? In our opinion—no,” he said. “It doesn’t make sense because at some point the plants become saturated with light and the growers are wasting money. The plants may not be utilizing the light if the other environmental parameters are not adjusted accordingly.

And economically it doesn’t make sense. To achieve these light levels requires more lighting fixtures and there are increased electrical costs.”

Impact of light color

Results of OptimIA studies have confirmed the importance of blue light on plant growth.

“Blue light has a strong effect on inhibiting leaf size, which means plants are smaller compared to plants grown under lower intensities of blue light,” Runkle said. “Blue light also controls the coloration of leaves as well as other quality attributes, including the nutrient density and perhaps taste.

“OptimIA researchers weren’t the only ones to discover the effects of blue light, but we are building upon other blue light research to learn how important it is and what different intensities of blue light do to leafy greens crops.”

Runkle said the light spectrum or the color of the light is more important in indoor farms than in greenhouses.

“In a greenhouse there is sunlight and the ability to change the spectrum is influenced by how much sunlight is entering the greenhouse,” he said. “During winter when supplemental lighting is used the most in greenhouses, is when lighting is most valuable and the ability for the spectrum to influence plant growth is also the greatest. Because blue light has such a strong effect on the shape of plants, the percentage of blue light chosen for an indoor farm can be a much bigger decision than the percentage of blue light in a greenhouse.”

Runkle said the verdict is still out on whether or not far-red light is necessary in indoor farms.

“Far-red light is similar to blue light and how much light should be given to plants,” he said. “Blue light and far-red light act antagonistically. Far-red light increases leaf expansion, which often leads to more growth because the plants can intercept more light. This growth increase is somewhat countered by a decrease in the quality. Plants exposed to far-red light typically produce leaves that are lighter green in color or the leaf texture is affected, including thinner leaves and leaves that are not as crisp or firm.

“Applying far-red light can lead to tradeoffs between maximizing biomass and plant quality. There are usually tradeoffs between the harvestable index or what can be harvested and the quality of that harvest.”

Verdict still out on UV light

There has not been a lot of research done with UV light in the indoor production of leafy greens.

“There are various reasons research with UV light hasn’t been done,” Runkle said. “LEDs that deliver UV light are not very efficient and they typically don’t have a very long life span.

“We have done a few studies looking at the efficacy of using UV-A light compared to blue light. We found that blue light and UV-A light are similarly effective in terms of plant responses. But blue light is a lot cheaper to deliver. Blue light LEDs are cheaper and last a lot longer. If the same response can be achieved with blue light LEDs than UV-A LEDs, then at least in our research we haven’t seen any reason to include UV-A light.”

Relationship between light and carbon dioxide

Ambient carbon dioxide level is about 400 parts per million (ppm). Lopez did studies with lettuce supplementing plants with 400, 800 and 1,200 ppm.

“Going from 400 ppm to 800 ppm there was an increase in yield,” he said. “Going above 800 ppm there wasn’t much of an appreciable increase. There is definitely a limit and beyond 800 ppm, there wasn’t any economic benefit as well.

“Whenever any of these three environmental factors are limiting, a grower could provide optimal light levels and the optimal temperature, but if carbon dioxide is limiting, then ultimately photosynthesis is limited, which impacts crop yields. It’s important to measure, monitor and control all three parameters. In a greenhouse it is challenging to do this. With an indoor farm it is possible to have much more control of these environmental parameters.”

For more: Erik Runkle, Michigan State University, Department of Horticulture; runkleer@msu.edu; https://www.canr.msu.edu/people/dr_erik_runkle.
Roberto Lopez, Michigan State University, Department of Horticulture; rglopez@msu.edu; https://www.canr.msu.edu/people/dr_roberto_lopez?profileDisplayContent=contactInfo.

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

OptimIA is a research and outreach project aimed at offering production and economic information that is useful and can be applied to the indoor farm industry.

The concept of OptimIA originated when Erik Runkle at Michigan State University, Chieri Kubota at Ohio State University and Cary Mitchell at Purdue University were involved in an LED lighting project focused on greenhouse applications.

“It was getting to the end of the project and we asked ourselves what is the next frontier of lighting and growing,” said Runkle, who is a horticulture professor at Michigan State. “We came to the realization that the greatest opportunity and need for information was managing the environment for vertical farming production. We saw the next frontier as growing indoors and the need for research-based information. The name OptimIA came from our focus on optimizing indoor agriculture–Opti for optimizing and IA for indoor agriculture.”

In 2015 the three researchers submitted a USDA Specialty Crop Research Initiative grant proposal for funding that would focus on lighting, but would include other aspects of growing indoors.

“We went through the proposal submission process for several years before the USDA approved the grant for the OptimIA project,” Runkle said. “The proposal that was finally approved was to study the aerial environment as well as economics for indoor leafy greens. The aerial environment refers to air circulation, humidity, carbon dioxide concentration, light and temperature. Some of our team members are also studying root zone management of hydroponic crops using additional funding.”

USDA awarded $2.4 million to the OptimIA project in September 2019, which was scheduled to be completed in four years. Runkle is the project director with the funding split between six researchers. In addition to Runkle, Kubota and Mitchell, the OptimIA team consists of Roberto Lopez, horticulture professor at Michigan State, Simone Valle de Souza‬, ag economist at Michigan State, and Murat Kacira, director of the Controlled Environment Agriculture Center at University of Arizona. Besides these co-principal investigators, other collaborators on the project include Chris Peterson, ag economist emeritus at Michigan State, Jennifer Boldt, a research horticulturist at USDA-ARS, and Nadia Sabeh, president and founder of Dr. Greenhouse Inc., which specializes in the design of HVAC systems for indoor plant environments.‬‬‬‬‬‬‬

Focused on the needs of indoor growing

The OptimIA project objectives were based on feedback from commercial vertical farms.

“Erik, Cary and I visited several commercial vertical farms before we started this project,” said Chieri Kubota, who is director of the Ohio Controlled Environment Agriculture Center at Ohio State University. “We received feedback from growers as to what to work on using USDA funding.”

Based on input from commercial indoor growers, three areas of research were identified:

1. Develop economic information, including the costs, potential profits and conduct an economic analysis to determine the strategies to improve profitability based on that information.

2. Vertical farms have the capacity to optimize multiple environmental factors at the same time. The information for co-optimizing more than two of these factors together didn’t exist. OptimIA is looking at co-optimization of multiple factors in order to optimize production performance of plants to increase yields.

3. OptimIA is looking to provide extension outreach to educate the professionals who are involved in vertical farming. Often the people who are trying to develop commercial indoor farms are educated in the business sector or other sectors like agronomy and may not have training in controlled environment production.

“Economics is a major part of this project,” Runkle said. “There is no doubt that high quality leafy greens can be grown in indoor farms. The challenge is how to do this profitably and sustainably. The economists on our team are working to quantify the costs of production and then determine the greatest opportunities to reduce input costs.

“There is very little financial information available about this sector of the controlled environment industry. It is very competitive and secretive, so it is difficult to get a clear sense of the economics. There are more researchers studying the plant production side, but the OptimIA team realizes the importance of the economics.”

Industry participation opportunities

Commercial growers and allied trades people can become involved with OptimIA by attending OptimIA’s annual stakeholder meeting.

“In the stakeholder meetings those people or companies willing to collaborate or who have been collaborating with us can participate in determining specific collaboration opportunities and to provide feedback to our research outcomes,” Kubota said. “We have on-site trials planned for testing some of OptimIA’s research findings in commercial settings. These findings might include the optimum light spectra for growing specific leafy greens or sensing the environmental inputs that might cause nutrient disorders like tipburn. If any stakeholders or companies are interested in testing a new approach in their facilities through this on-site collaboration we welcome that opportunity.”

Another form of support from the industry can come through in-kind support pledges.

“Initially this project proposal was submitted to USDA with a pledge of in-kind support,” Kubota said. “Many companies, including lighting, growing media and fertilizer manufacturers have provided in-kind support pledges. We can add additional in-kind support contributions if other companies want to provide technologies useable in the project, as well as on-site trials if a company wants to conduct trials. Doing the trials means a company has to be willing to spend the time, production space and employee participation. These are evaluated as in-kind support.”

Need for more grower collaboration

Because of the competitiveness currently within the indoor farm sector, there has been some hesitancy from commercial growers to share production and economic information.

“Some of these indoor farm growers are of the mindset that they want to dominate their sector,” Kubota said. “They aren’t thinking that the industry is new so let’s help each other in order to establish the sector together so that it can grow.

“Another issue is most of the funding for the indoor farming sector comes from venture capital. These indoor farms are chasing a limited number of investors. The potential leafy greens and other indoor farm crops market is huge. If growers work together to try to bring the technology together and develop some type of standardization, it would be easier to introduce new supporting technologies.”

Kubota said many indoor farms are designing and developing unique production systems.

“Because of the unique technology being incorporated into these farms, it is not easy to develop automation or adapt other existing technologies to support current systems because they are not standardized,” she said. “Because of the funding issues and the culture it can be difficult to get started in the indoor farm sector.”

OptimIA researchers said at times it has been difficult collecting specific information from indoor farm companies.

“The challenge is indoor farm companies don’t like to share much about their technology or about their production,” Runkle said. “They don’t like to share what their light set points are or what their production cycles are. They don’t like to get into specifics because it is their intellectual property.

“When we have opportunities for input on our research, we do receive some helpful information. One example is with our light studies, we have been delivering light intensities that were common three years ago, but now indoor farms are delivering more light. Growers would like to see studies done with higher light intensities, which shows the industry is developing very quickly. It’s good that the indoor farms provide input, but they need to share more of their interests and feedback related to our studies. This could influence what our treatments might be.”

Disseminating research findings, educational information

One of the major ways OptimIA is disseminating information about its research findings is through its monthly Indoor Ag Science Café webinars.

“We often include our own research findings in the webinars, but we also invite other presenters to share educational information,” Kubota said. “Originally the webinars were supposed to be a closed forum so that people could discuss things without having to worry about comments or information being publicized. When the Café started in 2018 there were about 60 participants in the listserv who received information of the monthly topics. Since then the number of people participating in the webinars has increased to over 1,300. 

“Many of the participants are international because they don’t have these kinds of events in their own countries. That is one of the reasons we wanted to improve communication. We want to respond to their needs more effectively. We keep looking for ways to provide information to the indoor farm industry.”

Researchers, who are not members of the OptimIA team, have also done presentations for the Café.

“These other researchers are working on critical areas of indoor vertical farms,” Kubota said. “For example, Paul Fisher at the University of Florida has discussed biofilm, food safety and water quality. A.J. Both at Rutgers University talked about the basics of sensors, how to use them and how to install the appropriate sensors.”

Although some commercial indoor farms, including Plenty, 80Acres Farms, Oishi and Harvest Moon Farms have done webinars, some have declined because the presentations are usually recorded.

“Many representatives from commercial indoor farms do not like to be recorded. Consequently there aren’t as many commercial corporation presentations on the OptimIA archive page. Some companies do not want me to record their presentations. Companies that do presentations sometimes deliver very general information that lacks specifics.”

For more: Erik Runkle, Michigan State University, Department of Horticulture; runkleer@msu.edu; https://www.canr.msu.edu/people/dr_erik_runkle. Chieri Kubota, Ohio State University, Department of Horticulture and Crop Science; kubota.10@osu.edu; https://hcs.osu.edu/our-people/dr-chieri-kubota. OptimIA, https://www.scri-optimia.org/.

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

The oxygen level and temperature in the root zone can have a major impact on rate of plant growth and inhibiting root diseases.

When it comes to hydroponic vegetable production the root zone environment, including oxygen levels and root temperature, play a critical role in the success of the crop.

“For true hydroponics, which would include deep water culture and nutrient film technique (NFT), both have different oxygen profiles,” said Neil Mattson, greenhouse horticulture professor at Cornell University. “Typically with NFT, there is near saturation with oxygen because of mechanical aeration from the water recirculation that is occurring. The water that is pumped through an NFT system and is emitted by spaghetti tubing becomes essentially saturated with oxygen. This water is running across the plant roots continuously.”

Deep water culture, which usually has a sizable water reservoir, has a large storage capacity for dissolved oxygen.

“Deep water culture systems are less prone to temperature and pH swings,” Mattson said. “Growers looking to add oxygen to a deep water culture system have to actively add oxygen to make sure there is a sufficient level in the water.

“Typically growers do one of two things to add oxygen. The first option is to install a Venturi pump to bubble in outside air into the water reservoir and then distribute the oxygen throughout the pond. Oxygen doesn’t diffuse well through water so a grower has to make sure not to place the pump in one location and not distribute the oxygen throughout the pond. A grower also has to install tubing and a manifold system so that the oxygen is distributed to numerous points throughout the pond. Smaller growers tend to use the Venturi system.”

In addition to bubbling or pumping in air, growers with deep water culture systems can inject liquid oxygen or incorporate a nanobubble oxygen generation system.

“The oxygen comes either from tanks of liquid oxygen or from an oxygen-generation system,” Mattson said. “Growers who choose these options would still need a pond distribution system. But instead of using a lot of pumping capacity to bubble in the air (about 21 percent oxygen), the air would be circulated with a pump.”

Seasonal variations in oxygen levels

Mattson said growers using deep water culture need to monitor the oxygen level with a dissolved oxygen meter. The oxygen level should be adjusted over time as the crop is growing.

“Factors that affect the oxygen level in the water include the absorption of oxygen by the plant roots,” he said. “How quickly the oxygen is depleted depends on how quickly the plants are growing and the water temperature.

“Other factors affecting the oxygen level include microbes and algae in the water that might be competing for the oxygen. There is also diffusion of some oxygen off the surface of the pond. It is a dynamic system and there is not a hard-and-fast rule for every square foot of pond water that a specific amount of oxygen has to be added.”

Growers usually have to pay closer attention to the oxygen level during the summer because warmer water temperatures hold less oxygen. During the winter if the air temperature is cooler, the pond water temperature is going to track that way as well unless a grower heats, cools or adjusts the pond water temperature.

“During the summer when the water temperature is warmer, because of its physical properties, water holds less dissolved oxygen,” Mattson said. “This is also the time of year when the plants are growing more quickly and the roots are respiring (consuming oxygen) more quickly.”

Mattson said another issue growers may face is the impact of water temperature on disease infestation.

“There are certain species of the root disease pathogen Pythium that proliferate more quickly under warmer temperatures,” he said. “Typically growers are more concerned about the spread of these pathogens during the summer with the warmer pond water temperatures. Chilling the pond water to keep the temperature between 68ºF-72ºF can help to deter these pathogens from proliferating quickly.”

Paul Fisher, professor and extension specialist/ floriculture at the University of Florida, said the target oxygen level should be at saturation in the root zone in all parts of a hydroponic growing system.

“A crop should be grown close to saturation (8-9 parts per million at 68ºF-72 ºF water temperature),” Fisher said. “As oxygen levels drop, especially down to 2-3 ppm, this is where Pythium infection is favored. Even with high-wire tomato and cucumber crops where the plants are being grown in rockwool or coir slabs, the substrate should not be allowed to become waterlogged. Pythium and Phytophthora are water molds that can infect plants at any point of the crop cycle.

“Every hydroponic grower should have a dissolved oxygen meter. A tip for taking readings is to have the nutrient solution flowing over the meter to obtain a good stable reading.”

Oxygen requirements for different crops

Mattson said although some hydroponically-grown crops appear to be more sensitive to low oxygen in the root zone, there hasn’t been a lot of research to group plants according to their root zone oxygen requirements.

“Strawberries and cannabis seem to be relatively sensitive to root diseases if there is a low oxygen level in the root zone,” he said. “This is in contrast to tomatoes, cucumbers and fresh cut roses, which are quite tolerant of low root oxygen levels.

“Future research to determine target oxygen levels would help us understand why some crops are more sensitive than others to low oxygen levels and that could help long-term breeding efforts. Plants could be selected by breeders for hydroponic production because they are more tolerant of low root oxygen levels and less susceptible to disease pathogens.”

Spinach varieties, in particular have been selected for root-disease resistance. Bowery Farming Inc., a commercial vertical farming company, has begun working with researchers at the Arkansas Agricultural Experiment Station to develop disease-resistant spinach for its proprietary indoor production systems.

“Spinach is one of the crops that are very sensitive to Pythium root rot,” Mattson said. “By selecting varieties that are more resistant to Pythium, it might be possible to grow the plants with lower root oxygen levels.”

Chieri Kubota, professor and director of Ohio Controlled Environment Agriculture Center (OHCEAC) at Ohio State University, is conducting extensive research studies with hydroponically-grown strawberries.

“Strawberries require more oxygen in the root environment compared to other greenhouse vegetable crops,” Kubota said. “Indoor strawberry growers need to pay close attention to make sure the oxygen level is not depleted in the root zone.”

Based on a study done in Japan with strawberry, the oxygen requirement per grams of root mass is higher for strawberry than other food crops. There is a significant difference in the oxygen requirement between hydroponic crops.

“Comparing strawberry with cucumber and tomato at different temperatures, the oxygen level is crop specific,” Kubota said. “At 20ºC (68ºF), which is a typical root zone temperature, strawberry requires nearly double the amount of oxygen content than cucumber. It’s about 40 percent more than the oxygen requirement compared to tomato. More research needs to be done in regards to determining the target root zone oxygen requirements of other hydroponic crops like lettuce and cannabis.”

Mattson said the oxygen requirements for a crop may change as the plant growth stage changes.

“A more mature plant that is actively growing has an extensive root biomass that is going to have a larger oxygen requirement than a smaller younger plant,” he said. “With a deep water culture lettuce crop there is typically going to be all ranges of growth stages with young plants on one side of the pond and more mature plants on the other side. In that case, there is kind of an established equilibrium in regards to the plants’ average oxygen requirements. Regardless of the crop, if there is a large root system there is potentially more biomass that is going to be respiring at a higher rate so the plants’ oxygen needs are going to be greater.”

Maintaining target temperatures

One of the benefits of deep water culture systems is the large volume of water that is slow to change in regards to water temperature, pH and dissolved oxygen levels. If the water is at an optimum temperature, it is going to take a lot to change the temperature.

“In a NFT system there is a lot of exposed surface area because of the shallow channels or troughs and water is continuously recirculating on these channels,” Mattson said. “There is a lot of surface area that is not well insulated compared to a deep water culture system, which is insulated and has a large volume of water. The deep water culture plants are also usually grown in a foam insulation board.”

With a NFT system the water temperature is going to closely match the air temperature because of the exposed surface area. During the winter if the air is being heated to the desired air temperature, the water temperature is going to be comparable to the air temperature.

“Floriculture crop studies in containers have shown if root-zone heating is used, a grower may be able to lower the greenhouse air temperature in order to conserve energy,” Mattson said. “Similarly growers who are using deep water culture can heat the water temperature to 72ºF and then maintain a cooler air temperature because the pond water is held at the desired temperature.”

During the summer for deep water culture systems growers can use inline water chillers to lower the water temperature. This enables the water to hold more oxygen and reduce the chances of disease infestation.

“With a NFT system trying to warm or cool the water temperature is not as practical,” Mattson said. “The heated or chilled water is exposed to a lot of surface area in a greenhouse. This is going to cause the water to lose heat relatively quickly in a cold greenhouse during the winter and warm up quickly on a hot summer day.”

Fisher said root zone chilling is very important for greenhouse growers trying to use hydroponics in the summer in Florida. Chilling the nutrient solution can lower the temperature of the plant crown which can help to reduce heat stress and increase the dissolved oxygen level. University of Florida horticulture professor Germán Sandoya is doing breeding work on heat-tolerant lettuce varieties for both greenhouse and field production.

Kubota said lowering the water temperature so the root zone temperature is around 20ºC (68ºF) helps when growing leafy greens.

“For spinach, the root zone temperature should be even lower,” she said. “From a pathogen management standpoint, the recommendation is 15ºC (59ºF) for the root zone. But this could have a drawback of reducing the overall growth of the plants.

“The root zone temperature is similar to the average 24-hour temperature. Growing at 18ºC (64.4ºF) at night and 24ºC (75ºF) during the day, the average temperature is around 22ºC-23ºC (71.6ºF-73.4 ºF) for long day conditions. For fruiting vegetables, the aerial temperature for fruiting is more important than the growing point temperature which is a long distance away from the root zone. This is probably why growers don’t try to control the root zone temperature with these crops.”

The root zone temperature has an impact on the oxygen level. The oxygen saturation point declines with increasing temperature.

“Water loses the capacity to hold oxygen as the temperature increases,” Kubota said “It is an unfavorable condition when the temperature increases because the respiration requirement increases also. The roots need more oxygen at higher temperatures. However, water loses the capacity to dissolve oxygen so it is easy to suffocate the roots at high temperatures.”

For more: Neil Mattson, Cornell University, School of Integrative Plant Science, Horticulture Section, nsm47@cornell.edu; https://cea.cals.cornell.edu. Chieri Kubota, Ohio State University, Department of Horticulture and Crop Science; kubota.10@osu.edu; https://hcs.osu.edu/our-people/dr-chieri-kubota. Paul Fisher, University of Florida, Environmental Horticulture, pfisher@ufl.edu; https://hort.ifas.ufl.edu/faculty-profiles/paul-fisher/.

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

The International Meeting on Controlled Environment Technology and Use gave representatives from academia and the CEA industry an opportunity to discuss the advancements and challenges facing researchers and growers.

After a two-year hiatus because of the pandemic the 6th International Meeting on Controlled Environment Technology and Use was held in September in Tucson, Ariz. Hosted by the University of Arizona, the meeting was organized by North Central Extension & Research Activity–101 (NCERA-101) in collaboration with UK Controlled Environment Users’ Group (UK-CEUG) and Australasian Controlled Environment Working Group (ACEWG). NCERA-101 is a USDA committee organized to assist plant scientists understand how to use controlled environment technology effectively and consistently.

“It was exciting for the University of Arizona to welcome and host our colleagues at this industry event,” said Murat Kacira, past chair of NCERA-101 committee and director of the Controlled Environment Agriculture Center at the University of Arizona. “The international meeting brought together 215 participants from 12 countries and five continents for three days. For the NCERA annual meetings there is usually about 100-120 participants.

“Every four years NCERA host’s an international meeting which includes our international members or collaborating working groups from the U.K., Australia and Canada. We also now have collaborations from Mexico. The international meetings have been rotating mainly between the U.S., U.K. and Australia. We now have some industry representatives and colleagues in Mexico who will be hosting the next international meeting there in 2025.”

Although NCERA has not had an official collaboration membership from Japan or South Korea, Murat said this has been discussed and there is an opportunity to extend the collaborations with NCERA’s Asian colleagues as well.

“I believe we will have that in place for upcoming years as part of our international collaborations for the meetings,” he said. “In regards to inviting speakers from those countries, that will definitely happen.”

Technology’s relationship with energy, labor efficiency

The international meeting hosted 20 speakers, two keynote speakers as part of the technical program and three panel discussions on indoor agriculture.

“This was a great opportunity for attendees to hear from not only researchers, but also those who are practicing in real world settings from commercial companies,” Murat said. “Speakers included industry participants, consultants, start-up companies and those who have been in the business for a long time, including company CEOs and CSOs. We also had students, our young minds, who participated.

“There were discussions about research with implications to commercial settings. There were also presentations by representatives from companies discussing what is applicable, what is practical and what can be incorporated into commercial operations. For example, Marc van Iersel at the University of Georgia talked about optimizing light efficiency in controlled environments from plant physiology to engineering. He presented direct applications currently happening in commercial settings. Another presentation from Jeff Jia at Heliospectra discussed from science to commercial applications focusing on light use efficiency.”

Murat said some of the heavily emphasized topics were the optimal use of energy, energy costs and labor costs.

“This included what are the technologies, what are the techniques, what are the approaches to consider to better manage resources such as electrical energy as well to address the challenges with labor through automation and environmental control applications,” he said. “Another subject that was emphasized was related to benchmarking. What is the terminology that should be used towards benchmarking sustainability and optimizing resource-use efficiency? There is a need towards defining benchmarking and terminology related to sustainability.

“There was also a discussion about data sharing. Where is the data coming from? What is the quality of that data? And how is this data helping to better implement technologies in commercial settings.”

The relationship between light and plant physiology

Murat said a primary focus of the lighting sessions was on the relationship between light and plant physiology.

“Topics discussed included what are the variables that significantly impact the physiological characteristics of plants,” he said. “What factors does attention need to be paid to and how can those factors be controlled in order to manage the quality and yield in controlled environments production? What are the requirements for quality and yield when it comes to controlled environments?

“This starts with defining a plant’s physiological requirements and then identifying the strategies or techniques around light intensity, quality, as well as other significant variables. Light interacts with other variables, it does not stand alone. When light intensity and quality are changed that triggers other environmental variables as well. These variables are connected so how can they be better used?”

Quality may mean different things to researchers and between different commercial operations.

“Quality measures or attributes for the industry vs. the quality measures for a grower can be quite different,” Murat said. “How can technology be used to achieve these quality attributes not only from an industry perspective, but also from a community-desired perspective? And how does achieving this quality relate to economics? How do growers manage the economics and cost factors to target, achieve and maintain these quality attributes?”

Future collaborations

Murat was particularly excited about the number of students who participated in the meeting

“There was great participation from graduate students, both from U.S. institutions and internationally,” he said. “They asked questions and participated in speaker session discussions. There was also a segment during the poster session when they were able to discuss their own research projects.”

On the final day of the meeting during the tours of the University of Arizona’s Controlled Environment Agriculture Center the university’s graduate students were the tour leaders giving them the opportunity to present detailed information about their own research activities.

“Also, during the meeting, opportunities were discussed and collaborations were formed,” Murat said “These collaborations were between academia and industry members as well as academia and academia, and industry and industry. These will help us to move innovation and technology forward.

“During future meetings we will have more opportunity to talk about and fine tune what is benchmarking and what are its requirements. Also, we will be able determine what sustainability measures and terminologies need to be considered. Another topic that was emphasized was how does the industry and academia continue to keep educating the next generation of controlled environment researchers, industry-related employees and commercial growers.”

For more: Murat Kacira, University of Arizona, Biosystems Engineering Department; mkacira@arizona.edu; http://ceac.arizona.edu/.

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

Big Tex Urban Farms announced in July that using its controlled environment production systems it had grown enough vegetables to deliver a million servings to the local Dallas community.

When Jason Hayes, vice president of branding and cofounder of Big Tex Urban Farms in Dallas, came up with the Million Servings Mission project in 2018, there was some question as to when the non-profit operation might achieve this lofty goal. Big Tex Urban Farms got its start in 2016 as an outdoor gardening project by the State Fair of Texas to better serve the local South Dallas community.

“Big Tex Urban Farms started with a small budget in 2016 using 100 mobile planter boxes to grow food outdoors,” said Drew Demler, who is the state fair’s director of horticulture and the other cofounder of the farm. “At the time Jason and I started planning the farm, the goal was to grow produce and then donate it to the community.”

During that first year of outdoor production the farm produced food that was donated to two local charitable organizations. Growing and donating fresh vegetables gave Demler and his staff an opportunity to develop good relationships with the organizations they were assisting.

“These local organizations were very happy with what we were doing to assist them in their efforts to feed people in the community that really needed help,” he said. “We also received some good media coverage which helped generate more interest in what the farm was doing.”

The positive feedback from organizations that benefitted from the fresh vegetables and favorable media coverage led to a major increase in the farm’s budget in 2017. The budget increase enabled Demler and his staff to build an additional 429 outdoor planters. An even bigger opportunity to grow more fresh vegetables came in September 2017 when a 30- by 15-foot hydroponic deep water culture pond was installed in the fair’s largest 7,200-square-foot greenhouse. The greenhouse had been used to grow ornamental plants including palm trees and bougainvillea, and to overwinter hanging baskets. It was also used as a plant exhibit room during the state fair.

“We worked with the staff at Hort Americas to design and install the deep water culture system,” Demler said. “We also installed six 8-foot tall vertical tower gardens. This was our first venture into hydroponic growing.”

Expanding controlled environment production

Demler and his staff were impressed with the amount of produce they were able to grow with the hydroponic production systems. In the short amount of time that the systems had been installed and production was ramped up enabled the farm to distribute fresh vegetables to more community organizations in South Dallas.

“Our total production indoors and outdoors in 2017 was around 2,800 pounds of produce,” Demler said. “By the end of April 2018 we had exceeded what we produced for all of 2017. This was one of the main reasons that we decided to expand our hydroponic systems. It is such a better and more efficient way to grow.

“Another reason we expanded the hydroponic systems was the overwhelming positive response from the public during the 2017 fair. In 2018 we turned the greenhouse into an indoor growing exhibit. The public had access to the hydroponic systems all 24 days of the fair.”

Focused on hydroponic production

With the help of Hort Americas, Demler and his staff began to expand the farm’s hydroponic production. 

“In 2018 we added a second deep water culture pond, a nutrient film technique (NFT) system, a Dutch bucket system for vine crops and additional grow racks,” Demler said. “We continue to add systems and do modifications to them.

“Our main greenhouse, which is part of the Innovations in Agriculture exhibit during the state fair, has been repurposed 100 percent for food production. We have nearly completely filled the greenhouse with different hydroponic systems. We also have added a gutter slab system for vine crops which we are currently using to grow tomatoes. A second larger NFT system will enable us to produce five times more plants than the original NFT system. ”

In addition to the 7,200-square-foot greenhouse the farm has installed a 40-foot shipping container that was nicknamed GroZilla.

“Hort Americas staff designed the shipping container production system,” Demler said. “Currently we use it primarily for demonstration and as an introduction to controlled environment horticulture. We have grown a variety of crops in the container. All of the produce feeds into the different local community groups including providing lettuce blends for schools. We have also grown Asian greens, baby kale and arugula in the shipping container in collaboration with another community action group called Restorative Farms. With what we are doing hydroponically, we have nearly eliminated any soil-based production here on site.”

Much of the equipment that has been installed in the Big Tex Urban Farms greenhouse was previously used in Hort Americas’ demonstration and research greenhouse in Dallas.

“Hort Americas has changed its focus from having its own demonstration greenhouse to putting our energy and resources behind making Big Tex Urban Farms successful,” said Chris Higgins, president at Hort Americas. “Hort Americas is providing human resources and grower knowledge along with access to innovative technology. The biggest thing that we are doing is teaching the Big Tex Urban Farms employees how to grow hydroponically.”

Big Tex Urban Farms is currently using LED grow lights on a variety of its crops.

“We have a few different versions of Current’s Arize LEDs along with a few OSRAM LED lamps,” Demler said. “We recently installed the new Current L1000 LED fixtures over our vine crop systems. Those will increase growth and we already have tomatoes setting fruit.”

Overcoming major obstacles

Demler said although the farm reached its goal of producing a million servings of fresh vegetables earlier than expected, there were several obstacles to overcome to achieve the goal. “The COVID-19 pandemic and February 2021 power outages that affected many parts of the state had a major impact on what the farm was able to produce,” Demler said. “We were not able to host a state fair in 2020 because of the pandemic. The state fair did a modified drive-thru event, which impacted the farm’s budget. It took having us to get through a full state fair in 2021 to get our budget reinstated. Our farm is funded 100 percent by the state fair. A portion of the proceeds of whatever our guests and patrons spend at the fair helps to fund projects like our farm.

Another major obstacle the farm had to overcome was the power outages that occurred during the winter in 2021.

“There were multiple electrical outages that occurred in February that killed many of our crops,” Demler said. “Surprisingly our deep water ponds by-and-large made it through those outages.”

Another thing that helped the farm reach its million servings goal earlier than expected was the cooperative project it began with Texas A&M AgriLife to produce outdoor crops at one of the extension service’s satellite locations.

“We donated several of our raised planter beds and then the extension service received funding to install additional planter beds,” Demler said. “There is about 1 acre of outdoor raised bed production at this location.

“We were able to harvest a large outdoor tomato crop this summer. In addition to tomatoes, we will also be producing a number of root crops including potatoes, onions, carrots, turnips, sweet potatoes and other crops that soil is just more efficient for growing compared to hydroponic production. Those outdoor crops are going to feed into our program as well.”

Push for education

Now that Big Tex Urban Farms has reached its million servings goal Demler is looking to make a bigger push for education.

“We are looking to educate both people who would come to the greenhouse to learn about the farm’s production systems and the farm reaching out to local schools,” he said. “We want to be able to teach more children about growing their own food. Some of the churches and community groups coming through the greenhouse are interested in learning more about the production systems. Some of these groups are interested in putting some of these systems into schools. 

“Most of the school groups we are working with want to do something with a vertical hydroponic system such as grow racks or tower gardens. Space is limited in the classrooms so they are looking at some type of vertical system. In a lot of cases they are going to locate the system near sunny windows and probably add some LED lighting to supplement the natural light.”

For more: Big Tex Urban Farms, (214) 565-9931; info@BigTex.com; https://bigtex.com/urbanfarm.

Editor’s note: This year’s State Fair of Texas is scheduled for Sept. 30-Oct. 23 in Dallas, https://bigtex.com/.

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

Depending on whether you are looking to control photoperiod or increase plant growth will determine the grow lights you need to get the best results. 

Before growers even consider choosing a grow light for their controlled environment operation they need to have some basic information.

“One consideration is whether their objective is primarily to regulate flowering or to increase growth,” said Erik Runkle, horticulture professor at Michigan State University. “There is still some confusion among growers that they can screw in LEDs and expect to generate supplemental light that will increase plant biomass. Growers need to know whether they need low intensity light to regulate photoperiod or high intensity light to increase plant growth. This is one of the first things that needs to be clarified.”

Lighting to regulate flowering

Photoperiod lighting would be used to either inhibit or promote flowering.

“Usually photoperiod lighting is very low intensity so it’s a lot cheaper lighting solution,” Runkle said. “Where photoperiod lighting can go wrong is some growers will install these very low intensity lighting fixtures and say they are seeing a positive growth response similar to what would be expected with a high intensity fixture. What they are really seeing is a change in the leaf shape or the leaf habit that suggest there is more growth. If the biomass of the plants was measured it would show there is no increase in plant growth.”

Previously most growers used incandescent bulbs for photoperiod control. Today many growers are replacing incandescent bulbs with screw-in LED bulbs.

“If they screw the bulbs into a light socket that is a low intensity light,” Runkle said. “The cost for these LED bulbs has decreased, but they are still more expensive than incandescent bulbs.

“One advantage of LEDs is they are going to last at least 15 times longer than incandescent bulbs. Typically photoperiod bulbs are only operated four hours during the middle of the night. These LED bulbs are expected to last 15,000-25,000 hours. A grower might have to replace them in 30 years.”

The biggest advantage of LEDs over incandescent bulbs is energy efficiency.

“Energy consumption will drop significantly with LEDs,” Runkle said. “Growers are going to receive significant savings. Their energy usage will be cut at least 80 percent and maybe as high as 85 percent. This is a compelling reason to replace incandescent bulbs with LEDs.”

Lighting to increase growth

Growers who want to increase plant growth will need to know the light intensity they want to deliver to the crops they are producing.

“The first thing greenhouse growers will need to determine is how much light does their geographic location receive from the sun and how much do they want to increase the light intensity beyond the natural light,” Runkle said. “This might seem obvious, but sometimes growers say they want to deliver a specific light intensity, but they really don’t have a good basis for the intensity. The lighting needs of a grower in one state may be very different than a grower in another state. They may also be different for growers in the same state but producing different types of crops.”

Runkle, who works primarily with ornamental plant growers, said most of them want to provide high intensity supplemental light during the darkest months of the year.

“Flower growers are using supplemental light primarily for propagation and increasing plant growth during December, January and February,” he said. “Those are the three months growers try to key in on. Knowing how much light is delivered by the sun and the desired daily light integral (DLI) for the crops they are producing, growers can then determine the light intensity they need to deliver with grow lights.

“Most growers start lighting their young plants because that’s where they have a lot of plants per unit growing area. The cost of lighting on a per plant basis is very low because they are able to produce many plants in a given area.”

Runkle said growers may choose to light their finished crops depending on the crop and the economics.

“The target light intensity for growing ornamentals is going to be similar among the different stages of growth,” he said. “There is one exception during the propagation of unrooted cuttings. Growers may not need as a high an intensity to root cuttings vs. propagating seedlings or during later stages of production. In some cases, growers propagating unrooted cuttings in substrate under high intensity lighting may provide too much light resulting in a bleaching of the leaves. This seems to occur more often with high intensity LED fixtures than high pressure sodium lamps, but doesn’t occur in every crop. This phenomenon merits further investigation.”

Determining your crop lighting needs

The benefit of high intensity lights decreases as the solar light level increases.

“From an economical perspective, usually once crop production moves into late March or early April there is little economic benefits to use lights for most ornamental crops,” Runkle said. “Greenhouse tomato growers may be lighting eight to nine months during the year because every photon of light could potentially lead to higher yields. It’s really a driver of whether growers are producing a plant as a unit or marketing a product from the plant like a tomato, pepper or cut flower.

“For most structures, determining the lighting needs is going to be comparable whether it’s for a greenhouse, vertical farm or indoor grow. Regardless of the structure there is a target DLI, whether it is an indoor crop or greenhouse crop. The only complicating factor is how much light is delivered by the sun. In an indoor production facility all of the light is coming from the installed lights. There is an added complexity to determining the light need for a greenhouse. Once the desired DLI is determined, it is a matter of how to deliver the intensity that is needed for how many hours per day.”

Runkle said he prefers to use the term target DLI rather than optimum DLI.

“Optimum DLI is a subjective term,” he said. “Optimum DLI can depend on other environmental conditions and the grower’s market. Also, an optimal DLI may or may not be economical.”

Choosing a light spectrum

There is a variety of light spectrum commercially available. Runkle said light spectrum affects plant growth, efficiency of the fixture and human vision capabilities.

“The light spectrum affects plant growth, but it also affects the color of light and how it influences people working in a production facility,” he said. “Some workers may complain about working under purple or pink LED lights.

“From the plant’s perspective, the light spectrum has a big effect on the shape of the plant. More blue light typically results in more compact plants. When I talk with growers about lighting their crops I ask if height control or more height control is one of their goals. Red LEDs are the most efficient type of LEDs. That is one of the major reasons why more red LEDs are used in grow light fixtures. The most efficient LED fixtures have more red LEDs than white or blue.”

Lighting companies experienced with working with ornamental, vegetable and cannabis growers should be able to suggest what spectrum growers should use and justify why they support it.

“Light companies should be able to assist growers by providing them with the lights to match their crop needs,” Runkle said. “I don’t usually give a specific recommendation of a certain spectrum because it is subjective and situational.”

Choosing a light fixture

Greenhouse growers are going to connect grow lights to their greenhouse environmental control computer and based on the weather, the lights will automatically turn on or off.

“One of the advantages of LEDs is they can be turned on and off without influencing the light’s longevity,” Runkle said. “With HPS fixtures the start-and-stop cycles can negatively impact the bulb’s longevity.

“In a greenhouse the lights can be operated based on the current natural light level. There is new control software and hardware available that considers not only the current light level, but also the target DLI and how much natural light the plants receive during the course of a day. This new technology enables growers to potentially achieve a target DLI each day. In the case of an indoor facility, the lights can be operated on a timer making it much easier from a control standpoint.”

Looking at grow lights from an energy efficiency perspective, the Design Light Consortium (DLC), offers a qualified products list. Runkle said if a light is a DLC-listed product growers have some assurances not only about its efficiency, but also eligibility for rebates and durability.

“The DLC list ties into energy efficiency and potential grow light rebates,” Runkle said. “Usually if a light meets the criteria to be on the DLC Qualified Products List, there is good chance it will be eligible for some type of rebate. There are other criteria necessary for a grow light to be a DLC-listed fixture. These include having at least a five-year warranty and having a tolerance to damp conditions.

“Generally the relative humidity conditions are going to be higher in a greenhouse than in an indoor facility. For propagation there might be 100 percent relative humidity. There may be some indoor farms that don’t have adequate HVAC systems to provide sufficient air conditioning capacity resulting in high humidity that can cause major problems. Under these environmental conditions growers are going to need grow lights that can tolerate high humidity.”

Choosing a lighting company

Runkle advises growers to consider a lighting company’s reputation and reliability.

“There are so many different LED lighting companies marketing their products to the horticulture industry,” he said. “Unfortunately some have gone out of business. There could be a company that offers a five-year warranty, but if it goes out of business the company is not in a position to support that warranty. Having a warranty is good, but equally important is whether the company will be around to support that warranty if the fixture doesn’t perform.

“We’re all looking for a good deal. But if a good deal seems too good to be true, it probably is. Talk to other growers who are using the products to find out about performance and company reliability, especially if you haven’t heard of the company before.”

For more: Erik Runkle, Michigan State University, Department of Horticulture, runkleer@msu.edu; https://www.canr.msu.edu/people/dr_erik_runkle.

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

Growers using containers to produce vegetable crops have options when it comes to growing in plant-based substrates.

Small- to medium-size growers of vining vegetable crops including cucumbers and tomatoes have traditionally used Dutch buckets filled with perlite as the growing substrate. While some growers may be concerned with the sustainability of perlite because of disposal issues, there are options when it comes to using alternative plant-based substrates.

Improving sustainability of controlled environment production

Uttara Samarakoon, who is associate professor and program coordinator for greenhouse and nursery management at Ohio State University, CFAES Wooster, has been studying ways controlled environment growers can improve sustainability of containerized vegetable production. Samarakoon is working with Teng Yang, a post-doctoral researcher at Ohio State University, CFAES Wooster, and James Altland, research leader Application Technology Research, USDA-Agricultural Research Service in Wooster. Their research is being funded by USDA-ARS.

“The main theme of my research program is on sustainability for controlled environment agriculture,” Samarakoon said. “The research we are currently doing focuses specifically on high wire crops, including cucumbers and tomatoes, produced in Dutch bucket systems.

“My experience when visiting small- to medium-size vegetable growers is that many of them are using perlite as the substrate in Dutch bucket systems. In addition to concerns with disposal issues for perlite, it also has a low water-holding capacity resulting in higher rates of leachate. I have been using perlite in my research for some time because that is the traditional substrate for Dutch buckets.”

Dutch buckets are not the common production system used in most large-scale controlled-environment vegetable operations.

“Large-size vegetable operations tend to use hanging gutters with rockwool or coir slabs for high wire crop production of cucumbers, tomatoes and peppers,” Samarakoon said. “Recirculation of the fertilizer solution occurs primarily with large-scale commercial growers. Most small- to medium-size growers don’t have the capacity to do recirculation.”

Identifying alternative substrates

Although Dutch buckets are primarily used for growing vining crops, Samarakoon said this method of production  is very similar to other types of containerized crop production. Even though the alternative substrate trials she conducted used Dutch buckets, she said the findings from her studies can be applied to any type of containerized crop production.

When Samarakoon was selecting substrates to compare with perlite she considered both sustainability and availability. In the first trial with cucumber, the researchers chose plant-based substrates, including sphagnum peat moss, two different grades (medium and course) of pine bark, coir and wood fiber (HydraFiber). All of these substrates were trialed against perlite, which was used as the control.

For the study, Dutch buckets were filled with 100 percent of each of the substrates.

“Our key finding was growing cucumbers in Dutch buckets, the amount of leachate can be significantly reduced with any of these plant-based substrates compared to perlite,” Samarakoon said. “The sustainability of this production system can be increased by using any of these alternative substrates. Although the substrates we trialed were not certified organic, there is the potential for growers to use similar substrates that are certified organic.”

The researchers found there was no difference in terms of time to fruiting and number of cucumbers produced regardless of the substrate trialed. One difference that occurred with medium-grade pine bark was an increase in fruit weight compared to perlite. However, the fruit weight of plants grown in medium-grade pine bark was similar to the other plant-based substrates.

Tomatoes in alternative substrates

Based on their success with cucumber, Samarakoon and the other researchers looked to repeat the study with tomatoes grown in the plant-based substrates. For these trials the Dutch buckets were filled with 100 percent sphagnum peat moss, medium-grade pine bark or wood fiber with perlite again as the control under two different irrigation regimes. The response was similar to cucumber with the number of fruit and individual fruit weight in plant-based substrates compared to perlite. Irrigation rates used did not influence the yield except in peat.

“The leachate rates were different among the substrates throughout the crop production with perlite having the highest amount of leachate,” Samarakoon said. “Therefore sphagnum peat moss, medium-grade pine bark or wood fiber can replace perlite without any yield reduction and the added advantage of reduced leachate for both cucumber and tomato.”

The tomato trial ran for 20 weeks until the plants reached the top wire support.

“We did not grow the tomatoes beyond that stage because it would have required lowering the vines and that could affect the type of data we collected,” Samarakoon said. “In our next tomato trial we will be using the same substrates but growing the plants in a nine-month production cycle. We will be lowering the vines and training them to continue growing for a nine-month production cycle in order to determine how the alternative substrates sustain the plants. We are also focused on optimizing the propagation of vine crops when using alternative substrates.”

For more: Uttara Samarakoon, Ohio State University, CFAES Wooster; samarakoon.2@osu.edu; https://ati.osu.edu/uttara-samarakoon-phd.

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

An increasing number of upscale resorts, restaurants and affluent individuals have begun operating their own greenhouses to produce the fruits and vegetables they want to prepare and consume.

While many restaurants across the country lost sales or went out of business during the COVID-19 pandemic, some had no problem maintaining their customer base. Serge Boon, founder of Boon Greenhouse Consultancy in Hendersonville, N.C., said he has seen an increase in business for restaurants and resorts that serve a high-end clientele. He has also seen a growing demand from people who want to establish greenhouse programs to produce crops that are not readily available to ensure they have a consistent supply of quality food.

“These include luxury resorts that employ chefs who want specific types of fruits and vegetables,” Boon said. “More of these up-scale resorts are looking to produce their own food so they have more control over what is available and the quality of the food produced. This enables these companies to be less dependent on outside suppliers. Producing their own food enables these companies to offer their guests a more high-end dining experience.”

Boon said the pandemic also didn’t have much effect on his customers who wanted to increase their food security by producing their own crops.

“The grocery stores which were having supply side issues had less food to offer,” he said. “If someone has the opportunity and ability to build their own greenhouse so food can be produced year round that eliminates having to rely on what’s available at the grocery stores. This is an up-and-coming market no matter what happens with the pandemic.”

Controlling quality, quantity and variety

A major advantage for companies starting to produce their own food is they can control the quality and don’t have to purchase and bring in as much food on a daily basis.

“These companies can tailor the type of produce and quality that they want for their menus,” Boon said. “The chefs provide a lot of input on what is grown in the companies’ greenhouses. This is almost the reverse of how it normally works for many restaurants. Generally chefs have to take what is available from local growers and suppliers. In the case of these high-end restaurants, which operate their own greenhouses, the chefs ask that specific varieties are grown for them.”

Boon, who was a grower for the luxury resort Brush Creek Ranch in Wyoming, said most of the companies and individuals he works with put up smaller size greenhouses ranging from 5,000 to 20,000 square feet. The greenhouse at Brush Creek Ranch is a 20,000-square-foot facility that is used year round to grow fresh produce.

“A large percentage of the produce that is grown is for in-house use,” Boon said. “About half of the greenhouse owners I work with operate their own restaurants. In most cases, they are producing for their own restaurants or their own consumption. There is only a handful that sells the produce commercially.

“There are also individuals who can afford to build a greenhouse because they are seeking certain fruits and vegetables that would normally be difficult to source. They want to be self-sustaining by growing their own food on land they have purchased. They hire someone to grow the produce and chefs to prepare their food.”

Boon said some of these affluent individuals want certain crops grown on their property for personal consumption because they may be difficult to source from local growers or suppliers.

“They want fresh, pesticide-free produce year round,” he said. “There are individuals who want specific produce year round like locally-grown heirloom tomatoes that aren’t available so they have to grow them themselves.”

Production requirements

Boon said any food crop can be grown in a greenhouse, it just depends on whether it makes economic sense to produce it. 

“For the companies and individuals I work with, it’s more a case of them wanting specific crops and then building a greenhouse to be able to produce them,” he said. “It’s also important as to whether they want to produce those crops year round. Wanting heirloom tomatoes year round is different than only wanting them during the summer.” 

Boon designs a succession plan for crops that will be grown year round and seasonally.

“We determine how much needs to be planted each week to be able to deliver a certain yield,” he said. “We predict yields across the year to determine where and when the crops should be planted. We make a specific internal plan in regards to crops, i.e. two rows of tomatoes, two rows of peppers in one zone. In the next zone they may plant strawberries. We walk them through how to set up the production zones and how to run them”.

Boon said he does sometimes get asked to design a greenhouse for a crop that he hasn’t grown.

“I will research the crops to see what the production requirements are for the crops,” he said. “Occasionally I am asked about unfamiliar crops and then I have to research as to the best way for growing a particular crop. Sometimes it doesn’t make economic sense, but if they can afford to grow the crop and the need is there, it can be done.”

Boon said he can also assist with the best cultural practices for producing the crops.

“We can walk them through the whole production plan,” he said. “This varies between clients because if they employ an experienced grower we don’t have to do that. Sometimes it’s from scratch with us helping with crop scheduling and production.”

Greenhouse, production system options

Boon said in most cases he advises his customers to grow in soilless substrates or hydroponically for ease of management.

“We advise them of their options for producing the crops they want to grow and provide them with a list of pros and cons,” he said. “In regards to environmental control, it can be harder to provide the specific climate conditions for each of these specialty crops. The larger the greenhouse the more zones that can be created and the more we can tailor the environment for the crops.

“Because there are multiple crops being grown in some of these smaller greenhouses, there has to be some give and take. There is so much variability between crops that it’s difficult to provide the best growing conditions for every crop. Most of these companies are installing the same type of sophisticated environmental control systems being used in most commercial greenhouse operations. These are literally a smaller version of commercial greenhouses just with a lot more different crops.”

Production opportunities for growers

Boon said growers who are interested in selling to this high-end clientele need to be able to offer these resorts, restaurants and individuals exceptional quality produce.

“There is really a need for this type of produce,” he said. “It’s becoming harder and harder to find some of these crops in certain areas. Some examples include specialty broccoli, rainbow carrots, heirloom tomatoes, mushrooms, specialty herbs and edible flowers.

“Growers interested in serving this clientele definitely have to know their market. They have to know the up-scale customer base that is near them, including sportsmen’s clubs, resorts and restaurants. The growers need to determine these potential customers’ needs in regards to specialty produce. Growers need to first do their market research before they start building a greenhouse.”

Boon said this up-scale clientele is an up-and-coming market.

“These are people who want to have greenhouses in their backyards so they always have fresh produce available rather than being dependent on growers and suppliers from outside the U.S.,” he said. “I’m not a believer in shipping fresh produce around the world. Right now this up-scale market is for those people who can afford to grown their own produce. Over time I’m hoping that more people will get involved with growing their own food.”

For more: Boon Greenhouse Consultancy, serge@boongreenhouse.com

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

As in other industries, greenhouse vegetable operators are facing challenges finding enough skilled workers to produce their crops.

Before the COVID-19 pandemic began, employers were having a difficult time finding enough workers. The coronavirus has only exasperated that challenge.

U.S. Bureau of Labor Statistics projects overall employment of agricultural workers will rise 2 percent from 2020 to 2030. That is the slowest average for all occupations. During this 10-year period the bureau expects there will be on average about 138,900 openings each year for agricultural workers. The majority of these openings will be the result of having to replace workers who have left for different occupations or have exited the labor force.

In 2020, according to the U.S. Bureau of Labor Statistics, agricultural workers held about 869,000 jobs. Greenhouse along with nursery and farm laborers accounted for the majority of agricultural employment with 526,300 jobs. Half of the workers employed in agriculture were involved in crop production.

Need for skilled labor

“The challenges to finding workers are enormous,” said Jose “Pepe” Calderon, head grower at Local Bounti, a greenhouse producer of fresh greens and herbs in Hamilton, Mont. “Companies worldwide are expressing the same concern about a lack of labor. Employers need them promptly, but aren’t always successful at finding them.

“In recent years, finding people who want to work in agriculture has been complicated, especially in the greenhouse sector, because the people required to perform the jobs associated with greenhouse food production need specific skills.”

Calderon said some tomato production activities, including twisting and clipping, require specific abilities to complete these tasks in a timely and quality manner. Failure to perform these tasks properly can lead to plant damage resulting in a reduction in fruit quality and yield.

The U.S. Bureau of Labor and Statistics reports that even though the demand for crops and other ag products continues to increase, employment growth is expected to be limited. One of the reasons for this slow growth is the move by ag businesses to implement technologies that increase worker productivity. According to the Bureau, the increased use of mechanization on farms will lead to more jobs for equipment operators compared to traditional farm workers. From 2020 to 2030, hiring of equipment operators is projected to increase 13 percent.

Rising costs, losses

“As a result of the lack of skilled workers, the greenhouse industry is trying to automate certain activities,” Calderon said. “However, many greenhouse operators don’t know how long it will take to recover these equipment investments due to the high costs associated with these purchases.

“Greenhouse food production is currently affected by a shortage of trained workers since all activities are not completed on time. As a result, crop growth is out of balance, affecting productivity and product quality while raising production costs.”

New American Economy reports the shortage of agricultural workers has had a major impact on the U.S. economy because agriculture is so closely intertwined with many other industries. This research and advocacy organization which advocates for equitable immigration policies, estimates U.S. growers would have produced $3.1 billion more in fresh fruits and vegetables per year by 2014 had farm labor not been an issue.

Due to the rising demand for skilled workers in all agricultural sectors, Calderon said wages will continue to rise dramatically, leading to increased production costs. 

“At this time in the industry, greenhouse vegetable operations are having issues with workers carrying out crop labor activities such as crop management and maintenance, irrigation and harvesting,” he said. “It is also challenging to find people with skills to supervise the workers and help them to reach their full potential quickly in order to make businesses profitable.

“At this moment, the greenhouse industry is also experiencing a lack of growers who can handle every aspect of the business, including quality of work, training of new generations of growers and the management of cutting-edge technologies. It is also critical that growers have administrative skills to keep business costs low.”

Employee cost of production

USDA National Agricultural Statistics Service (NASS) reported that farm operators paid their hired workers an average gross wage of $16.59 per hour during Oct. 2021, up 5 percent from the same time period in Oct. 2020. For greenhouse vegetable production, Calderon said the average wage for workers in California is $17 per hour and $16 per hour in Kentucky and Montana.

He said a U.S. greenhouse vegetable facility requires three to four employees per acre (six to eight employees per hectare) depending on the tomato crop. Small tomatoes require more intensive labor to produce and harvest, requiring 1.6 employees per acre (four per hectare) for the production of the crop and an additional employee per acre (two per hectare) to harvest the tomatoes.

For greenhouse lettuce production the number of employees varies with the amount of automation being used. A 1-acre hydroponic operation equipped with automation, including seeding, planting and harvesting for one product SKU, would require one to two employees per acre (three to four employees per acre). This would not include the labor needed to package the product.

Finding more workers

The H-2A Temporary Agricultural Workers program could go a long way in resolving many of the issues facing agricultural producers including greenhouse vegetable operations. Ag America Lending reports inefficiencies in the H-2A program are making it increasingly difficult for agricultural producers to bring in workers in a timely and affordable manner.

Calderon said the H-2A program could be a good alternative for agricultural producers if federal officials can resolve some of the problems currently associated with it. In most cases, the productivity of H-2A contract workers can be substantially higher than local workers. He cited his experience with a greenhouse tomato operation which was able to operate with two H-2A workers per hectare, but required 9.8 locally-hired workers per hectare to perform the same tasks.

For more: Jose “Pepe” Calderon

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

Vertical farm advancements in technology and plant genetics will lead to resource-use savings and increased profitability.

As more retailers like Kroger, Albertsons and Walmart purchase produce grown by vertical farm operations, this segment of the agriculture industry will continue to gain market share. Walmart has taken its commitment to supporting vertical farming a step further by investing in vertical farming company Plenty Unlimited.

Charles Redfield, chief merchandising officer at Walmart, said his company is focused on investing in innovative food solutions in order to deliver its customers affordable, high-quality, fresh food.

“We believe Plenty is a proven leader in a new era of agriculture, one that offers pesticide-free, peak-flavor produce to shoppers every day of the year,” Redfield said. “This partnership not only accelerates agricultural innovation, but reinforces our commitment to sustainability, by delivering a new category of fresh that is good for people and the planet.”

Some retailers are taking their commitment in vertical farming a step further by investing in the production of fresh produce. Publix Super Markets’ GreenWise market in Lakeland, Fla., has installed a 40-foot container hydroponic farm in its parking lot. The store will produce over 700 heads of lettuce weekly which are sold in the store.

Kroger has installed modular vertical farms manufactured by Infarm in two of its Seattle stores. The systems start with seedlings germinated at Infarm’s nursery and then are transplanted into the stores’ production systems to finish and harvest the crops.

Maintaining consistent growing conditions

One of the biggest advantages of vertical farming over other forms of crop production is a consistent finished product. 

“There is consistency for produce yield and quality with vertical farms because it enables complete control of optimal conditions for crops independent of outdoor climatic conditions,” said Murat Kacira, director of the Controlled Environment Agriculture Center and professor in the Biosystems Engineering Department at the University of Arizona. “Delivering a system that can maintain desired conditions also brings the need for resources including the energy to run the grow lights, HVAC systems or other hardware components to deliver those desired growing conditions. 

“The consistent vertical farm environment delivers consistent yield and quality independent of the outdoor environment. When you transplant something in a vertical farm, you know at the end of a given time period what you are going to get in terms of the yield and quality of that product.”

Murat said greenhouses also provide a controlled environment, but the consistency of that environment is still dependent on outdoor climate conditions.

“There is a certain level of independency from the outdoor that can be achieved in a greenhouse, but there is still the dynamics of the inconsistent outdoor environment. This inconsistency also brings the need for energy and resources to maintain desired optimal indoor growing conditions and to minimize crop seasonality effects for crop yield and quality attributes.”

Maximizing resource-use efficiency

Murat said the ultimate goal in any type of controlled environment production is resource-use efficiency. This can apply to the amount of kilowatt hours of electricity used in production, the amount of water, fertilizer, carbon dioxide and labor needed to achieve a specific crop yield and quality attributes outcome.

“There is a resource demand that must be met,” he said. “For any type of agricultural production system, at the end of the day the comparison will be based on yield and quality attributes vs. what goes into the production. This will be factored into the profitability.”

One of the biggest obstacles or opportunities, depending on how you look at it, is the lack of standardization in the systems being used by vertical farms. 

“There are differences in terms of the technologies used and in the systems that are constructed and being operated,” Murat said. “Hopefully some level of standardization will be incorporated. This will take into consideration commercially-available proven products and best practices in the design of production systems that are suited for unique requirements of the systems and crops. Research and development outcomes will further support the advancement of vertical farming systems contributing to enhanced resource-use efficiency and profitability.”

An example is increasing the fraction of the light that is intercepted by the plants can enhance resource-use efficiency.

“This means delivering the light to the plants in very effective, efficient and economic ways so that the light is not lost to other structural elements including walls, aisles and floors,” Murat said. “Considering how plants grow and changes in the plant architecture may require dynamic rather than fixed light controls. There is an opportunity to manipulate the light to achieve substantial savings as much as 20-50 percent from the current levels of electrical energy being used. This may be accomplished through innovative system designs and enhanced environmental controls.”

Murat said there are several areas where grow light enhancements will be combined with lighting techniques to improve energy-use efficiency.

“There will continue to be improvements in LED efficiency and efficacy, but there will be limits as well,” he said. “These improvements can be combined with system designs including light uniformity, light exposure and penetration to the plant canopy, and potential dynamic controls during the production phase. Also, consider the pricing for the electricity, including off-peak hours, pulsing or modulating the light, alternative energy systems and pricing, along with implementing strategic environmental controls to reduce energy use and costs associated with energy inputs.”

While many of the vertical farm advancements may come in technology, Murat said there is also an opportunity for changes in plant genetics.

“Looking at the genetics may lead to breeding new varieties that are better suited for vertical farm environments,” he said. “We can only do so much with engineering and the physical space. Combining the technology advancements with new genetics will help to capture the optimization leading to resource savings and to ultimately increased profitability.’

Integrating automation and robotics

Murat said automation and robotics will play an increasing integral role in vertical farm operations.

“We are already seeing different levels of automation and robotic applications implemented in vertical farms,” he said. “Automation and robotics will be key with vertical farms in regards to labor requirements. The labor input for vertical farms is in the 20-30 percent range of production costs. These costs can be minimized with automation and robotics integration.

“Robotics are able to do many of the repeated processes performed by human operators from seeding to harvesting to packaging. Robotics can also be implemented for scouting and monitoring the crops. This would include making sure the plants in each vertical farm tier are growing properly. The quality attributes that are observed or accounted for by human labor are going to be robotized in future vertical farm systems.”

Murat also expects to see increased implementation of automation for enhanced resource–conserving environmental control strategies related to cooling, dehumidification and fertigation.

“We are going to see more innovation and implementation around how data is related to the crop to further enhance quality attributes and yield and for resource savings,” he said. “For example, this could relate to how light is delivered to enhance quality attributes. Rather than delivering a specific spectrum all the way from transplant to harvest, there might be specific time intervals or times when it makes more sense to provide a unique wavelength to enhance a quality attribute. There will also be increased applications of artificial intelligence, modeling and sensing towards conserving resources and smarter environmental control applications.” 

Murat said the demand for controlled environment educated and experienced graduates remains high.

“Educational programs will continue to produce the next generation workforce with the skill sets most critical to support that need and help grow the CEA industry,” he said. “We will look at what is practical, what is economical, what really makes sense. How technology integration improves the profitability may be the decision-making point.”

For more: Murat Kacira, University of Arizona, Biosystems Engineering Department; mkacira@ arizona.edu; http://ceac.arizona.edu/.

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