What are the production and training issues facing controlled environment agriculture growers?


Ohio State University professor Chieri Kubota is focused on helping to resolve the production and training challenges facing controlled environment growers.

Trying to produce vegetables in hot, humid conditions can be difficult for controlled environment growers whether growing in a greenhouse or a warehouse.

“The challenges of greenhouse growing in Ohio and the Midwest are different than the challenges faced by growers in Arizona,” said Ohio State University horticulture professor Chieri Kubota. Kubota, who joined the faculty at Ohio State this past June will continue the controlled environment agriculture research she was doing while at the University of Arizona.

“Some people think I’m an expert at dealing with heat stress because I was doing my research in an Arizona greenhouse,” she said. “But in Arizona growers don’t really have to worry about the heat inside a greenhouse if they are using an evaporative cooling system to lower the temperature. In Arizona the outside temperature can be 110ºF, but the temperature in the greenhouse can be lowered to 75ºF-80ºF (25ºC-27ºC) as long as the air is dry enough and water is available. In Arizona the dryness can be a challenge, causing tip burn on sensitive crops such as lettuce and strawberry.

“I really didn’t have to deal with heat stress much in Arizona. But there are other parts of the country like the Midwest and East Coast that have to deal with hot, humid summer conditions and very cold winters. I would like to work on those issues and develop technologies, including climate control strategies that can mitigate the issues of growing crops year-round. In Ohio and the Midwest summer heat stress is a major issue for crops causing all kinds of physiological disorders including incomplete pollination and fruit ripening disorders. During the winter, heating and humidity can also be an issue. There is also an issue with low light levels so supplemental lighting is more important.”

Ohio State University horticulture professor Chieri Kubota is planning to continue the controlled environment research she started at the University of Arizona and plans to expand her program to study LED lighting and new crops.
Photos courtesy of Chieri Kubota, Ohio St. Univ.


Because of the limited optimum growing season in greenhouses in the Midwest, Kubota said using indoor productions systems makes more sense compared to Arizona.

“In this part of the country it is very difficult to maintain the optimum temperature range year round,” she said. “And because of the increased interest in vertical farming, I expect to put more effort in warehouse production systems, including the use of LED lighting.”


Improving vegetable grafting

Some of the projects Kubota started at the University of Arizona that she will continue to work on are vegetable grafting and hydroponic strawberry production. She is a member of a research team lead by North Carolina State University plant pathologist Frank Louws that is working on vegetable grafting.

“I am continuing my research on improving grafting methods and the handling of grafted plants so that they can be shipped long distances,” Kubota said. “I am also creating a simple tool for growers to schedule grafted plant production. Having the grafted plants ready at exactly the same size is always a challenge for growers. The research group is working to develop a simple plant growth model based on environmental conditions to predict how many days are needed to finish a grafted crop.”

Kubota said the grafting research team is looking at a variety of plants, including tomato, watermelon, cucumber, eggplant, pepper and muskmelon.

“Growers are commercially producing grafted tomato and watermelon plants, but there are many more crops that can use grafting technology to reduce loss from soil-borne diseases and to increase yields. My program is looking at all of these potential crops.”

Kubota said the grafting research also has application to greenhouse crops.

“The grafting technology was originally developed for soil-based production, but greenhouse vegetable growers discovered that even though they are doing soilless production, using grafted plants can increase crop yields,” she said. “In North America, greenhouse growers were the first group who started using grafting technology. The field growers are now more interested since they have fewer means to control disease. In terms of potential market, field production in the U.S. is much larger in terms of number of plants.

“Currently tomato accounts for the majority of grafted plants in greenhouses. Increased tomato yields have been the driver for greenhouse growers to use grafted plants. Some greenhouse growers have been trialing grafted cucumbers and some research has shown that grafted eggplants can increase yields.”


Improving strawberry production

Kubota who has been working on greenhouse strawberry production for nine years will continue working on this crop with an interest in the use of LEDs.


Chieri Kubota will continue her greenhouse strawberry research with an interest in increasing yields using supplemental light.


“Strawberry fruit production is not as productive as leafy greens or tomatoes in terms of dollars of return relative to the input of light,” she said. “I’m interested in studying the increase in yields relative to the increase in light. What is the dollar value of that increase of yield by adding for example, 1 mole of light? Unless there is an improvement in lighting technology, it may not make sense to grow strawberries under supplemental lighting.

“I would like to come up with a smart lighting system to reduce the lighting cost based on the understanding of strawberry physiology and how plants are grown in a greenhouse. I think we could reduce lighting energy use and costs quite a bit by doing that. Strawberries are physiologically unique in terms of light saturation and also in terms of the sink-and-source relationship of how much sugar can be translocated from the leaves so that the photosynthetic rate can be maximized.”


Developing new crops

Another area that Kubota would like to expand for CEA production is the development of new crops.

“Controlled environment growers whether they are growing in greenhouses or warehouses need to diversify and increase the number of crops they are producing,” she said. “Although I don’t have any new crop projects coming up, I am particularly interested in small fruits. Since Ohio and the Midwest have a cold climate, there may be an opportunity to do more with small fruit crops like raspberries, blueberries, blackberries and other berry crops for greenhouse production.”

Kubota is also interested in revisiting the study of spinach production in greenhouse and warehouses.

“Controlled environment growers seem to have a particularly difficult time managing diseases including Pythium on spinach,” she said. “I am interested in determining if there is a practical way to manage these diseases. Cornell University researchers had previously done a lot of studies on this issue years ago. I wanted to see what the difference was between the successful hydroponic growing of spinach in Asia and other countries and why U.S. growers can’t do that too.”


Expanding professional training, research programs

As part of her extension efforts at Ohio State, Kubota wants to expand the opportunities for growers to receive professional training.

“I want this training to go beyond Ohio and to go nationwide and even international,” she said. “I’m interested in training professionals with online courses and other programs at a reasonable cost.

“The heart of the horticulture industry is in this part of the country. There are many different types of growers, supporting vendors and technology providers here. They are well connected.”


Chieri Kubota said having an extensive group of CEA researchers and extension specialists at Ohio State will enable her to expand training programs for growers not only in the state but potentially worldwide.


Kubota said at the University of Arizona research in the plant science department was focused more on basic science such as how a particular gene functions in plants, but not necessarily horticultural plants.

“Here at Ohio State I am in the horticulture and crop science department so the other faculty members understand what horticulture is,” she said. “There are a number of people here working on controlled environment agriculture including horticulture, which covers floriculture, hydroponics and high tunnels, and ag engineering, entomology, plant pathology and food safety. There is a complete set of researchers and extension specialists who can work on a variety of controlled environment agriculture issues related to horticulture crops. This makes it advantageous for not only developing research projects together, but also professional training for commercial growers.”


For more: Chieri Kubota, The Ohio State University, Department of Horticulture and Crop Science, kubota.10@osu.edu; http://u.osu.edu/cepptlab; https://hcs.osu.edu/our-people/dr-chieri-kubota; https://www.facebook.com/CEPPTLAB.


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


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