What are your substrate options for container vegetable production? – Urban Farming News

The amount of leachate from cucumber plants grown in Dutch buckets can be significantly reduced with plant-based substrates compared to perlite.
Photos courtesy of Uttara Samarakoon, Ohio St. Univ., CFAES Wooster

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

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

Improve the sustainability of production in a controlled environment

Uttara Samarakoon, associate professor and coordinator of the Greenhouse and Nursery Management Program at Ohio State University, CFAES Wooster, has studied ways in which controlled-environment growers can improve the sustainability of the production of vegetables in containers. Samarakoon is working with Teng Yang, postdoctoral fellow at Ohio State University, CFAES Wooster, and James Altland, research director Application Technology Research, USDA-Agricultural Research Service at Wooster. Their research is funded by USDA-ARS.

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

“My experience when visiting small and medium vegetable growers is that many of them use perlite as a substrate in Dutch bucket systems. In addition to the disposal problems of perlite, it also has a low capacity water retention resulting in higher leachate rates I have used perlite in my research for some time as it 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-scale vegetable farms tend to use hanging gutters with rockwool or coir slabs for 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-sized growers do not have the ability to do recirculation.

Tomato plants grown in Dutch buckets filled with sphagnum peat moss, medium-grade pine bark, or wood fiber produced a similar number of fruit of comparable weight to plants grown in perlite.

Identification of alternative substrates

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

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

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

“Our main 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 tested were not certified organic, growers may use similar substrates that are certified organic.

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

Researchers from Ohio State University, CFAES Wooster and USDA will expand their study of tomatoes grown in Dutch buckets filled with plant substrates to a nine-month production cycle.

Tomatoes in alternative substrates

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

“Leachate rates were different among substrates throughout 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 reduction in yield and the added benefit of reduced leachate for cucumber and tomato.”

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

“We didn’t grow the tomatoes beyond this stage because that would have required lowering the vines and that might affect the kind of data we collected,” Samarakoon said. “In our next tomato trial, we will use the same substrates but grow the plants on a nine-month production cycle. We will be pulling the vines down and training them to continue growing for a nine month production cycle to determine how the alternative substrates support the plants. We also focus on optimizing the propagation of vine crops when using alternative substrates.

For more: Uttara Samarakoon, Ohio State University, CFAES Wooster; [email protected]; https://ati.osu.edu/uttara-samarakoon-phd.

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