Curtain call

Growing in central Illinois, University of Illinois at Urbana-Champaign Plant Care Facility researchers see cold winters, cool nights and grow fairly input-intensive crops that require warm day conditions and warm nighttime conditions, says Nathan Deppe, Plant Care Facility coordinator.

The researchers utilize shade curtains to meet various plant needs, Deppe says. “Some of the ones that we have here have a thin strip of aluminum, which helps push out more of the solar radiation in the summer, so you don’t get a lot of that solar gain, but also then retains at night,” he says. “That aluminum helps retain heat into the canopy.”

When considering upgrading their shade curtain systems, growers should ask curtain manufacturers questions, Deppe says. “Ask them [about] the longevity of cloth in a typical system,” Deppe says. “For the most part, seven to 10 years is [a] fairly customary [lifespan], and then you would look for tears or runs in your cloth.”

With his shade curtains, Deppe has found that the curtain contains a stationary piece of material that acts as a gasket. It prevents heated air from getting around the curtain and through the peak, and forces the air to stay in the lower canopy, Deppe says.

“This would pertain to those who would want to shade that have maybe used conventional whitewash techniques in the past for shading their structure when it’s overly warm out or when the sun’s intensity supersedes what their plant material needs for good growth,” Deppe says. “You can certainly use those to your advantage in that within a shade system like that, you don’t necessarily always have to shade. You can open and close these, or you could use your greenhouse controller to implement opening and closing based on the solar radiation.”

If solar radiation is too high in these systems, growers can draw the curtains shut during the day and open them at night to optimize natural light, Deppe says.

Owners and technicians of large production facilities need to look at the mechanics that drive shade curtain systems open and closed, and make sure they fit their operations, Deppe says.

The Plant Care Facility has an outdoor weather station equipped with light sensors. “For a given room I want this curtain to start shading when the sun’s radiation is at 500 watts per square meter per second,” Deppe says. “That sensor would always be looking and once it gets to that point, it tells the system to start running.”

With around 50 individual curtain systems at the site, Deppe checks the shade curtains annually for system components that need upgrades or repairs. When growers check for shade curtain system parts that may require upgrades, they should look at the amount of money they have spent on their systems and the return on investment they are getting, he says. “Part of that’s just going to be the grower, the situation that they have before them, on when they would want to replace those,” he says.