Greenhouse operations producing in the summer will not have many significant changes when transitioning to fall production, according to Peter Ling, an assistant professor in Ohio State University’s Department of Food, Agricultural and Biological Engineering. The one major difference is the change in temperature at night during the fall as opposed to the summer, he says.
“The only difference is that the temperature is a little bit cooler [in the fall],” Ling says. “Temperatures can get really low, so there can be a really big swing in temperature. You don’t want to over-cool the plants going into the night.”
He adds that transitioning from fall, and optimizing cooling and heating systems, is the main adjustment growers have to make between summer and fall.
“It’s really transitioning from cooling season to heating season,” Ling says.
Properly evaluating energy needs between seasons
Growers should start planning fall production, and ultimately making the transition to growing cool-season crops, by making sure heating and cooling systems are working properly, Ling says. After a long summer where the cooling system is likely used regularly, it’s vital to make sure it’s still working up to the standard a grower expects it to.
“You want to make sure it’s in good shape,” Ling says. “Make sure the in-load is in good shape. In the summer, you might use a cooling pad heavily and see algae build-up.”
Proper cooling system maintenance, Ling says, is key because of how quickly temperatures can rise in a greenhouse. He says that, in as few as 30 minutes, temperatures inside the greenhouse can jump 10-15o F. That quick of a spike in temperature, if left unchecked, can kill plants.
“If your cooling system fails, and you’re not there, your crop is basically cooked,” Ling says. “It depends on the duration and temperature. It won’t take very long to kill the plants.”
He says that this problem most commonly occurs when growers do not produce, or produce very little, in the summer and have not done the proper maintenance. Growth issues can also occur if a heating system is not maintained properly, although Ling says over-cooling is “highly unlikely.”
How to properly plan for fall production
Fall weather can be fickle, alternating between cooler temperatures and hotter days that resemble the peak of summer. Greenhouse operations, depending on what geographic region they are located in, can be subject to these weather changes. According to Ling, the way to combat this is by remaining energy-efficient.
“When temperatures are fluctuating outside, there is a tendency to over-correct,” he says. “If the temperature is high, then you crank up your cooling system. But if it cools down outside very quickly, and your cooling system is still working, then temperature is going to drop lower than you want it to be.”
Ling, though, doesn’t believe this issue can kill plants if a range of temperatures is selected based on what is being grown. He adds that it can also increase production costs and lower plant quality and growth over time.
The key to avoiding these issues, Ling says, is preparation. He recommends checking cooling systems in March or April for any necessary repairs or maintenance needs. Ling adds that early fall production is different than late fall production. In the beginning of the season, the climate largely resembles late summer conditions that growers were already operating in. But as the season goes on, he says greenhouses can start to have issues with humidity levels spiking and causing larger plants to transpire more. Bringing in cool, lower air, and lowering the greenhouse temperature, is one option to drive out moisture and lower humidity levels.
“It’s not doing anything special for fall [production],” Ling says. “Just make sure you continue to work.”