When it comes to using supplemental lighting on their crops, growers have options whether they’re trying to achieve a photoperiodic or a growth response.
By David Kuack
An increasing number of growers are using supplemental lighting for photoperiodic control and for accelerating plant growth. Growers have a variety of options when it comes to the type of lights available and how to use them most effectively. Growers who decide to use supplemental light to accelerate crop growth should expect to have to modify production schedules and possibly change some of their cultural practices.
HIGH INTENSITY DISCHARGE LIGHTS
James Grouzos, U.S. greenhouse consultant at P.L. Light Systems, said 90 percent of the greenhouse growers in the United States and Canada who are using supplemental light to increase plant growth are operating high pressure sodium lamps. High pressure sodium and metal halide are high intensity discharge (HID) lights. “The bulbs contain a mixture of gases that are hit with electrical energy. Basically the energy is vaporizing the gases,” Grouzos said. “It’s high intensity discharge since there is a lot of energy being produced by these gases. The mixture of gases in the bulb can be changed to create a blue spectrum or a yellow spectrum. When the electricity goes through the tubes the gases burn at a specific temperature called a Kelvin temperature. For high pressure sodium it’s usually around 3,400 Kelvin and it’s around 4,500 Kelvin for metal halide.”