Producing greenhouse-grown tomatoes during the winter in the North is a complex and financially draining task. Or is it? This is the basis of the ongoing experiment, “LED versus HPS Supplemental Lighting Effects on Fruit Quality of Greenhouse Tomato.” Michael Dzakovich, a senior and Horticulture Science major from Northbrook, IL, recently won first place at the annual American Society for Horticultural Science (ASHS) meeting in Miami, FL for his oral presentation of the project, as well as first on the Association of Collegiate Branches (ACB) general horticulture comprehension test, which Dzakovich says he took “on a whim.”
The goal of the project, funded by a grant provided by NIFA/SCRI, is to find ways to use newer types of lighting to see if it is feasible to grow tomatoes in greenhouses while cutting the cost of energy, one of the biggest expenses in greenhouses. The project consists of two experiments per year. The first trial ran from January, when natural light is low, to June 2012, when natural light is abundant. The second trial, currently in progress, began in July and will end in December 2012. “As we approach December, the lights will become increasingly important as they compensate for the diminishing natural light,” Dzakovich explains. He predicts the yield to be the same as in the first experiment, but anticipates a greater difference in the quality of the tomatoes.
Two commercial varieties of tomatoes, one of the highest valued crops in the world, were grown hydroponically (a way to grow plants in a soilless media). The tomatoes were started from seed in a foam block, and as they grew the roots spread out in a coco coir (fiber made from shredded coconut husks) slab. Using this method allowed Dzakovich and PhD student Celina Gomez to control how much nutrients the plants were absorbing, unlike when they are planted in soil. The tomatoes from the different light treatments, LED and HPS (standard light in greenhouses), were then harvested a couple of times a week. LED lights are an alternative to the normal HPS lights because they last longer and consume less energy.
The heart of the project is to look at the yield of tomatoes produced using different lighting systems. But it was Dzakovich who wondered how the tomatoes would taste, asking himself, “if they taste terrible, what’s the point?” Not only did Dzakovich take various measurements of the sugar-to-acid ratio to determine taste, but he also conducted tasting panels where the tasters ranked the color, aroma, sweetness, acidity, texture, and overall appeal of the tomatoes without knowing which lighting treatment they were from. It was “like wine tasting, but with tomatoes,” Dzakovich says. Overall, the first experiment was a success. The tomatoes grown with LED side lighting yielded the same as what was produced under HPS lights. Even more promising, the LEDs used 75% less electricity and ranked higher in taste. “Even if the tomatoes tasted the same, it would have still been a victory because we maintained high yields while drastically reducing our energy inputs,” Dzakovich affirms.
Next year Dzakovich is hoping to try his hand at heirloom varieties, a flavorful but delicate tomato. If it is possible to grow them in greenhouses in northern climates off season (they are impossible to ship in winter) then the experiment could yield a new avenue for the tomato market. “Resurrecting heirloom varieties that are suitable to greenhouse production could help reverse the trend of having to import our food, especially during the winter. If we continue to demonstrate that LEDs can make it economically feasible to grow produce in northern climates off season, it will be possible to have an abundance of high quality, locally grown food during the winter. This will create jobs, boost the local economy, and lower our carbon footprint in the long run,” Dzakovich conveys.
“One of our concerns is that we are still a ways from perfecting LED technology. LED lights are relatively new and the towers we have were custom built,” Dzakovich shares. Although LED lights are a work in progress, they are a step in the right direction. “Like CD players in the 1990s. Once manufacturers figured out how to produce them efficiently, the price went down and everyone began adopting the technology. When engineers make enough breakthroughs to make LEDs more accessible to the public, we will be ready,” Dazkovich states.
When reflecting on his experience at Purdue, Dzakovich says there is nothing he would have done differently. He reveals that he actually applied on impulse. Dzakovich had been looking at other schools, but explains that they just “didn’t feel right.” It wasn’t until he visited campus and saw the greenhouses that he became “super excited… I was overwhelmed with the complexity and importance of greenhouses in relation to food supply.” The greenhouses brought back fond childhood memories of working outside with a neighbor who “indoctrinated me into plant sciences,” Dzakovich recalls. Purdue’s Horticulture program opened a new door for him. “I always knew I liked plants and science, but I never knew I could put them together…I never knew about plant science.” After graduation Dzakovich plans to attend grad school, either at Cornell (Ithaca, NY) or UC Davis (Davis, CA), where he will continue his research with plants.
Written by Erin Lane