COMPARISON OF FOUR ARTIFICIAL LIGHTING TECHNOLOGIES FOR INDOOR AQUAPONIC PRODUCTION OF COLLARD GREENS Brassica oleracea

George J. Pate*, Janelle V. Hager, Luke A. Oliver, Chelsea T. Watts, Leigh Anne Bright, Shawn D. Coyle and James H. Tidwell.
Aquaculture Research Center  
Kentucky State University  
103 Athletic Road  
Frankfort, KY 40601  
George.pate@kysu.edu

Aquaponics is a sustainable food production system that combines hydroponic plant growth with fish rearing in a recirculating aquaculture system. Aquaponic systems operating in temperate climates are constructed in insulated buildings, to achieve year-round production.  In this setting, all environmental requirements for plant production are provided artificially.  Information regarding optimal artificial lights for plant growth is needed to ensure producers are able to maximize their production.

This study evaluated and compared four leading light technologies on the growth of collard greens (Brassica oleracea) over a 22-day cycle. Four replicate systems were used which included a 415-L fish tank, a 190-L settling tank, a 115-L clarifier, and two 1.5 m2 floating raft beds Plants were stocked at sixteen plants/floating raft. Each system contained all four light types using a Randomized Complete Block Design. Light technologies evaluated included light emitting diode (LED), metal halide (MH), induction (IND), and fluorescent (FL), the lights were then all standardized to 200 photosynthetic active radiation (PAR) measured from just above the canopy. Nile tilapia (Oreochromis niloticus) were fed a floating 32% protein feed and stocked at a rate allowing a feeding rate of 60 grams per square meter of plant grow space per day. At harvest, the four plants in the center of each raft were weighed whole, then separated between roots and leaves, then measured and weighed. Light effects were compared based on biomass accumulation, leaf surface area, root/shoot ratio, and biomass/square meter/kilowatt-hour.

Results from this study indicate that the average fresh weight of collard greens raised under LED lights (48.9g), was significantly greater (P≤0.05) than the weights of plants grown under MH (13.8g), IND (18.6g), or FL (15.3g) lights. Relatedly, the root/shoot ratio for plants raised under LED lights (31:100) were significantly (P<0.05) greater than the ratio for plants grown under FL (18:100), IND (18:100), and MH (19:100) lights. This data indicates faster growth and maturation under the LED lighting based on characteristic of climax vegetal phases. These results indicate superior performance by LED lights for Collard greens under indoor aquaponics production.