Hemp, a U.S. legal classification for cannabis cultivars that produce a low quantity of THC, is gaining popularity in the United States as a source of CBD, a non-psychoactive compound purported to have a range of beneficial effective for its consumers. Due to the current regulatory environment in the United States, cannabis is generally produced in close proximity to markets (owing to a prohibition on interstate transport) and cannabis grow operations are required to maintain a heavy security infrastructure around the zone of production. Aquaponics, the combined culture of fish and plants in a recirculating aquaculture system, is a technology that may be particularly suited to culturing cannabis in these circumstances. This is of particular relevance to producers with indoor, urban operations. Indoor operations rely on artificial lighting for plant production, and the rapid growth of the industry has flooded the market with different styles of lighting at a wide range of costs.
To this end, an experiment was conducted at the Kentucky State Aquaculture Center’s replicated aquaponic research systems to test a variety of light sources, differentiated by their purchasing and operating costs. A hemp cultivar of cannabis sativa was cultured in the aquaponic systems using a blend of common commercial production techniques. These included planting in an expanded clay media, continuous drip irrigation, and partial submersion of the planted container in the nutrient-carrying recirculating water. A variety of LED (SpiderFarmer, MarsHydro, NeoSol) and High-Pressure Sodium (Efinity) lights were employed in each growing system, and plants were analyzed afterward for THC/CBD content, terpene content, flowering mass, and overall biomass. Power consumption metrics and plant production:electrical use ratios were also recorded.
Results showed that the light source employed had significant effects on several plant production and electric use ratios, including kWh per gram of flower bud and electrical cost per gram. Differences in the majority of THC/CBD content appeared to be negligible, except for % CBD content. Given the amount of focus high-end lighting systems receive as determinants of quality for cannabis, our findings suggest that more affordable lights may be used by aquaponic cannabis producers without sacrificing production.