LED Lighting Improves the Yield and Quality of Hydroponically Grown Basil

The application of Light Emitting Diode (LED) lighting systems in greenhouse production is rapidly increasing due to improved energy efficiency, increased spectral quality control, and reduction in manufacturing costs. However, research is needed to determine the value of LED lights in comparison to traditional lighting systems. The objective of this study was to determine the impact of LED lighting on greenhouse hydroponic basil (Ocimum basilicum var. ‘Genovese’) production in comparison to traditional lighting systems. Overall biomass accumulation and nutrient uptake were evaluated. Basil was chosen because of its high demand and value among restaurants and professional chefs. Three light treatments were used for this experiment: 1) Natural light supplemented with LED lighting of 20% blue (447 nm) / 80% red (627 nm) at 100 µmols m-2 sec-1, 24h per day; 2) Natural light supplemented with high pressure sodium (HPS) at 100 µmols m-2 sec-1, 24h per day; and 3) Natural light only (control). The daily light integral (DLI) averaged 9.5 mol m^-2 d^-1 (ranged from 4 to 18 mol m^-2 d^-1) during the growth period. The supplemental light treatments each provided 8.64 mol m^-2 d^-1. Each treatment was grown in 75% relative humidity with day temperatures averaging 29.4°C and night temperatures averaging 23.8°C. All treatments were harvested forty-five days after seeding. The LED treatment had the greatest total biomass accumulation, both in fresh (FM) and dry biomass (DM). The LED treatment biomass was approximately 25% greater than HPS, and 208% greater than the natural light control. Biomass partitioning revealed that the LED treatment had more FM and DM for the individual main stem, shoots, and leaves of each plant. The LED treatment had 28% biomass increase over HPS and 55% increase over the natural light treatment. The LED treatment also resulted in greater plant height and main stem diameter, approximately 24% greater than HPS treatment and 45% greater than the natural light treatment. The HPS treatment was not significantly different than the LED treatment for many of the experiment parameters; however, both treatments were significantly greater than the natural light control. Mineral analysis also suggests that both macro and micronutrient accumulation was improved with supplemental lighting. On average, the LED treatment improved macronutrient uptake by 21% over HPS, and 33% over natural light control. The application of LED lighting systems to supplement natural photoperiods may be beneficial for improving overall biomass accumulation, as well as nutrient accumulation in basil.