HYDROPONIC LETTUCE PRODUCTION INFLUENCED BY INTEGRATED SUPPLEMENTAL LIGHT LEVELS IN A CONTROLLED ENVIRONMENT AGRICULTURE FACILITY: EXPERIMENTAL RESULTS

Bibb lettuce (Lactuca sativa L., cv. Ostinata) was grown in peat-vermiculite plugs placed in a recirculating hydroponic (NFT) system. Supplemental lighting was used to reach different PPF_target levels in each of 35 treatments. A second order exponential polynomial was developed to predict DW accumulation for PPF_target levels between 8 and 22 mol m^-2 d^-1. Little difference in DW production was noted between lettuce grown under daytime and nighttime lighting. Tipburn was prevented using a fan blowing greenhouse air vertically down onto the lettuce plants. Marketable (150 g FW) lettuce heads were produced in 24 days after transplant while receiving an average PPF_integral of 17 mol m^-2 d^-1.