We tested the efficacy of the Full Spectrum and Red-Blue HORTILED TOP LED fixtures manufactured by PL Light. Both fixtures had an 80° light distribution.

The efficacy of the fixtures was measured using flat plane integration as described by Nelson and Bugbee (2014)1 (see adjacent photo). The fixtures were suspended at 0.65 m above the floor in a 3 × 3 m room with flat black walls. The photosynthetic photon flux density (PPFD, μmol · m-2 · s-1) was measured with a recently calibrated quantum sensor (LI-COR model 190R). Measurements were made 2.5 cm apart near the center, increasing to 10 cm near the edge, and extrapolated to infinity using an exponential decay function.