Evaluation of the light use efficiency and water use efficiency of sweet peppers subjected to supplemental interlighting in greenhouses

• Published in: Horticulture, environment and biotechnology Vol. 64; no. 4; pp. 605 - 614
• Main Authors: Kwon, Sungmin, Kim, Dongpil, Moon, Taewon, Son, Jung Eek
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.08.2023; Springer Nature B.V
• Subjects: Agriculture; Biomedical and Life Sciences; Canopies; Crop yield; Dry weight; Efficiency; Flux density; Fruits; Greenhouses; Hydroponics; Interception; Life Sciences; Light; Light emitting diodes; Light interception; Lighting; Luminous intensity; Natural lighting; Peppers; Photosynthesis; Plant Breeding/Biotechnology; Plant Ecology; Plant Physiology; Planting density; Ray tracing; Research Report; Simulation; Three dimensional models; Transpiration; Water consumption; Water use; Water use efficiency; Weight; Water consumption; Intra-canopy lighting; Three-dimensional plant model; Photosynthesis; Growth stage
• ISSN: 2211-3452; 2211-3460
• DOI: 10.1007/s13580-022-00508-5

In greenhouses, the higher plant density causes poor light environments inside the canopy due to the mutual shading of adjacent plants. Interlighting has been introduced as a countermeasure to compensate for the lack of light in the middle and bottom canopies. However, most studies have focused on growth and yield, not light use efficiency (LUE) or water use efficiency (WUE). The objective of this study was to evaluate the LUE and WUE of sweet pepper plants subjected to light-emitting diode (LED) interlighting in greenhouses. Two lighting treatments, natural light (control) and supplemental lighting with red and blue LEDs, were applied. Interlighting began 34 days after transplanting. The ratio of red and blue light to photosynthetic photon flux density (PPFD) was 8:2, and the total PPFD was adjusted to 71 μmol m −2  s −1 at a distance of 20 cm. The daily transpiration was measured by subtracting the drainage from the supplied nutrient solution and the weight change of the hydroponic systems. The photosynthetic rate was obtained by measuring light response curves at light intensities of 0, 50, 100, 200, 400, 600, 900, 1200, 1500, and 2000 μmol m −2  s −l . The LUE was calculated based on the simulated light interception obtained by 3D-scanned plant models and ray-tracing simulation. WUE was calculated by dividing the measured dry weight by the accumulated water consumption. Under the interlighting, the LUE increased at the canopy level due to the improved vertical light distributions. The WUE for biomass and fruit yield were higher in the interlighting treatment than in the control. These results were due to the higher increase rates of plant dry weight and fruit yield than that of water consumption by interlighting. In this study, the improvement of LUE and WUE by interlighting could be quantified by optical simulation and a measurement of water consumption throughout the entire growth period.