Use of Light Emitting Diodes for Supplemental Lighting in Viticulture Field Research

Abstract

A light emitting diode (LED) system was evaluated as a tool for field research to investigate light effects on grapevines. Preliminary laboratory trials were conducted to develop response curves for photosynthetically active radiation (PAR) and temperature in relation to distance from LED light source. LED panels were subsequently deployed in a three-year field study comprising three light exposure treatments on developing fruit clusters of Vitis vinifera cv. Cabernet Sauvignon: 1) clusters exposed to direct sunlight, 2) clusters shaded by canopy, and 3) canopy-shaded clusters exposed to supplemental LED light. Laboratory trials and vineyard field studies demonstrated LED panels could provide supplemental light over a broad range of PAR, up to and exceeding the photosynthetic light saturation point for exterior leaves of grapevine, by adjusting distance of LED panel to target. Although bench trials indicated significant convective heat close to the LED panel, field studies detected few temperature differences among cluster treatments. Varying results were primarily attributed to temperature measurement locations related to experimental objectives; bench trials measured target surface temperature, whereas field studies monitored whole cluster temperature. LED panels were effectively deployed to provide supplemental light to shaded grape clusters without significantly altering cluster temperature.