Ben-Min Chang,* Brad Estergaard, and Steve Marsh
*Agriculture & Agri-Food Canada – Summerland Research & Development Centre, 4200 Highway 97, Summerland, BC V0H 1Z0, Canada (ben-min.chang@agr.gc.ca)

The majority of vineyards in British Columbia are located in the Okanagan Valley. Vineyards are often located on the slopes between lakes and mountains in this area. North-south row orientation is not always suitable for vineyard sites with slopes facing east or west. The highly diverse row orientations in the valley makes a complex puzzle for researchers and growers to comprehend the dynamic light environment at canopy level. Since solar energy drives transpiration by heating leaves and increasing vapor pressure deficit, a better understanding of light conditions might facilitate water stress monitoring. A simple model was developed in Excel for calculating and visualizing solar energy intercepted by the canopy. In this model, the canopy is simplified as a box with infinite length, and the row orientation, row spacing, height, and width of a canopy are entered as canopy structural characteristics. Other data inputs include vineyard latitude, longitude, time zone, date, and solar radiation. The model simulates sun position, shaded area, and intercepted solar energy in a vineyard within an hour interval on a designated date. The simulation suggested that a canopy with east-west orientation intercepted the highest amount of incident solar energy at noon, while a north-south orientated canopy intercepted more energy at 0900 hr and 1500 hr on a day in late July. When incident light direction paralleled with the row orientation, the canopy might intercept less energy in a vertical shoot-positioning canopy. To validate the model, solar panels will be used to estimate solar energy intercepted by the canopy in different vineyards. Whether the model can predict the optimum timing for measuring maximum stem water potential will be tested. This model may help growers adjust water potential measurement timing precisely, based on the day of year and row orientation.

Funding Support: Sustainable Canadian Agricultural Partnership - Wine & Grape Cluster