An energy balance model for predicting berry temperature and scheduling sprinklers for cooling in northern highbush blueberry

Authors: YANG, FAN-HSUAN - Oregon State University; Bryla, David; PETERS, TROY - Washington State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2021
Publication Date: 4/1/2021
Citation: Yang, F., Bryla, D.R., Peters, T. 2021. An energy balance model for predicting berry temperature and scheduling sprinklers for cooling in northern highbush blueberry. HortScience. 56(4):447-453. https://doi.org/10.21273/HORTSCI15459-20.
DOI: https://doi.org/10.21273/HORTSCI15459-20

Interpretive Summary: Blueberry fruit is sensitive to high temperatures and readily damaged after major heat events. The problem is particularly prevalent in the Pacific Northwest, and many growers in the region are interested in finding a solution for reducing heat-related fruit damage in blueberries. An ARS researcher in Corvallis, OR and collaborators from Oregon State University and Washington State University developed a simple climatological model to predict blueberry fruit temperatures based on weather data and used it to simulate the effects of using over-canopy sprinklers for cooling the fruit. Two significant outcomes were achieved. First, the model successfully predicted fruit temperature based on local weather measurements and eventually will be incorporated into a weather forecast program to predict the incidence of heat damage on any given day. Second, the model successfully predicted the fruit temperature patterns during evaporative cooling practices and was used to identify feasible cooling practices for preventing heat damage in blueberry.

Technical Abstract: Heat-related fruit damage is a prevalent issue in northern highbush blueberry (Vaccinium corymbosum L.) in various growing regions, including northwestern United States. Here, we developed a simple climatological model to predict blueberry fruit temperatures based on local weather data and to simulate the effects of using over-canopy sprinklers for cooling the fruit. Predictions of fruit temperature on sunny days were strongly correlated with the actual values (R2 = 0.91) and had a root-mean-square error of approximately 2 degrees C. Among the parameters tested, ambient air temperature and light intensity had the greatest impact on fruit temperature, while wind speed and fruit size had less impact, and relative humidity had no impact. Cooling efficiency was successfully estimated under different sprinkler cooling intervals by incorporating a water application factor that was calculated based on the amount of water applied and the time required for water to evaporate from the fruit surface between the intervals. The results indicated that water temperature and nozzle flow rate affected the extent to which cooling with sprinklers reduced fruit temperature. However, prolonging the runtime of the sprinklers did not guarantee lower temperatures during cooling, since cooling efficiency declined as temperature of the fruit approached the temperature of the irrigation water. The outcome of this study provides increased understanding of how fruit temperature changes under various conditions in northern highbush blueberry and presents a useful means for evaluating feasible cooling practices and making cooling decisions according to local weather conditions.