Location: Horticultural Crops Research UnitTitle: Evaporative cooling with sprinklers to reduce heat-related fruit damage in northern highbush blueberry
|YANG, FAN-HSUAN - Oregon State University|
Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2016
Publication Date: 12/8/2016
Citation: Yang, F., Bryla, D.R. 2016. Evaporative cooling with sprinklers to reduce heat-related fruit damage in northern highbush blueberry. HortScience. 51(9):S331.
Technical Abstract: Hot and sunny weather can cause a considerable amount of fruit damage in blueberries and results in millions of dollars of crop loss each year. The objective of this study was to evaluate the efficacy of using sprinklers to reduce the damage. The study was conducted for 2 years in a mature planting of northern highbush blueberry (Vaccinium corymbosum L. ‘Elliott’) located in western Oregon. Treatments included sprinkler irrigation (at night) and cooling when daytime air temperature reached set points of either 90 or 95 degrees Fahrenheit, sprinkler irrigation (at night) with no cooling, and drip irrigation with no cooling. For cooling, sprinklers were turned “on” for 15 min every hour until ambient air temperature dropped below the set point. Heat damage occurred primarily on sun-exposed berries and happened at both green and blue stages of fruit development. Early damage resulted in poor fruit color at harvest and produced large crevices on the berry surface. Berry temperatures were usually higher than the air temperature between 10 AM and 6 PM and reached up to 117 degrees in sun-exposed clusters and 100 degrees in shaded clusters. Berry temperatures dropped to less than 90 degrees within the first 15 min of cooling and never exceeded ambient air temperature during the cooling cycle. While the percentage of fruit with heat damage was low even without cooling (less than 2%), cooling reduced the damage to nearly 0% each year, and increased the size of the berries. However, cooling had no effect on yield, fruit firmness, soluble solids concentration, titratable acidity, thickness of the waxy bloom on the fruit, or concentration of phenolic compounds in the fruit. Based on these results, cooling should begin at the “late green fruit” stage at critical temperatures greater than 95 degrees.