Strategies for Maintaining Fruit Quality in Blueberry under Water Limited Conditions

David Bryla

USDA-ARS, Corvallis, OR

The research was conducted by Khalid Almutairi, who is currently working on his Ph.D. with me at the Oregon State University. He is co-advised by Dr. Bernadine Strik.

 

Many commercial blueberry fields are irrigated, but mandatory water restrictions may soon limit the availability of irrigation water in several important blueberry growing regions, such as California and eastern Washington. New strategies are needed to maintain fruit quality with less water. Two potential options, including crop thinning and deficit irrigation, were evaluated for two years in a mature planting of ‘Elliott’ blueberry. Treatments included a combination of normal and 50% reduced crop loads and either no drought or 6 weeks of drought (little rain and no irrigation) during early (Stage I-II) and late stages (Stage II-III) of fruit development. Early drought had no effect on yield, while late drought reduced yield at both crop loads by an average of 40% (Figure 1). Crop load reduction had no effect on the water status of the plants or on photosynthesis during drought at either stage of berry development, but, compared to the normal crop load, it increased berry diameter and average berry weight by 2% to 20% (Figure 2). Plants exposed to early drought had greater fruit bud set than those that were well-irrigated, while plants exposed to late drought had lower fruit bud set. Overall, the results suggest that blueberry may be minimally affected by drought during early stages of fruit development, and thinning the crop to 50% may result in larger fruit at harvest when plants are exposed to drought at any stage of fruit development.

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Figure 1. ‘Elliott’ blueberries during early (A–B) and late stages (C–D) of fruit development.  Plants were either well-irrigated (A, C) or exposed to 6 weeks of drought (B, D). Drought during early fruit development reduced berry size initially but had no effect on yield by harvest. Drought during late fruit development, on the other hand, caused considerable damage and reduced yield by 40%.

Figure 2. Diameter of ‘Elliott’ blueberries from plants with normal or light crops that were either well-irrigated (control) or exposed to drought during early or late stages of fruit development.

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