Age-related changes in response of highbush blueberry plants to drip irrigation.

A study was conducted in the Fraser Valley of British Columbia, Canada, to determine the effects of drip configuration (one or two lines with emitters spaced every 0.3 or 0.45 m) and irrigation at moderate or heavy rates (5 or 10 L/plant) in a mature planting of ‘Duke’ highbush blueberry (Vaccinium corymbosum L.). Results were compared with those published previously from the first 4 years after planting. Although plant size increased with irrigation rate when the plants were younger, there was no added benefit of heavy irrigation on growth in the older plants. However, the plants became more sensitive to soil water deficits with age and, therefore, unlike when they were younger, had greater yields when more water was applied. Berry size and fruit firmness were little affected by irrigation in the older plants, but antioxidants, measured as oxygen radical absorbance capacity (ORAC), were higher with than without irrigation, suggesting that irrigation has the potential to improve the health benefits of blueberries. Growth, yield, and fruit quality were unaffected by drip configuration in any year. Overall, the results revealed that the response of highbush blueberry to drip irrigation changed over time and indicated that irrigation management should be adjusted as a planting matures.