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Pat Bowen and Brenda Frey

Effects of staking, drip irrigation frequency and fertigated N rate on dry matter partitioning and yield of bell peppers (Capsicum annuum L.), grown using polyethylene mulch and mini-tunnels, were determined in two years. In the second year, which had higher early-season temperatures and more hours of direct sunlight, plants were larger, more productive and had larger fruit with thicker pericarps and a higher water content than in the first year. In both years, staked plants fertigated with 31.5 vs. 63 kg·ha-1 N produced higher yields due to increased fruit size and pericarp thickness. Compared with the response to monthly irrigation plus rainfall, additional irrigation applied when the soil moisture tension averaged below -25 and -20 kPa in the two years, respectively, affected yield only in the second year when it increased yield and the number of fruits produced by staked plants and decreased that of non-staked plants. Patterns of vegetative development and dry matter partitioning indicate that resources were remobilized from leaves to support fruit development.

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David L. Ehret, Brenda Frey, Tom Forge, Tom Helmer, and David R. Bryla

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.

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David L. Ehret, Brenda Frey, Tom Forge, Tom Helmer, and David R. Bryla

A 4-year study was conducted to establish the effects of drip irrigation configuration and rate on fruit yield and quality of young highbush blueberry plants (Vaccinium corymbosum L. ‘Duke’). Plants were grown in a silt loam soil on raised beds and were non-irrigated or irrigated using either one or two lines of suspended drip tape. Each line configuration had in-line emitters spaced every 0.3 or 0.45 m for a total of four drip configurations. Water was applied by each drip configuration at two rates, a moderate rate of 5 L/plant per irrigation event, and a heavy rate of 10 L/plant. The frequency of irrigation was guided by measurements of soil matric potential. Irrigation was applied each year, and plants were cropped beginning the second year after planting. Rainfall was above normal in the first 2 years of the study, and differences in soil moisture were most evident in the last 2 years, in which soil matric potential increased with irrigation volume. Neither the number of irrigation lines nor emitter spacing had an effect on yield or fruit quality. Yield was unaffected by irrigation rate until the fourth year after planting and was only higher when 5 L/plant was applied. The yield increase was the result of differences in fruit weight during the second of two harvests and was associated with delays in fruit maturation. Irrigation affected plant mineral concentrations but leaves and berries responded differently; affected minerals tended to decrease in leaves but increase in the fruit. Many irrigation-induced changes in fruit quality were evident 1 or 2 years before changes in yield. Higher irrigation volume increased fruit size and water content but reduced fruit firmness and soluble solids. Irrigation reduced fruit water loss during storage and thereby promoted longer shelf life. Irrigation also resulted in a change in anthocyanin composition in the fruit but did not affect antioxidants or total anthocyanin content.