Number of drip laterals and irrigation frequency on yield and exportable fruit size of highbush blueberry grown in a sandy soil

Wetted area is an important factor in the production of blueberries. The effects of the number of drip laterals (wetted area) and irrigation frequency on fruit production were evaluated in two seasons in a mature field of northern highbush blueberry (Vaccinium corymbosum L. 'Brigitta'). The field was located on a sandy soil in south-central Chile. Seven-year-old plants were irrigated from Sept. to April with two, four or six drip laterals per row, either four or six days per week. All treatments received the same amount of water per week for a total of 532 mm per season, according to the irrigation schedule established by the grower. During the 2008-2009 season the volume of water applied through irrigation plus precipitation corresponded to 90% of the theoretical crop evapotranspiration (ETc), and in the 2009-2010 season (until harvest) it was 122% of the ETc. Blueberry production on sandy soil was affected by the number of drip laterals per row, and total berry yield was the greatest when plants were irrigated with four drip laterals per row. The two irrigation frequencies evaluated did not affect the blueberry production under drip irrigation, although a barely noticeable trend of greater yield was observed under the irrigation treatments of six days per week, compared with those that were irrigated only four days per week. An interaction effect was observed between irrigation frequency and number of laterals on the percentage of exportable fruit (caliber ≥10 mm). Plants irrigated four days per week produced a significantly larger percentage of exportable fruit, compared with those irrigated six days per week. Nevertheless, when plants were irrigated six days per week the increase in number of drip laterals per row increased the percentage of exportable fruit. Therefore, it is recommended to use four drip laterals per row for commercial production of highbush blueberry in sandy soils.