Mechanical Harvest Potential of Three Southern Highbush Blueberry Cultivars

Three southern highbush blueberry cultivars, (‘Sweetcrisp’, ‘Farthing’, and Meadowlark™) were evaluated for their mechanical harvest potential in north-central Florida. Four replicates of hand and machine harvested plots were randomly assigned within a single row (20 plant plot for machine-harvest and 6 plant plot for hand-harvest). Hand-harvested plots were picked prior to machine harvest to remove all mature fruit at each harvest date, and the harvesting head on the harvester was turned off when passing over the hand-harvested plots. A Korvan 8000 harvester was used for three harvests: early-, mid- and late-season. After each harvest, all dropped berries beneath four tagged plants from each plot were collected, sorted by color stage (green, red, blue), and weighed. All machine-harvested berries were stored in lugs overnight at 10 ^oC prior to sorting on a commercial packing line the next morning. Fresh weights of cull (soft or off-color) and marketable berries were determined for each plot. Marketable berries were packed into 170 g (6 oz) clamshells and into flats (12 clamshells/flat). Subsamples from machine- and hand-harvested fruit were evaluated the day of packing for the percentage of soft and/or mechanically injured berries and then frozen at -30°C for further analysis (soluble solids content, titratable acidity, pH). Four clamshells per cultivar/harvest method were stored at 1°C for 14 days. Initial and final weights were measured for each clamshell per storage period to calculate percent moisture loss. After 7 and 14 days, stored berries were evaluated for overall quality including shrinkage, firmness, mold, and general appearance. After 14 days of storage, fruit were frozen at -30°C for future quality analysis (soluble solids content, titratable acidity, pH). Packout differed between mechanical- and hand-harvested berries of all cultivars, with94% of the hand-harvested berries graded as marketable on the day following harvest versus 81% for mechanically-harvested berries. The lower percentage of marketable berries was due primarily to a greater proportion of immature (red and green) berries from mechanically- versus hand-harvested plots. During grading, a greater percentage of soft berries were noted for mechanically- versus hand-harvested treatments, but this difference was small compared to differences in the amount of immature fruit harvested. The greatest challenge for mechanically harvested blueberries was increased fruit softening during storage where hand-harvested fruit remained firmer than mechanically harvested fruit for all cultivars and harvest times. Soft fruit were most prevalent for mechanically-harvested berries after 14 days of storage.