Harvest of southern highbush blueberry with a modified, over-the-row mechanical harvester: use of handheld shakers and soft catch surfaces

Authors: SARGENT, STEVEN - University Of Florida; Takeda, Fumiomi; WILLIAMSON, JEFFREY - University Of Florida; BERRY, ADRIAN - University Of Florida

Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2019
Publication Date: 12/21/2019
Citation: Sargent, S.A., Takeda, F., Williamson, J.G., Berry, A.D. 2019. Harvest of southern highbush blueberry with a modified, over-the-row mechanical harvester: use of handheld shakers and soft catch surfaces. Agriculture. https://doi.org/10.3390/agriculture10010004.
DOI: https://doi.org/10.3390/agriculture10010004

Interpretive Summary: Production costs and labor availability issues are increasing grower interest in mechanical harvesting (MH) options for picking fresh market quality blueberries. An over-the-row harvester was modified to reduce purchase cost and to make harvesting more efficient. The mechanical picking heads were removed and worker stations were installed on each side of the harvester. Harvesting was performed by workers standing on the platform using air-powered mechanical olive shakers. Also, experimental catch surfaces were installed over rigid catch plates and conveyor belts. Southern highbush ‘Meadowlark’ and ‘Farthing’ blueberries were harvested by this system in 2017. Fruit firmness and bruise incidence were determined after one day at room temperature, and after seven and 14 days of cold storage. Fruit firmness was lower in machine-harvested fruit compared to hand harvesting. After seven days in cold storage, up to 18% of MH fruit had bruise severity >20% compared to less than 4% for hand-harvested. Adoption of MH for blueberries requires the coordination of many factors. The potential of using soft catch surfaces to improve the pack-out to the level achieved by hand harvesting was demonstrated in this study. However, other additional harvester design improvements are necessary to further reduce bruise damage.

Technical Abstract: Fresh market southern highbush blueberries are typically hand-harvested which requires an extensive labor force over a relative short period of time. With rising production costs and labor availability issues, interest in mechanical harvesting options is increasing. In 2017, an over-the-row harvester was modified to reduce purchase cost while making hand labor more efficient. The picking heads were removed and dual worker stations were added on each side of the unit. Handheld olive shakers were suspended at each station, and experimental catch surfaces were installed on one side of the catch plates and over the rigid conveyors on both sides. ‘Meadowlark’ and ‘Farthing’ blueberries were harvested with this system and manually by a commercial harvest crew. Samples from each harvest method were then commercially cooled and packed to determine pack-out data. Fruit firmness, bruise severity and composition (soluble solids content; total titratable acidity) were determined after 1 day at room temperature (22 °C), and after seven and 14 days of storage at 1 °C. Average pack-outs were very high, 87% for ‘Meadowlark’ and 91% for ‘Farthing’. Initial firmness of both ‘Meadowlark’ and 'Farthing' was lower for mechanically harvested fruit (208 g/mm) compared to hand-harvested (243 g/mm). Although there were no significant differences in fruit firmness due to catch surfaces, mechanically harvested fruit had >85% more bruising than hand-harvested. ‘Meadowlark’ fruit remained firmer than ‘Farthing’ fruit during storage. After seven days at 1 °C, up to 18% of mechanically harvested fruit had bruise severity ratings >20%, making them unmarketable. ‘Farthing’ had slightly higher soluble solids content and significantly higher total titratable acidity values compared to ‘Meadowlark’. Installation of soft catch surfaces over the rigid conveyor belts reduced bruise severity, although there was no noticeable effect of catch surface type.