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Abstract.  The fresh onions grown in south Texas are short-day varieties with a high-water content and softer skin. While harvesting machines for long-day onions are available, they have not been successful with short-day varieties.   Mechanical harvesting of onions involves two operations: lifting, and harvesting, but must be considered as a system that includes the variety harvested. During 2021 and 2022, Rio Grande Valley onion fields mechanical harvesting trials were conducted with three onion varieties and machines from two manufacturers. Damage to bulbs by the machine operations was determined by collection of samples and visual inspections.

In 2021, testing with the Univerco machines was conducted in two fields with different production systems and varieties. Although tested with a range od operating conditions, the Univerco system had an average bulb damage of 5.14% for lifting and for harvesting of 8.0%, meaning the harvester contributed approximately 3% to the total. The Top Air system was tested on Veronica variety in 2021 and 2022, plus Hellcat variety in 2022. Lifting of Veronica, showed bulb damage of 1% both years. Lifting of Hellcat in 2022 had higher damage levels (4.6 to 16.2%, 10..6% overall mean) and no clear trend with operating conditions. In 2022, Hellcat was harvested on two dates with six and twelve days of field curing after lifting. The average damaged mass was 3.4% after six days and 1.6% after 12 days.

Impact testing of bruising of four varieties was included. Durometer firmness did not predict bruising severity for any of the varieties.