Short-day onions such as Vidalia are vital in warmer climates, but their delicate skins make them prone to an average of 8% bruise damage during mechanical harvesting. As a result, manual hand harvesting remains the preferred method despite its high cost of $3,951/hectare for labor, according to the 2019 Onion Irrigated Budget (University of Georgia). Addressing issues of mechanical harvesting could offer a more cost-effective alternative while solving the labor shortage problem. This study aimed to evaluate the bruise tolerance of five Vidalia varieties (Vidora, Sweet Magnolia, Sapelo, Red Maiden, and Monjablanca) under different impact conditions and identify the specific sections of mechanical harvesters that contribute to bruising. Identifying the most bruise-tolerant varieties can guide growers in selecting onions better suited for mechanical harvesting, reducing labor costs and postharvest losses and by understanding which sections of the harvester cause the most damage, modifications can be made to reduce bruising. Controlled pendulum tests were conducted to simulate onion-to-surface impacts, using onions embedded with Impact Recording Devices (IRDs) to measure impact forces at two maturity stages (80% tops down and one week after 80% tops down) and two drying durations (0 and 7 days). Drop heights were selected based on bruise damage results for Vidora, with two levels for each surface type: 10 cm and 30 cm for flat surfaces, and 30 cm and 55 cm for padded surfaces. A total of 320 impacts were recorded. To identify the most bruise-prone sections of the harvester, 23 field trials were conducted using a Top Air Harvester, with IRDs embedded within onions and placed on field, to capture real-time impact data. The Top Air Harvester, consisting of a collecting belt, elevator, sorting belt, and conveyor, transferred onions to the bulb collection truck within 36 seconds. Early results for Vidora variety indicate that bruising severity increases with higher drop heights, on flat surfaces, while padded surfaces significantly reduce damage. Testing all five varieties will provide a comprehensive profile of bruise tolerance, helping growers select varieties better suited for mechanical harvesting, potentially reducing labor costs. Initial analysis of field trials revealed that the conveyor-to-bin transition generated the highest impact forces, significantly contributing to bruising. These preliminary results indicate the need for design improvements in this section to reduce impact damage and enhance mechanical harvesting efficiency. Further testing will validate these findings and guide the development of improved mechanical harvesting practices.
