Performance Evaluation of a Double-Conveyor Type Sweet Potato Harvester according to Soil Texture

The shortage and aging of the agricultural workforce in Korea have increased the need for mechanization, particularly in field crop harvesting. Although sweet potatoes are a major root crop in Korea, their mechanized harvesting is limited due to the fragile outer skin, which is highly susceptible to damage during mechanical digging and transfer. To address this issue, a tractor-mounted double-conveyor type sweet potato harvester was developed and evaluated in this study, aiming to minimize outer skin damage and improve harvesting efficiency. Field performance evaluations were conducted in Gimje (loam soil) and Haenam (clay loam soil), Korea. A single tractor model (73 PS) with a constant driving speed (1 km/h) and PTO speed (540 RPM) was used in all field tests to minimize experimental variability. The evaluation included measuring the sweet potato digging ratio and damage ratio, comparing the developed double-conveyor harvester with conventional harvesters, including plow-type, vibration-type, independent-row type, and vibration conveyor-type harvesters. Results indicated that the double-conveyor sweet potato harvester showed a digging ratio of 99.1% in loam (Gimje) but slightly lower performance (89.6%) in clay loam (Haenam). Regarding the damage ratio, the developed harvester achieved 36.3% in loam soil and notably lower damage (12.6%) in clay loam soil compared to other conventional harvesters. These findings suggest that the double-conveyor harvester effectively reduces outer skin damage, especially in clay-rich soils, although its digging performance varies depending on soil texture. Further research should focus on optimizing conveyor speed, angle, and vibration intensity according to different soil textures to enhance both digging efficiency and skin protection of sweet potatoes.