Targeted Shake-and-catch Harvesting for Fresh Market Apples in Trellis-trained Trees
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    Abstract:

    Currently, fresh market apples are picked manually around the world, which requires a huge seasonal labor force to complete the job within the narrow harvest window. In addition, the shortage of skilled labor and high labor cost are increasing every year, which have threatened the sustainability of apple production. To address these issues, it is essential to develop mechanical harvest solutions for fresh market apples and other tree fruits. Shake-and-catch harvesting system offers an alternative solution to potentially obtain high harvest efficiency. Research on shake-and-catch harvesting for fresh market apples has been conducted for several decades. However, commercial machine is still unavailable. The crucial problem is that the damage rate and degree induced during harvesting is too high. Apple orchards in USA are being planted in modern trellis trained architecture, including formally trained horizontal limbs. The ready access to the limbs and fruit in formally trained orchard creates the potential for controlled localized fruit removal at the limb level. To verify the hypothesis that the newest apple tree canopies provide opportunities for targeted shaking and catching with minimal fruit damage, a new targeted shakeandcatch method was proposed. To realize this method, we developed a set of limb shaking device and corresponding capturing platform. A set of data acquisition system based on computer was also integrated to the shaking device to monitor and control the forced vibration frequency of a targeted limb. According to the capturing platform with/without separation buffer strips and horizontal/tilted capturing, four capturing patterns were tested in a commercial-grade ‘Jazz’ apple orchard (Prosser, Washington State, USA), in which trees were trained to a vertical fruiting wall architecture with seven layers. The harvesting test was conducted by shaking a tree limb and capturing the removal fruit right underneath the targeted limb. Each capturing pattern was involved in 20 samples, each of which including two adjacent limbs growing in a same layer of two trees. During testing, the shaking location was approximately at the middle of the targeted limb. Shaking frequency selected 20Hz with 5 seconds duration time for all test; shaking amplitude of the device was 3.2cm. According to USDA (United States Department of Agriculture) standards for fresh market apples, the fresh-market percentage was adapted to evaluate fruit quality. The percentage defined was that the number of apples satisfying fresh market grade divided by the capturing number in one sample shaking. Obtained results showed that fruit removal efficiency was around (81±14.5)% under the 20Hz shaking frequency and 3.2cm shaking amplitude; the fresh-market percentage in the four capturing patterns ranged from 89.5% to 96.3%; there was no significant difference in terms of the fresh-market percentage among the four capturing patterns. These results indicated that the targeted shake-and-catch harvesting method was feasible and showed a promise for mechanical solution for mass harvesting of fresh market apples; it could be permitted to adjust tilted angle within a certain range that couldn’t significantly affect fruit quality for the special trellis trained ‘Jazz’ apple trees.

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History
  • Received:July 10,2017
  • Revised:
  • Adopted:
  • Online: December 10,2017
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