Abstract
The introduction of a mechanical harvesting process for oranges can contribute to enhancing farm profitability and reducing labour dependency. The objective of this work is to determine the spread of the vibration in citrus tree canopies to establish recommendations to reach high values of fruit detachment efficiency and eliminate the need for subsequent hand-harvesting processes. Field tests were carried out with a lateral tractor-drawn canopy shaker on four commercial plots of sweet oranges. Canopy vibration during the harvesting process was measured with a set of triaxial accelerometer sensors with a datalogger placed on 90 bearing branches. Monitoring of the vibration process, fruit production, and branch properties were analysed. The improvement of fruit detachment efficiency was possible if both the hedge tree and the machinery were mutually adjusted. The hedge should be trained to facilitate access of the rods and to encourage external fructification since the internal canopy branches showed 43% of the acceleration vibration level of the external branches. The machine should be adjusted to vibrate the branches at a vibration time of at least 5.8 s, after the interaction of the rod with the branch, together with a root mean square acceleration value of 23.9 m/s2 to a complete process of fruit detachment.
Highlights
Citrus fruits, whether for fresh consumption or industrial processing, are mainly harvested by hand
The results showed a high variability in the distribution of fruit in the canopy and in the morphology of the branches
This variability is important for the outcome of mechanical harvesting systems and was considered by Gupta et al [15,16] for modelling the tree and simulating the harvesting process in order to improve the canopy shaker system
Summary
Whether for fresh consumption or industrial processing, are mainly harvested by hand. Spain is the sixth largest producer of citrus fruit in the world, with an approximate production in 2017–2018 of more than seven million tonnes. In Spain, the predominant citrus orchards are trained for manual harvesting, with an orientation towards the fresh market. Harvested orchards experience problems due to the availability of labour and the high cost of operation. Within the citrus production process, harvesting is a phase of enormous economic importance due to its high impact on the final cost of production. The manual harvesting in Southern Spain requires an average of 95 days’ work per hectare and represents between 25% and 35% of the final cost of production [2]. With the current approach to citrus production, the high costs of Sensors 2019, 19, 1760; doi:10.3390/s19081760 www.mdpi.com/journal/sensors
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