The Effects of Shaking Frequency and Amplitude on vibratory harvesting of Almond (Prunus dulcis L. cv. 7Shahrood)

Abstract

A portable limb shaker with adjustable shaking frequency and amplitude was used to harvest Almond (Prunus dulcis l. cv. 7Shahrood). The aim of this study was to determine the most suitable shaking amplitude and frequency to obtain the maximum fruit removal with minimal leaf shattering and branch damage. A 4x3 factorial experiment with a completely randomized design was conducted to investigate the effects of shaking frequency and amplitude on fruit detachment. Four levels of oscillating frequency (10, 12, 14 and 16 Hz) and three levels of shaking amplitude (20, 32.5 and 45 mm) were investigated. Analysis of variance and mean comparison showed that the shaking amplitude and shaking frequency both had significant effect on fruit detachment. The percent of fruit detachment increased at higher levels of shaking amplitude and frequency. Complete fruit detachment (100%) was observed at shaking amplitude of 45 mm and frequency of 16 Hz, but bark injury and leaf shattering was high. Bark injury was 33% and 16% at 45 and 32.5 mm shaking amplitude tests, respectively. Finally, shaking amplitude of 20 mm and shaking frequency of 16 Hz was recommended in which fruit detachment was high (94.8%) with no bark damage and low leaf shattering. Harvesting rate during the first five seconds of shaking was measured and showed that the optimum time needed for shake harvesting a limb is only 4s. The fruit detachment force (FDF) per fruit mass ratio (FDF/M) during the harvesting season varied from 4.53 to 1.39 with the mean value of 2.42 N g-1.