EFFECTIVE DEBRIS REMOVAL METHODS FOR MECHANICAL WILD BLUEBERRY HARVESTER

Abstract

Commercial management of wild blueberry fields is improving, and plant density/ leaf foliage have increased. Select weed and grass species have developed resistance to commonly applied herbicides and thrive in wild blueberry fields despite the continuous control efforts. As a result, increased amounts of debris have been collected during harvesting and berry processing facilities are suggesting that producers reduce the excess amounts to decrease shrink and increase fruit quality. The main objective of this study was to evaluate the existing debris removal system on the commercial mechanical wild blueberry harvester and make improvements for optimization while increasing harvesting efficiency and berry quality. The existing single blower fan system was replaced with a new dual fan system increasing air flow and effective debris cleaning capabilities. An apparatus to measure terminal velocity of blueberries and common weed and grass species was developed and tested to measure optimum air velocities for effective debris removal. Wild blueberries were found to have a significantly higher terminal velocity (15.65 m/s) as compared to common debris samples (< 5.64 m/s) tested in both dry and wet experimental conditions. The significantly lower surface area to mass ratio (61 mm^2/g) of berries proved to aid the effective removal of harvested debris using air. Experimental testing of the cylindrical debris cleaning brush suggested the importance of proper maintenance and accurate adjustments within the field was essential to remove debris from the picker teeth while harvesting. Evaluation in commercial wild blueberry fields found the new dual fan blower system with an increased air velocity of 18 to 23 m/s was optimum for removing more than 99% of unwanted debris from the harvested fruit before it drops in the storage bins. The debris cleaning brush was found to have the highest level of debris removal from picker teeth with a bristle length of 120 mm operating at a bristle tip speed of 13.88 m/s. Using these settings, harvesting field efficiency was increased by 41.95% as compared to using a brush with a bristle length of only 87 mm. Results of this study emphasize the importance of knowing and understanding the components of the mechanical wild blueberry harvester and have led to increased field efficiency, picking performance, berry quality and factors that lead to reduced shrink at the processing facilities.