Selective Harvester 2004 Trials
by Trent Ball*
A selective mechanical asparagus harvester was tested in Washington State’s Columbia Basin to evaluate its commercial viability in the spring of 2004. The one row harvester uses a sensing system that detects when a spear crosses at a pre-selected height and sends an appropriate blade to cut the asparagus, anywhere from one inch below ground to one inch above ground. The spears taller than roughly 6-7 inches are engaged in a pickup unit and are lifted onto a cross conveyor if the spear is cut by the machine. Otherwise the spears pass through the pickup unit and remain for harvest the following day. Harvested spears are transported via conveyors to a station at the rear of the machine where an individual sorts and aligns the asparagus. Although the harvester has the capability to harvest three rows simultaneously, the current evaluation procedure is focused on one cutting mechanism until it harvests satisfactorily.
The machine harvester travels at approximately 2 miles per hour. If it was a three-row harvester it is estimated that the machine could harvest approximately 50 acres in a 16-hour period. One driver would be necessary in addition to two manual sorters on the back of the machine.
The spring trials revealed that on average the machine-harvested product had a grade of 15% butts, 19% culls, 53% 9-inch spears, and 13% 8-inch spears, for a number one grade of 66%. Although the grades are satisfactory, the amount of product harvested compared to the hand crew needs improvement. Several mechanical issues during the spring 2004 trials resulted in dropped spears that were cut by the machine. Had all spears cut by the harvester been collected the machine would have an estimated pay weight of 56% compared to manual harvesting.
In the fall of 2004 additional improvements were made including adding more blades with smaller knives to reduce potential damage in the field. Further, the sensing system and electronics were altered to increase the sensitivity of detecting asparagus spears. These improvements in addition to other changes should increase the efficiency of the harvester. In January further trials are planned to test the modifications in anticipation of redesigning the machine to run trials in Washington for the entire harvest season in 2005.
*Trent Ball is an Associate in Research, working with Dr. Ray Folwell, on the asparagus project. He recently, Spring 2004, traveled to the Columbia Basin, Washington to study the Selective Machine Harvester and its affects on the asparagus industry.
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