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ASPARAGUS HARVESTER EVALUATION
EL CENTRO TEST
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March 29, 2005 |
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Prepared
by
Carter Clary and Trent Ball
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 Printer
friendly version of report in pdf |
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BACKGROUND |
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During the
2004 Washington asparagus harvest, a prototype single row asparagus
harvester was evaluated in the Pasco/Mesa area. The harvester head
employs parallel pairs of counter-rotating “brushes” that
engage asparagus spears that have reached a specified height. When
the optical system senses a spear as the machine moves down the row,
it actuates a cutting system that drives the closest blade into the
soil at the base of the spear. The spear is pulled through counter-rotating
brushes onto a back stop and falls onto a conveyer that transports
spears to the rear of the machine. |
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Each picture is linked to a larger
picture. Just click to download.
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The recovery
efficiency in 2004 was affected mostly by problems with reliability.
Cylinders failed to actuate and cut, the optical system experienced
interference from dirt and dust, and there was no way to maintain
consistent header height above the bed. It was proposed that harvester
efficiency be improved by upgrading the electronics, changing the
number and angle of the knives, using faster cylinders and employing
better air management to improve the reliability and increase the
life of the cylinders. These changes were tested in El Centro, California
in early 2005. |
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SUMMARY (excerpts from
report) OF EL CENTRO TRIAL RESULTS |
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The harvester
was tested in a trial consisting of ten replicated plots for hand
harvesting and ten replicated plots for the machine. The plots for
each treatment were randomized in two ¼ mile rows of asparagus.
Twenty plots were evaluated for spear yield during harvest and sorted
for acceptable fresh grade, including butts, short spears, 9 and 8
inch spears and dropped spears. Pay weight was calculated for each
plot. |
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This is a large file mpg file
and may be slow to download. |
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The asparagus
beds were raised and uneven, as were the furrows which was a problem
for the machine since it was designed for use on flat ground such
as in the Columbia Basin. The field was not prepared for mechanical
harvesting, therefore it is estimated the conditions had a negative
impact on the recovery. Flat ground or beds prepared for mechanical
harvesting would increase the efficiency of the harvester dramatically.
Nonetheless, the El Centro trials provided the ability to test the
effectiveness of previous modifications prior to the Washington asparagus
season. |
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Results of El Centro
Test
Economic analysis indicates that
a four row harvester must recover 65% of hand harvested yield to be
viable. Therefore, the daily mean pay weight of the machine harvested
product from each plot was compared to the mean pay weight of the
hand harvested plots multiplied by 0.65 (65% of the hand harvested
pay weight). Based on the composite of all five days, the harvester
had a recovery efficiency of 56%, which is lower than the 65% requirement.
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It was noted, however, that a large portion of what the harvester
cut successfully was dropped. Based on the assumption dropped spears
can be recovered after the machine has been modified, average recovery
would be greater than 70%.
Based on this analysis, it was recommended to proceed with
modifications to the harvester and conduct a full scale evaluation
in Pasco starting April, 2005.
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PASCO
TEST- SPRING 2005 The selective harvester
will be tested for durability and for harvesting efficiency compared
to a hand crew. A plot size of 2 acres will be used. Each row will
be split and each half harvested by hand and machine. The harvested
asparagus from each half row plot will be weighed and sub-sampled
for and acceptable fresh grade including butts, short spears, 9
and 8 inch spears and dropped spears. Samples of hand and machine
harvested asparagus will be provided to the WSU Horticulture team
for post-harvest storage evaluation to compare shelf life and long-term
quality.
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