In preparation for on-the-fly variable rate crop thinning trials…

By Cain Hickey

One of the many firsts for the CLEREL Efficient Vineyard project team in the 2016 field season was an informal evaluation of on-the-go, variable rate crop thinning.  Vineyard canopies were scanned with NDVI sensors before bloom.  The resultant NDVI map showed the inherent growth variation across the vineyard, and directed crop estimation sampling around 30 days post-bloom (the thought here is that “blind” crop estimations are inferior to those directed by spatial variation in vineyard growth as it relates to yield).  The resultant map of estimated spatial crop yield variation was uploaded into GPS-equipped software housed in the cab of the mechanical harvester.  This enabled the grower to drive down the vineyard row and thin crop in a variable rate fashion without any manual adjustments; in general, the harvester would take off little or no crop where estimation was low, and take off more crop where estimation was high.  Figure 1 shows what was anticipated: a positive relationship between harvester paddle speed and the amount of crop thinned, and a negative relationship between harvester paddle speed and the amount of crop harvested.  This system has potential to mitigate unnecessary as well as direct necessary crop thinning, thereby saving growers time and money and improving fruit ripening and perennial vineyard health. Plans are taking shape to conduct formal experiments in the 2017 field season to evaluate the applicability and value of the “scan-estimate-thin” formula.

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