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Mechanized Variable Rate Shoot Thinning for Grapevines

Efficient Vineyard Project, LWC and Gallo Host Demo
by Ted Rieger
May 02, 2019
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Variable rate shoot thinning at Gallo's Borden Hills Ranch in the Lodi AVA is performed on two rows of Cabernet Sauvignon with rotating shoot thinning paddles on a VMech Tool Carrier. Photos by Ted Rieger
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Closeup of rotating shoot thinning paddles removing shoots above the vine cordon

A vineyard field demonstration of tools and technology to program and operate vineyard equipment to perform variable rate shoot thinning to more uniformly manage crop load and achieve target yields was held April 23 in cooperation with the Lodi Winegrape Commission, the Efficient Vineyard Project, and E&J Gallo Winery.

The demo was hosted at E&J Gallo’s Borden Hills Ranch, located within the Borden Hills American Viticultural Area (AVA), a sub-appellation within the larger Lodi AVA east of Galt, CA. The vineyard is managed for Gallo by Pacific AgriLands, Inc. a farm management company based in Modesto. The vineyard was planted in 2014 with Cabernet Sauvignon on a high-wire cordon, about 60-inches high, with a quadrilateral trellis system. The vines are mechanically pruned and mechanically harvested, and other seasonal vineyard practices are mechanized as much as possible.

Dr. Terry Bates of Cornell University based at the Cornell Lake Erie Research and Extension Laboratory in New York, is director of the national Efficient Vineyard Project (www.efficientvineyard.com), a multi-year project funded by the USDA National Institute for Food and Agriculture (NIFA) and supported by the National Grape Research Alliance. Bates visited California in April to test and demonstrate Efficient Vineyard technologies at cooperator vineyard sites.

The goal is to develop technology, tools and systems to more efficiently mechanize and manage U.S. vineyards, given the uncertain availability of labor, and the increasing costs of labor and vineyard management. But as Bates pointed out, “One of the big drawbacks of mechanization is we’re trying to apply uniform treatments to a non-uniform grape growing system. With this project, we’re trying to collect data to make better decisions in order to apply variable rate management in the vineyard at the appropriate locations.”

Determining Shoot Thinning Rate

The Efficient Vineyard Project is using and evaluating multiple methods to collect and manage vineyard data, and digitally organizing multiple seasons of data into maps and layers of graphics to make management decisions for specific vineyard sites. In the case of shoot thinning, the researchers are using a combination of past season data (crop yields by GPS location from on-board harvester yield monitors), and current season data on vine growth.

Normalized Difference Vegetation Index (NDVI) images are taken of the vine canopy to map data on vine canopy growth and size differences during the current growing season. This can be done with overhead aerial NDVI imaging from aircraft or drones, or by ground imaging. The researchers use Crop Circle NDVI sensors, from Holland Scientific, mounted on the sides of an ATV “mule”, to record canopy growth while driving down the vine rows. “Ground truthing” of the NDVI data is done at sample sites in the vineyard to look at shoot counts and lengths to confirm what the NDVI images and spatial maps indicate. As Bates described it, “We want to know where in the vineyard block the vines are strong or weak in order to adjust shoot counts.”

The data can then be used to make decisions for prescriptive rate thinning that is programmed into an on-board computer and monitor attached to the shoot thinning tractor and equipment. Bates is working with AgLeader hardware/software, originally designed for Midwest commodity crop agriculture. The researchers have adapted this technology for vineyard use, and it is expected to be further improved over time.

The computer program regulates the liquid flow of the tractor hydraulic system to speed up or slow down the rotation (RPM) of the shoot removal paddles based on location in the vine row as determined by on-board GPS. Bates explained, “We’re applying this technology to a shoot thinning machine, but it can also be applied to a harvester for fruit thinning. Theoretically, it can be applied to any hydraulic equipment system used on vineyard equipment.”

Shoot Thinning Equipment and Operation

The shoot thinning was performed with a VMech 2220 Tool Carrier with four shoot thinning attachments, each a rotating head with two flexible plastic paddle blades, with one thinning head on each side of the vine row and configured to thin two vine rows in one pass. The tool carrier was also outfitted with lower mounted rotating brushes, consisting of numerous plastic, flexible rods that can provide shoot thinning and removal below the cordon. Given the vine growth stage in the Gallo vineyard, and the presence of only vertical shoots growing above the vine cordon, only the paddle blades were needed for shoot thinning for this demo. The VMech tool carrier was also outfitted with two rotating brushes in front of the tractor available to perform vine trunk sucker removal, not needed at this time, but showing the equipment can perform multiple functions in one pass.

Shoot thinning with this equipment should ideally be performed when the shoots are short enough and not yet lignified (about 8 to 12 inches long or shorter) in order to be easily and cleanly removed from the vine.

Bates said the researchers normally shoot thin at a tractor speed of about 1.5 mph; however, he believes speeds up to 3 mph could be done without a problem, depending on vineyard conditions. Regardless of tractor speed, the computer program is designed to vary thinning paddle speed based on GPS location within the vine row to achieve the desired target. In the Gallo demo, the target vineyard yield was set for about 6.5 tons per acre.

During machine harvest later this season, an on-board harvester yield monitor will gather data on actual yield based on vineyard location. Bates said, “We will come in at the end of the season and evaluate how well the target yields were achieved based on shoot thinning and other factors. The overall goal is to reduce variation in the vineyard to achieve desired crop yields and quality.”

Earlier in April, Bates and the Efficient Vineyard Project held a similar shoot thinning demo in conjunction with Scheid Vineyards in a machine pruned Pinot Noir vineyard in Monterey County. A post written by team member Heather Barrett about that demo is available at: https://efficientvineyard.com/blog/scheid-vineyards

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Monitor of an AgLeader hardware/software system used to control shoot thinning paddle speed at variable rates based on GPS location of tractor and vineyard data inputs
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Efficient Vineyard Project director Dr. Terry Bates of Cornell University explains the variable rate shoot thinning process and technology

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