Maximize your trellis investment: continuously monitor your vines and estimate yields
Major funding provided by the USDA-Agriculture Research Service and a grant from the Washington Wine Industry Foundation in Cooperation with USDA-Risk Management Agency. Other substantial funding provided by the Viticulture Consortium-West, a USDA-CSREES special grants program.
Electronic devices and wireless communications are part of today's farm, and used to their potential, they can provide a grower with rapidly updated information on the status of the vineyard. To maintain competitiveness in the global market, the grape and wine industry must maximize the utility of all its inputs and farming tools, including the trellis system.
We have devised a way to give a grower a nearly continuous stream of information related to vine growth and crop development by measuring the tension in the trellis wire and plotting its increase during the season. Surf this page and its links for a description of our system, explanatory diagrams, and plots of 
actual trellis wire tension across the season in 12 different vineyards around the Yakima Valley of Washington State.
Background
Imagine booting up your computer and watching your vines and fruit grow week by week. Rather than “guesstimating” the progress of the crop, your computer screen would display this season's progressing growth curve and the complete growth curves from key previous years.
Wineries and fruit processors want accurate and early crop estimates to manage harvest scheduling, processing, storage, and marketing of the final product.
Historically, crop yield in grapes has been estimated by collecting and weighing clusters or specified numbers of berries, a labor-intensive and thus expensive operation. These estimates are snapshots—fixed at one time of a dynamic process.
What if this practice could be automated, and what if a grower could use the same equipment for multiple purposes, thereby increasing the return on investment?
In 2001 our research team began to investigate an innovative method of monitoring a trellised crop and automating yield estimation. In 2005, we were awarded a U.S. patent for the apparatus and method of doing so (see Tarara et al. 2005, U.S. Patent no. 6,854,337). Our approach exploits the fact that trellised crops, of which grapes are a prime example, are physically supported by a system of vertical posts and horizontal wires. A row of grapevines can be thought of as a “load” that hangs from the support wire, in our case a cordon wire. As the load increases so does the tension in the wire. Measuring the tension in the wire continuously allows us to monitor the increasing load throughout the growing season, and from the increase in tension, monitor shoot growth and overall crop development.
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