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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #307208
Title: Use of cordon wire tension for static and dynamic prediction of grapevine yield

Author
item Tarara, Julie
item CHAVES, BERNARDO - Washington State University
item SANCHEZ, LUIS - E & J Gallo Winery
item DOKOOZLIAN, NICK - E & J Gallo Winery

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2014
Publication Date: 12/8/2014
Citation: Tarara, J.M., Chaves, B., Sanchez, L., Dokoozlian, N. 2014. Cordon wire tension can be used for static and dynamic prediction of grapevine yield. American Journal of Enology and Viticulture. 65:443-452.

Interpretive Summary: Continuously measuring the tension in the main trellis wire (cordon wire) with a load cell can be used to track fruit growth and estimate yield in grapevines. In this system, the load cell can detect changes in fruit weight up to 80 feet from the sensor, meaning that as many as 10 vines are being monitored in a vineyard with eight feet between plants, or 13 vines in a vineyard with seven feet between plants. In a three-year study where the crop varied four-fold, yield was estimated for two vineyards. The estimates were made at lag phase (static), and daily from lag phase to harvest (dynamic). The static estimate could be made up to 10 days after lag phase. The most robust use of the static method is to collect a few years' data as comparisons to the current year. Evaluating the growth curves of similar years resulted in yield predictions with errors of 14 to 22% per vineyard. For the dynamic method, the years that were most similar in growth patterns estimated each other the best, and the estimates became stable several weeks before harvest. This gives growers and wineries the ability to see late-season changes in crop growth.

Technical Abstract: An automated system was used over the course of three growing seasons to monitor the change in tension ('T) in the load-bearing wire of a trellis to estimate yield in vineyards. Actual yield varied nearly four-fold among the three study years, but in each year the fruit was uniformly distributed along the length of the wire. The automated sensor detected sequential harvests up to about 12 m to either side of the sensor, or 24 m total wire length, in a non-linear fashion. Yield was predicted statically from 'T at the 'lag phase' (L) of berry growth ('TL), and dynamically from continuous output of 'T. Relationships between 'TL and yield were linear. Estimated yield was not sensitive to the date of 'TL, within 10 d. In using the ratio between the current year's 'T and that of a specific previous year, the differences between estimated and observed yields depended upon the choice of predictor year(s), where years with similar 'T were the most accurate. Across an estimation period of L to harvest, the precision of dynamic estimates was determined by the similarity in the day-to-day shapes of the double-logistic curves of 'T over time. Due to a catastrophic frost in the second year of the study, an extremely small crop and an uncharacteristic growth curve made it difficult to predict yield either statically or dynamically. In practice, the method requires a grower to collect multiple years of growth curves from which to build a robust linear relationship between 'TL and yield (static estimates) or to apply an average of multiple years' 'T values dynamically.