Use of Cordon Wire Tension for Static and Dynamic Prediction of Grapevine Yield

• Autores: J. M. Tarara, Bernardo Chaves, Luis A. Sanchez, Nick K. Dokoozlian
• Localización: American Journal of Enology and Viticulture, ISSN 0002-9254, Vol. 65, Nº 4, 2014, págs. 443-452
• Idioma: inglés
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• Resumen

  • An automated system was used during 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 ~12 m to either side of the sensor, or 24 m total wire length, in a nonlinear 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 days. In using the ratio between the current year ?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 interval 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.