Project Number: 5358-21000-034-16
Project Type: Trust

Start Date: Mar 01, 2005
End Date: Sep 30, 2009

Objective:
In a well-watered juice grape vineyard trained on a single-curtain trellis, compare the finite-length load cell system with open-ended load cell measurements; collect continuous data to monitor the crop and estimate yield; collect intensive supplemental data on vegetative and reproductive growth. In a deficit-irrigated wine grape vineyard on a modified sprawl trellis, compare the finite-length load cell system with open-ended load cell measurements; collect continuous data to monitor the crop and estimate yield; collect intensive supplemental data on vegetative and reproductive growth. In ten commercial juice grape vineyards, couple a local processor's sentinel vine system for yield estimation via hand sampling with measurements of trellis wire tension using the finite-length load cell system; compare processor's 10-site yield estimate with that derived from the tension measurements. Post data from the research vineyard to the WSU viticulture website with the assistance of Dr. Mercy Olmstead, WSU-Extension Viticulturist.

Approach:
We developed a novel approach to estimating yield in grapevines by continuously measuring the tension in the horizontal (cordon) support wire of a single-curtain trellis. Load cells and temperature sensors installed in-line with the cordon wire are connected to an automated data acquisition system, a major departure from the industry's standard method of collecting fruit samples by hand two or three times per growing season. Each row in the experimental vineyard is calibrated at the beginning of the season to determine the change in tension in that row in response to an increase in known mass (weight) hung on the cordon wire. The effects of temperature on wire tension are removed by post-processing with a regression-based empirical protocol, which corrects the raw data to a standard temperature. Because data are averaged over 15 min, wind gusts have little detectable effect on the tension measurement. A smoothing algorithm removes remaining transient disturbances in the data without masking significant events like crop thinning or harvest. There appears to be a linear relationship between wire tension and fruit mass (yield) that varies among rows, but not within a row, during a single season. Documents Trust with Washington Wine Grape Industry Foundation. Log 28976.