1a.Objectives (from AD-416)
Statistical analyses of 7-year database from Trellis Tension Monitors (TTM) in Washington state and three-year database from TTM installations in California, to determine. 1)spatial distribution needed for yield estimation with TTMs;. 2)accuracy of yield estimation;. 3)accuracy of detecting key grapevine phenological stages from the continuous tension trace; and. 4)accuracy of yield estimation under physically constrained and open-ended TTM systems.
1b.Approach (from AD-416)
Complete field data collection; compute classic univariate descriptors; define linear and nonlinear models; complete geostatistical characterization of yield at research sites; and model yields from dynamic trellis tension values.
Most yield estimation practices for commercial vineyards are based on longstanding but variable industry protocols that rely on hand-sampling fruit at a small number of dates during the growing season. Limitations associated with these static estimates may be overcome by deployment of Trellis Tension Monitors (TTMs), systems that provide dynamic measurement of changes in the tension of the main trellis wire, referred to as the 'cordon' wire. TTMs were installed in several commercial vineyards. On average, TTM data produced more accurate estimates of actual yield at harvest than did the protocols of the juice processors. Three years' data from wine grape vineyards demonstrated the sensitivity of detection by the TTM of the 'lag phase' of grape berries, commonly used to time traditional hand sampling. The TTM also offers real-time information that can be used to manage crop level or to revise yield estimates on-the-fly, something that is not feasible currently. Other data will be used for determining the spatial sensitivity of the TTM.
Methods of project monitoring included meetings, e-mail, and phone calls.