Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2004
Publication Date: 11/2/2004
Citation: Tarara, J.M., Blom, P.E., Ferguson, J.C., Peirce, F.J. 2004. The bridge: a compact, unobtrusive system to measure trellis wire tension to estimate vineyard yields. Agronomy Abstracts. Interpretive Summary:
Technical Abstract: An automated method of estimating crop mass (yield) in grapevines is based on measuring the increase in tension in the support wire of the trellis. To implement this approach in commercial vineyards, confounding issues must be accounted for, including environmental influences on the wire, sensitivity to initial tensions, and an exponential decay in sensitivity with distance from the load cell, the function of which varies from row to row. Calibration with known mass has been necessary to correlate changes in tension with changes in crop mass in the research vineyard, an intractable proposition for the commercial setting with sampling units of indeterminate length. To simplify the system, a steel structure ("Bridge") was devised to fix the distance between trellis posts, isolating the support wire within a span; a load cell within the span measures increases in tension over this known distance. The relatively short Bridge length (less than 10 m) circumvents issues of distance decay and makes calibration feasible in production vineyards. Initial tensions within the Bridge span are set pre-season. Ten Bridge units (steel structure plus load cell) were deployed in juice grape vineyards. Each Bridge unit was paired with a load cell placed within an indeterminate length of row for comparison of estimates of crop mass and predictions of yield.