New Grape Crop Monitor: A Diagram

From the July 2007 article "New Grape Crop Monitor: An innovative trellis tension technology could allow winegrape growers ro fine-tune their crop estimates."

Research horticulturist Julie Tarara and her ARS colleagues have developed an automated system for estimating grape yields based on the changes in tension on the trellis wires that support the vines. The system will allow growers to continually monitor their crops, allowing them to make more informed pruning and irrigation decisions. Such a system would also allow growers to avoid situations such as that occurred in California two years ago, says Tarara. "The problem was that the fruit really sized up at the end of the season," she says. "No one knew until harvest because the snapshot (of the crop size) was taken so much earlier."

A load cell detects increases in the tension of the trellis wire as clusters form and the berries enlarge. The wire-tension signals are recorded by a data logger every five seconds, which formulates an average every 15 minutes. By taking so many measurements, such anomalies as gusts of wind, perching birds, or even the wire’s natural expansion and contraction can be factored out to provide an accurate measurement.

Researchers then analyze the raw data to weed out any further anomalies, and then it’s run through a software package. After processing, the information can be used in computer modeling, providing crop size estimates. Tarara says that as the system moves out of the research arena and into commercial practice, many of the steps will be automated, speeding the process and providing further savings.

A diagram of the model is below.