Growers Can Improve Harvest Planning with Yield Estimates

By Blake Jackson

Estimating vineyard production before harvest can help growers make better management and marketing decisions, according to Amaya Atucha, Professor at the University of Wisconsin-Madison.

Knowing expected yields months in advance allows vineyard managers to adjust crop loads, schedule labor, prepare storage capacity, and coordinate with buyers before harvest begins.

Crop estimation is based on a simple formula: the number of bearing vines multiplied by the average number of clusters per vine and the average cluster weight. Since cluster weight changes throughout the growing season, growers typically rely on two proven methods to estimate yields.

Accurate sampling is the first step. Instead of evaluating every vine, growers should select representative sample vines throughout the vineyard, avoiding damaged or unhealthy plants.

Marking these vines allows for consistent monitoring during the season and improves long-term accuracy. Vineyard managers should also calculate the actual number of bearing vines by subtracting missing or non-productive vines from the total planted vines.

The first approach, known as the Harvest Cluster Weight Method, involves counting clusters on selected vines early in the season, from pre-bloom through pre-veraison. Growers then multiply the average clusters per vine by the number of bearing vines and an average harvest cluster weight.

Historical vineyard records provide the most reliable cluster weight data, though published averages can be used when records are unavailable. The final estimate is converted into tons per acre.

The second technique, the Lag-Phase Method, provides an in-season estimate. Around 50 to 60 days after bloom, berries enter the lag phase, when growth temporarily slows.

During this period, growers weigh sample clusters and multiply the average weight by two to estimate harvest weight before applying the standard yield formula. While weather conditions can influence final accuracy, this method serves as a valuable mid-season check.

Over time, maintaining records of cluster counts, harvest weights, and lag-phase measurements helps improve forecasting accuracy.

Even estimates within 15% of actual harvest yields are considered successful, giving growers valuable information for production planning and vineyard management year after year.

Photo Credit: istock-jimfeng