It’s a long way from upstate New York, where Concord grapes grow on the banks of Lake Erie, to Fresno, where winegrape vineyards bake in dry heat.
Terry Bates, a viticulturist from Cornell University, made that trip to discuss an issue close to the hearts of grape growers everywhere: labor scarcity for vineyards, and how precision ag and mechanization can help.
“A lot of our Concord vineyards are mechanized and we do a midseason mechanical crop estimation,” Bates told the California growers. “The only way for them to stay profitable is to stay as efficient as possible.”
The approach Bates is taking: developing multiple sensors, collecting spatial data, validating it with viticulture measurements, layering that data, and then coming up with a vineyard management plan.
"I know what my crop load and pruning weight should be. Overcropped is bad, undercropped is bad, balanced is good,” Bates said, describing the fruit load on vines. “That’s what we’re trying to measure with our sensors.”
Soil types are a factor, Bates said, and growers should take county soil maps with a grain of salt, as they can be shifted from the correct areas, or very low resolution.
Aerial imagery for vineyards is difficult in New York State, he said, because of both weather and ample green in row centers that throws NDVI measurements off.
Bates’ research team uses ATVs to run through the vineyard capturing images of berry clusters mid-season.
Another tactic to get a handle on crop size is destructive harvesting, when a small area is harvested when grapes are 40% of harvest size.
The result of the mapping is a protocol for on-the-go, variable rate mechanical crop adjustment for the vineyard.
Overcropped areas are mapped out into thinning zones. The management maps are created by research technicians who process spatial data.
Once the management shapefile is imported into software, target flow rates are set for hydraulic slapper equipment.
“We’re taking an off-the-shelf system that’s meant to do liquid flow control, liquid (fertilizer)…and it’s talking to hydraulic valves on the machine,” Bates said. “We’re feeding the map into the machine and as that drives down the row, the shaker heads speed up or slow down to harvest more or less fruit.”
Bates said the thinning has been effective: the mean for vines has shifted closer to the ideal cropping levels, and the standard deviation has gone down as well.
“After we did the variable rate fruit thinning we have shifted the mean closer to a balanced population for Concord grapes,” he said. “We’ve made it more uniform by taking the bell-shaped curve and making it more narrow.”
For more information, go to his research website EfficientVineyard.com, which hosts webinars for growers.