Watching Michigan ‘‘Concord’’ grape growers struggle with stagnant and sometimes declining prices, a team of researchers at Michigan State University have been developing methods to significantly boost yield for growers.
Tom Zabadal, professor and viticulturist at the Southwest Michigan Research and Extension Center in Benton Harbor, says the costs of inputs at vineyards growing ‘Concord’ have risen with the times, but the price per ton of those juice grapes has been flat.
“The prospect is that prices for ‘Concord’ grapes will not moderate upwards appreciably in the near future,” he says. “Our ‘Concord’ industry in Michigan is at risk. Prices for ‘Concord’ have stagnated for many years. And of course costs have not.”
An answer, as Zabadal and his colleagues see it, is to boost yield without adding on to the costs. For more than 11 years, they’ve tested some methods for doing that, including a two-tier cordon system that has been showing promise.
Zabadal updates the progress on the project at the Southwest Michigan Research and Extension Center in Benton Harbor, Michigan, in a YouTube video earlier this year.
The two-tier cordon system is a throwback of sorts to a similar system developed in the mid-1800s by William Kniffin in the Hudson Valley of New York. The system fell out of favor, however, as grape-growing methods improved and fuller canopies blocked out the sun for the lower tier.
But Zabadal believes mechanization can solve that problem, giving ‘Concord’ vineyards two full growing zones, with the potential to double yield.
One of the keys is a mechanical shoot positioner that takes unruly shoots, described in the video as looking like a jungle, and orients those shoots vertically, exposing both fruit zones to light again.
“Shoot positioning mechanically opens it up and allows us to maintain fruit zones lower on the trellis,” Zabadal says.
The two-tier cordons are a maximum 7 feet high so that current vineyard tools, such as sprayers, harvesters and other machines, can be used with little or no modification.
The vineyard’s 2015 yield was higher than Zabadal expected — significantly more than double Michigan’s usual 5 tons to 6 tons per acre. He believes this year’s crop will be more in line with the yields he’s hoping for.
“Our goal is consistent, sustainable, marketable higher yields of around 10 tons per acre or more,” Zabadal says.