Breaking the weed cycle
Replanting Concords after Concords is complicated.
Wapato, Washington, grape grower Mike Sauer has experience with replanting both wine and juice grapes. Wine grapes, when following wine grapes in a vineyard with wide spacing between vine rows, are relatively easy, but Concords following Concords are a different problem, he says.
Sauer’s early wine grape vineyards were planted to wide spacings (ten feet between vine rows), similar to juice grape spacing; however, he used drip irrigation for the wine grapes. He has had good success in replanting wine grapes that were originally on wide spacings by moving the vine row over five feet and planting where the old row middle was.
Root systems on drip do not stray far from the drip line and are not found in the row middles, he explained. “The ground is basically like virgin soil that’s not had roots growing in it and very little compaction for the last 25 years. We’ve had excellent results replanting like this.”
But simply moving the row for Concords that follow Concords doesn’t work because of the overhead sprinkler systems. Most Concord vineyards use sprinkler irrigation, and roots are found everywhere, Sauer said.
For Concords, his preference is to plant Concords in new ground, but that’s not always possible.
Several years ago, Sauer began experimenting, using alfalfa as a rotation crop to help break the weed cycle
. Alfalfa helps disrupt perennial weeds that often occur in old vineyards and adds nitrogen to the soil. However, gophers are attracted to alfalfa, and the hay crop can turn into a weed itself later in the new vineyard. Lately, he’s shifted to planting Sudan grass as his rotation crop.
Sudan grass has nematicidal properties, and the crop residues provide organic matter to the soil. Sudan must be planted when the weather is warm. Sauer follows the alfalfa with Sudan, planting the field in June. “It grows like a weed, five to six feet tall in five or six weeks,” he said, adding that the Sudan hay makes great forage. He plans to plant Concords in the block this spring.
“It’s something we’re trying,” he said. “We’ve broken the weed cycle, and we’ll see if Sudan works as a nematicide.”
A drawback to growing any rotation crop is the relatively short turnaround time for Concord growers to get back into production. Sauer said that his contract with the National Grape cooperative only gives him three years to be back in production.