St. Helena, Calif.
Sheep graze in a trial vineyard farmed by Kelly Mulville in California's Alexander Valley.
—The Napa Valley Grapegrowers
held its seventh annual Organic Winegrowing Conference on July 25, attracting growers and suppliers from far beyond the Napa Valley to discuss the latest findings, products and practices for sustainable and organic grapegrowing.
The event was held at Spottswoode Estate Vineyard & Winery
in St. Helena, which was a pioneer in adopting organic farming of grapes. Winery president Beth Novak Milliken said that the company started using organic practices in 1985 because, “It was the right thing to do. We grow in a residential neighborhood, and we did it for neighbors, ourselves and our staff.”
Speakers covered items from practical to esoteric. Grapegrower Ted Hall of Long Meadow Ranch Winery
set the stage by countering the usual negative view of organic farming—not using synthetic pesticides, herbicides and fertilizers—to a positive view of organic as a system that considers farming in a holistic manner. “Using chemicals has unintended consequences,” he pointed out.
Hall added, “We farm organically because it results in higher quality at lower cost—especially if considered over a long term.” He claimed that organic vineyards could have twice the lifespan of those farmed with chemicals.
Useful and theoretical sessions
During the next talk, Walt Mahaffee of the USDA and Seth Schwebs of Coastal Viticultural Consultants
described how measuring spore counts with new commercially available instrumentation could reduce the costly application of sprays against powdery mildew. Mahaffee said the technique reduced applications by 2.3 times on average by delaying spraying when it wasn’t needed. He also noted that untended vineyards can be a major source of spores.
One of the most interesting sessions, however, was about using sheep in vineyards—not just in the winter and before the vines’ buds open, but during much of the year.
Kelly Mulville of Holistic Viticulture developed a technique using electrically charged wires in the fruiting zone to teach sheep to avoid the grape bunches. This allowed the sheep to be used past bud break, and Mulville claimed there are many benefits. “The biggest benefits come when growth is fastest,” not in the winter when sheep are normally used to keep down weeds.
Using sheep can save costs for human labor, fertilizer and fuel while helping the environment. It also provides a salable product or food. The sheep are moved through the vineyard to minimize over cropping and compaction of soil. A typical vineyard might support 30 sheep per acre.
Mulville, who has used his approach in sheep-rich Australia, added that growers there are paid to provide grazing land, unlike here where they have to pay for the sheep to tend their vineyards.
Specifically, Mulville claims the sheep eliminate the need for any mechanical cultivation, tillage or mowing both between rows and under the vines. This eliminates four to eight tractor passes per row per year. The sheep also remove suckers, saving eight hours of labor per year per acre.
The sheep eat the canopy laterals and leaves that growers often remove by hand. (Although Clay Shannon
in Lake County has had success with small sheep leafing vines, too.)
The sheep convert all forage, suckers and thinnings into manure and eliminate the need for disking them into the soil. The dung eliminates the need to haul in compost or other fertilizers, he said. Mulville added that urine is a better fertilizer as it contains more nutrients and is immediately available in water-soluble form.
Mulville claimed that in his trial the use of the sheep for extended grazing also reduced irrigation by 90% compared to neighboring vineyard (conventionally managed using the same clones, rootstock and soil). His results have not been independently verified.
The year of the trial (2009) and the previous year were both drought years. The rootstock was 039-16 on all vines. He added that yield increased yield by 1,245 pounds per acre over the previous year.
Mulville has tested the system with VSP trellising system in Alexander Valley and in Australia, where it is now used in a commercial vineyard. He thinks that it would likely prove viable with other trellising methods with modifications.
The electric wire is powered by solar energy, though the sheep quickly learn to avoid the wires. However, Mulville referred to a video of a mountain lion killing a sheep, but backing into the electric wires. “He thought the sheep did it to him, so he kept away!”
Overall, Mulville claimed that the cost of farming drops by $400 per acre per year with potential for a combined savings and income improvement of $1,000 per acre per year.
He also noted that use of sheep instead of tractors also improves the soil’s ability to sequester carbon while reducing atmospheric carbon emissions.