Grazing Sheep and Growing Soil:
Debby Zygielbaum at Robert Sinskey Vineyards
Debby Zygielbaum, farm manager of almost 200 acres of land at Robert Sinskey Vineyards (RSV) in Napa, CA, operates on the philosophy that the quality of a wine has as much to do with the winegrowing as it does the winemaking. And growing good wine, according to Debby, is fundamentally rooted in growing good soil. RSV’s use of sheep to graze vineyard floors is one way that they achieve this goal.
Weeds and cover crops compete with grapevines for beneficial nutrients and water, so they must be managed. Debby points out it is also important in early spring, especially during budbreak, to prevent unruly weeds and cover crops from raising the frost level up to the height of the cordon (the “arms” of the vine).
Conventional farming methods usually involve a combination of tractor mowing, herbicide application, and cultivation to manage cover crops and keep thistles, poison oak, and blackberry brambles at bay. Conscious of the detrimental impacts these practices, especially herbicides, can have on the environment – never mind on the quality of the grapes – Rob Sinskey is one of a handful of California vintners trying a different approach: he rents herds of sheep that mow their way up and down the vineyard rows, rain or shine, in the winter and spring.
How do these wooly workers compare with machines fueled by diesel and manpower? Erosion control is among the advantages of using sheep grazing rather than tractor mowing during the winter. “We farm on a mud patty,” Debby notes, and especially during wet winter months, machine mowing runs the risk of hillside erosion, not to mention tractors stuck in the muck.
Heavy machinery also compacts wet earth, changing the soil structure by removing oxygen and, thus, reducing the amount of beneficial living organisms and biodiversity present in healthy soils. Sheep hooves, on the other hand, till into the ground the residual plant material not eaten by the sheep combined with their nutrient-rich manure, a natural substitute for synthetic fertilizers.
There is some evidence that high-frequency rotational grazing of livestock significantly reduces water usage and may improve the capacity of soil to sequester carbon from the atmosphere. [1],[2],[3] More research is needed to conclusively demonstrate these effects.
As Debby’s management of the vineyards suggests, building resilience often comes down to “having as many tools in the toolbox as possible” and smart problem solving. For example, she is thinking about how RSV might be able to graze sheep later in the spring (when weeds and cover crops tend to grow vigorously), without sacrificing the budding grapes and leaves to ovine appetites. She wonders if there might be a way to raise the vines out of harm’s way. Other advocates of livestock grazing have proposed methods like using smaller breeds, installing electric fencing, and even training sheep to have an aversion to grape leaves.
As growers face a future of increasing climate variability and extremes, it will be more important than ever to innovate and seek methods with multiple economic and ecological benefits. Robert Sinskey Vineyards is an admirable example of a dedicated group of wine-lovers doing just that.
[1] Mullville, Kelly. Increasing vineyard profits and sustainability. Available at http://www.scribd.com/doc/55856714/AusNZgrapegrowerprintcopy
[2] Silveira, Maria et al. Carbon Sequestration in Grazing Land Ecosystems. Available at http://edis.ifas.ufl.edu/pdffiles/SS/SS57400.pdf
[3] Follett, R. F et al. The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect. Chapter 16. Available at http://eco.ibcas.ac.cn/group/baiyf/pdf/gxzy/9_The_Potential_of_U.S._Grazing_Lands_to_Sequester_Carbon_and_Mitigate_the_Greenhouse_Effect.pdf
