The use of grazing animals in vineyards is increasing as a beneficial management tool integrated with no-till practices and cover crops, and for its compatibility with organic, biodynamic and regenerative agricultural management systems.
Research indicates that sheep grazing can enhance carbon sequestration and improve soil health, microbial biomass and nutrient content in vineyards. The University of California Cooperative Extension (UCCE) and UC Davis presented a webinar in July, "The Art and Science of Vineyard Grazing," featuring vineyard managers, grazing specialists, livestock service providers, and researchers who study the environmental and soil impacts and benefits of grazing in vineyards.
UC Davis Ph.D. candidate and agroecology researcher Kelsey Brewer provided information from a 10-year study of four different North Coast vineyard sites that compared differences in soil carbon (C) storage, soil health and nutrients measured at three depths for vineyard sites with regular sheep grazing for 10 years compared with control sites with no sheep grazing for the same period. He listed the following conclusions from the study:
- Total soil organic carbon (SOC) sequestration was increased under sheep grazing. Stable mineral-associated organic carbon storage was significantly higher. SOC storage occurred mainly in sub-soils (around 45 cm depths).
- Active soil C pools indicate increased C flux with sheep grazing. Microbial biomass was substantially higher.
- Grazed plots had higher nitrogen (N) and phosphorous (P) available. It is believed that sheep dung and urine increased C lability and solubility and increased N and P availability.
- Vineyard soil structure was not impacted by sheep grazing.
Considerations before grazing a vineyard
Morgan Doran, UCCE livestock and natural resources advisor for Napa, Solano, Yolo and Sacramento Counties provided advice on what vineyard owners should know before grazing a vineyard.
Generally, sheep are most often grazed in vineyards from winter to early spring/budbreak to "mow" cover crops and native ground vegetation. In some cases, sheep can be used in spring to sucker vines and for hedging and leafing shoot tips. Post-harvest vine and floor clean-up after vines begin leaf drop is another seasonal operation as long as it does not harm newly seeded cover crops.
Doran said, "Under certain circumstances, it is possible to graze sheep year-round if using a small breed (such as Babydoll sheep) or in vineyards with high cordon trellis systems, to prevent eating of canopy and crop." He listed several considerations for vineyard grazing.
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