Issue link: http://winesandvines.uberflip.com/i/70673
nor T h W e S T norThWeST B.C. WASHINGTON Seattle Chateau Yakima Ste. Michelle OR Spokane Ancora Estate Walla Walla ID offset the regular depletion that occurs with each year's crop of fruit—the single biggest cause of vineyard nutrient loss. Vineyards with divided cano- pies, which maxi- mize crop density, are particularly vulnerable to nutri- ent depletion. Among the species native to California that have been success- fully used as cover crops are Blando brome, Zorro fescue, purple vetch and certain clovers. Grant has little experience with most of these plants other than in trials, noting that expense and soil management objectives typically place mixes of other main- stream seeds at an advantage in commercial settings. "Native cover crop seed is expensive, and domesticated cover crop plants are often better suited to meet specific soil manage- ment objectives," he said. Arid Northwest environments Outside California, in the arid environments of British Colum- bia's Okanagan Valley and the high desert of Eastern Washington, wheatgrasses and other drought-hardy species are what farm advi- sor and Wines & Vines columnist Glenn McGourty recommends. Some perennial cover crops can slough off about half their roots each year, returning nutrients directly into the soil (about 1.6 tons per year on average for a conventional vineyard). McGourty recommends some of the old ranchland stand- bys such as crested wheatgrass or Siberian and streambank wheatgrass (sodar) to help stabilize the vineyard floor. He also recommends a mix of grasses and legumes, because the two complement each other in terms of nutrients returned to the soil, and conditions change from year to year. He estimates the cost of establishing an effective cover crop system at $50 to $500 per acre. But native species offer an alternative to conventional seed mixes. Working with Jim Holmes of Ancora Estate in Washing- ton state's Red Mountain AVA, Dr. Steven Link of Native Plant Landscaping and Restoration LLC in West Richland, Wash., has been investigating the potential of native nitrogen-fixing plants such as silky lupine and antelope bitterbrush as vineyard cover crops. The plants serve the same purpose as traditional cover crop mixes but lend a natural diversity to the vineyard and are typically more efficient in their use of resources such as water. "Classical cover crops, classical wheatgrasses and crested wheatgrass—which is in Jim's field—are a very old-fashioned idea in my personal opinion," Link said. "They're easy and cheap, so they've taken over. I think there are reasons, and good reasons to look for alternatives." Local beneficial insects Plant biodiversity is one reason, as is the creation of habitat for local beneficial insects that might not be as attracted to cover crop mixes that meet viticultural purposes alone. "That adds something of value to the system," Link said. "I don't find too many people opposed to it; it's more a matter of trying to do it (Continued on page 57) Wines & Vines FeBRUARY 2011 55