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44 Wines&Vines January 2015 grapegrowing R yan Decker, grower relations manager for Rodney Strong Wine Estates, admits that he cannot control the climate, but he can deliver prescribed amounts of irrigation water to a constellation of vineyards located in one of the most diverse grapegrowing regions in Califor- nia. He tends Chardonnay growing from dark clay near the San Pablo Bay, Petite Sirah, Touriga Nacional and Zinfandel planted in alluvial soil not far from the Russian River and Cabernet Sauvignon growing from a rocky, inland hillside close to the Sonoma-Mendocino county line. Near the confluence of the Alexander Valley, Chalk Hill, Russian River Valley, Sonoma Coast and Sonoma County AVAs, the winery overlooks a river basin that meanders 32 miles, or nearly a third of its length, to the sea. During the grow- ing season, warm air rises from inland valleys drawing fog through the Peta- luma Gap and along the Russian River Valley where it gathers near Healdsburg, Calif., before spilling into the Alexander Valley. South of the winery, fog dampens daytime temperatures and helps drive a seemingly endless cycle of misty morn- ings, warm days, windy afternoons and cool nights. To the north, fog dissipates from the river basin early in the day giv- ing way to warmer afternoon and night- time temperatures. Alexander's Crown, a rolling hillside vineyard located at the southern end of the Alexander Valley, records an average temperature of nearly 60º F from bud break to harvest. Twelve miles upriver, Brothers Ridge, a steep hillside vineyard, averages more than 67º. Variations in climate help explain the diversity of this growing region. "The farther you are from the (Petaluma) Gap," Decker says, "the weaker the ma- rine influence." At the boundary be- tween maritime and continental air masses, the Alexander Valley, alone, produces 66 varieties of wine grapes. Following a budget Decker must consider several wide-rang- ing variables before he calculates a water budget for each of the 14 estate vine- yards that he oversees. A carefully crafted budget allows him to efficiently irrigate a diverse landscape, conserving water, enhancing quality and increasing yield. Along with evaluating the weather, he keeps track of nutrients, soil mois- ture, transpiration rates and yield for 1,158 acres of vines or nearly 125 vine- yard blocks. The lay of the land shapes the char- acter of each estate. The River East vineyard, for example, yields Pinot Noir and Chardonnay from clay loam 90 feet above sea level. Brothers Ridge bears Cabernet Sauvignon, Merlot and Mal- bec from loam underlain by sandstone, fractured shale and ancient greenstone at an elevation of 400 to 1,030 feet. Soil type, depth and texture affect irrigation rates and growth. Typically, alluvial soils are more fertile and retain more moisture than hillsides. Clay con- tains micro-pores holding irrigation water and roots closer to the surface, while rocky soils form macro-pores per- mitting them to penetrate deeper into the earth. Elevation matters. Wind, a higher concentration of UV light, temperature inversions, rocky and shallow soil can sap vigor from the vines. Variety makes a difference, too. Red grapes require less water than white. Vines grown for light-bodied wines de- mand more water than vines harvested for full-bodied wines. And varieties handle stress differently. Syrah shows KEY POINTs Conserving irrigation water can increase yield and improve quality. Versatile software and sensors lead to continuous improvement. Reducing water-use cuts production and energy costs. Growing More with Less Water Rodney Strong Wine Estates uses multiple technologies to closely manage irrigation By Tom Ulrich Rodney Strong's vineyards in the Russian River and Alexander valleys are equipped with Adcon weather stations. "It might take three hours at 1 gallon per hour to saturate coarse-textured soil or six hours to saturate heavy clay soil." —Ryan Decker