Salinity issues are a wine grape grower's nightmare. Figuring out if there is a problem, where it is or where it is headed is invaluable.
Mark Battany, San Luis Obispo County UCCE farm advisor has initiated a soil salinity survey in the growing Paso Robles grape growing area.
He has uncovered surprising salinity levels.
“My goal is to assess overall soil salinity status in the area east of Paso Robles, and to track changes over time,” he says.
Battany began the trial last year taking samples from 100 locations. He plans to repeat sampling at the same sites every three years with the help of funding from the American Vineyard Foundation.“As electrical conductivity goes up, vine growth goes down,” Battany says. “It's a very linear relationship. I chose the Paso Robles area because it is more likely to have salinity problems than other areas within the San Luis Obispo and Santa Barbara areas.”
At each site, Battany took 10-15 auger cores, sampling the top foot of soil within the vine row. He sampled at random distances from drip emitters and trunks and marked the location through global positioning satellite (GPS) technology.
“The Paso Robles area is generally considered to have naturally high pH soils,” he says. “However, the native soils are actually acidic. The bicarbonates in our irrigation water are raising the pH of our soils.”
Preliminary results of the survey have shown that sampled sites ranged from 0.7 to 6.6 in terms of electrical conductivity. That's a huge range, according to Battany, when anything above 2.5 is considered dicey for growing wine grapes.
“I started this survey in 2006 after two very wet preceding years,” he says. “I think if I had started it earlier I would have seen even higher numbers.”
Battany will be publishing his findings in more detail in upcoming UCCE editions of his newsletter, which can be accessed online at: http://ucanr.org/grapenotes