Issue link: http://read.dmtmag.com/i/51841
VINEYARD OPERATION For field measurement, a "full sun" reading should first be taken outside the vine row at the same height that shaded readings will be taken. This electrical current value on the multi-meter screen must be recorded as a reference value for later calculations. Then the shaded readings in the vine rows are taken. The readings should be taken for reference vines or reference rows, taken quickly, with as many read- ings as necessary to obtain an accu- rate characterization of the block of interest, such as an irrigation block. Battany commonly takes 40 to 50 readings within a row over a period of a few minutes. Each reading from the digital multi-meter must be recorded to make calculations. Battany uses a portable, digital voice recorder with clip-on microphone to verbally record each reading. This enables him to take many more readings during the one-hour midday solar noon period without stopping to write down readings. He later plays the recording while at a computer to type numbers directly into the spreadsheet to do the calculations. Battany's website shows sample calculations for converting the read- ings in amps to a shaded percent- age of the solar panel and then to a Kc factor. Battany listed several parameters for using the Paso Panel effectively: It should be used in clear-sky conditions, when no clouds obstruct direct sunshine to the solar panel. Measurements should only be taken near solar noon. In Cali- fornia, solar noon in summer is at about 1 p.m., due to Daylight Savings Time. Battany suggests only taking measurements between 12:30 and 1:30 p.m. East-west oriented rows will be less affected by changes in the shaded area outside these time constraints compared to north- south oriented rows. The panel should be positioned 86 VINEYARD & WINERY MANAGEMENT JAN - FEB 2012 WWW.VWM-ONLINE.COM as close as possible to the underside of the canopy and at this same position for each mea- surement. The solar panel must be kept free of dust and debris, and held level for each reading. Windy conditions should be avoided, as moving vines and leaves will cause fluctuations in the meter readouts. The push-button switch should only be engaged briefly (about 1 second per reading). The switch short-circuits the solar panel and if engaged for long periods, this can burn out the solar panel wiring. "For irrigation calculations, it's designed to work on trellised grapes when the canopy fills out the trellis," Battany added. "It's more useful for mature vineyards, rather than younger vines still developing." He suggested taking readings of reference blocks at least once a month after bud break to get read- ings for how the canopy develops and establish a reference pattern for Kc. Once the canopy reaches full maturity, the readings taken at this point should provide a good Kc value for each location for the rest of the irrigation season. E. & J. Gallo has been using three Paso Panels made by Bat- tany in vineyards in different growing regions, from Sonoma to Fresno counties, taking mea- surements with different trellis systems and different cultivars. The panels were made in sizes to accommodate different sized cano- pies. "Once we got this tool, it was easy to go to any vineyard and get a more site-specific crop coeffi- cient," said Gallo research viticul- turist Martin Mendez-Costabel. "It has helped us improve the efficien- cy of irrigation scheduling." He said the Paso Panel provides the abil- ity to take a lot of measurements more easily and obtain many more data points with which to work. "It's much better than the tools and methods we had before," Mendez- Costabel said, "and it's been more accurate than the older methods for measur ing canopy-shaded areas." Battany said some growers in Argentina are using the device, and he hopes more growers will try it and provide him feedback on their experiences. "I think as it is used more, people will find other applica- tions for evaluating and managing their vineyards," Battany said. Ted Rieger, CSW, is a writer and photographer based in Sacramento, Calif., and has been a contributing editor for V&WM since 1990. Comments? Please e-mail us at feedback@vwm-online.com.