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WINERY & VINEYARD EQUIPMENT 34 WINES&VINES March 2015 O ne can safely assume that in com- ing years water will continue to get more expensive, more scarce or (most likely) both. Yet the technology to measure soil-mois- ture content has continued to improve, and today growers can choose from a variety of sensors. The data from such sensors is vital to ensure an irrigation program is using water as effectively and efficiently as possible and can be incorporated into a precision-agricul- ture system to help growers make even better vineyard-management decisions. Several companies sell individual sensors as well as other equipment for data logging or to download and interpret data. Other firms like Hortau, Fruition Sciences and Ranch Systems use soil moisture sensors as part of broad networks that provide ex- tremely detailed irrigation reports, analysis and recommendations. When it comes to just moisture sensors, there are two main categories: those that measure the water content of soil and those that measure water tension or how easy it is for roots to take up moisture. Moisture con- tent, volumetric or capacitance sensors use time domain reflectometry (TDR) and trans- missometry (TDT) while water tension is determined with tensiometers and matric potential sensors. Neutron probes are another option that are quite accurate and draw data from a large area, but they are expensive and require extra permits and training because they use radioactive material. Most companies that use neutron probes either have the resources to train someone to use them full time or work with a consulting firm that uses them. First, find the right spot Viticulturist Fritz Westover is the founder and owner of Houston, Texas-based Westover Viticulture and the former technical program manager for the Vineyard Team in Atas- cadero, Calif. During his time with Vineyard Team, Westover wrote a guide about using soil moisture sensors for irrigation management. The guide is still available at the group's website, vineyardteam.org. Part of the re- port appeared in the June 2015 issue of Wines & Vines (see "Where to Install Soil Moisture Sensors"). Before choosing and investing in what type of sensor to purchase, Westover said growers should first determine the best spot to locate sensors. He said the first step is to understand one's soil profile through soil maps, excavation pits or soil core samples pulled with a hand auger. Westover said his soil auger by AMS is one of his most valuable vineyard tools. "The real important thing is putting it in the right spot and making sure it's installed correctly," he said of sensors. "That's probably more important than the type of sensor you pick." After determining soil type and stratifica- tion, a grower should then analyze vine vigor through his or her own observations or normal- ized difference vegetation index (NDVI) map- ping. The goal is to place the sensor in a location that has the soil profile and charac- teristics that represents an "average" of the entire block. Doug Beck, a soil scientist and agronomist with the large grapegrowing enterprise Mon- terey Pacific, has a Ph. D. in soil science from the University of California, Davis, and has worked with moisture sensors in vineyards along California's Central Coast since 1998. "One of the most important attributes for me is that the data is recorded on a regular basis and then stored for viewing as a graphic," he said. "This way the full point (field capacity) and fill point (when moisture becomes limit- ing) for the soil can be easily understood." He said most sensors offer logging capa- bility and, if installed correctly, almost all can provide good data. For Monterey Pacific, Beck said he chose to install Gro Point sen- sors from Environmental Sensors Inc. (ESI) because they use time domain reflectivity and measure moisture content in a fairly large area. "It is accurate if installed cor- rectly, and most of the sensors I installed in the late '90s are still working and showing the same fill and full points for the sites where they are installed." Monterey Pacific's sensors are located about 15 inches deep near the main root uptake area and at the bottom of the root zone, which is around 4 feet. Beck said such a setup offers a clear view of when a vineyard needs to be irrigated and when it does not. Tracking Soil Moisture for Better Water Use Find the right sensor for your vineyard By Andrew Adams Having accurate and timely data can make irrigation more efficient. ADCON