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64 P R A C T I C A L W I N E R Y & V I N E YA R D June 2015 G R A P E G R O W I N G tially reducing excess water application. In areas where water quality is affected by high salt concentration, soil moisture sensors can provide valuable feedback regarding the effectiveness of irrigation or rainfall with regard to potential leach- ing of salts below the root zone. Proper placement of soil sensors is critical for obtaining data that will be useful to improve vineyard irrigation scheduling. Selecting a representative location Ideally, a grower would install soil mois- ture sensors in multiple locations per irrigation block to obtain an average of soil moisture across a site. However, the cost of sensors and the associated teleme- try devices required to retrieve data from a large number of data-logging stations is often a limiting factor when choosing the number of sensors to install. For this reason, it is most common for growers to install moisture sensors in only one or two sites within an irrigation block. When implementing a small number of data points across a vineyard, it is important to choose a soil profile that best represents the majority of the irriga- tion block. For example, installing soil moisture sensors in an area of shallow soil or with less water-holding capacity than is typical of the whole block can potentially result in sensor readings that overes- timate the frequency of irrigation sets needed within that block. Conversely, the installation of sensors in an area having deep, heavy clay soil than is not typical of the block will result in sensor readings that potentially underestimate the water needs of the whole block. Mapping vineyard soils Ideally, a vineyard soil will be fully mapped prior to designing a vineyard and establishing irrigation blocks to be irrigated differently as needed. Soil maps are available online from the U.S. Department of Agriculture's National Resource Conservation Service (USDA- NRCS) Web Soil Survey. (websoilsurvey. sc.egov.usda.gov/) These maps show the approximate boundaries of distinct soil series and can serve as a good starting point for deter- mining where a soil may change within a site. Maps from the USDA-NRCS are help- ful to describe the soil type of an area, however they are not accurate enough to be used alone when selecting where to install a soil-moisture sensor. On-site mapping of vineyard soils by a soil sci- entist or vineyard soil expert is rec- ommended to understand the precise boundaries of different soil types. Soil characteristics that may change across a soil series include effective root- ing depth, depth to bedrock or hardpan, soil texture and depth of distinct soil horizons. The process of soil mapping involves the excavation of multiple soil observa- tion pits across a site in order to estab- lish where changes in soil characteristics occur. The potential influence of different soils on vine growth is then estimated based on the knowledge and prior expe- rience of the soils expert. Before a vineyard is planted, soil pits can be excavated using a backhoe. Additionally, hand-operated soil augers can be used to capture disturbed soil profile samples and assist in delineating changes in soil across a block. Hand- or electric-powered augers will disrupt less soil volume on a site. In established vine- yards, large excavation equipment can be more difficult to maneuver, making use of portable hand or mechanical augers more accessible. Figure 3: An 8-acre block of Cabernet Sauvignon (block G, Figure 2 ) is planned as a single unit for irrigation. Soil cores extracted to a depth of 4 feet from west to east (A, B, C, D) reveal differences in depth of soil horizons across the block. Soil cores B and C represent the soil profile observed in the majority of the block, where the soil moisture sensors should be installed. Figure 4. Before installing soil-moisture sensors under the drip line, a series of observation points can be evaluated a short distance from the desired sensor placement location. This extra step can identify abnormalities in soil that influence water movement, such as hard pans or pockets of rock or sand. Promote your wines to leading Zinfandel enthusiasts and extend your winery's relationship in the market. Join Us! We are champions of Zinfandel— America's Heritage Wine Become part of our proud legacy zinfandel.org • 530-274-4900 Zinfandel Advocates & Producers is a 501(c)(3) non-profit organization. ZAP is dedicated to advancing public knowledge of and appreciation for American Zinfandel and its unique place in our culture and history. You know how good your Zinfandel is...