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Joan R. Davenport and Mary J. Hattendorf

Potatoes (Solanum tuberosum L.) are grown extensively throughout the Pacific northwestern United States as a high value crop in irrigated rotations with other row crops such as wheat (Triticum aestivum L.) and both field and sweet corn (Zea mays L.). Center pivots are the predominant irrigation systems. Soil texture ranges from coarse sands to finer textured silt loams and silts and can vary within one field, particularly in fields with hilly topography. Site specific management is being evaluated as an approach to help to optimize inputs (water, seed, agricultural chemicals) to maintain or enhance yield and reduce potential negative environmental impacts from these farming systems. Currently, variable rate fertilizer application technology and harvest yield monitoring equipment are commercially available for potato. Variable rate seeding and variable rate irrigation water application technologies are developed but not fully commercialized and variable rate pesticide application equipment is in development. At the Irrigated Agricultural Research and Extension Center in Prosser, Wash., we have a team of research scientists, interested individuals from local industry, and other key organizations (e.g. local conservation districts) who are working together to evaluate different site specific technologies, improve the ability to use available tools, and to improve decision-making ability by conducting research both on farm and in research plots.

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Arnold W. Schumann

organic matter is a major factor in causing yield variability, a field can be divided into different characteristic zones for variable rate application of fertilizer or water. Babcock and Pautsch (1998) compared single rate and variable rate application

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Ronnie W. Heiniger

New technologies such as differential global positioning systems (DGPS) and geographical information systems (GIS) are making it possible to manage variability in soil properties and the microenvironment within a field. By providing information about where variability occurs and the patterns that exist in crop and soil properties, DGPS and GIS technologies have the potential of improving crop management practices. Yield monitoring systems linked to DGPS receivers are available for several types of horticultural crops and can be used in variety selection and/or improving crop management. Precision soil sampling and remote sensing technologies can be used to scout for infestations of insects, diseases, or weeds, to determine the distribution of soil nutrients, and to monitor produce quality by measuring crop vigor. Combined with variable rate application systems, precision soil sampling and remote sensing can help direct fertilizer, herbicide, pesticide, and/or fungicide applications to only those regions of the field that require soil amendments or are above threshold levels. This could result in less chemical use and improved crop performance. As with any information driven system, the data must be accurate, inexpensive to collect, and, most importantly, must become part of a decision process that results in improvements in crop yield, productivity, and/or environmental stewardship.

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Qamar Uz Zaman, Arnold Walter Schumann and David Charles Percival

slopes. These maps could be used to develop appropriate management zones based on slope variation for variable rate application of agrochemicals within wild blueberry fields. A smoothed map of slopes developed by interpolation of individual measured SS

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R. Karina Gallardo, Kara Grant, David J. Brown, James R. McFerson, Karen M. Lewis, Todd Einhorn and Mario Miranda Sazo

( Schimmelpfennig and Ebel, 2011 ), with relatively few producers using remote sensing, soil sensing, or variable rate application technologies. Lagged adoption has been attributed to several factors, including capital requirements ( Pierpaoli et al., 2013

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), normalized vegetative index (NDVI) and variable rate treatments applied “as needed” for correction of soil Ph and nutrient deficiencies in sweetpotato. Use of variable-rate applications has several benefits, including effective use of treatment resources, a