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Kelly T. Morgan, Lincoln Zotarelli, and Michael D. Dukes

. Often a combination of both approaches is used. Several devices are available to determine in situ soil moisture status. Soil moisture measurement Electromagnetic techniques (resistive, capacitance, and time-domain reflectometry sensor) include methods

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Erik Lichtenberg, John Majsztrik, and Monica Saavoss

Improvements in sensor technology coupled with advances in knowledge about plant physiology have made it feasible to use real-time substrate volumetric water content sensors to accurately determine irrigation timing and application rates in soilless

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Amir Ali Khoddamzadeh and Bruce L. Dunn

harvesting leaves that are then dried and chemically analyzed. This process takes time, is expensive, and most importantly may not meet grower needs for adjusting N for the current crop. Use of nondestructive handheld sensors can provide an instant indication

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Arnold W. Schumann

rates of agrochemicals that are targeted only under crop canopies and therefore over root zones. Various sensors are used to quantify this spatial variation which includes soil electrical conductivity (EC), yield, canopy size, and canopy color. Sensor

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L. Corelli Grappadelli and D. C. Coston


A sensor for measuring photosynthetically active radiation was constructed using a silicon photocell in combination with a glass absorption filter. A trimmer potentiometer was used for standardization of sensor output. The sensors were calibrated using a commercially available quantum sensor. Average correlation coefficient between constructed sensors and the standard was 0.94. The sensors had a quantum response, were sensitive only in the wavelengths between 400 and 700 nm, exhibited a linear response to varying PAR light levels, and were inexpensive to construct.

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Marc W. van Iersel, Matthew Chappell, and John D. Lea-Cox

. Sensor networks and water use models have been suggested as ways to improve irrigation efficiency and reduce water use in ornamental horticulture ( Lea-Cox, 2012 ; Million et al., 2010 ). Using sensors to collect quantitative information about crop water

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George Kargas, Nikolaos Ntoulas, and Panayiotis A. Nektarios

analysis have led to the development of alternative dielectric sensors that also use substrate dielectric properties to determine moisture content ( Seyfried and Murdock, 2004 ). Capacitance and frequency techniques offer an excellent alternative to TDR due

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Gregory E. Bell, Dennis L. Martin, Kyungjoon Koh, and Holly R. Han

texture and that a combination of turfgrass color and turfgrass cover accounted for most of the variability in models used to predict sensor measurements from human evaluations. These results were further confirmed by Kenworthy et al. (2006) on

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Charles Barnes, Theodore Tibbitts, John Sager, Gerald Deitzer, David Bubenheim, Gus Koerner, and Bruce Bugbee

PPF sensor with identical specifications and a similar spectral response to the LI-CORPPF sensor, but, unfortunately, we were notable to include the Skye PPF sensor in this study, The cost of publishing this paper was defrayed in part by the payment of

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William D. Wheeler, Paul Thomas, Marc van Iersel, and Matthew Chappell

). Automated irrigation through precision soil moisture sensing has been shown to be an efficient means of regulating irrigation application ( Lea-Cox et al., 2013 ; Majsztrik et al., 2013 ). Although a number of different soil moisture sensors exist