title: Ultrasonic Sensing of Plant Water Needs for Agriculture.
abstract: Fresh water is a key natural resource for food production, sanitation and industrial uses and has a high environmental value. The largest water use worldwide (~70%) corresponds to irrigation in agriculture, where use of water is becoming essential to maintain productivity. Efficient irrigation control largely depends on having access to reliable information about the actual plant water needs. Therefore, fast, portable and non-invasive sensing techniques able to measure water requirements directly on the plant are essential to face the huge challenge posed by the extensive water use in agriculture, the increasing water shortage and the impact of climate change. Non-contact resonant ultrasonic spectroscopy (NC-RUS) in the frequency range 0.1-1.2 MHz has revealed as an efficient and powerful non-destructive, non-invasive and in vivo sensing technique for leaves of different plant species. In particular, NC-RUS allows determining surface mass, thickness and elastic modulus of the leaves. Hence, valuable information can be obtained about water content and turgor pressure. This work analyzes and reviews the main requirements for sensors, electronics, signal processing and data analysis in order to develop a fast, portable, robust and non-invasive NC-RUS system to monitor variations in leaves water content or turgor pressure. A sensing prototype is proposed, described and, as application example, used to study two different species: Vitis vinifera and Coffea arabica, whose leaves present thickness resonances in two different frequency bands (400-900 kHz and 200-400 kHz, respectively), These species are representative of two different climates and are related to two high-added value agricultural products where efficient irrigation management can be critical. Moreover, the technique can also be applied to other species and similar results can be obtained.
authors.affiliation: Instituto de Tecnolog&#237;as F&#237;sicas y de la Informaci&#243;n, Spanish National Research Council (CSIC), Serrano 144, Madrid 28006, Spain. t.gomez@csic.es.
authors.forename: Tomas
authors.initials: T
authors.lastname: Gómez Álvarez-Arenas
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigaci&#243;n y Tecnolog&#237;a Agroalimentaria-Instituto Agroalimentario de Arag&#243;n (IA2), Gobierno de Arag&#243;n, Av. Monta&#241;ana, 930, Zaragoza 50059, Spain. egilp@cita-aragon.com.
authors.forename: Eustaquio
authors.initials: E
authors.lastname: Gil-Pelegrin
authors.affiliation: Escuela de Ingenier&#237;a Mec&#225;nica, Ed. 351, 2011, Ciudad Universitaria- Mel&#233;ndez, Universidad del Valle, Cali 760032, Colombia. joao.ealo@correounivalle.edu.co.
authors.forename: Joao
authors.initials: J
authors.lastname: Ealo Cuello
authors.affiliation: Instituto de Tecnolog&#237;as F&#237;sicas y de la Informaci&#243;n, Spanish National Research Council (CSIC), Serrano 144, Madrid 28006, Spain. md.farinas@csic.com.
authors.forename: Maria Dolores
authors.initials: MD
authors.lastname: Fariñas
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigaci&#243;n y Tecnolog&#237;a Agroalimentaria-Instituto Agroalimentario de Arag&#243;n (IA2), Gobierno de Arag&#243;n, Av. Monta&#241;ana, 930, Zaragoza 50059, Spain. dsancho@cita-aragon.com.
authors.forename: Domingo
authors.initials: D
authors.lastname: Sancho-Knapik
authors.affiliation: Escuela de Ingenier&#237;a Mec&#225;nica, Ed. 351, 2011, Ciudad Universitaria- Mel&#233;ndez, Universidad del Valle, Cali 760032, Colombia. david.collazos@correounivalle.edu.co.
authors.forename: David Alejandro
authors.initials: DA
authors.lastname: Collazos Burbano
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigaci&#243;n y Tecnolog&#237;a Agroalimentaria-Instituto Agroalimentario de Arag&#243;n (IA2), Gobierno de Arag&#243;n, Av. Monta&#241;ana, 930, Zaragoza 50059, Spain. jjpeguero@aragon.es.
authors.forename: Jose Javier
authors.initials: JJ
authors.lastname: Peguero-Pina
mesh_terms: D057914:Agricultural Irrigation; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D057231:Climate Change; D018515:Plant Leaves / Q000378:metabolism; D014465:Ultrasonics / Q000295:instrumentation* / Q000379:methods*; D014867:Water / Q000032:analysis* / Q000378:metabolism
chemical_list: D014867:Water
keywords: air-coupled ultrasound; irrigation control; non-contact sensing; non-destructive sensing; relative water content; resonant spectroscopy; water potential