Sensors 2012, 12, 13349-13392; doi:10.3390/s121013349 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Review Ion-Specific Nutrient Management in Closed Systems: The Necessity for Ion-Selective Sensors in Terrestrial and Space-Based Agriculture and Water Management Systems Matthew Bamsey 1,2, Thomas Graham 2, Cody Thompson 2, Alain Berinstain 1, Alan Scott 3 and Michael Dixon 2,* 1 Canadian Space Agency, Space Science and Technology, 6767 route de l’aéroport, Longueuil, QC J3Y 8Y9, Canada; E-Mails:
[email protected] (M.B.);
[email protected] (A.B.) 2 Controlled Environment Systems Research Facility, School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; E-Mails:
[email protected] (T.G.);
[email protected] (C.T.) 3 COM DEV Ltd., 303 Terry Fox Dr., Suite 100, Ottawa, ON K2K 3J1, Canada; E-Mail:
[email protected] * Author to whom correspondence should be addressed; E-Mail:
[email protected]; Tel.: +1-519-824-4120 (ext. 52555); Fax: +1-519-837-0442. Received: 31 July 2012; in revised form: 3 September 2012 / Accepted: 10 September 2012 / Published: 1 October 2012 Abstract: The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution.