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 Title: Multi-ISFET sensor system for soil analysis Author(s): Birrell, Stuart James Doctoral Committee Chair(s): Hummel, John W. Department / Program: Agricultural Engineering Discipline: Agricultural Engineering Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Soil Science Chemistry, Analytical Engineering, Agricultural Abstract: Site-specific crop management aims to improve production efficiency by adjusting crop treatments, especially fertilizer and chemical application, to local conditions within the field. The implementation of spatially selective field operations is dependent on field mapping of the variations in soil and crop parameters. The development of soil nutrient sensors may both improve the accuracy of soil nutrient maps and decrease the cost of soil sampling.Ion-selective field effect transistors (ISFETs) have inherent features such as small dimensions, low output impedance, high signal-to-noise ratio, low sample volumes and the potential for mass production, which are required for a real time soil sensor. However, ISFETs have the disadvantage of long-term drift, which is diminished by the use of a Flow Injection Analysis (FIA) system. In fact, FIA and ISFETs are complementary since the small sample volumes and rapid response of ISFETs allow the miniaturization of the FIA system, dramatically decreasing the sample dispersion and thereby increasing both sample resolution and sample frequency. This study involved the production and testing of nitrate ISFETs and the development of a FIA system using ISFETs as detectors for soil nitrate sensing.A multi-ISFET nitrate sensor was developed and integrated into a flow injection system to measure soil nitrates. The multi-ISFET sensor was successful in measuring soil nitrates in manual soil extracts (r$\sp2$ $>$ 0.9). The precision and accuracy of the system was highly dependent on maintaining precise, repetitive injection times and maintaining constant flow parameters during the testing cycle. During tests almost all of the errors in prediction can be traced to these two factors. The rapid response of the system allowed samples to be analyzed within 1.25 seconds, which is satisfactory for real-time soil sensing. The development of an automated soil extraction system was not particularly successful and requires considerable improvement. However, the concept of using ISFETs for the real-time analysis of soil nitrates is sound. The extremely rapid response and low sample volumes required by the multi-sensor ISFET/FIA system make it a strong candidate for use in real-time soil nutrient sensing. Issue Date: 1995 Type: Text Language: English URI: http://hdl.handle.net/2142/23157 Rights Information: Copyright 1995 Birrell, Stuart James Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9624290 OCLC Identifier: (UMI)AAI9624290
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