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Title: REAL-TIME MULTI-ISFET/FIA SOIL ANALYSIS SYSTEM WITH AUTOMATIC SAMPLE EXTRACTION

Author
item BIRRELL, STUART - IOWA STATE UNIVERSITY
item HUMMEL, JOHN

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Successful implementation of site-specific crop management relies on accurately measuring the spatial variability of factors such as soil nutrients. High intensity data collection using conventional manual and/or laboratory methods is often cost prohibitive. There is a need for the development of sensors to more accurately characterize within-field variability. On-the-go real-time nitrate sensors might be used to locate areas of fields where additions of nitrogen fertilizer will be beneficial, and other areas where soil nitrate levels are such that additions of nitrogen fertilizer may have no economic benefit and could result in environmental degradation. The ion-selective field effect transistor sensor technology has been tested, and can rapidly measure soil nitrate levels in soil extracts. We incorporated this technology into a flow injection system to rapidly analyze soil nitrate level in soil extracts. A prototype high-speed soil sample collection and extraction system was investigated with some success. When a satisfactory system has been designed and commercialized, soil nitrate levels could be used to control the nitrogen fertilizer application rates in corn production. Use of the technology could benefit agricultural producers economically, and reduce the adverse effect of commercial fertilizers on the environment.

Technical Abstract: The objective of this work was to develop an integrated multi-sensor ISFET/FIA analysis system. A real-time soil analysis system, for on-the-go soil nitrate monitoring, requires the analysis to be completed within 5 s and preferably within 3 s. An ISFET/FIA analysis system was developed and FIA parameters optimized to obtain the shortest sampling period possible. The inherent disadvantages of the ISFET, such as long-term drift, are essentially eliminated using the FIA system. The fast response of ISFETs and the low sample volumes required are advantages in the FIA system, allowing very high sampling rates since dispersion is decreased. The correct selection of flowrate and injection time allow a sample period of less than 2 s. The precision of the overall response of the multi-ISFET/FIA system is determined by the FIA system parameters and not the accuracy of the ISFETs. The multi-ISFET/FIA system is capable of determining the nitrate concentration of samples within the time limits required for real-time soil analysis.