MULTI-ISFET SOIL NITRATE SENSOR DEVELOPMENT

Authors: BIRRELL, STUART - UNIV OF ILLINOIS; Hummel, John

Submitted to: American Society of Agricultural Engineers Transactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Concern about the intensive application of nitrogen fertilizers, and their potentially adverse effects on the environment, has provided impetus for development of improved fertilizer management. Different soil nitrate levels, and different soil types with differing crop producing capabilities within a field, suggest that application levels might be adjusted across the field, supplying just the supplemental amount of nutrient needs to produce the crop. The cost and time required for the intensive sampling needed, using conventional sampling and analysis techniques, makes implementation of a variable-rate nitrogen fertilizer management system based on soil nitrate tests impractical. 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. A sensor technology has been tested that can rapidly measure soil nitrate levels in soil extracts. When coupled with a high-speed soil sample collection and extraction system (yet to be developed), 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: Successful implementation of site-specific crop management relies on accurate quantification of spatial variation of important factors. Data collection on a finer spatial resolution than is feasible with manual and/or laboratory methods is often required but cost prohibitive. The objective of this work was to develop a nitrate ion-selective field effect transistor (ISFET) that could be integrated into a flow injection analysis system for real-time soil analysis. Several different ion selective membranes were tested to identify potential candidates for the development of a nitrate ISFET. All of the evaluated membranes proved to be viable candidates for the development of a nitrate ISFET. The MTDA membranes showed a better response to nitrates at low concentrations while the TDDA membranes showed superior selectivity for nitrate ions. A multi-ISFET nitrate sensor was successfully developed. The sensitivities of the nitrate ISFETs were lower than the theoretical Nernst sensitivity but within acceptable limits. The electrical responses to the ISFETs were consistent and predictable. The nitrate ISFETs proved to be viable sensors for the development of a real-time soil nitrate analysis system.