Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2002
Publication Date: 6/1/2003
Citation: PRICE, R.R., HUMMEL, J.W., BIRRELL, S.J., AHMAD, I.S. RAPID NITRATE ANALYSIS OF SOIL CORES USING ISFETS. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2003. V. 46(3). P. 601-610.
Interpretive Summary: Nutrient loads in tile outflows, and subsequently in surface streams and drinking water reservoirs, continue to indicate a need for improved matching of commercial fertilizer application rates with projected crop needs. 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 needed to produce the crop. The cost and time required for the intensive sampling needed make implementation of a variable-rate nitrogen fertilizer management system based on conventional soil nitrate sampling and analysis 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. Sensor technology is being developed to 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 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: An intact core extraction procedure that might be used in the field for real-time prediction of soil nitrates was tested. An extraction solution was pushed through a soil core held between two filters, and an ion- selective field effect transistor/flow injection analysis (ISFET/FIA) system was used to sense soil nitrates in real time. Laboratory tests were econducted using four soil types and two levels of nitrate concentration, soil moisture, core density, core length, core diameter, and extraction solution flow rate. The extraction solution flow was sampled at the exit face of the core and routed to the ISFET/FIA system. The ISFET output voltage was sampled at 100 Hz. Results of the test indicate that nitrate extraction from the soil cores was successful and that data descriptors based on response curve peak and slope of the ISFET nitrate response curve might be used in tandem in a real-time prediction system.