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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #167217
Title: DEVELOPMENT OF COMPONENTS OF A REAL-TIME SOIL MACRONUTRIENT SENSOR

Author
item HUMMEL, JOHN
item BIRRELL, STUART - IA STATE U
item PRICE, RANDY - LA STATE U
item KIM, HAK-JIN - U OF MO
item YILDIRIM, SAADETTIN - IA STATE U

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/20/2004
Publication Date: 10/11/2004
Citation: Hummel, J.W., Birrell, S.J., Price, R.R., Kim, H., Yildirim, S. 2004. Development of components of a real-time soil macronutrient sensor. In: Proceedings 2004 International Commission of Agricultural Engineering (CIGR) International Conference, October 11-14, 2004, Beijing, China. CD-ROM.

Interpretive Summary:

Technical Abstract: Soil macronutrients, especially nitrate nitrogen, can vary both spatially and temporally. A real-time sensor that automatically collects and analyzes soil samples could provide data to optimize variable-rate fertilizer application. This paper discusses progress on the development of three major components of a real-time soil macronutrient sensor based on ion-selective field effect transistor technology. The technology dictates that a sample of soil be collected so that an extracting solution can be used to obtain a liquid sample containing the soil macronutrient ions. This paper discusses research on 1) design of an electro-pneumatic device for rapid soil sample collection, 2) laboratory investigations of membranes and extracting solutions that might permit a single extraction to support real-time analysis of soil nitrate and potassium, and 3) techniques for rapid extraction of macronutrient ions from the soil sample. In the soil sampler design research, a range of soil types was included in the laboratory study. Soil bin testing of a soil sampling shank using the electro-pneumatic method showed that air pressure, pulse duration, soil moisture content, and travel speed had highly significant effects on the mass of the sample collected. The extraction studies showed that TDDA-based nitrate membranes were capable of detecting low concentrations in soils to about 10**-5 mole NO3-/L. The valinomycin-based potassium membranes showed satisfactory selectivity performance in measuring potassium in the presence of interfering cations such as Na+, Mg++, Ca++, Al+++, and Li+ as well as providing a consistent sensitivity when DI water, Kelowna, or Bray P1 solutions were used as base solutions. The TDDA-based nitrate membrane and the valinomycin-based potassium membrane, used in conjunction with Kelowna extracting solution, would allow determination of nitrate and potassium levels, respectively, for site-specific control of fertilizer application. The extraction research showed that rapid extraction of nitrate from soil cores appears feasible, and that data descriptors based on response curve peak and slope of the ISFET nitrate response curve are good candidates for a real-time nitrate prediction system.